A METHOD AND AN APPARATUS FOR DETERMINING AN INDIVIDUAL'S ABILITY TO STAND EXPOSURE TO ULTRAVIOLET RADIATION

Abstract: A method and an apparatus for determining an individual's ability to become tanned or to stand exposure to ultraviolet radiation without causing a skin reaction, such as skin cancer or erythema. According to the method, at least part of said individual's skin surface is exposed to electromagnetic radiation of first and second wavelengths and of predetermined intensities. The first and second wavelengths at which erythrodermic skin reflection is high and low, respectively. The intensity of electromagnetic radiation reflected from the individual's skin surface is measured so as to determine first and second coefficients of reflection of said first and second wavelengths, respectively. The first and second coefficients are compared to sets of coefficients of reflection representing coherent sets of coefficients of reflection of specific states of redness, and the first and second coefficients of reflection are corrected into a set of corrected first and second coefficients of reflection of a specific state of redness. The corrected first coefficient of reflection is further converted into a measure representing the individual's ability to become tanned or to stand exposure to ultraviolet radiation without causing said skin reaction.

Description: A method and an apparatus for determining an individual's ability to stand exposure to ultraviolet radiation. The present invention relates to the technique of determining an individual's ability to become tanned or to stand exposure to ultravio¬ let radiation without causing a skin reaction, such as skin cancer or erythema, which technique is described in US Patent No. 4.882.598, to which US Patent reference is made, and which US Patent is herewith in¬ corporated in the present specification by reference. According to the technique described in the above US Patent, the individual's ability to become tanned or to stand exposure to ultravio¬ let radiation without causing a skin reaction may be determined by ex¬ posing a skin surface part of the individual to electromagnetic radia¬ tion, e.g. visible light, and determining the coefficient of reflection of the individual's skin surface part to the electromagnetic radiation and converting the. coefficient of reflection to a measure representing the individual's ability to become tanned or to stand exposure to ultra¬ violet radiation. The technique described in the above US Patent is based on clinical experiments revealing a linear relationship between a number of individuals coefficients of skin surface reflection in loga¬ rithmic representation and the same individuals' ability to stand expo¬ sure to ultraviolet radiation of a predetermined intensity and of a pre¬ determined spectral composition. According to the above-mentioned US Pa¬ tent, individuals who are erythrodermic or erythematous may further be identified by performing the determination of the individuals' coeffi¬ cient of reflection to electromagnetic radiation at two distinct wave¬ lengths, one of which is a wavelength at which erythrodermic skin re¬ flection is high, and another one of which is a wavelength at which erythrodermic skin reflection is low. The basis of the present invention is the realization that the de¬ termination of the individual's coefficient of reflection or reflections to electromagnetic radiation is to a high degree influenced by the blood flow of the individual at the site or the skin surface part at which the measurement is carried out. An obvious solution solving the problem of eliminating the blood flow influence on the determination of the measure representing the individual's ability to become tanned or to stand ex¬ posure to ultraviolet radiation in accordance with the teaching of the above US Patent is to specify a "normal" measuring routine involving that the individual is kept in a normalized position and state, e.g. specifying the site or the part of the individual's skin surface at which the measurement is to be performed, the position of the site or skin surface part in question, and the position of the individual and further a specific increased or reduced blood flow accomplished through an occlusion of a body part of the individual, on which body part the site or skin surface part is positioned, or alternatively a state of ex¬ treme blood flow, e.g. provoked through heating the site or the skin surface part at which the measurement is to be performed. In numerous instances, the individuals cannot be maintained in a normalized position and state corresponding to the above specified circumstances or similar relevant specified circumstances for numerous reasons. Also, a so-called normalized state may often result in an extreme variation of the measu¬ ring results obtained, which makes the overall measuring technique unre¬ liable and inadequate. An object of the present invention is to provide a method of de¬ termining an individual's ability to become tanned or to stand exposure to ultraviolet radiation without causing a skin reaction, which method is independent of the blood flow of the individual, and which method renders it possible to provide a measure representing said individual's ability independent on the blood flow of the individual. A further object of the present invention is to provide a method of determining an individual's ability to become tanned or to stand expo¬ sure to ultraviolet radiation, which method produces normalized measu¬ ring results which are readily comparable, rendering it possible to ob- tain a high degree of reproducibility of the determination. A further object of the present invention is to provide an appara¬ tus for determining an individual's ability to become tanned or to stand exposure to ultraviolet radiation, which apparatus is capable to perform a measuring routine and generate a measuring result independent of the blood flow of the individual, the ability of which is to be determined. A still further object of the present invention is to provide an apparatus of the above type of an extreme reliability and producing measuring, results of high reproducibility and high accuracy. According to a first aspect of the present invention, a method of determining an individual's ability to become tanned or to stand expo¬ sure to ultraviolet radiation without causing a skin reaction, such as skin cancer or erythema, comprising the following steps: exposing at least part of said individual's skin surface to electromagnetic radiation of a first wavelength and of a predetermined intensity, said first wavelength being a wavelength at which erythro¬ dermic skin reflection is high, measuring the intensity of electromagnetic radiation reflected from said part of said individual's skin surface so as to determine a first coefficient of reflection of said skin surface part to said electromag¬ netic radiation of said first wavelength, exposing said skin surface part to electromagnetic radiation of a second wavelength and of a predetermined intensity, said second wave- length being a wavelength at which erythrodermic skin reflection is low, measuring the intensity of electromagnetic radiation reflected from said part of said individual's skin surface part so as to determine a second coefficient of reflection of said skin surface part to electro¬ magnetic radiation of said second wavelength, comparing said first and second coefficients of reflection with sets of coefficients of reflection representing coherent sets of coeffi¬ cients of reflection of said first and second wavelengths of specific states of redness so as to determine said individual's skin surface part's state of redness, converting said first and second coefficients of reflection into a set of corrected first and second coefficients of reflection of a specific state of redness, so as to determine said indi¬ vidual's skin surface part's coefficients of reflection of said first and second wavelengths at a specific state of redness, and converting said corrected first coefficient of reflection into a measure representing said individual's ability to become tanned or to stand exposure to ultraviolet radiation without causing said skin reac¬ tion. Basically, in accordance with the teaching of the present inven¬ tion, it has been realized through clinical investigations that the first and the second coefficients of reflection determined in accordance with the teaching of the above US Patent may be converted to a set of corrected first and second coefficients of reflection of a specific state of redness since the first and the second coefficients of reflec¬ tion at different states of redness, and consequently different blood flows, fulfil specific mathematic relations, as will be evident from the description below, rendering it possible to convert a set of first and second coefficients of reflection to a set of corrected first and second coefficients of reflection of a specific state of redness. Preferably, according to the teaching of the present invention, the specific state of redness to which the first and second coefficients of reflections measured in accordance with the method according to the present inven¬ tion and in accordance with the teaching of the above US Patent corre- sponds to an average zero blood flow state, i.e. a state in which the individual's blood flow is zero or extremely low, eliminating to any substantial extent the influence of the redness of the individual on the coefficients of reflection. According to a further realization according to the teaching of the present invention, the method advantageously further comprises the step of determining the individual's skin surface part's degree of pigmenta¬ tion from the corrected first and second coefficients of reflection of the first and second wavelengths at the specific state of redness. The basic clinical investigations on which the present invention is based have revealed that provided the coefficient of reflection of said second wavelength is represented in logarithmic representation, the mathematic relation through which sets of coefficients of reflection re¬ presenting coherent sets of coefficients of reflection of said first and second wavelengths are linearly related, rendering the conversion of the first and the second coefficients of reflection into a set of coherent first and second coefficients of reflection extremely simple and readily adaptable to automatized conversion, e.g. by means of a computer, such as a microprocessor. In accordance with a second aspect of the present invention, an apparatus is provided for determining an individual's ability to become tanned or to stand exposure to ultraviolet radiation without causing a skin reaction, such as skin cancer or erythema, comprising: a first electromagnetic source for generating electromagnetic radi¬ ation of a first wavelength and of a predetermined intensity and for di- recting said electromagnetic radiation of said first wavelength to a part of said individual's skin surface so as to expose said part of said individual's skin surface to said electromagnetic radiation of said first wavelength, a second electromagnetic source for generating electromagnetic ra- diation of a'second wavelength and of a predetermined intensity and for directing said electromagnetic radiation of said second wavelength to said part of said individual's skin surface so as to expose said part of said individual's skin surface to said electromagnetic radiation of said second wavelength, a light-detecting means for measuring the intensity of electromag¬ netic radiation reflected from said part of said individual's skin sur¬ face, a measuring means connected to said light-detecting means for mea¬ suring the intensity of electromagnetic radiation reflected from said part of said individual's skin surface so as to determine a first and a second coefficient of reflection of said skin surface part to said electromagnetic radiation of said first and second wavelength, respec- tively, a comparison and converting means connected to said measuring means for comparing said first and second coefficients of reflection with sets of coefficients of reflection representing coherent sets of coefficients of reflection of said first and second wavelengths of specific states of redness so as to determine said individual's skin surface part's state of redness, for converting said first and second coefficients of reflec¬ tion into a set of corrected first and second coefficients of reflection of a specific state of redness, so as to determine said individual's skin surface part's coefficients of reflection of said first and second wavelengths at a specific state of redness, and for converting said cor¬ rected first coefficient of reflection into a measure represent"ig said individual's ability to become tanned or to stand exposure to ultravio¬ let radiation without causing said skin reaction. Basically, the apparatus according to the present invention may be implemented in accordance with the above embodiments of the method according to the present invention. Furthermore, according to a first embodiment of the apparatus, separate light detector means for detecting electromagnetic radiation of the first and the second wavelengths, re¬ spectively, may be provided. Preferably, the apparatus according to the present invention, however, comprises a single light-detecting means constituted by a single light detector, first of all simplifying the structure of the apparatus and secondly ensuring that the reflection of light of the first and the second wavelength is generated at one and the same part of the individual's skin surface and further eliminates any difference in sensitivity and consequently measuring accuracy between the measurement of the reflection of electromagnetic radiation of the first and the second wavelength. " Due to the high accuracy of the measuring technique according to the present invention, the UV treatment of e.g. psoriasis patients may be adapted so as to carry out a full-body scanning of the body of the patient for carrying out an optimum UV treatment of the entire body of the patient, at which treatment, any differences as to UV sensitivity of different skin surface areas of the patient are complied with, so that, independent of the difference in UV sensitivity of the differnet skin surface areas of the patient, any skin surface area of the patient is exposed to an optimum UV treatment. The present invention will now be further described with reference to the drawings, in which Fig. 1 is a diagram illustrating the correspondence between the co¬ efficient of skin surface reflection and the wavelength of the electro¬ magnetic radiation, to which the skin surface part has been exposed, further illustrating a-curve A illustrating the response of an average, non-sun-tanned and non-erythrodermic skin surface part of an individual and a curve B illustrating the response of an erythrodermic or sun-burnt skin surface part of an individual, Fig. 2 is a diagram illustrating the correspondence between the co¬ efficient of skin surface reflection and the wavelength of the electro- magnetic radiation, to which the skin surface part has been exposed, further illustrating the same curve A as shown in Fig. 1 and a curve C illustrating the response of a non-erythrodermic and extremely pigmented skin surface part of an individual, Fig. 3 is a diagram illustrating the linear relationship between the logarithmic representation of a number of individuals' coefficients of skin surface reflection and the individuals' ability to stand expo¬ sure to ultraviolet radiation of a predetermined intensity and of a pre¬ determined specific spectral composition, Fig. 4 is an overall schematic and perspective view of an apparatus implemented in accordance with the teaching of the present invention, Fig. 5A is an overall schematic and partly cut-away view of a pho- todetector constituting a component of the apparatus shown in Fig. 4, Figs. 5B and 5C are elevational views of an optic guide and light diode and light detector supporting component of the photodetector shown in Fig. 5A. Fig. 6 is a diagram illustrating the relation between measurements carried out on a total of 49 individuals, further illustrating the cor¬ respondence between the coefficient of reflection to red light and the coefficient of reflection to green light in logarithmic representation in dependency of the blood flow, Fig. 7 is a diagram similar to the diagram shown in Fig. 6, from which diagram an individual's corrected coefficient of reflection to red light and the same individual's pigmentation may be determined from a set of measuring results and related to a specific state of redness, Fig. 8 is a diagram similar to the diagrams of Figs. 6 and 7, il¬ lustrating the relation between the coefficient of reflection to red light and the coefficient of reflection to green light in logarithmic representation of individuals of different degrees of redness caused by ultraviolet radiation, Fig. 9a is a diagram illustrating the relation between the corre¬ spondence between the corrected coefficient of reflection to red light in " logarithmic representation of individuals and the UV dose in B-MED of the same individuals, Fig. 9b is a diagram illustrating the relation between the corre¬ spondence between the pigment% and the UV-dose in B-MED of the same in¬ dividuals, Fig. 10 is a diagram illustrating the linear correspondence between clinically evaluated redness of individuals and the degree of redness of the same individuals, Fig. 11 is a circuit diagram of the electronic circuitry of the ap¬ paratus shown in Fig. 4, Fig. 12 A and B are circuit diagrams of a microprocessor block of the electronic circuitry shown in Fig. 11, Fig. 13 is a circuit diagram of the electronic circuitry of the photodetector shown in Fig. 5, Fig. 14 is a diagram illustrating the linear relation between laser-induced skin changes of individuals subjected to laser treatment and the degree of pigmentation of the same individuals, Fig. 15A-15L are diagrams further illustrating the correspondence between the laser-induced effects and the degree of pigmentation of the individuals exposed to laser treatment, Fig. 16 a diagram illustrating the linear relationship between in- dividuals' basic MEDs after UV treatment and the degree of pigmentation of the same individuals, Fig. 17 is a diagram illustrating the difference between an experi¬ mentally found dose and a calculated dose to reach a certain degree of redness, and Fig. 18 is a diagram illustrating the difference of an individual's sensitivity to UV treatment compared to a normal sensitivity. According to the present invention, non-invasive measuring tech- niques for measuring pigmentation and redness of a skin surface part of an individual are provided. Basically, the present invention constitutes a refinement or improvement of the technique described in US Patent No. 4.288.598, to which US Patent reference is made and which US Patent is herewith incorporated in the present specification by reference. Accord- ing to the non-invasive measuring technique according to the above US Patent and according to the present invention, a conversion from pigmen¬ tation to UV-sensitivity is established and an objective measurement of pigmentation and redness is provided, which objective measurement may be converted ' into UV-sensitivity of the individual in question. According to the teachings of the present invention, phototherapy and photochemo- therapy during treatment is adjustable so as to optimize the treatment of an individual at all times, taking into due consideration the action spectra for phototherapy and photochemotherapy. The basic teachings of the present invention are based on the below described measurements. Spectrophotometric measurements of the reflection of skin surface parts of individuals were carried out within the wavelength area 260 nm - 800 nm. A laboratory system comprising a 150 W Xenon arc lamp (manu¬ factured by Zeiss, FRG) was used irradiating the entrance slit of a single grating monochromator (manufactured by Jobin-Yvon H20, France, 200 nm focal length, f/3.5). An 8 nm band-pass filter was used for all measurements. From the exit slit of the monochromator the light beam was directed to the skin surface part of an individual via one branch of a fused silica bifurcated fiber optic cable (manufactured by Oriel, Strat- ford, CT, USA). Said one branch of the fiber optic cable was held perpendicular to the skin surface part at a distance of 5 mm by means of a spacer device. The other branch of the fiber optic cable was used for directing the radiation reflected from the skin surface part to a calibrated multiprobe (manufactured by EG & G 550 - 2) connected to a radiometer (manufactured by EG & G 550, Salem, MA, USA). The measure¬ ments were performed at every second nm from 260 nm to 800 nm using the reflection from a calcium carbonate plate as the 100% reflection re¬ ference at all wavelengths. On the basis of the measurements, spectra were recorded, and calculations based on the measurements were performed by a HP computer (manufactured by Hewlett Packard, Palo Alto, CA, USA). A total of 22 individuals were used for recording reflection spectra, which 22 individuals had different skin complexion. Within the skin surface areas of the 22 individuals within which skin surface areas the measurements were performed, the MED (Minimum Erythema Dose for an individual person 24 h after exposure) was determined using the radia¬ tion from a Solar Simulator (manufactured by Solar Light Company, Phila¬ delphia, PA, USA). Spots of a diameter of 1 cm were irradiated, and the redness of the skin surface parts was classified as one MED when minimal redness had clearly demarcation lines to the surrounding non-irradiated skin. For all 22 individuals, spectra were recorded from closely spaced minimally pig ented and pigmented areas. A comparison of these spectra showed that the best discrimination between the curves was between 507 nm and 512 nm. In Fig. 1, a diagram is shown illustrating the correspondence be¬ tween the coefficient of skin surface reflection and the wavelength of the electromagnetic radiation, to which the skin surface part has been exposed and illustrating a curve A representing the response of an average non-sun-tanned and non-erythrodermic skin surface part of an in¬ dividual and a curve B representing the response of an erythrodermic or sun-burned skin surface part of an individual. The maximum difference between the curves A and B was between 503 nm and 512 nm for all indivi- duals. In Fig. 2, a diagram similar to the diagram of Fig. 1 is shown, comprising the curve A also shown in Fig. 1 and further a curve C repre¬ senting the response of a non-erythrodermic and extremely pigmented skin surface part of an individual. The maximum difference between the curves A and C was between 503 and 512 nm. In Fig. 3 a diagram is shown, which diagram corresponds to the dia¬ gram shown in Fig. 1 in US Patent No. 4.882.598, and which diagram il¬ lustrates the linear relationship between the coefficient of reflection to light of a wavelength of 510 nm in logarithmic representation and the time to reach 1 MED using the Solar Simulator recorded for a total of 26 individuals. On basis of the measuring results illustrated by the curves A, B, and C shown in Figs. 1 and 2, it is concluded that redness influences the measurements of pigmentation when wavelengths between abt.380 nm to abt.600 nm are used. Also the valleys corresponding to the absorption of hemoglobin (abt.540 - 580 nm) are clearly observed. Reflection with¬ in the wavelength area 540 - 580 nm is consequently to be used for esti- 5 mating redness of the skin and wavelengths above approx. 600 nm and be¬ low approx.380 nm should be used for estimating pigmentation as mea¬ surements at these wavelengths are to no substantial extent affected by redness. Consequently, light sources to be chosen for this purpose are e.g. 10 light-emitting diodes with peak wavelengths at 550 nm (Green) and 660 nm (Red). A unique measuring probe comprising two light-emitting diodes emit¬ ting light of the above wavelengths was designed, which measuring probe is shown in Fig. 5 and is to be discussed in greater detail below. 15 A further experiment involving 49 volunteers with different pigmen¬ tation was made, which experiment revealed relations between the skin surface reflection of red light and green light, which relations consti¬ tute the basic realization of the present invention. In order to investigate in what way redness of the skin influences 20 the estimation of pigmentation, the following test was conducted: For the above-mentioned 49 individuals green reflection and red re¬ flection were recorded on the antebrachium both on the volar side and on the dorsal side, provided the skin surface of the individual was not too hairy. A total of four situations were tested in one and the same spot 25 ensuring a constant pigmentation. The four situations were: Zero flow, the arm in vertical position, the arm in horizontal position, and a si¬ tuation in which reactive redness was generated after Zero flow. Zero flow was obtained by pressing all blood out of the arm using elastic bandage followed by obstruction of the blood flow by a cuff on the upper 30 arm. In all cases, the individual was lying in a horizontal position and the skin changes were monitored until the changes had stabilized. Fig.6 is a diagram in which the coefficient of skin reflection to red light and the skin reflection to green light in logarithmic repre¬ sentation are listed for all 49 individuals. From the measuring results, 35 it is first of all verified that the coherent sets of skin surface re¬ flection to red light and skin surface reflection to green light in lo¬ garithmic representation of the four above listed situations are posi¬ tioned along straight lines A, B, C, and D, respectively, having a com- mon intercept at 1.54 at the ordinate axis. The slope of.the curve A re¬ presenting the average Zero flow was deduced from the diagram being 0.03977, and the slope of the straight line D representing the reactive redness situation was also deduced from the diagram being 0.03247. The straight lines B and C representing the vertical and the horizontal po¬ sition of the arm of the individual, respectively, had slopes in between the slopes of the straight lines A and D. For one and the same individu¬ al, the pigmentation should be considered constant in all four situa¬ tions, and the red reflection should consequently be identical in all four situations. This is, however, not the case. The test revealed that the measurements corresponding to the above described four situations, i.e. corresponding to the straight lines A, B, C, and D, performed on a single individual could be presented by a straight line which, however, w?-; not a verti-cal line in the diagram shown in Fig. 6. Examples of the straight line corrections are shown in Fig. 6 which straight lines con¬ nect points on the Zero flow line and the corresponding points on the lines B, C, and D corresponding to the above described situations. On the basis of the straight line correction, any set of measuring results representing the skin surface reflection to red and the skin surface re- flection to green in logarithmic representation may be, so to speak, normalized as far as redness is concerned by correcting the measuring results to a normalized or standard situation, e.g. a Zero flow situa¬ tion. In Fig. 6, a straight dotted line 0 is also shown, representing the • average Zero flow plus 2 SD (Standard Deviation) corresponding to a slope of 0.0427, including 95% of the Zero flow measurements. By con¬ verting any measuring results representing the skin surface reflection to red and the skin surface reflection to green in logarithmic represen¬ tation to the straight, dotted line 0, the best possible correction for redness of the skin for calculating the pigmentation may be performed, as will be evident from the discussion below with reference to Fig. 7. An extremely white individual exhibit a skin surface reflection to red of 70% which is consequently named 0% pigmentation, whereas 100% pigmen¬ tation corresponds to 0% skin surface reflection to red. In Fig. 7, redness and pigmentation of a specific individual are calculated on the basis of skin surface reflection measurements to red and green light, the skin surface reflection to green light being pre¬ sented in logarithmic representation. Thus, Fig. 7 is a diagram, the ab- scissa and ordinate axes of which are identical to the abscissa and or- dinate axes of the diagram shown in Fig. 6. The straight line correction discussed above of the measuring results generated by measuring the co¬ efficients of skin surface reflecction to red and green light of an in- dividual and by converting the green light skin surface reflection coef¬ ficient into logarithmic representation is performed along a dotted line C, so to speak transforming the measuring results represented by the point P to a point P' of the line 0, i.e. the line intercepting the or¬ dinate at 1.54 and having a slope of 0.0427. The abscissa of the point P' represents the corrected red reflection coefficient and also the pig¬ mentation degree represented in a percentage varying from 0% to 100% as indicated in Fig. 7. Consequently, a specific degree or state of redness for different individuals of different pigmentation is represented by a straight line of constant slope intercepting the ordinate at 1.54. Thus, the degree or state of redness of an individual is readily measurable on the basis of the diagram shown in Fig. 7, as a specific degree or state of redness corresponds to a specific straight line intercepting the or¬ dinate at 1.54 and having a specific slope. In Fig. 8, a diagram similar to the diagrams shown in Figs. 6 and 7 is shown, representing lines representing different degrees of redness caused by ultraviolet radiation exposed to individuals having different pigmentation. The lines intercept the ordinate axis at 1.54 like the straight lines shown in Figs. 6 and 7. The highest degree of redness corresponding to 100% redness is chosen to include individuals having naevus flammeus of very dark-bluish red colour and corresponds to a straight line of a slope of 0.015. Table 1 below illustrates the correspondence between clinical red¬ ness as defined below, redness percentage and the read-out from an appa¬ ratus to be described below with reference to Fig. 4 and implemented in accordance with the teachings of the present invention ' . Table 1: Display Reading <30 33 37 ++ 43.9 44 +++ 51 .6 52 Zero redness corresponds to the highest UV dose of Philips TL12 tubes, which dose may be given before redness appears. (+) redness corresponds to faint, spotted redness without a clear demarcation to the surrounding, non-irritated skin surface areas. + redness corresponds to faint redness with a clear demarcation to the surrounding skin surface areas. ++ redness corresponds to clear redness with slight edema to be felt in the tissue. +++ redness corresponds to heavy redness with edema to be felt or seen above the surrounding skin surface areas. The measurements were made after having irradiated the 49 individu¬ als on the buttocks with different doses of UV from Philips TL12 lamps. 2 The doses used were in B-MED (Basic Minimal Erythema Dose being 312 J/m at 296 nm. ((24 h erythema) Parrish). 24 h after irradiation, the red¬ ness degree was estimated by means of the above listed "+" system. In Fig. 9a, a diagram is shown, illustrating the correspondence between the corrected coefficient of reflection to red and the UV dose in B-MED to reach different levels of erythema. Since all curves exhibit a common intercept at the ordinate axis, a common equation may be de¬ duced which can be used to predict the treatment dose, taking into con- sideration the degree of pigmentation of the skin surface part in quest¬ ion and further what level of redness is to be produced 24 h after irra¬ diation. The equation used is: Treatment time = 24.2 + (0.1709 x speci¬ fic redness - 5.668) x In KR (corrected coefficient of reflection to red) x number of seconds to reach a B-MED (the intensity of the light source). The sensitivity of a specific skin surface area of the indivi¬ dual's body relative to the tested part of the buttocks has to be taken into consideration when predicting the treatment dose. The curves shown in Fig. 9a are almost parallel, and further calcu¬ lations, according to which calculations the correspondence between the UV dose in B-MED is related to the degree of pigmentation, have proven that dose versus pigmentation may also be used to predict the treatment time. In this case, the additional dose to shift from UV reaction of 0 to +, from + to ++, and from ++ to +++ were identical and independent of pigmentation (0.69 B-MED). Under these ci cumstances, the equation is: Treatment time = (-0.206 + 0.689 x ord. redness (ord. means prescribed) + 0.0829 x pigmentation) x the number of seconds to reach a B-MED (the intensity of the light source). In Fig. 9b, a diagram is shown, illustrating the correspondence between pigmentation% and the UV-dose in B-MED to reach different le¬ vels of erythema. Since all curves are parallel, the curves shown in Fig. 9b are preferably used instead of the curves shown in Fig. 9a, thus substituting the curves shown in Fig. 9a in calculations similar to the above calculations. The redness "plus" system may be converted into specific figures or numbers as illustrated in Fig. 10, which illustrates the relation be¬ tween estimated redness and the degree or state of redness in % measured in accordance with the present invention and represented by straight lines. In Fig. 4 an overall perspective view of an apparatus according to the present invention is shown, which apparatus is designated the refe¬ rence numeral 10 in its entirety. The apparatus 10 comprises a housing 12 defining a sloping top surface 14 in which a display 16 is arranged together with a 2-digit thumb wheel switch 18 and a 4-digit thumb wheel switch 20. The top surface 14 is further provided with a recess in which a photodetector 40 to be described in greater details below with refe¬ rence to Fig. 5 is received in the idle mode of the apparatus. The pho¬ todetector 40 is connected to the electronic circuitry of the apparatus 10 through a multicore cable 42. The apparatus 10 is a mains supplied apparatus and is consequently provided with a mains cable 22 and a mains plug 24. The electronic circuitry of the apparatus 10 is to be described in greater details below with reference to Figs. 11, 12A, 12B, and Example 1. In Fig. 5A, a schematic and partly cut-away view of the photode¬ tector 40 is shown. The photodetector 40 comprises a cylindrical housing 44 in which a printed circuit board 46 is received, which printed circu¬ it board includes the electronic circuitry of the photodetector 40, which electronic circuitry is to be described in greater details below with reference to Fig. 13 and Example 1. The electronic circuitry of the printed circuit board 46 is connected to the multicore cable 42 which extends from the left-hand end of the cylindrical housing 44 through a coiled bushing 48. At the opposite, right-hand end of the cylindrical housing 44, a light guide and light-emitting diode supporting and light detector supporting component 50 is received, supported in a fixed posi¬ tion relative to the right-hand end of the photodetector 40 by means of an annular support component 52. In Fig. 5A, a light-emitting diode 54 and a light detector 56 are illustrated received within the component 50 and connected to the printed circuit board 46 through conductors 55 and 57, respectively. In Figs. 5B and 5C, the component 50 is shown in greater details from the left-hand side and the right-hand side, respectively, relative to the position of the component 50 within the cylindrical housing 44 shown in Fig. 5A. From Figs. 5B and 5C, it is evident that a total of three apertures are provided extending through the component 50 for re¬ ceiving two light-emitting diodes, one of which emits red light and one of which emits green light, and a light detector. The through-going apertures of the component 50 are designated the reference numerals 60, 62, and 64, respectively. The through-going apertures 60, 62, and 64 are geometrically spaced so as to minimize the risk that any false light may influence the light reflection measurement to be carried out by means of the photodetector 40 in accordance with the teaching of the present in- vention and also in accordance with the teaching described in the above- mentioned US Patent No. 4.882.598. The apertures 60, 62, and 64 are further arranged in a specific angular and sloping relation so as to ob¬ tain an optimum light transmission path from the light-emitting diodes to the light detector from a reflecting surface and further so as to eliminate any light scattering effects from light scattering surfaces, which light scattering might erroneously influence the measurement to be carried out by means of the photodetector 40 and the apparatus 10 ac¬ cording to the present invention, to which apparatus the photodetector 40 is connected. In Fig. 11, an overall circuit diagram of the electronic circuitry of the apparatus 10 implemented in accordance with the teaching of the present invention is shown. The electronic circuitry is in its entirety designated the reference numeral 100. The electronic circuitry 100 ba¬ sically comprises the following sections, a mains supply section 102, a photodetector input section 104, an A/D (Analog/Digital) converter sec¬ tion 106, a central microprocessor section or block 108, and an inter¬ face section 110 through which interface section, the sections 102, 104, 106, and 108 are connected to one another and further interfaced to the display 16, the 2-digit thumb whe°l switch 18, the 4-digit thumb wheel 20, and a printer output port 112. The components of the electronic circuitry 100 are listed in the below Example 1. In Fig. 12, an overall circuit diagram of the microprocessor sec¬ tion or block 108 is shown, which microprocessor block is implemented by an electronic circuit of the type MCS 52, manufactured by the Danish company Circuit Design. The individual components of the microprocessor block or section 108 are listed in the below Example 1. In Fig. 13, a circuit diagram of the electronic circuitry of the printed circuit board 46 of the photodetector 40 is shown. The individu¬ al components of the electronic circuitry 46 are listed in the below Example 1. Example 1 The electronic circuitry 100 of the apparatus 10 implemented in accordance with the teaching of the present invention was constructed from the components identified in Fig. 11. The microprocessor block or section 108 of the electronic circuitry 100 was implemented by a circuit of the type MCS-52 supplied by the Da¬ nish company Circuit Design. The electronic components of the circuit diagram shown in Fig. 12 were: LI 150 uH ICI 80C31 25 The photodetector 40 was constructed from the components identified in Fig. 13. The apparatus according to the present invention fulfilled the be¬ low technical specifications: Light source LED green 550 nm peak value LED red 660 nm peak value Power Requirements Power 220 V Dimensions Weight kg Height, length and depth 71x234x272 mm Environment Ambient Temperature 17 - 28°C Humidity 40 - 80% RH Max. variabil ty between measurements under standardized conditions On brown tile: Green LED 0,2% Red LED 0,3% On white standards: Green LED 0,3% Red LED 0,6% Max. interapparatus variability +/- 2,5% on skin Measuring time (from 1st to last beep) -4,5 sec Example 2 The microprocessor of the microprocessor section or block 108 of the apparatus according to the present invention was operated by means of the programme listed in Table 2 or alternatively operated by means of the programme listed in Table 3. This programme is working in the same way as the programme listed in Table 2 but is giving a warning when the patient is read instead of recalculation of the dose. That allows the operator or the doctor to decide if any reduction in treatment time should be performed. Provided the 2-digit thumb wheel is set to 15, the number of joules/sqc will be calculated for PUVA-treatment (- 300 + 2200 x ord. redness (ord. means prescribed) + 205 x pigment%). This dose should come from a Philips TL 09 lamp or a lamp with a similar spectral distribu¬ tion. Likewise, it is possible to have the treatment dose in joule or m joules/sqcm for different lamp types when the thumb wheel to the left in Fig. 4 is set to 1-13. 14 is the code used when only pigment protection factor, skin redness, and skin pigmentation is to be shown on the dis¬ play. ' Table 2: . 0 REM 25. 1 . 1992 PRG . BA^ 20 R ' EM 100'/, re 1 =900 mV 30 REM FFE7H=6551 1 =CONTROL-REG . 40 REM FFE6H=65510= C-PORTE 50 REM FFE5H=6550<?= E-PORTE . 60 REM FFE4H=65508= A--PQRTE. 70 BAUD 2400 : REM BAUDPATE TJL DISPLAY 80 XBV( 5511;=145 : REM A IWPUT.B OUTPUT,:! Low ir.PUT , i. -HT oΓPUT 90 BOSUB 2010 100 ΘOSUB 203'!' 1 10 PRINT #" ιεo JUMPER=XBY(65508 > . ND.128 IF JUMPER^-' THE !i4«: 130 FOP P=0 TO 5 140 XBY( 5509 - =e**P 150 SIJ(P)=XBY<65510) .AN .15 lά>0 NEXT P 170 SW2=1OøO-*SW.3 ■ +100*SW(2>+1ø*SW < 1 )-s-S.-. < ,: ' PEN S -'MED Fι " ι |-.ll_r-F(J 180 SW1=1Θ*SU < -i ' +SN<4.' 185 ORD=SWl*.l : REM OPUINERET 84H ROD i \ FECTMAL 190 IF B 2=0 THEN 1630 SO 1"1 XBV.65510>=--0 r, REM DIODES OFF 220 N=0 E30 BOSUB 640 240 IF MtNV'. O THEN 130 250 IF SWl>3ø THEN 300 260 BOSUB 2010 270 BOSUB 2030 280 PRINT #" 290 GOTO 340 3Θ0 GOSUB 2010 310 BOSUB 2050 320 FRINT -Ii" 330 GOTO 130 340 N=N+1 350 IF N<3 THEN 230 360 XBY(65509)=128 REM PB7=LYDGIVER ON 370 FOR T=0 TO lø NEXT T 330 XBY 65509,>=0 : REM PB7=LYDGIVEP OFF 390 XBV(65510)=16 : REM PC4 HI GREEN DIODE ON. Θ0 FOR T=0 TO 200 : NEXT T 10 FOR N=0 TO 4 420 GOSUB 640 430 G(N)=M(N) 440 NEXT N 450 XBY< 5509)=128 460 FOR T=θ TO 10 NEXT T 470 480 XBY( 5510)=0 : REM DIODES OFF 490 FOR T=ø TO 200 : NEXT T 500 FOR N=0 TO 4 510 GOSUB 640 520 S<N)=M(N) 530 NEXT N 540 XB < 5509)=120 550 FOR T=0 TO 10 ; NEXT T 22 560 XBY(65509)=© 570 XBY(65510)=64 : REM PC6 HI RED LODE ON. JGV. FOR T=0 TO 2øø : NEXT T 590 FOR N=0 TO 4 A QvAftv GOSUB 640 610 R<N)=MCN) 620 NEXT N 630 GOTO 830 640 DO 650 I=XBY(65508) C=I.AND.112 660 UNTIL C=112 REM I.E.PA6,PA5 08 PA4 HI. 670 DO 680 1=XEY( 550S) C=I.AND.H2 690 UNTIL C=48 REM I.E. PA6 LQ I.E. HUNDREDS SELECTED, 700 H=I.AND.15 710 DO 720 I=XBY<65508) C=I.AND.112 730 UNTIL C=96 REM I.E. PA4 LO I, E. UNITS SELECTED. 740 U=I. ND.15 750 DO 760 I=XBY( 5508) C=I.AND. HE 77© UNTIL C=80 REM I.E. PAS L I.E. TENS SELECTED 780 T=I.AND.15 7<-? FT=1 IF H=10 THEN H=-θ : FT -1 SIO M«N)=FT*Cløø+.H+1-.Θ-.r+lJ) 820 RETURN 330 XBY(6550 )=123 ; XBY( 5510>-=ø 840 FOR T=θ TO IΘO : NEXT T 850 XBY i6550 )=0 860 GMIN=løθO t SMIN=1000 : RMI =100O 870 8MAX=0 i SMAX=0 : RMAX=0 880 BΞ=0 : SS=Θ : RS=0 890 FOR N=θ TO 4 9øø SS=GS+G(N) Ϊ SS=SS-t-S(N) : RS=RS+P(N) 910 IF G (N XGMIN THEN GMIN=G ( N ) 920 IF G (N ) >GMAX THEN GMAX=B (N - 93ø IF SCNXSMI THEN SMIN=S(N) 940 IF S(N ) >SMAX THEN SMAX=S( N ) 950 IF R(N XRMIN THEN RMIN=R(N ) 960 IF R(N) RMAX THEN RMAX=R(N ) 970 NEXT N 980 IF GMAX-GMIN>40 THEN F=l 990 IF SMAX-SMIN>.10 THEN F=l løøø IF RMAX-RMIN 40 THEN F=l lølø RG=.l*INT((GS-SS)/4.5) 1020 RR=.1*INT((RS-SS)/4.5) 103ø IF RG<5 THEN F=l 1050 IF F=l THEN 1180 1100 GI=LQG(RG)-1.54 : REM In(RS)-intercept lllø SL=SI/RR : REM slope 1120 KR=RR+17.5*<1-SL/.-0427- ; REM ORR. RED REFL. 1130 KGI=.0427*KR : REM KORR GR REFL IISO IF KR=0 THEN F=l 1160 IF KR<0 THEN F=l 1170 IF F=0 THEN 1350 1180 GOSUB 2010 1190 GOSUB 20"0 J 200 GOSUB 2090 1210 FOR T=0 TO 00 ; NEXT T 1. 20 GOTO 90 1350 PMT=100V(7<:—. R) >' ~~ IF PMT 0 THEN FliT=0 1360 PEDN=100^( .04Ξ7-SD .0277 ■ . IF REDN 0 THEN REDN=» " > 1365 IF PMT -60 THEN SD=1 1370 PMT=I r(PMT^ 1380 REDN-INT ( REDN) 13*0 PF'INT ttCHP•' B ~~ ) . " I " .CHP•' 17 ) ,CMPf22 > , 1 00 PRirJT it" PIGMENT T101J ' • .,PMT, " ♦ '." 1 -i05 IF SB=1 THEN PRINT 1t" REDNESS UNREL [ADLE " : GOTO I ¬ 1 -0 PRINT ft" REDNESS ",PEDM,"V." 1 CO FOR T=0 TO 1500 : NEZXT T 1 30 PP=2H .2-5.4 0 71*LOGα P) : REM PIGM-BE3I .FA! Tijf 14 ώ, .> PP=.1*INT' 10*PP) 1450 PRINT #CHR <2") - "I" ,CHR .1" ) .CHR'.22 ' . 1 60 PRINT " PJGMEN T PROTECTION" 1 6'' PRINT ft" UNRELIABLE 1468 FOP T=0 TG 1500 : NEXT T 1 =? GOTO 90 1470 PRINT ft" FACTOR " .PP 1480 FOR T=0 TO 150O : NEXT 1485 ARD=16. 7-491.5*3L : REM ACTUELL REDNESS 1487 IF PMT? 0 THEN 1500 1490 IF REDN>29.6 THEN 1510 1500 TT=.5*-(24.2+• .1709#0RD-5.668)*LOG( Y'P ) )-SN2 GOTO 1520 1510 TT=.1709*(ORD-AR )*-LOG( R)*SW2 1520 PRINT #CHR(27) , "I" ,CHP( 17) ,CHRf22) . 1530 TT=INT(TT) : IF TT-'O THEN TT=0 1540 H=INT(TT/3600) 1550 M=INT< (TT-36øø*H)/60 ~ 1560 S=TT-M*60-H*3600 1570 PRINT #" TREATMENT TIME " 1580 IF H=0 THEN 160O 159Θ PRINT ft" ",H,"HOUR",M-"MIN" GOTO 1622 1600 IF M=0 THEN 1620 1610 PRINT ft" " ,M,"MIN ",3,"SEC : GOTO 1622 1620 PRINT #" ",S,"3EC GOTO 1622 1622 FOR T=0 TO 1500 : NEXT T 1624 GOTO 120 1630 PRINT #CHP(27) , "I",CHR.17) ,CHR(22) , 1640 PRINT #"*CALIBRATE*- PLACE" 1650 PRINT ft"DETECTOR ON STAND RD" 1660 XBY( 5509)=1 1670 SW=XBY(65510) .AND.15 IF SW 0 THEN 10 1680 XBY(65509)=2 1690 SW=XBY<65510) .AND.15 IF SW 0 THEN 10 1700 XBY( 550 1 ?)=4 1710 S =XBY( 5510 . ND.15 IF SW-0 THEN 10 1720 XBY(65509)=8 1730 SW=XBY(65510). ND.15 IF SW -0 THEN IO 1740 FOR T=0 TO løøø : NEXT T 1750 XBY(65510 =32 1760 FOR T=ø TO 200 : NEXT T 177ø GOSUB 640 17Sø S=M(N) 1790 IF S>40 THEN 1630 1800 XBY(6551ø)=4B 1810 FOR T=ø TO 2øø NEXT T 1820 BOSUB 640 1830 G=M(N) 180 BP=.1*.INT(<-B-S). 1850 XBY( 5509)=128 I860 FOR T=0 TO 5 : NEXT T 1370 XB 5509)=0 1880 PRINT #CHRC27) 5 "I" ,CHR(17) r .CHR(22) , 1890 PRINT #BP,": ", TAB (9),"BREEN 19øø XB (65510 =96 1910 FOR T=ø TO 200 NEXT 1920 BOSUB 640 1930 R=M(N) 19 0 XBY(65510)=32 195ø RP=.1*INT. <R-S). ,9) I960 XBYC65509)=128 197ø FOR T=0 TO 15 i NEXT T 1980 XBY 65509)=0 199ø PRINT #RP,"«", TAB (9), "RED 2OΘ0 BOTO 1660 2ølø PRINT #CHRC27) , "I",CHR(17) ,CHR(22) 2O20 RETURN 2030 PRINT #" *•**- READY *** " 20 0 RETURN 2O50 PRINT #" CHECK DOSE SETTINB" 206O RETURN 207Θ PRINT #" ERROR ERROR ERROR" 2080 RETURN 209Θ PRINT #" REPEAT MEASUREMENT" 2100 RETURN 2110 REM 2120 REM *** 2130 REM *** 214Θ REM TESTPB FOR HUDREFLEKTANSMETER . TEST . BAS 215Θ REM *** • INITΓALISERINB 216© REM løøy. ref l=9øø mV 2170 REM FFE7H=65511=C0NTR0LREB. 2180 REM FFE6H=6551Θ= C-PORTE 2190 REM FFE5H=65509= B-PORTE. 220O REM FFE4H=655Θ8= A-PORTE. 2210 BAUD 2400 : REM BAUDRATE TIL DISPLAY 2220 XBY(65511)=145 : REM A INPUT.B OUTPUT,C-LOW I PUT,C-HI OUTPUT 2230 PRINT #CHRCΞ7) ,"I",CHR<17) ,CHR(22) , 224Θ REM *** I IT SLUT 2250 PRINT #"TESTER LYDGIVER' 226Θ FOR N=ø TO 1 2270 XBY(655ø9)=128 2280 FOR T=0 TO 50 : NEXT T 229Θ XBYC 5509)=ø 23øø FOR T=0 TO 50 : NEXT T 2310 NEXT N 2320 PRINT #" TESTER OMSKIFTERE" 2330 DIM SW<6) 2340 FOR P=0 TO 5 2350 XBY(65509)=2**P 2360 SW(P)=XBY(6551O) .AND.15 2370 NEXT P 2380 FOR P=5 TO 4 STEP -1 2390 PRINT #SW(P) , 24O0 NEXT P 2410 PRINT #" " . 2420 FOR P=3 TO O STEP -1 2430 PRINT #SW(P) , 2440 NEXT P 2450 PRINT # 2460 SW2=1OøO*SW(3)+100*BW(2)+10*SW( 1 )+SW(O) 247Θ SW1=10*SW(5)+SW(4) 2480 IF SW2=0 THEN 2500 2490 GOTO 2340 25O0 PRINT #CHR(27) , "I" ,CHR(17) ,CHR(22) , 2510 PRINT #" A/D-CONV.UDS. V" 2520 GOSUB 2750 2530 PRINT #" ",M, TAB (lø)," 2540 PRINT #"" . 2550 XBY(65509)=1 : SW(0)=XBY(65510) .AND.15 2560 IF SW(ø)=l THEN 2600 2570 IF SW(0)=2 THEN 2670 2580 BOTO 2520 259ø BOTO 2520 26Θ0 XBY(65510)=16 : REM PC4 HI GREEN DIODE ON. . 2610 FOR T=0 TO 2O0 : NEXT T 2620 GOSUB 2750 2630 XBY(65510)=0 : REM DIODES OFF 2640 PRINT #" ",M, TAB <10),"GREEN 2650 PRINT #"" 2660 BOTO 2550 2670 XBY(65510)=64 : REM PC6 HI RED DIODE ON 2680 FOR T=0 TO 200 : NEXT T 2690 BOSUB 2750 27øø XBY( 5510)=0 : REM DIODES OFF 2710 PRINT #" ",M, TAB (lø),"RED 2720 PRINT #"" 2730 BOTO 2550 2740 REM ***AFLAESNINS AD A/D-CONVERTER 2750 DO 2760 I=XBY( 5508) : C=I.AND.112 2770 UNTIL C=112 : REM I.E.PA6,PA5 OG PA4 HI. ' 2780 DO 2790 I=XBY( 5508) : C=I.AND.112 2300 UNTIL C=4S 5 REM I-E. PA6 LO I.E. HUNDREDS SELECTED, 2810 H=I.AND.15 2820 DO 2830 I=XBY(65508) : C=I. ND.112 ' 2840 UNTIL C=9ά : REM I.E. PA4 LO I.E. UNITS SELECTED. 2850 U=I. ND.15 2860 DO 2870 I=XBY(65508) : C=I.AND.11E 2S80 UNTIL C=30 : REM I.E. PAS L I.E. TENS SELECTED, 2890 T=I.AND.15 29øø FT=1 2910 IF H=10 THEN H=0 : FT=-1 2930 RETURN 294Θ REM **-* AFLAESNINB SLUT Tabl e 3 : REM 18 . 1 . 1 993 PRG2 . BAS MOD TIL SPEC 3 . BAS REM 100 % ref l = 900 mV REM FFE7H= 6551 1 =CONTROLREG . REM FFE6H= 65510= C-PORTE REM FFE5H=65509= B-PORTE. REM FFE4H= 65508= A-PORTE. BAUD 2400 : REM BAUDRATE TIL DISPLAY ' XBY(65511)=145 REM A INPUT,B OUTPUT,C- LOW INPUT,C-HI OUTPU GOSUB 2010 0 GOSUB 2030 0 PRINT # " 0 JUMPER=XBY( 65508) .AND.128 IF JUMPER=0 THEN 2140 0 FOR P=0 TO 5 0 XBY(65509)=2**P 0 SW(P)=XBY( 65510) .AND.15 NEXT P 0 SW2=1000*SW(3)+100*SW(2)τlO*SW(l)+SW(0) REM S/MED FOR KILD SW1=10*SW(5)+SW(4) 5 ORD=SWl*.l : REM ORDINERΞT 24H ROD (1 DECIMAL) 0 IF SW2=0 THEN 1630 0 XBY(65510)=0 : REM DIODES OFF F=0 : SB=0 0 N=0 0 GOSUB 640 0 IF M(N)>100 THEN 130 IF SW1>40 THEN 300 0 GOSUB 2010 0 GOSUB 2030 0 PRINT #" 0 GOTO 340 0 GOSUB 2010 0 GOSUB 2050 0 PRINT #" 0 GOTO 130 0 N=N+1 0 IF N<3 THEN 230 0 XBY(65509)=128 : REM PB7=LYDGIVER ON 0 FOR T=0 TO 10 : NEXT T 0 XBY(65509)=0 : REM PB7=LYDGIVER OFF 0 XBY(65510)=16 : REM PC4 HI GREEN DIODE ON. 0 FOR T=0 TO 200 : NEXT T 0 FOR N=0 TO 4 0 GOSUB 640 0 G(N)=M(N) 0 NEXT N 0 XBY{65509)=128 0 FOR T=0 TO 10 NEXT T 0 XBY(65509)=0 0 XBY(65510)=0 : REM ' DIODES OFF 0 FOR T=0 TO 200 : NEXT T 0 FOR N=0 TO 4 0 GOSUB 640 0 S(N)=M(N) 0 NEXT N 0 XBY(65509)=128 0 FOR T=0 TO 10 NEXT T 28 560 XBY(65509)=0 570 XBY(65510)=64 : REM PC6 HI RED DIODE ON. 580 FOR T=0 TO 200 NEXT T 590 FOR N=0 TO 4 600 GOSUB 640 610 R(N)=M(N) 620 NEXT N 630 GOTO 830 640 DO 650 I=XBYC65508) C=I.AND.112 660 UNTIL C=112 REM I.E-PA6,PA5 OG PA4 HI- 670 DO 680 I=XBY(65508) 690 UNTIL C=48 : . HUNDREDS SELECTED. 700 H=I.AND-15 710 DO 720 I=XBY(65508) 730 UNTIL C=96 : UNITS SELECTED. 740 U=I.AND.15 750 DO 760 I=XBY(65508) 770 UNTIL C=80 TENS SELECTED. 780 T=I.AND.15 790 FT=1 800 IF H=10 THEN H=0 : FT=-1 810 M(N)=FT*(100*H+10*T+U) 820 RETURN 830 XBY(65509)=128 : XBY(65510)=0 840 FOR T=0 TO 100 : NEXT T 850 XBY(65509)=0 860 GMIN=1000 : SMIN=1000 : RMIN=1000 870 GMAX=0 : SMAX=0 : RMAX=0 880 GS=0 : SS=0 : RS=0 890 FOR N=0 TO 4 900 GS=GS+G(N) : SS=SS+S(N) : RS=RS+R(N) 910 IF GCNXGMIN THEN GMIN=G(N) 920 IF G(N)>GMAX THEN GMAX=G(N) 930 IF S .NXSMIN THEN SMIN=S (N) 940 IF SCN)>SMAX THEN SMAX=S(N) 950 IF R.NXRMIN THEN RMIN=R(N) 960 IF R(N)>RMAX THEN RMAX=R(N) 970 NEXT N 980 IF GMAX-GMIN>40 THEN F=l 990 IF SMAX-SMINM0 THEN F=l 1000 IF RMAX-RMIN>40 THEN F=l 1010 RG=.1*INT( (GS-SS./4.5) 1020 RR=.1*INT{ (RS-SS)/4.5) 1030 IF RG<5 THEN F=l 1050 IF F=l THEN 1180 1100 GI=LOG(RG)-1.54 : REM In(RG)-intercept 1110 SL=GI/RR : REM slope 1120 KR=RR+17.5*(l-SL/.0427) : REM KORR. RED REFL. 1130 KGI=.0427*KR : REM KORR GR REFL 1150 IF KR=0 THEN F=l 1160 IF KR<0 THEN F=l 1170 IF F=0 THEN 1350 1180 GOSUB 2010 1190 GOSUB 2070 1200 GOSUB 2090 1210 FOR T=0 TO 600 NEXT T 1220 GOTO 90 1350 PMT=100*(70-KR)/70 : IF PMT<0 THEN PMT=0 1360 REDN=100*( .0427-SL)/ 0277 : IF REDN<0 THEN REDN=0 1365 IF PMT>60 THEN SB=1 1370 PMT=INT(PMT) 1380 REDN=INT(REDN) 1390 PRINT #CHR(27) , "I" ,CHR( 17) ,CHR(22) , 1400 PRINT # " PIGMENTATION " ,PMT, "%" 1405 IF SB=1 THEN PRINT # " REDNESS UNRELIABLE GOTO 1420 1410 PRINT #" REDNESS ",REDN,"%" 1420 FOR T=0 TO 2000 : . NEXT T 1430 PP=.483+.0829*PMT REM PIGM.BESK.FAKTOR 1440 PP=.1*INT(10*PP) 1450 PRINT #CHR(27) "I' ,CHR(17) ,CHR(22) , 1460 PRINT #" PIGMENT PROTECTION 1 1465 IF PP> .483 THEN 1470 REM IF PMT=0 1467 PRINT # " UNRELIABLE 1468 FOR T=0 TO 2000 : NEXT ' 1469 GOTO 90 1470 PRINT # " FACTOR " ,PP 1480 FOR T=0 TO 2000 : NEXT 1485 ARD=16.97-491.5*SL : REM ACTUELL REDNESS 1486 IF PMT<13 THEN PMT=13 : REM TAALES ALTID 1488 IF SW2>0.AND.SW2<16 THEN GOTO 3000 1490 IF PMT>60 THEN 1500 1491 REM IF REDN>29.6 THEN 1510 erstattet af advarsei 1492 IF REDN<29.6 THEN 1500 1493 PRINT #CHR(27) , ■ I".CHR(17) ,CHR(22) 1494 FOR T==0 TO 4 1495 PRINT #"' CHECK SKIN REDNESS 1496 FOR P=0 TO 200 : NEXT P 1497 PRINT r 1498 FOR P=0 TO 50 NEXT P 1499 NEXT T 1500 TT=(-0.9+.689*ORD+.0829*PMT)*SW2 1502 IF SW15=1 THEN TT=-2300+2200*ORD+205*PMT SW15=0 1503 REM -2000 PGA REGIONSFORSKELLE. 1506 GOTO 1520 1510 REM TT=.689* (ORD-ARD)*SW2 1520 PRINT #CHR(27) ,"I",CHR(17) ,CHR(22) , 1530 TT=INT(TT) : IF TT<0 THEN TT=0 1531 IF LSW=0 THEN 1540 1532 PRINT #" TREATMENT DOSE' " 1533 IF TT<1000 THEN PRINT # " ,TT, "MJ/SQCM" GOTO 1537 1534 TT=INT(TT/100) : UVD=TT/10 1536 PRINT #' ,UVD, • J/SQCM" 1537 FOR T=0 TO 2000 : NEXT T 1538 LS =0 1539 GOTO 120 1540 H=INT(TT/3600) 1550 M=INT( (TT-3600*H)/60) 1560 S=TT-M*60-H*3600 1570 PRINT #" TREATMENT TIME " 1580 IF H=0 THEN 1600 1590 PRINT " " ,H,"HOUR" ,M-"MIN' GOTO 1622 1600 IF M=0 THEN 1620 1610 PRINT #" ",M,"MIN ",S,"SEC t GOTO 1622 1620 PRINT #" " ,S,"SEC GOTO 1622 1622 FOR T=0 TO 2000 : NEXT T 1624 GOTO 120 1630 PRINT #CHR(27) , "I" ,CHRC17) -CHRC22) 1640 PRINT r'*CALIBRATE* PLACE" 1650 PRINT §"DETECTOR ON STANDARD" 1660 XBYC65509)=1 1670 SW=XBY(65510) .AND.15 IF SW>0 THEN 10 1680 XBY(65509)=2 1690 SW=XBYC65510) .AND:15 IF SW>0 THEN 10 1700 XBY(65509)=4 1710 SW=XBY(65510) .AND.15 IF SW>0 THEN 10 1720 XBY(65509)=8 1730 SW=XBY(65510) .AND.15 IF SW>0 THEN 10 1740 FOR T=0 TO 1000 : NEXT T 1750 XBY(65510)=32 1760 FOR T=0 TO 200 : NEXT T 1770 GOSUB 640 1780 S=M(N) 1790 IF S>40 THEN 1630 1800 XBY(65510)=48 1810 FOR T=0 TO 200 : NEXT T 1820 GOSUB 640 1830 G=M(N) 1840 GP=.1*INT((G-S)/ .9) 1850 XBY(65509)=128 1860 FOR T=0 TO 5 : NEXT T 1870 XBY(65509)=0 1880 PRINT #CHR(27) , "I" ,CHR(17) ,CHR(22 1890 PRINT #GP,"%", TAB (9) , "GREEN 1900 XBY(65510)=96 1910 FOR T=0 TO 200 : NEXT T 1920 GOSUB 640 1930 R=M(N) 1940 XBY(65510)=32 1950 RP=.1*INT((R-S)/ .9) 1960 XBY(65509)=128 1970 FOR T=0 TO 15 : NEXT T 1980 XBY(65509)=0 1990 PRINT #RP,"%", TAB (9),"RED 2000 GOTO 1660 2010 PRINT #CHR(27) , "I",CHR.17) ,CHR(22) 2020 RETURN 2030 PRINT #" *** READY *** 2040 RETURN 2050 PRINT #" CHECK DOSE SETTING' 2060 RETURN 2070 PRINT #' * ERROR ERROR ERROR' 2080 RETURN 2090 PRINT " REPEAT MEASUREMENT' 2100 RETURN 2110 REM *** 2120 REM *** 2130 REM *** 2140 REM TESTPG FOR HUDREFLEKTANSMETE .TEST.BAS 2150 REM *** INITIALISERING 2160 REM 100% refl=900 mV 2170 REM FFE7H=65511=CONTROLREG. 2180 REM FFE6H=65510= C-PORTE 2190 REM FFE5H=65509= B-PORTE. 2200 REM FFE4H=65508= A-PORTE. 2210 BAUD 2400 : REM BAUDRATE TIL DISPLAY 2220 XBY(65511)=145 : REM A INPUT,B OUTPUT,C-LOW INPUT,C-HI OUTPU 2230 PRINT #CHR(27) , "I" ,CHR< 17) ,CHR( 22) , 2240 REM *** INIT SLUT 2250 PRINT #"TESTER LYDGIVER" 2260 FOR N=0 TO 1 2270 XBY(65509)=128 2280 FOR T=0 TO 50 : NEXT T 2290 XBY(65509)=0 2300 FOR T=0 TO 50 : NEXT T 2310 NEXT N 2320 PRINT # " TESTER OMSKIFTERE" 2330 DIM SW(6) 2340 FOR P=0 TO 5 2350 XBY(65509)=2**P 2360 SW(P)=XBY(65510) .AND.15 2370 NEXT P 2380 FOR P=5 TO 4 STEP -1 2390 PRINT #SW(P) , 2400 NEXT P 2410 PRINT # " " , 2420 FOR P=3 TO 0 STEP -1 2430 PRINT #SW(P) , 2440 NEXT P 2450 PRINT # 2460 SW2=1000*SW(3)+100*SW(2)+10*SW(1)+SW(0) 2470 SW1=10*SW<5)+SW(4) 2480 IF SW2=0 THEN 2500 2490 GOTO 2340 2500 PRINT #CHR(27) , "I" ,CHR( 17) ,CHR(22) , 2510 PRINT # " A/D-CONV.UDG. mV" 2520 GOSUB 2750 2530 PRINT #" ",M, TAB (10)," 2540 PRINT #"" 2550 XBY(65509)=1 : SW(0 )=XBY(65510 ) .AND.15 2560 IF SW<0)=1 THEN 2600 2570 IF SW(0)=2 THEN 2670 2580 GOTO 2520 2590 GOTO 2520 2600 XBY(65510)=16 : REM PC4 HI GREEN DIODE ON. 2610 FOR T=0 TO 200 : NEXT T 2620 GOSUB 2750 2630 XBY(65510)=0 : REM DIODES OFF 2640 PRINT #" " ,M, TAB •( 10), "GREEN 2650 PRINT # " " 2660 GOTO 2550 93/0007 32 2670 XBY(65510)=64 : REM PC6 HI RED DIODE ON 2680 FOR T=0 TO 200 NEXT T 2690 GOSUB 2750 2700 XBY(65510)=0 : REM DIODES OFF 2710 PRINT if " ",M, TAB (10) ,"RED 2720 PRINT" # "" 2730 GOTO 2550 2740 REM ***AFLAESNING AD A/D-CONVERTER 2750 DO 2760 I=XBY(65508) C=I.AND- 112 2770 UNTIL C=112 REM I.E.PA6,PA5 OG PA4 HI. 2780 DO 2790 I=XBY(65508) 2800 UNTIL C=48 HUNDREDS SELECTED. 2810 H=I.AND.15 2820 DO 2830 I=XBY(65508) 2840 UNTIL C=96 UNITS SELECTED. 2850 U=I.AND.15 2860 DO 2870 I=XBY(65508) 2880 UNTIL C=80 ENS SELECTED. 2890 T=I.AND.15 2900 FT=1 2910 IF H=10 THEN H=0 FT=-1 2920 M=FT*(100*H+10*T+U) 2930 RETURN 2940 REM *** AFLAESNING SLUT 3000 LSW=1 3010 IF SW2=1 THEN SW2=334 : REM INCL CORR 1.85 3020 IF SW2=2 THEN GOTO 3200 3030 IF SW2=3 THEN GOTO 3200 3040 ' IF SW2=4 THEN GOTO 3200 3050 IF SW2=5 THEN GOTO 3200 3060 IF SW2=6 THEN GOTO 3200 3070 IF SW2=7 THEN GOTO 3200 3080 IF SW2=8 THEN SW2=52880 3090 IF SW2=9 THEN SW2=21081 3100 IF SW2=10 THEN SW2=52880 3110 IF SW2=11 THEN GOTO 3200 3120 IF SW2=12 THEN SW2=82 3130 IF SW2=13 THEN GOTO 3200 3200 GOSUB 2010 3210 GOSUB 2070 3220 FOR T=0 TO 2000 NEXT T 3230 GOTO 90 In case the programme is adapted to control the microprocessor of the apparatus according to the present invention in accordance with the above described alternative calculations relating to the comparison of the UV dose in B-MED and the degree of pigmentation, the lines 1500 and 1510 of the programme are amended into: 1500 TT=(-0.206+0.689xORD+0.0829xPIG ) and 1510 TT=.689x(0RD-ARD). The apparatus according to the present invention should be operated in accordance with the below measuring guidelines: The undressed patient should acclimate before the measurement. This ' is to evaporate sweat from the skin and cool. Measurements is performed on normal or relatively normal skin avoiding discoloration from treat¬ ment, freckles, hairy areas even after shaving, flushing zones, and skin irritated from rubbing by the person himself or from the back of a chair. If fullbody treatment is performed the best place to measure is on the back above a horizontal line through the lower part of the scapu¬ lae, and on the upper part of the abdomen and the breast. Measurements on the extremities will only be reproducible if the patient is placed horizontally and relaxing. Redness will change with level and activity. The detector is held perpendicular to the surface of the skin gent¬ ly touching the skin in order to eliminate light from entering the de¬ tector from the environment. Light sources used for the treatment of skin diseases may have very different biological activity. And since the limiting factor for the treatment dose is redness of the skin, the use of a basic MED has been chosen as the basic dose. The basic MED being calculated from the ery¬ thema action spectrum CIE (Mc inlay & Diffey) and the MED dose of 31,2 mJ/cm2 at 296 nm (Parrish). The correct number of seconds to reach that dose, i.e. 1B-MED, is entered into the microprocessor by means of the the thumb wheel 20 at the right-hand side of the display 16. By means of the thumb wheel 16 at the left-hand side of the display 20, the "24h erythema level" is input. This level has to be decided by the person operating the apparatus. 0.0 Corresponds to the highest dose which can be given before redness will appear. 0.5 Corresponds to (+) redness, weak spotted redness without sharp borders to the untreated surroundings. 1.0 Weak redness with a clear demarcation to the surroundings. Often named +. 2.0 Corresponds to redness ++ with clear redness and a weak edema to be felt. 3.0 Corresponds to +++ redness. There is heavy redness with edema above the surroundings. Therefore, the following schedule is recommended for the treatment of psoriasis: 1. Week of treatment setting 1.0 2. Week of treatment 3.0 3. week of treatment 6.0 4. Week of treatment 9.0 A constant erythema level setting may be used for atopic dermatitis mycosis fungiodes, pruritus etc. Pigmentation The scale has been chosen so that people with a very wide range of pigmentation covering all races are represented in the scale. Pigmenta¬ tion is given on a scale from 0% to 100%. 0% pigmentation represents the degree of pigmentation of previously unirradiated buttocks of an ex¬ tremely white person. 100% pigmentation represents the degree of pigmen¬ tation of previously unirradiated buttocks of a black person. In the first few days after intensive UV irradiation redness cor¬ responding to ++ and +++ etc. will result in a lower measure of pigmen- tation than the measurement preceding irradiation. This phenomenon is a result of edema following heavy erythema and is caused by erythema it¬ self. Erythema The scale is chosen so that people with zero blood flow and dark blue red naevus flammeus can be fitted into the scale. 0% redness has been chosen as the redness of the skin on the ante- brachium of persons who had their arm emptied for blood and the blood supply stopped by a cuff on the upper arm. 100% has been chosen so that even very blue-red naevus flammeus o the face may be included. 0-30% corresponds to what is found under normal conditions in con¬ nection with people acclimated to room temperature. • The relations between the clinical degree of redness and the ave¬ rage % of UV irradiated people or individuals are listed in Table 1. The pigment protection factor indicates how much higher UV dose an individual can take before obtaining + in redness compared to a person reacting with + redness. After exposure to 1 B-MED from a Philips TL 12 equipped radiation source. All background measurements are to be performed on previously unexposed buttocks. Treatment time shown on the display 16 is the time used for full body irradiation. Therefore, the irradiation dose matches the most sen¬ sitive larger areas of the body. It should be noted that the treatment time depends on the radiation source and the setting of the thumb wheel switch 20. When the thumb wheel switch 20 at the right-hand side of the dis¬ play 16 is adjusted to 0000 (no radiation) the apparatus automatically jumps into calibration mode. Keeping the detector close to the tile which is delivered togethe with the apparatus a reflection % for the red and green light is shown on the display. This reflection should be within the limits written on the tile. Before calibration, the apparatus must be in temperature equili¬ brium with the room in which the apparatus is to be used. The calibration values is traceable to standard ISO 2469. Using this standard will display 100% both for red and green reflection. The detector is constructed to demand a minimum of cleaning. Only plastic ring is in contact with the skin. This may be cleaned by an al coholic solution. In Fig. 14 a diagram is shown illustrating the basic realization that a linear relationship exists between light- or laser-induced skin changes to individuals and the degree of skin pigmentation of the same individuals. The diagram shown in Fig. 14 was based on the below test. Thirteen individuals with a varying degree of epidermal skin pig¬ mentation, objectified by skin reflectance, were on the inside of the upper arm treated with a total of six hexagonal areas by an argon laser (AL, 488 nm) and a copper vapor laser (CVL, 578nm). The lasers were con¬ nected to a Hexascan device, and physical parameters were identical for the two laser types, except for the wavelengths. Beam diameter was 1 mm, pulse duration 200 msec, intensities 0.7, 1.0, and 1.3 W/spot, resulting in the following spot doses 17.8, 25.5, and 33.1 J/cm 2 . A correlation was demonstrated between pre-treatment skin pigmenta¬ tion and the clinical effects obtained immediately after and 6 months after the laser treatment. Assessment of the chronic response was based on distinction between pigmentary changes and scarring. The CVL induced a significantly higher degree of acute results at the 0.7 and 1.0 W/spot treatment level as compared with the AL. For the clinical response 6 months after the laser treatment it turned out that the AL at the 1.0 and 1.3 W/spot induced a significantly higher degree of hyperpigmentation and scarring as compared with the CVL. An inverse relation was found between the degree of pre-treatment pigmentation and the threshold intensities required to induce wound for¬ mation, scar formation and postinflammatory hyperpigmentation, respec- tively. Detailed measuring results obtained by the above test are illu¬ strated in the diagrams 15A-15L. In Fig. 16, a diagram is shown, illustrating the relation of using the degree of skin pigmentation as a predictor of minimal phototoxic dose to be given to the same individual. The diagram represents the re¬ sult of the following test or experiment. Fourteen individuals with skin type (II) (11) and skin type III (3) participated in the test. The sensitivity to irradiation with Philips TL12 tubes was determined without medication on previous unexposed but- tocks (MED). The sensitivity to irradiation with Philips TL09 tubes was determined 1 h after oral administration of (0.44-0.63 mg/kg) 8-M0P in a similar way (MPD). The pigmentation of the test areas before irradiation was quantitated with an apparatus according to the present invention, the erythema reaction was assessed clinically using a (+)-+++ scale 24 after TL12, and 72h after TL09 exposure. The pigmentation % of the unexposed test areas vs. the energy needed to elicit MED or MPD was plotted in scattergra s. There was a po sitive relation between pigmentation and the dose of TL12 needed to eli cit a (+) or + erythema! reaction. The lines of the (+) and + reaction had identical slopes. Similar results were observed with TL09 exposure after ingestion of 8-MOP. Spearmanns test for correlation between pig¬ mentation and dose to erythema! reaction was significant for the + reac tion after TL12 exposure, p<0.05. The correlation coefficient for the other parameters was non-significant (0.4>p>0.05). A further experiment was made: Seventeen volunteers were tested with Philips TL12 and TL01 tubes on previous unexposed buttocks. Biological doses ranging from 0.25 to 3.00 B-MEDs were used. B-MED derived from the erythema action spectrum of McKinlay and Diffey and 1 MED = 312 J/m 2 at 296 nm (Parrish). The physical doses cor responding to 1 B-MED are 0.62 J/m 2 for the TL01 tube and 0.082 J/m 2 fo the TL12 tube (TL12:TL01 - 117.5). The redness % and pigment protection factor (PPF) were measured be fore and 24 h after exposure with an apparatus according to the present invention. Also the test sites were evaluated clinically after 24 h. " Test sites with redness %>30 measured by the apparatus or clinical red¬ ness ((+)-+++) were included in the study. The results were given as redness % as a function of dose. Since a linear reciprocity between PPF before exposure and dose to give a specific effect is assumed to exist, the results were also given as redness % as a function of dose/PPF. As the intercept of the four lines did not differ significantly, a common intercept of 22.5 was used. Since identical biological doses were given of the TL12 and TL01, an identical redness was expected. However,it was found that the dose ratio between TL12 and TL01 to obtain the same redness values was 1:0.55, the TL01 being 1.85 times stronger than TL12. The results are i accordance with the assumption that a linear reciprocity between PPF an the dose needed to produce a specific response exists, since it was found that 1 MED/PPF from the TL12 tube resulted in a redness of 37.1%, not significantly different from the expected 36.9%, the value corre¬ sponding to the clinical reading +. In Fig. 17, a diagram is shown illustrating the correspondence or the difference between experimentally found UV doses and doses calcu¬ lated to reach a certain redness. The diagram is based on measuring re¬ sults obtained from the same 49 individuals investigated and used for the experiments or tests on basis of which the diagram shown in Fig. 6 is derived. In Fig. 18, a diagram is shown, which diagram illustrates the adap¬ tation of the present invention as to determining the sensitivity of an individual who has been exposed to UV treatment. The individual has af- ter determination of the individual's ability to stand exposure to UV radiation, by employing the method and the apparatus according to the present invention, been exposed to UV treatment, i.e. been exposed to a specific UV dose. After the UV treatment, the redness of the individual is as discussed above with reference to Fig. 8 determined. The redness % is converted into a B-MED measure or difference at + redness and ++ red¬ ness, which B-MED measure represents the difference between the UV dose to which the individual has been exposed, and the UV dose which the in¬ dividual may stand. DEFINITIONS 2 B-MED Basic Minimal Erythema Dose is 312 J/m at 296 nm. ((24 h erythema) Parrish). MED Minimal Erythema Dose for an individual 24 h after exposure. PPF PPF x B-MED = MED The Pigment Protection Factor is the number of B-MEDs which elicit + redness in an individual 24 h after exposure. Erythema Action Spectrum: CIE (McKinlay & Diffey).

Claims: CLAIMS 1. A method of determining an individual's ability to become tanned or to stand exposure to ultraviolet radiation without causing a skin re- action, such as skin cancer or erythema, comprising the following steps: exposing at least part of said individual's skin surface to electromagnetic radiation of a first wavelength and of a predetermined intensity, said first wavelength being a wavelength at which erythro¬ dermic skin reflection is high, measuring the intensity of electromagnetic radiation reflected from said part of said individual's skin surface so as to determine a first coefficient of reflection of said skin surface part to said electromag¬ netic radiation of said first wavelength, exposing said skin surface part to electromagnetic radiation of a second wavelength and of a predetermined intensity, said second wave¬ length being a wavelength at which erythrodermic skin reflection is low, measuring the intensity of electromagnetic radiation reflected from said part of said individual's skin surface part so as to determine a second coefficient of reflection of said skin surface part to electro- magnetic radiation of said second wavelength, comparing said first and second coefficients of reflection with sets of coefficients of reflection representing coherent sets of coeffi¬ cients of reflection of said first and second wavelengths of specific states of redness so as to determine said individual's skin surface part's state of redness, converting said first and second coefficients of reflection into a set of corrected first and second coefficients of reflection of a specific state of redness, so as to determine said indi¬ vidual's skin surface part's coefficients of reflection of said first and second wavelengths at a specific state of redness, and converting said corrected first coefficient of reflection into a measure representing said individual's ability to become tanned or to stand exposure to ultraviolet radiation without causing said skin reac¬ tion. 2. A method according to Claim 1, further comprising the step of determining said individual's skin surface part's degree of pigmen¬ tation from said corrected first and second coefficients of reflection of said first and second wavelengths at said specific state of redness. 3. A method according to Claims 1 and 2, said specific state of • redness corresponding to an average zero blood flow state. 4. A method according to any of the Claims 1-3, further comprising the steps of: converting said second coefficient of reflection into logarithmic representation, and said sets of coefficients of reflection representing coherent sets of coefficients of reflections of said first and second wavelengths comprising coefficients of reflection of said second wave¬ length- presented in logarithmic representation. „-. An apparatus for determining an individual's ability to become tanned or to stand exposure to ultraviolet radiation without causing a skin reaction, such as skin cancer or erythema, comprising: a first electromagnetic source for generating electromagnetic radi¬ ation of a first wavelength and of a predetermined intensity and for di¬ recting said electromagnetic radiation of said first wavelength to a part of said individual's skin surface so as to expose said part of said individual's skin surface to said electromagnetic radiation of said first wavelength, a second electromagnetic source for generating electromagnetic ra¬ diation of a second wavelength and of a predetermined intensity and for directing said electromagnetic radiation of said second wavelength to said part of said individual's skin surface so as to expose said part of said individual's skin surface to said electromagnetic radiation of said second wavelength, a light-detecting means for measuring the intensity of electromag- netic radiation reflected from said part of said individual's skin sur¬ face, a measuring means connected to said light-detecting means for mea¬ suring the intensity of electromagnetic radiation reflected from said part of said individual's skin surface so as to determine a first and a second coefficient of reflection of said skin surface part to said electromagnetic radiation of said first and second wavelength, respecti¬ vely, a comparison and converting means connected to said measuring means for comparing said first and second coefficients of reflection with sets of coefficients of reflection representing coherent sets of coefficients of reflection of said first and second wavelengths of specific states of redness so as to determine said individual's skin surface part's state of redness, for converting said first and second coefficients of reflec- tion into a set of corrected first and second coefficients of reflection of a specific state of redness, so as to determine said individual's skin surface part's coefficients of reflection of said first and second wavelengths at a specific state of redness, and for converting said cor- rected first coefficient of reflection into a measure representing said individual's ability to become tanned or to stand exposure to ultravio¬ let radiation without causing said skin reaction. 6. An apparatus according to Claim 5, said light-detecting means comprising separate first and second light detector means for detecting electromagnetic radiation of said first and second wavelengths, respec¬ tively, reflected from said part of said individual's skin surface part. 7. An apparatus according to any of the Claims 5-6, said comparison and converting means further determining said individual's skin surface part's degree of pigmentation from said corrected first and second coef- ficients of reflection of said first and second wavelengths at said spe¬ cific state of redness. 8. An apparatus according to any of the Claims 5-7, said specific state of redness being an average Zero blood flow state. 9. An apparatus according to any of the Claims 5-8, said comparison and converting means further converting said second coefficient of re¬ flection into logarithmic representation, and said sets of coefficients of reflection representing coherent sets of coefficients of reflection of said first and second wavelengths comprising coefficients of reflec¬ tion of said second wavelengths represented in logarithmic representa- tion. 10. An apparatus according to any of the Claims 5-9, said first wavelength being of the order of 660 nm, and said second wavelength be¬ ing of the order of 550 nm.

Inventors: WULF HANS CHRISTIAN, WULF, HANS, CHRISTIAN
Applicants: CHROMO LIGHT APS, CHROMO-LIGHT APS
Application year: 1993
Main classification: A61B5
IPC codes: A61B5