Abstract:
A method and apparatus for removing hairs from living skin is provided involving the measurement with a colorimeter of the color of the area of the skin where the hair is to be removed to obtain a representative color value, employing the color value to select an optimum range of laser energy necessary to inactivate hair follicles in the area, yet minimize any inflammatory reaction, and directing laser energy of optimum range at the skin area to depilate such area.

Description:
REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation-in-part of U.S. application Ser. No. 09/394,171 filed Sep. 13, 1999, now U.S. Pat. No. 6,514,242 B1, by the present inventor David B. Vasily and his then co-inventor Peter L. Dorogi, which claims the benefit of Provisional Application Ser. No. 60/110,732, filed Dec. 3, 1998. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to the field of laser dermatology and more particularly concerns a method and apparatus for removing hair from living skin while minimizing irritation or injury to the skin. 
   2. The Related Art 
   Location, location, location. Just as in real estate, the beauty of hair is where it rises. A forest of hair on the scalp is considered a blessing. On the upper lip it may be less desirable, most especially less desirable for females. Location on the legs is deemed also not at all attractive. 
   Removal of unwanted hair is commonly achieved by shaving for short-term results. Mechanical epilation with wax or other devices provides a longer respite. Several disadvantages accompany these methods. Frequently they cause irritation, folliculitis and on rare occasions scarring. There are presently several FDA-approved treatments for hair removal. Electrolysis involves resistive heating around an electrode placed deeply into a hair follicle, causing complete or partial destruction of such follicle. Such treatment is painful, tedious and only moderately effective. About 50 to 85% of treated hairs, furthermore, re-grow. There are also significant risk effects here of folliculitis and infection. 
   Another FDA-cleared treatment (Thermolase technique) involves exposure to a Q-switched Nd:YAG laser designed for tattoo removal, following wax epilation and topical application of a suspension of amorphous carbon particles. This treatment is mildly painful. Despite aggressive marketing, its effectiveness appears to be minimal or nonexistent. The potential complications of this treatment are those of laser surgery in general (infection, scarring, pigmentary changes), plus the risk of inadvertent tattooing by introducing carbon into the dermis through ruptured follicles. However, these complications presumably occur at an acceptably low incidence. 
   A safer and more effective system has been described by Dr. Rox Anderson of the Harvard Medical School and commercialized by Palomar Corporation. The system uses a ruby laser with light delivered through a transparent actively-cooled sapphire hand piece held directly in contact with the skin. The hand piece conducts heat away from the epidermis before, during and after each pulse. 
   Transient inflammatory reaction (erythema, edema) and pigmentary changes (hypopigmentation, hyperpigmentation) are routine and expected whenever a laser is used to injure some component of the skin. Compared with pulsed dye, Q-switched and other lasers used for cosmetic procedures, the Palomar laser produces similar skin injury followed by rapid healing requiring minimal wound care. Compared with electrolysis, in which bacteria are frequently repeatedly introduced into follicles from the skin surface by a needle-like electrode, the laser system may cause less folliculitis. Nonetheless, it is very evident there is a need for much safer procedures to avoid skin damage and to also minimize the number of treatments required for effective hair removal. 
   Patent References 
   In addition to the above general prior art, applicant is familiar with the following prior art patents of interest. 
   U.S. Pat. No. 5,671,735 issued to MacFarlane et al. on Sep. 30, 1997 discloses broadly the use of a colorimeter in the diagnosis of medical conditions. MacFarlane&#39;s technique involves basically the taking of a preliminary colorimeter reading of the skin before a disease condition occurs, storing this for reference in an associated computer and then later taking another reading to see if a skin color change has occurred, which, if present, may indicate a disease condition has occurred. Later readings may be used to monitor recovery. Various color instruments are disclosed. A later MacFarlane et al. U.S. Pat. No. 6,308,088 issued Oct. 23, 2001 includes expanded tables of colors including extensive hair color tables. 
   U.S. Pat. No. 6,015,404 issued to Altshuler et al. on Jan. 18, 2000 includes the use radiation type temperature detection devices to monitor the use of a dermatology laser device. 
   U.S. Pat. No. 6,050,990 issued to Tankovich et al. on Apr. 18, 2000 includes a comprehensive discussion of the use of lasers for various skin treatment purposes, including, in particular, the removal of hair, or depilation. Tankovich et al. teaches that the laser beam can be adjusted in terms of wave length, fluence, pulse repetition rate and pulse duration and that it should be adjusted in accordance with the type and condition of the patient&#39;s skin and hair. Information concerning these is to be obtained by the use of a set of questions including the color of the skin and hair and the possible use of photography to document the answers. Tankovich does not teach or even mention the use of a calorimeter to aid in determining the settings or treatment with the laser. 
   U.S. Pat. No. 6,149,644 issued to Xie on Nov. 21, 2000 discloses a method of treating the skin by actinic light, i.e. light sufficient to form a chemical change or induce photochemical activity, one use being hair removal. Xie discloses broadly that skin is less effected by light in the 600 to 999 nm range than hair follicles. In order to decrease the light to any specific portion of skin Xie continuously moves his light beam, whether continuous or pulsed as in a laser, along narrow contiguous paths thereby reducing the amount of energy applied to any specific spot while fully covering over a discrete period a full area. 
   U.S. Pat. No. 6,168,589 to Tobinick which contains a good description of the state of the art of laser depilation of the skin at the time of Applicants&#39;filing date and suggests that the treatment should be customized according to the skin color, hair color, hair diameter and anatomy of the particular site being treated and points out that dark skinned persons and light skin persons must be treated differently as darker skin are more easily burned. Tobinick&#39;s particular solution was to divide patients into groups or categories of darkness of skin and coarseness and darkness of hair, determine the “thermal relaxation time,” i.e. the time for a uniform amount of heat to diffuse from a volume of material and adjust his laser pulses in pulse sequence time so as not to exceed the thermal relaxation time of the structure or the structures to be destroyed or damaged, i.e. the hair follicle, but to exceed the thermal relaxation time of the structures that are desired not to be damaged. There is no disclosure whatsoever of the use of a colorimeter. 
   U.S. Pat. No. 6,251,100 to Flock et al. teaches the use of lasers to perforate the epidermis pursuant to the application of topical anesthetics and the like to and through the skin in place of an injection. The aim is to perforate the skin with as little damage as possible. Flock sets forth a number of examples and in example 12 used a colorimeter to detect erythema or reddening of the skin as a sign of skin damage or irritation. Flock discloses the use of laser beams for other treatments as well, including, in example 17, the removal of nose hairs, but there is no disclosure of the use of a calorimeter to monitor the results. 
   Non-Patent References 
   
       
       1. Fitzpatrick T. The validity and practicality of sun-reactive skin types I–VI. Arch Dermatol 1988; 124:869–871. 
       2. Nanni C A, Alster T S. Laser-assisted hair removal: side effects of Q-switched Nd:YAG, long-pulse diode and alexandrite lasers. J Am Acad Dermatol 1999; 41:167–171. 
       3. Takimaki, H. Measurement of skin color: practical application and theoretical consideration. The J of Med Invest 1998; 44:121–125. 
       4. Fullerton A, Fischer T. Laht; et al. Guidelines for measurement of skin color and erythema. Contact Dermatitis 1995; 35:1–10. 
     
  
   OBJECTS OF THE INVENTION 
   Accordingly, it is an object of the present invention to provide a method for epilation which minimizes transient inflammatory reactions and pigmentary changes. It is a still further object of the invention to provide a method of depiliation or epilation of the skin which prevents any accompanying injury to the skin. 
   It is a object of the present invention is to provide an epilation method based on laser energy levels or doses which minimize the number of treatments necessary to effect full epilation. 
   It is a still further object of the invention to provide a simple easily determined reading of skin color using particular ranges of remitted light that provide a reliable indication for a physician or technician of the laser energy to be used in depilation of the skin of various patients without injury to the skin. 
   It is a still further object of the invention to provide a method of depilation using the green and blue remittance of light from the skin to make reading which can be altered to an accurate calculation of the energy to be fed to a laser for depilation of the epidermis without injury. 
   These and other objects of the present invention will become more apparent from the following summary and detailed description. 
   SUMMARY OF THE INVENTION 
   Prior to treatment with a laser to incapacitate the hair follicles in order to effect depilation of the skin, the area of the skin to be treated is read with a colorimeter adapted to obtain readings respecting the amount of remittent light in the green and blue range and these readings are used in a previously validated mathematical formula to provide a therapeutic dosage of laser light effective to inactivate hair follicles in the skin area. Normally the so-called L.a.b. calorimeter system using the b/L relationship will be used. However, any equivalent system measuring light in the green and blue range may be used such as the related X, Y, Z color coordinates with a suitable previously validated formula to provide equivalent laser light dosages. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagrammatic block diagram type depiction of one possible embodiment of a combined apparatus for practicing the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following detailed description is of the best mode or modes of the invention presently contemplated. Such description is not intended to be understood in a limiting sense, but to be an example of the invention presented solely for illustration thereof, and by reference to which in connection with the following description and the accompanying drawings one skilled in the art may be advised of the advantages and construction of the invention. 
   Human skin color is extremely difficult to characterize accurately by clinical observation alone. In general, in light skin, containing very little or minimal melanin, the primary light absorbing chromophore is hemoglobin. Absorption of incident green light by hemoglobin results in reddish skin colors, whereas absorption of blue light by more melanized skin results in a green-red blend, with the resultant appearance of browner tones of skin. In addition, identical skin tones under one light can appear very different under a different light. This varying color, or so-called metamerism, renders it essentially impossible to consistently and/or accurately characterize the true color of skin. Human skin is metameric due to variable optical properties of epidermal melanin. 
   In earlier times ruby laser dosimetry was based on so-called Fitzpatrick skin types. This typing, which predicts ability to melanize, rather than degree of melanization, was found to be unreliable and patients so treated experienced an unacceptably high incidence of tissue complications, including crusting, blistering, and pigmentary changes. In some instances, pigmentary changes such as hypopigmentation were long-lasting and took as much as up to one year to resolve. 
   In an effort to develop a better and more reliable quantitative method for determining proper dosimetry that would allow reproducible complication-free and highly effective laser hair removal in a high percentage of patients, the present inventor tried to correlate the readings of a reflectance spectrophotometer to determine the color of the skin of potential patients and to correlate this with the results of subsequent laser treatment. 
   Reflectance spectrophotometry is based on the principle of the measurement of an object&#39;s spectral reflectance, determined after illumination with a uniform amount of delivered light from a visible light source. The reflected light from the object typically passes through spectral sensors and microcomputers that calculate and assign numerical values L* a* b* to an object. These values are algebraic expressions of the XYZ tristimulus values, defined by the CIE (Commission International de l&#39;Eclairage) in 1931, to characterize an object&#39;s color with X (red), Y (green) and Z (blue) spectrum values. 
   The L* a* b* color space is a commonly used source for quantitating color data. Defined by the CIE 1976, this space or system was designed to provide uniform values corresponding to or allowing for differences in human visual perception. The L* in this space or system indicates lightness, the a* the+(red),−(green) direction and b* the+(yellow)−(blue) directions. 
   At first a handheld reflectance spectrophotometer to determine various reading, initially, b* readings only was experimented with and, subsequently after more experimentation and correlation&#39;s, the b*/L* ratio was concentrated upon. Ultimately it was determined that this was the value that correlated most closely with the melanin content of skin. 
   The b/L ratio was found to be highly predictive of melanin content of human skin since it localizes color readings to the brown area of the color sphere. This ratio, after extensive experimentation, showed a strong linear correlation with effective, safe laser doses. 
   It has been discovered, therefore, that laser-based removal of hair can be rendered more effective while less irritating through guidance by skin coloration type in selecting the most efficient laser energy dosage. Colorimetry values obtained from a spectrophotometer can, therefore, with proper correlation now guide selection of the optimal laser energy. 
   According to a first step of the method of this invention, skin color is analyzed by a spectrophotometer/colorimeter. These instruments usually operate with at least one visible light source such as a light emitting diode (LED), xenon-arc, tungsten/halogen or other light source in the wavelength range of 400 to 900 nm. The visible light source may be co-housed with the sensor portion of the spectrophotometer/colorimeter. Both visible and infrared wavelength light may be utilized in connection with a sensor portion. A suitable hand-held instrument is commercially available from Minolta Camera Company Ltd., Japan (Minolta Spectrophotometer/colorimeter CM-2002), from Colortec Associates, Accuracy Measurements Inc. and X-Rite. 
   Skin coloration can be expressed in values of lightness, redness and yellowness respectively denoted by L*, a* and b* units. 
   The L*a*b* color space is related to the Individual Typology Angle, which is essentially the value of 57.3 arctangent [(L*−50)b*], identifying skin types. See Chardon et al., International Journal of Cosmetic Science, 13, 191–208 (1991). Type I, the very lightest skin color, covers an angle ranging from more than 55 to 60°; Type II, light skin color, covers an angle ranging from more than 41 to 55°; Type III, intermediate skin color, covers an angle ranging from more than 28 to 41°; Type IV, tan skin color, covers an angle ranging from more than 10 to 28°; and Type V, brown skin color, covers an angle ranging from 0 to 10°. 
   Individual Typology Angle correlates to a first approximation with visibly judged Skin Type and to a first approximation determines the correct laser setting. However, visual judgement of Skin Type may also be influenced by optical contributions from hemoglobin as well as that of melanin. A second shortcoming of the currently practiced art of Skin Typing is the phenomenon called metamerism, in which two skin colors that appear the same to the human eye under one light source are seen to be different under other lighting conditions. Human skin is metameric because people of different ethnic origins can have different optical types of melanin in their skin. The calorimeter used in the present method is designed to provide L*a*b* values that are the best metameric fit (average) for fluorescent lighting, daylight and incandescent light. Since the ruby laser interacts selectively with melanin, the primary optical parameters to be chosen must be those most sensitive to skin melanin content for more accurate selections of laser dosage for epilation. 
   The melanin absorption of incident light has a lower amplitude for lighter skin and a greater amplitude for darker skin, respectively. In the former case the skin color spectrum is partly dominated by hemoglobin absorbance, in the latter case by melanin absorbance. For lighter skin (low melanin), the absorbance of primarily green light by hemoglobin imparts a reddish remittance to the skin. For darker skin (high melanin content), the strong absorbance of blue light imparts a green-red combination to the remittance, giving skin a brownish color. For Caucasian skin, Types I–III, a change in melanin has a greater impact on total blue remittance than on green remittance, where hemoglobin dominates. It would appear that the best indicator of differences in skin melanin content is an optical parameter that compares remittance intensities in the blue part of the spectrum (heavily reduced by melanin absorbance) against the green remittance (heavily reduced by hemoglobin absorbance). Consequently, for Skin Types I–IV, one can treat the green band remittance as a melanin-independent baseline against which differences in blue-band remittance indicate differences in skin melanin content. 
   The standard definition of color was set in 1931 with the definition of three types of standard remitted spectra, X, Y and Z. Approximately, X is a red remittance spectrum, Y is a green spectrum, and Z is a blue spectrum. The psychological color perception parameters L*a*b* are actually algebraic transformations of X, Y, Z that accommodate the human mind&#39;s relative sensitivities to the X-, Y- and Z-spectra:
 
 L* =116( Y/Y   a ) 1/2 −16
 
 a* =500[( X/X   a ) 1/3 −( YY   a ) 1/3 )]
 
 b* =200[( Y/Y   a ) 1/3 −( Z/Z   a ) 1/3 ]
 
where X a , Y a , and Z a  are maximum values of the remittance for the particular illumination intensity. Looking at these three definitions reveals that the quantity b* compares blue to green remittance, Z versus Y, which is the object of the present method.
 
   Table I shows the range of Skin Types for sixty-seven panelists in a clinical study performed for the present invention. Data correlation between the measured angle and the Skin Type subjectively assigned in the study is weak, pointing out the inferiority of the known Skin Typing method. 
   
     
       
             
             
             
           
             
             
             
           
         
             
               TABLE I 
             
             
                 
             
             
               PATIENT 
               SKIN TYPE 
               (ARC TAN) ( (L-50)/B) ) 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               1 
               II 
               33.44 
             
             
               2 
               III 
               36.19 
             
             
               3 
               III 
               44.41 
             
             
               4 
               II 
               52.12 
             
             
               5 
               I 
               41.92 
             
             
               6 
               II 
               32.35 
             
             
               7 
               III 
               45.00 
             
             
               8 
               II 
               54.29 
             
             
               9 
               III 
               43.78 
             
             
               10 
               III 
               55.25 
             
             
               11 
               II 
               35.51 
             
             
               12 
               II 
               37.37 
             
             
               13 
               II 
               40.68 
             
             
               14 
               II 
               44.63 
             
             
               15 
               IV 
               20.24 
             
             
               16 
               II 
               50.37 
             
             
               17 
               III 
               33.85 
             
             
               18 
               III 
               28.79 
             
             
               19 
               II 
               50.07 
             
             
               20 
               II 
               23.92 
             
             
               21 
               III 
               58.20 
             
             
               22 
               III 
               22.85 
             
             
               23 
               II 
               34.80 
             
             
               24 
               III 
               37.54 
             
             
               25 
               III 
               48.45 
             
             
               26 
               III 
               51.51 
             
             
               27 
               III 
               43.15 
             
             
               28 
               III 
               60.96 
             
             
               29 
               II 
               48.57 
             
             
               30 
               II 
               41.13 
             
             
               31 
               III 
               33.38 
             
             
               32 
               III 
               41.36 
             
             
               33 
               III 
               24.25 
             
             
               34 
               I 
               38.63 
             
             
               35 
               IV 
               29.06 
             
             
               36 
               I 
               52.86 
             
             
               37 
               I 
               58.44 
             
             
               38 
               II 
               47.78 
             
             
               39 
               III 
               35.86 
             
             
               40 
               I 
               53.92 
             
             
               41 
               III 
               22.80 
             
             
               42 
               V 
               6.98 
             
             
               43 
               IV 
               31.88 
             
             
               44 
               II 
               36.67 
             
             
               45 
               II 
               28.28 
             
             
               46 
               I 
               59.56 
             
             
               47 
               II 
               54.52 
             
             
               48 
               III 
               49.43 
             
             
               49 
               I 
               60.54 
             
             
               50 
               II 
               52.97 
             
             
               51 
               II 
               51.50 
             
             
               52 
               II 
               51.63 
             
             
               53 
               II 
               52.14 
             
             
               54 
               II 
               31.94 
             
             
               55 
               II 
               51.17 
             
             
               56 
               IV 
               38.13 
             
             
               57 
               — 
               37.91 
             
             
               58 
               IV 
               35.60 
             
             
               59 
               II 
               46.49 
             
             
               60 
               III 
               49.52 
             
             
               61 
               — 
               48.53 
             
             
               62 
               III 
               31.05 
             
             
               63 
               III 
               25.52 
             
             
               64 
               III 
               44.20 
             
             
               65 
               III 
               41.45 
             
             
               66 
               II 
               63.19 
             
             
               67 
               II 
               33.58 
             
             
                 
             
           
        
       
     
   
   
     
       
             
           
             
             
             
             
             
             
           
             
             
             
             
             
             
           
         
             
               TABLE II 
             
           
           
             
                 
             
             
               L*a*b* (Laser Dose J/cm 2 ) 
             
           
        
         
             
                 
                 
                 
                 
                 
               LASER DOSE 
             
             
               PATIENT 
               SKIN TYPE 
               L* 
               a* 
               b* 
               (J/cm 2 ) 
             
             
                 
             
           
        
         
             
               1 
               II 
               60.26 
               11.94 
               15.54 
               18 
             
             
               2 
               III 
               60.74 
               14.72 
               14.68 
               21 
             
             
               3 
               III 
               65.40 
               6.10 
               15.72 
               18 
             
             
               4 
               II 
               66.84 
               6.68 
               13.10 
               20 
             
             
               5 
               I 
               64.22 
               8.80 
               15.84 
               17 
             
             
               6 
               II 
               60.88 
               13.04 
               17.18 
               12 
             
             
               7 
               III 
               64.80 
               8.70 
               14.80 
               18 
             
             
               8 
               II 
               69.58 
               5.70 
               14.08 
               18 
             
             
               9 
               III 
               64.68 
               9.88 
               15.32 
               16 
             
             
               10 
               III 
               72.92 
               4.70 
               15.90 
               19 
             
             
               11 
               II 
               61.15 
               14.68 
               15.63 
               16 
             
             
               12 
               II 
               61.96 
               11.10 
               15.66 
               18 
             
             
               13 
               II 
               63.70 
               10.06 
               15.94 
               16 
             
             
               14 
               II 
               60.80 
               14.20 
               10.94 
               20 
             
             
               15 
               IV 
               56.86 
               11.54 
               18.12 
               10 
             
             
               16 
               II 
               66.66 
               10.64 
               13.80 
               18 
             
             
               17 
               III 
               61.28 
               12.04 
               16.82 
               15 
             
             
               18 
               III 
               59.22 
               11.06 
               16.78 
               12 
             
             
               19 
               II 
               67.05 
               7.05 
               14.28 
               18 
             
             
               20 
               II 
               56.82 
               17.42 
               15.38 
               12 
             
             
               21 
               III 
               70.06 
               4.80 
               12.44 
               18 
             
             
               22 
               III 
               56.86 
               13.78 
               16.28 
               12 
             
             
               23 
               II 
               61.16 
               12.66 
               16.06 
               18 
             
             
               24 
               III 
               62.60 
               14.90 
               16.40 
               18 
             
             
               25 
               III 
               67.60 
               8.05 
               15.60 
               18 
             
             
               26 
               III 
               67.10 
               8.35 
               13.60 
               18 
             
             
               27 
               III 
               64.23 
               10.63 
               15.18 
               18 
             
             
               28 
               III 
               71.67 
               4.23 
               12.03 
               20 
             
             
               29 
               II 
               64.66 
               9.34 
               12.94 
               18 
             
             
               30 
               II 
               62.40 
               12.50 
               14.20 
               25 
             
             
               31 
               III 
               61.30 
               11.20 
               17.15 
               18 
             
             
               32 
               III 
               64.42 
               7.70 
               16.38 
               14 
             
             
               33 
               III 
               57.62 
               14.10 
               16.92 
               12 
             
             
               34 
               I 
               62.00 
               11.30 
               15.02 
               20 
             
             
               35 
               IV 
               59390 
               11.40 
               17.82 
               20 
             
             
               36 
               I 
               64.02 
               10.80 
               10.62 
               35 
             
             
               37 
               I 
               67.45 
               7.50 
               10.72 
               35 
             
             
               38 
               II 
               62.63 
               14.13 
               11.46 
               22 
             
             
               39 
               III 
               62.65 
               11.42 
               17.50 
               25 
             
             
               40 
               I 
               67.22 
               8.07 
               12.55 
               33 
             
             
               41 
               III 
               56.62 
               15.80 
               15.75 
               15 
             
             
               42 
               V 
               52.20 
               13.86 
               17.98 
               13 
             
             
               43 
               IV 
               61.32 
               11.92 
               18.20 
               21 
             
             
               44 
               II 
               60.70 
               13.65 
               14.37 
               20 
             
             
               45 
               II 
               65.47 
               12.47 
               13.70 
               25 
             
             
               46 
               I 
               66.42 
               10.65 
               9.65 
               25 
             
             
               47 
               II 
               67.70 
               9.23 
               12.62 
               30 
             
             
               48 
               III 
               65.80 
               9.65 
               13.53 
               20 
             
             
               49 
               I 
               70.00 
               7.07 
               11.30 
               30 
             
             
               50 
               II 
               66.30 
               9.90 
               12.30 
               25 
             
             
               51 
               II 
               67.60 
               7.40 
               14.00 
               25 
             
             
               52 
               II 
               66.90 
               9.86 
               13.38 
               30 
             
             
               53 
               II 
               66.80 
               7.87 
               13.06 
               30 
             
             
               54 
               II 
               60.26 
               13.20 
               16.46 
               22 
             
             
               55 
               II 
               68.96 
               8.80 
               15.26 
               30 
             
             
               56 
               IV 
               63.50 
               9.50 
               17.20 
               25 
             
             
               57 
               — 
               61.72 
               14.25 
               15.05 
               26 
             
             
               58 
               IV 
               61.67 
               13.12 
               16.30 
               15 
             
             
               59 
               II 
               62.85 
               11.95 
               12.20 
               35 
             
             
               60 
               III 
               65.85 
               9.85 
               13.53 
               20 
             
             
               61 
               — 
               68.80 
               5.82 
               16.62 
               30 
             
             
               62 
               III 
               58.97 
               16.12 
               14.90 
               22 
             
             
               63 
               III 
               57.70 
               16.06 
               16.13 
               25 
             
             
               64 
               III 
               63.37 
               14.40 
               13.75 
               20 
             
             
               65 
               III 
               63.00 
               12.58 
               14.72 
               20 
             
             
               66 
               II 
               67.15 
               4.57 
               9.68 
               25 
             
             
               67 
               II 
               57.90 
               17.45 
               11.90 
               20 
             
             
                 
             
           
        
       
     
   
   
     
       
             
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
               TABLE III 
             
             
                 
                 
             
             
                 
               LASER DOSE 
                 
                 
                 
             
             
                 
               (J/cm 2 ) 
               b*/L 
               b* 
               a*/b* 
             
             
                 
                 
             
           
           
             
                 
             
           
        
         
             
                 
               18 
               0.258 
               15.54 
               0.768 
             
             
                 
               21 
               0.242 
               14.68 
               1.003 
             
             
                 
               18 
               0.240 
               15.72 
               0.38 
             
             
                 
               20 
               0.196 
               13.10 
               0.510 
             
             
                 
               17 
               0.247 
               15.84 
               0.556 
             
             
                 
               12 
               0.282 
               17.18 
               0.759 
             
             
                 
               18 
               0.228 
               14.80 
               0.588 
             
             
                 
               18 
               0.202 
               14.08 
               0.405 
             
             
                 
               16 
               0.297 
               15.32 
               0.645 
             
             
                 
               19 
               0.218 
               15.90 
               0.296 
             
             
                 
               16 
               0.256 
               15.63 
               0.939 
             
             
                 
               18 
               0.253 
               15.66 
               0.709 
             
             
                 
               16 
               0.250 
               15.94 
               0.631 
             
             
                 
               20 
               0.180 
               10.94 
               1.298 
             
             
                 
               10 
               0.320 
               18.12 
               0.637 
             
             
                 
               18 
               0.207 
               13.80 
               0.771 
             
             
                 
               15 
               0.274 
               16.82 
               0.716 
             
             
                 
               12 
               0.283 
               16.78 
               0.659 
             
             
                 
               18 
               0.213 
               14.28 
               0.494 
             
             
                 
               12 
               0.271 
               15.38 
               1.133 
             
             
                 
               18 
               0.178 
               12.44 
               0.386 
             
             
                 
               12 
               0.286 
               16.28 
               0.846 
             
             
                 
               18 
               0.263 
               16.06 
               0.788 
             
             
                 
               18 
               0.222 
               16.40 
               0.909 
             
             
                 
               18 
               0.231 
               15.60 
               0.516 
             
             
                 
               18 
               0.203 
               13.60 
               0.614 
             
             
                 
               18 
               0.236 
               15.18 
               0.700 
             
             
                 
               20 
               0.168 
               12.03 
               0.352 
             
             
                 
               18 
               0.200 
               12.94 
               0.722 
             
             
                 
               25 
               0.228 
               14.20 
               0.880 
             
             
                 
               18 
               0.280 
               17.15 
               0.653 
             
             
                 
               14 
               0.254 
               16.38 
               0.470 
             
             
                 
               12 
               0.294 
               16.92 
               0.833 
             
             
                 
               20 
               0.242 
               15.02 
               0.752 
             
             
                 
               20 
               0.297 
               17.82 
               0.640 
             
             
                 
               35 
               0.166 
               10.62 
               1.017 
             
             
                 
               35 
               0.159 
               10.72 
               0.700 
             
             
                 
               22 
               0.183 
               11.46 
               1.233 
             
             
                 
               25 
               0.279 
               17.50 
               0.653 
             
             
                 
               33 
               0.187 
               12.55 
               0.643 
             
             
                 
               15 
               0.278 
               15.75 
               1.003 
             
             
                 
               13 
               0.344 
               17.98 
               0.771 
             
             
                 
               21 
               0.297 
               18.20 
               0.655 
             
             
                 
               20 
               0.237 
               14.37 
               0.950 
             
             
                 
               25 
               0.209 
               13.70 
               0.910 
             
             
                 
               25 
               0.145 
               9.65 
               1.104 
             
             
                 
               30 
               0.186 
               12.62 
               0.731 
             
             
                 
               20 
               0.206 
               13.53 
               0.713 
             
             
                 
               30 
               0.161 
               11.30 
               0.626 
             
             
                 
               25 
               0.186 
               12.30 
               0.805 
             
             
                 
               25 
               0.207 
               14.00 
               0.529 
             
             
                 
               30 
               0.200 
               13.38 
               0.737 
             
             
                 
               30 
               0.196 
               13.06 
               0.603 
             
             
                 
               22 
               0.273 
               16.46 
               0.802 
             
             
                 
               30 
               0.221 
               15.26 
               0.577 
             
             
                 
               25 
               0.271 
               17.20 
               0.522 
             
             
                 
               26 
               0.244 
               15.05 
               0.947 
             
             
                 
               15 
               0.264 
               16.30 
               0.805 
             
             
                 
               35 
               0.194 
               12.20 
               0.980 
             
             
                 
               20 
               0.205 
               13.53 
               0.728 
             
             
                 
               30 
               0.242 
               16.62 
               0.350 
             
             
                 
               22 
               0.253 
               14.90 
               1.082 
             
             
                 
               25 
               0.280 
               16.13 
               0.996 
             
             
                 
               20 
               0.217 
               13.75 
               1.047 
             
             
                 
               20 
               0.234 
               14.72 
               0.588 
             
             
                 
               25 
               0.140 
               9.68 
               0.472 
             
             
                 
               20 
               0.206 
               11.90 
               1.466 
             
             
                 
                 
             
           
        
       
     
   
   A stronger determinant of the correct Laser Dose is the ratio of Z/Y, which is derivable from the ratio of b*/L*, as can be seen from the above-shown algebraic relations. Table II shows the range of colorimetric values for skin sites from 67 individuals. These data have since the original experiments been extended to additional patients Table III shows the range of values for the Laser Dose versus b*, b*/L* and (for an arbitrary comparison) a*/b*. There is a strong linear correlation between laser dose and b* or b*/L* which can be seen when the values are graphed. In contrast, a*/b*, which is dominated by the X coordinate rather than the interrelationship of Z and Y, has a very poor correlation with Laser Dose. 
   Based on the calculation of statistical correlation coefficients (R 2 ), the strongest correlation with the correct Laser Dose was found for b*/L*. A linear fit to the data gives the mathematical expression for the Fluence (Laser Dose) in joules/cm 2  as
 
Laser Dose=39−84( b*/L *)
 
   The correlation&#39;s L* versus Laser Dose and a* versus Laser Dose were found to be weaker. This is expected since both L* and a* are independent of z and hence less sensitive to melanin. 
   Changes in the type of laser employed, cooling head configuration applied at the interface between skin and laser energy and temperature, as well as other physical factors may lead to different constants. Therefore the Laser Dose is best described by an overall general equation of the following type:
 
Laser Dose= k   1   −k   2 ( b*/L *)
 
Where k 1  ranges from 1 to 60, preferably from 25 to 50, optimally form 30 to 40; and k 2  ranges from 1 to 120 preferably from 10 to 110, more preferably from 50 to 100, optimally from 55 to 85.
 
   Any of the concepts and theories as well as the mathematical correlation of this invention should not be considered as limiting the actual invention itself. Adjustments to the theory may be deemed appropriate in the future but this will not negate the underlying discovery of using specific colorimetric parameters to determine the optimum laser energy dosage added for hair removal. 
   For purposes of this invention, most preferred is a ruby laser with output wavelength of 694 nm. Other types of lasers may also be employed. These include carbon dioxide based lasers and Q-switched Nd:YAG lasers pulsed at 1064 nm. Particularly useful may be an Alexandrite laser operating at 755 nm, a typical commercial instrument being the Gentle LASE available from Candela Corporation, Wayland, Mass. A still further potentially useful laser is the KTP Crystal Diode type emitting at 810 nm, available from Coherent Corporation. 
   Advantageously, probes of lasers according to the present invention may include a cooling head. Temperatures ranging from 0° C. down to minus 80° C., preferably between 0° C. and minus 10° C. are employed for this invention. For instance, the Palomar Ruby Laser 2000 model operates at minus 10° C. utilizing a Thermatech Pump with a sapphire tip. A TFE cryogen sprayhead may also be employed and is commercially available with the Gentle Las instrument from Candela Corporation. 
   Pulse duration is best when extended but only to the point falling short of skin damage. With the Palomar Ruby Laser (Epiwand instrument), there is a fixed duration of 3 milliseconds for each pulse. Generally pulse duration may range from about 0.5 to about 10 milliseconds. 
   For patients who are tanning or have tanned skin, and b/L ratios greater than 0.250 it is preferred to use the SLP810™ diode, not only to prevent tissue complications due to reduced melanin absorption at this wavelength, but because tissue tolerated ruby laser fluences for patients with b/L ratios greater than 0.250 are simply not adequate to achieve predictable and lasting permanent hair reduction. The use of the SLP810™ diode overcomes this problem and allow these tan patients to be treated with fluences necessary to prevent hair growth. 
   A first embodiment of equipment for purposes of this invention includes a spectrophotometer/colorimeter physically separate from the laser. Information gathered from L*a*b* measurement or color matching of skin type is utilized to adjust laser dose levels. Input to the laser on dosage may either be through manual adjustment or automatic by electronic transfer. Skin color values can be sent to a computer program which then automatically sets energy dosage in the laser. A second embodiment of equipment for purposes of this invention combines in a single instrument the spectrophotometer/colorimeter and laser. Circuitry and a logic chip allows color values to be measured and dosage level set in a seamless, fully automatic mode. 
     FIG. 1  is a diagrammatic illustration of one possible embodiment of a combination of a calorimeter and laser designed particularly for depilation or epilation of the skin, plus a coordination and control system for practicing the invention. In  FIG. 1  there is shown in diagrammatic form a laser apparatus  11  having a lens  13  at the lower end of a wand  15 , shown here in broken lines to indicate the surface of said wand, which is adapted to be held in the hand, not shown, of an operator with the terminal lens  13  against the skin of a patient, such skin being indicated by reference numeral  17 . Reference numeral  19  designates the outer layer of skin, or the epidermis, and  21  designates the middle layer of skin, or dermis, in which the various major components of the skin such as the hair follicles sebaceous glands minor blood vessels and the like are found. Melanin, the main coloring matter and light protective element in the skin is found mostly in the upper layer of the dermis, in the epidermis, which is principally a layer of dead outer cells, and around the hair follicles in the dermis. As shown, the lens  13  is pressed against the skin indenting the epidermis plus the upper portion of the dermis. A fiberoptic light transmission element  23  is contained in a suitable sheathing  25 , which extends from a laser light generator  27  to the lens  13 , which lens is diagrammatically indicated oversize to better illustrate how it can compress the upper layers of skin when in use and also how an illuminating light source  29  may conduct light preferably of a midrange light in the wavelength range of 400 to 900 nm through a second fiberoptic transmission element  31  and transmit it through transparent connecting element  33  to the lens  13 , which transmits said light to the skin surface or surface  35  of the epidermis  19 . Reflected or remitted light from such skin surface  35  or intersection of the epidermis  19  and lens  13  will be then transmitted to interconnecting element  37  on the opposite side of the top of the lens  13  and through fiberoptic transmitter  39  to coupling or transmitter  41  which transfers either such light or its analog in the form of another electromagnetic signal to colorimeter  43 , which detects at least the intensity of remittent green and red light and directs such information to computer  45 , which will convert the calorimetric indication through a suitable algorithm set forth above to a pulse dosage signal for the laser  27 . A timing device  47  provides suitable signals to coordinate signals from arming switch  48  upon the operator initiating a treatment cycle by pressing the lens  13  of the wand  15  against the epidermis  19  of a patient and pressing the activator button  49 . This activates illuminating light source  29  through suitable computer circuits which light source directs a light beam through fiberoptic transmission element  31  to the lens  13  where it illuminates the surface of the epidermis  19 . Reflected light, or remittance light, from such skin surface is then picked up by element  37  and is transmitted through fiberoptic element  39  to colorimeter apparatus  43  where it is separated into its component wave lengths and the blue and green wave lengths or components measured and directed as discrete signals to computer  45  which will calculate the laser signal to be provided by laser  27  and direct such signal, which will have been calibrated for the correct intensity and time. The sequence timer  51  will be set to determine if an initial analysis light beam will be directed at the patient and analyzed followed by as many laser pulses to the same or adjacent portions of the epidermis (directed usually at different hair follicles) or whether a complete light analysis cycle followed by a single laser pulse will be provided for each activation of the button or switch  49 . As explained above, the use of a colorimeter to analyze the skin characteristics has been found to be extremely effective and efficient in analyzing the skin type either using separate colorimeter and laser apparatus or combined apparatus if the dosage of laser light is calculated in accordance with the invention based upon the blue and green remitted light which it has been found by careful validation are the most predictive wave lengths for calculating the correct laser dosage which will inactivate hair follicles with minimum incidental damage to other portions of the skin. 
   While it is preferred to use a colorimeter which operates in accordance with the L* a* b* system which was originally designed to provide data representative so far as possible of the true appearance of colors, it will be evident that once the proper dosage of laser light is calculated correctly in the L* a* b* system that the same dosage can be accurately calculated also in the X, Y, Z coordinate system, since the L* a* b* system is actually an algebraic transformation of the X, Y, Z coordinates designed to accommodate the human eyes relative sensitiveness to X-, Y- and Z- spectra. Where the human eye does not enter into a calculation, however, once a correlation or validation is made between the amount of blue and green remitted light in which the green band remittance acts as a melanin independent baseline against which differences in blue-based remittance effectively indicates differences in the melanin content in the skin. Once it is known, therefore, that these two remittance values are the important ones and the validation of the dosage calculation using the green and blue remittance has been conducted to determine the proper dosage of laser light based upon such green and blue remittance a different system can be shifted to based upon the same data. In short, advantage of the present invention can be taken using any comparable calculation of a similar laser dosage based upon measurement of green and blue remittance based upon or calculated from the validating data or similar data of the present inventor or original inventors. 
   Except in the operating and comparative examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material ought to be understood as modified by the word “about.” 
   The foregoing description illustrates selected embodiments of the present invention. In light thereof variations and modifications will be suggested to one skilled in the art, all of which are within the spirit and purview and this invention. Consequently, while the present invention on has been described at some length and with some particularity with respect to the several described embodiments, it is not intended that it should be limited to any such particulars or embodiments or any particular embodiment, but it is to be construed with references to the appended claims so as to provide the broadest possible interpretation of such claims in view of the prior art and, therefore, to effectively encompass the intended scope of the invention.