FR2651112A1 - - Google Patents

Abstract

To quantify the behavior of the skin, on which a cosmetic product has been applied, with respect to solar radiation, an area (4) of the skin to be examined is illuminated with UVA radiation, and the intensity of the UVA radiation is measured. reflected at an angle (r) different from the angle of specular reflection so as to eliminate as much as possible the specular reflection and to appreciate essentially the diffuse reflection.

Description

!

  PROCESS FOR QUANTIFYING BEHAVIOR OF THE SKIN

  VIS-A-VIS THE SOLAR RADIATION, APPARATUS FOR

  IMPLEMENTATION OF THIS PROCESS, AND APPLICATIONS.

  The invention relates to a method for identifying the behavior of the skin, to which a cosmetic product has optionally been applied, vis

with respect to solar radiation.

  We know that the problem of evR] evaluation of the behavior of the skin vis 3. vis the radiation

  ! solar is complex but very important, in particular

  link for the determination of products to. apply

  on the skin to provide satisfactory protection

  doing. We also want to know the ability of the skin to resist aging caused by

solar energy.

  Various methods known at this time make it possible to assess the behavior of the

  skin, but ask to be am! iors.

  A first example of a known method consists in exposing the skin to UVB radiation (wavelength range 280 nm-327 nm) until it causes erythema. The measurement of the exposure time, for a given intensity of radiation, until the appearance of this erythema allows a certain quantification of the behavior of the skin with respect to solar radiation. This method, which involves a visual assessment of the erythema, is relatively

  empirical and gives approximate results.

  WO 88./05284 relates to an apparatus for 3- determining a sun protection index. This

  apparatus includes means for measuring the sensitivity

  ability of the skin to illuminate an area of the perau, preferably with a light emitting diode which: puts a green light with a wavelength of 560 nm, and suitable for measuring the radiation reflected by

the melanin layer.

Such a device while allowing

  to perform measurements is not fully satisfied

  doing because, on the one hand it works on wavelengths of the order of 568 nm whose action on the skin S is secondary and, on the other hand, it does not make a marked difference between specular reflection and

diffuse reflection.

  It has in fact been observed that the fraction of solar radiation which has the greatest share of responsibility for aging of the skin is that corresponding to the wavelength range 328 nm-A "nrm, that is to say - say the one corresponding to

UVA radiation.

  On the basis of the invention, it has also been found that the power of specular reflection of the skin to UIV radiation is substantially the same for the different types of skin while the power of

  diffuse reflection to UV radiation differs sensi-

  from skin to skin and that reflection differs

  92 fuse predominates over specular reflection.

  This diffuse reflection results from

  all the reflections from all the inter-

  skin faces encountered by the incident light beam, and takes place in various directions,

  92 while specular reflection takes place essential-

  ment in a direction of reflection symmetrical to the incident direction with respect to the normal to the

reflection surface.

  According to the invention, the method for quan-

  3 tifier, especially in vivo, the behavior of the skin, on which a cosmetic product has possibly been applied, with respect to a solar radiation is characterized by the fact that one illuminates an area of the little a. examine with UVA radiation, and that the intensity of the reflected UVA radiation is measured at an angle different from the angle of specular reflection so as to eliminate specular reflection as much as possible and to essentially assess the

diffuse reflection.

  Advantageously, we direct the beam

  UVA radiation incident in a normal direction

  male to the area to be examined and the intensity of the reflected LIVA radiation is measured in a direction of

  AS 'with respect to the incident direction.

  Preferably, the skin area to be studied is illuminated for a limited time, in particular less than

1 minute.

  The invention also relates to an apparatus for implementing the method defined above. UlJn such apparatus is characterized in that it comprises a source of UVA radiation arranged so that its beam is directed towards the area of skin to be studied and at least one reflection photoreceptor arranged so as to receive the radiation 2, UJVA reflected by the skin at an angle making it possible to eliminate specular reflection as much as possible and to essentially appreciate diffuse reflection, Preferably, the axis of the light source is arranged orthogonally to the area of the skin to be studied while the or each reflection photoreceptor is oriented at an angle of about 45 '

  relative to the axis of the light source.

  This light source is advantageously constituted by a directive halogen lamp, the spectrum of which is wide and the efficiency high for a low

  size. This lamp produces diffuse lighting.

  The lamp is combined with an IIUVA filter capable of only passing UVA radiation. This UVA filter

  is advantageously that known under the reference UG-

  3R I from the company SCHOTT Preferably, several reflection photoreceptors are provided for measuring the reflected intensity, these photoreceptors being arranged around the axis of the light source, with regular angular spacings. Reflection photoreceptors for ULVA radiation can in particular

link to be eight in number.

  The apparatus includes incident photoreceptor means capable of measuring the intensity of the light emitted by the source, to allow it to be compared with the intensity of the reflected light. The incident photoreceptors as well as the reflection photoreceptors are in particular constituted by photodiodes sensitive to LIVA; if these photodiodes are not already equipped with UVA and heat-resistant filters, such filters will be placed on the path of the incident light, in order to allow only the IUVA light to pass on the one hand and to avoid overheating of the diode on the other hand. The 29 photoreceptors can also be constituted by

  photoresistors sensitive to UIVA.

  The apparatus preferably includes a head comprising a cylindrical case fitted at the top with a halogen lamp and, in its lower half, a support for incident photoreceptors embedded in a cylindrical wall of said support and oriented radially, for the UVA filter arranged against a constriction of the support and for a sleeve comprising inclined cylindrical passages 3M regularly distributed corresponding to the

reflection photoreceptors.

  The device includes a timer, in particular

  culier controlled by a push button, suitable for

  switch on a13 light source for a relative time-

  ment short, in particular between one and thirty seconds. The device comprises means of storage, provided with digital displays, suitable for storing and displaying the relative information of a

  part at the intensity emitted and, on the other hand,.

  reflected intensity, before extinction of the source.

  Calculation means are provided in the apparatus for establishing, from this information, by comparison with a previously defined cell, a percentage

of reflection of UVA radiation.

  The invention also relates to applica-

  1M tions of the process defined above.

  A first application consists. when

  test the reflectivity of UrTVA radiation by 13 skin according to the subjects' phototype

  We were thus able to establish a significant correlation

  ficative between the percentage of reflection by the skin

and the assigned phoiotype.

  Another application is. quantifying the protective power against solar radiation

  of a product applied to the skin, as well as its

  92 resistance and its persistence @ .pr & s mechanical stress,

  biological, chemical or any other suscep-

  t aerate the presence of the product on the. skin.

  Finally, the method according to the invention makes it possible to determine the protection index of a product vis-à-vis UVA by means of the power of

  rf! exinn of this product measured with the device

  fnrme i l! 'nvention. There are currently two methods for valuating the protection coefficient of a substance against UVA. However, both have significant drawbacks:

  effect, the first (erythemogenic phototox-

  ) requires the local use of a photo-

  + oxic and does not allow immediate reading, the second (photo-oxidative pigmentogenic method) is only applicable to certain phototypes, and the reading of! pigment response is made delicate because of

thermal erythema.

  The invention consists, apart from the arrangements set out above, of a number of other arrangements which will be more explicitly discussed below in connection with an exemplary embodiment described with reference to the attached drawings but which

is in no way limiting.

  Figure 1 of these drawings is a diagram

  simplified device according to the invention.

  1 Figure 2 is a diagram illustrating the various phenomena of reflection and diffraction of a

  beam of light falling on an area of skin.

  Figure 3 is a vertical axial section of an embodiment of a device head according to

1 the invention.

  Figure 4 is a block diagram of a circuit

  electronic culits, of an apparatus according to the invention,

  associated with the head of the. figure 3.

  Figure S is a graph illustrating the 2.0 spectral distribution of the incident light, after passing through a UIVA filter, the wavelengths expressed in nm (nanometers) being plotted on the abscissa, while the intensity is plotted on the ordinate. 9 Figure 6 is a graph illustrating

the residual effect of a product.

  Figure 7, finally, is a graph illus-

  trating a classification into phototypes.

  Referring to the drawings, in particular to 3S in FIG. 1, it can be seen that a device A, according to the invention, making it possible to quantify the behavior of the skin with respect to solar radiation, comprises a source 1 of UVA radiation constituted by a directive 2 halogen lamp, having a wide spectrum, combined with a UIVA 3 filter placed on the path of the incident light and suitable for passing only

UVA light.

  Such a filter can be for example that

  designated by the reference UG-11 from the company SCHOTT.

  The spectrum of incident light, pro-

  coming from the halogen lamp 2, after having crossed the filter 3, is illustrated in FIG. 5 representing the intensity + range on the ordinate as a function of the wavelength plotted on the abscissa. We see that the intensity of the incident beam is concentrated in the wavelength range 320 nm-400 nm which

corresponds to UVA.

  The halogen lamp 2 has several advantages

  tages compared to lamps. class UV radiation

  sics. The halogen lamp is small and operates under low voltage, which simplifies insulation problems. Lamp 2 produces diffuse lighting distributed over an area of approximately 1

  cm2 ?, corresponding to the surface 4 of the skin examined.

  Unlike the halogen lamp, the

  ! am.pes UV clpssiques are in general! of significant size

  aunt and otherwise dangerous because of residual ULVC. In addition, conventional UV lamps require a high voltage which causes

insulation problems.

  The switching on of the lamp 2 can be controlled by a push button 5 which triggers a

  timer 6 ensuring the supply of the lamp 2 during

  advantageously limited and adjustable time

  between one and thirty seconds.

  The X axis of the lamp 2 is arranged ortho-

  gonally zone 4 of the skin to be studied.

  At least one incident photoreceptor 7 is provided to measure the intensity emitted by the lamp 2 and

  receive part of the beam of! incident light

  The photoreceptors 7 are advantageously constituted by photodiodes sensitive to UVA. If these

  are not already fitted with UIVA and antica filters! o-

  specific, such filters will be placed on the tra

  jet of incident light in order, on the one hand, to allow only the UIVA light to pass through and, on the other hand, to prevent the diode from heating up. As a variant, the incident photoreceptors 7

  may consist of photoresistors

  UVA, doji-capable with UIVA filter and anti

  calorific. ! The device comprises an electronic assembly 8, one terminal of which makes it possible to energize the photoreceptor 7 via a connection line 9, another terminal of the assembly R is connected to the energized terminal of the photoreceptor 7 by an electrical resistance 10 making it possible to obtain a signal representative of the incident light intensity falling on the photoreceptor 7. The other

  photoreceptor terminal 7 is connected to ground.

  At least one reflection photoreceptor 11 9 is provided for measuring the intensity of the UJVA radiation

  reflected by the surface 4 salivating an angle L allows

  so much to eliminate speculative reflection as much as possible and

  to essentially appreciate diffuse reflection.

  The angle r between the direction of the photoreceptor 11 and the. normal the surface A is different from the angle of specular reflection which, in the example considered, is bare! so that the direction of

  the axis of the incident beam is normal to the surface 4.

  Remember that the specular reflection is maximum

  3 for an equal angle of reflection! i the angle of incidence.

  The angle r enters! direction of the axis of the

  photoreceptor Jr of reflection 11 and normal to over-

  f2ce A is preferably equal to or close to AS ', which

  allows you to essentially appreciate the different reflection

fuse.

  The photoreceptor! 1 is connected in a similar manner to the photoreceptor 7) to terminals of the electronic assembly 8 by a ga link and a

resistanoe 1, B and to ground.

  Reference is now made to the diagram in FIG. 9 illustrating the phenomena of reflection and re-emission at level 1 of an area 4 of skin formed when the layer is passed from the outside to the inside. cornea 19, of the living epidermis! 3 and of the dermis a.,!. When a light beam 15 reaches the surface of the zone 4, a part 16 is reflected, by 11 horny layer 12, at an angle of reflection equal to the angle of incidence. Another part 17 penetrates into the skin where it undergoes diffraction and absorption phenomena. A fraction 18 is re-emitted, from a different angle from that of specular reflection, by the epidermis. Another fraction 19 corresponding essentially to diffuse reflection, is re-emitted by the dermis. It is these fractions 18 and 19 which are

  920 mainly taken into account by the device A

  form 3! invention. It has been demonstrated that these fractions 18 and 19, for incident UVA radiation, allow a good appreciation of the behavior of the skin with respect to the LIVA fraction of sonar radiation. It has been found that with a device conforming to

  the invention the measured intensity of the diffe

  fuse ensures a quantification of the behavior

  of the. skin allowing to find and specify -3.0 a classification in phototypes linked to that mentioned below, Figure 3 illustrates a replication of a tfte of device! according to the invention. This + fte includes a cy! Indric shoemaker 2_0 quip6, in the upper part of the halogen lamp 2, arranged coaxially with the shoemaker. The bottom case 27 is provided, in the upper part,! a fan 91 and openings making it possible to establish a circulation of cooling air, inside the case. the support 22, the shape of which is visible from FIG. 3, is provided in the lower half of the case 20 to support, appreciably at mid-length, the incident photoreceptors 7 embedded in a cylindrical wall of the support 99 and radially oriented. These photoreceptors 7 are two in number regularly and allow to

  measure the intensity of the incident light.

  The upper end of the support 22 surrounds

  the lamp 9 and is provided with holes 229 for a circulation

tion of air.

  L - UVA 3 filter is arranged orthogonally

  1! The axis of the boot 20 and is held against a strut

  regulation 23 of the support 29 on the side of the photoreceptors 7 opposite to the lamp 2. A sleeve 2A is mounted in the throttle 9-3 and has a central cylindrical passage. 1 9 of smaller diameter limiting 2.0! 'Opening of the incident beam on the surface A. The sleeve 24 has eight cylindrical passages 26 in! Ins 45' relative to its axis, regularly distributed. These passages 926 are diria4s towards! 'Lower end of the sleeve 22 formed by a 9 csorte of pisa washer 27 having a central opening 28 of reduced diameter, for example of the order of one centimeter. This opening 28 is suitable for being applied against the surface to be examined and

  determine the area on which the measurement is made.

  Eight reflection photoreceptors They are distributed regularly around the axis of the housing 29 and are arranged in housings 29 provided on the support 22 in the vicinity of the bottom of the passages 2 9R. Ies axes of photoreceptors 1il are located on a supple suppressor admitting the angle r = 45 'as a half-angle

  at the top and with the same axis as that of the bolt bolt 20.

  !! A cable 30 penetrates radially in the upper part of the boot 20 and comprises the conductors for the electrical supply of the lamp 2, and for the connections between the various photoreceptors 7 and 11 and the electronic means 8, the diagram of which is given.

in figure 4.

  The push button 5, control%% 'aliupmge of the lamp 2, is also provided in! cylindrical wall of the housing 20, in the upper part, so

1 To project radially.

  The electronic means R, as illustrated in FIG. 4, comprise an assembly 31 for the feed of the phoforemmturs 7 and 11 .; this

  together 31 also provides the power supply and I

  1 mende of display circuits 32, 33 respectively for the rf! Chi flow and for the incident flow, the power supply of the photoreceptors of

  reflection 1l is ensured by means of a circuit

  cooked conditioner 34 which further includes a 2? clean amplifier! receive and amplify the signa] from photoreceptors l! and i send, as an output, this signal representative of the reflected intensity on the display means 32 and on a terminal of an onnnector 35. Means 36, 37, in particular 92 constituted by potentiometers, are provided for adjustment of the amplifier gain and offset

conditioner circuit 3 /.

  A conditioner circuit 38, similar to circuit 34, is provided to supply the 3. photoreceptors 7 and process the signal produced by these photoreceptors to send this signal to the means of display 33 of the incident flux and to another terminal of the connector 35. Potentiometers 39, aP are

  provided for the adjustment of the daelge and the ain of the eir-

  cuit conditionneu1r 3.R es circuits 34 and 38 are re! 1 = i terminals of a connector 41 eL !! es are intended to be connected to the respective photoreceptors. the circuit 42 is provided for controlling the lamp 9. This circuit may include a timer triggered by the push button, two terminals of this circuit being connected to terminals of the connector 41. This circuit 42 has an output connected to a circuit a4 for regulating the intensity of the supply current of the lamp 2. The supply of this lamp 9 is carried out 1. by means of a circuit 44, under control of the circuit 43. The electrical supply to the fan 91 is also provided by the circuit 44, two terminals of which are connected to the connector 41. The lamp regulation circuit 43 is first connected. a terminal of connector 35, as well as the lamp control circuit 42. Connector 35 is

  designed to be connected to a mini-computer which takes

  would then be in charge of managing the measurements and

  operation of the apparatus according to the invention.

  9. This device allows the. implementation of

  method of the invention, in the following manner.

  As illustrated in Figure 3, the head of the device! is applied against area 4 of skin to

study.

  A measurement is then triggered by pressing the push button 5, which causes the irradiation, by UVA, of the zone 4 and the measurement of the quantity of reflected light, with display of the

  results. This measurement method is simple, not

  3 invasive, and can be applied both in vivo and

  in vitro to assess the behavior of the skin.

  with regard to solar radiation, especially to

With regard to UVA rays.

  Many applications are possible.

  3R5 The device allows, for example,

  tify the protective potential of a product intended to be applied to the skin, its persistence and persistence. A result of tests and measurements is given below, in conjunction with the diagram in FIG. 6. The measurements were intended to determine the protective power UVA of a foundation and the persistence of this power during time. The

  protective power was estimated by the apparatus con-

  form the invention, in vivo, raising the percentage

  1 tare for reflective skin of the make-up face! L. The

  The measurement protocol was as follows.

  A measurement of reflection was carried out on bare skin without makeup or care products, at the instant TO. The skin of the visa ge was then W made up by the foundation at a rate of 1 m / m2f.9 Fifteen minutes after application, pulis two hours, four hours and six hours later,

  reflective measurements were carried out.

  The study was carried out on seven models of 27 Il and Ilr phototypes (see below). The recorded parameter,] or measurements, was the percentage of reflection. This percentage was calculated from the measurements of the subject's skin, taking into account the calibration curve of the device. This curve is obtained by measuring standards with different reflection indices. This parameter corresponds to. the capacity of the surface measured To reflect the UVA radiation emitted by the lamp 2 and filtered by 3, The results are presented in the table

0 below.

% REFLECTION TIME

TO 3_ _2

  T15mn 29.59 3Sq T2h 29.51 Tàh 30.R82 1k T6h 31.77 If the surface of the skin is covered with a product capable of absorbing photons, the percentage of reflection will decrease compared to this same sur-

  bare face. This is what we have seen.

  An analysis of variance followed by a

  multiple parison indicates on the one hand that makeup

  by the foundation persists in the IUVA until T4h.

  1 However, only the comparison between T! 5 min after

  application and the T6h reveals a significant difference

t ive.

  In addition, the comparison between bare skin and make-up skin over time indicates a significant difference in the reflectivity of UIVA.

  for times T15 min after application and T2h.

  The results of these tests, summarized by the diagram in Figure 6, where time is increased.

  Pbscisse and the power of reflection on the ordinate, per-

  29. "put to conclude that the make-up of the skin of the vicsage by the foundation persists, in vivo,

until time T4h.

  The potential to filter radiation + RIVA from

  make-up facial skin is increased signif4-

  2 tively by the presence of the foundation 15 min and 2 h after application. This result confirms that the product

  tested is able to protect the skin of the face and

  kills an element of fight against skin aging caused in particular by UIVA radiation

3 sO3.ire.

  Another application quantifies the spontaneous ability of the skin to reflect UrVA

according to the phototypes.

  We give, below, the classific aion habi-

  rueelle des phototypes, which is not really a result of quantification but of observations

qualitative and arbitrary.

  The signs + used in this table indicate, according to their number, the importance, for the phototype considerS, of the parameter of the column in

S cause.

  These phototypes correspond to a classification

  according to the behavior of 1 skin vis-à-vis the rayon-

solar.

  ! 0 Photo- Cama Hair- Eph- Tanning shot type sun lides O albino whites O constant +++ O! milky red + + + constant ++ 1! light blonde + + constant + h! e! ger! IIA light blonde + frequent ha! ec! mir ou !! IF ch- mate + frequent hale fonc taina IV mate brown 0 rare fonc V mate brown O excep- trms dark tional Vr black black O absent black __ A study was carried out on a group of 31 people belonging to phototypes 1 !, tII and IV by measuring the ref! exion power in IUVA with a

apparatus according to the invention.

  _the results of this study are 3O represented schematically in Figure 7 by three

  points representing] the mean values for pho-

  totypes tl, III and IV, spaced along the x-axis. The average for the phototype It is established ^

a value of 35.6% reflection.

  For the JI phototype, the average is 39.8%. For phototype IV, the average is established

9.65%.

  The higher the e5t phototype, the more

  diffuse reflection is weak because the subjects of photo-

  high type have an epidermis rich in more suitable melanins. absorb UV radiation. This study therefore makes it possible to quantitatively differentiate the photnotypes; indeed, the device! quantifies the ability of the skin to react to UVI ef 1. this quantification is independent of

qual] itative assessments.

  The device according to the invention is portable and allows measurements to be made quickly and without difficulty, in vivo or in vitro. The support can be biological (horny layer, nails) or chemical (cellulose acetate, co sheets _ 1 ç_ A e A t7

Claims (11)

RESELL! CAT! 0 NS   1. Method for quantifying behavior   of the skin on which a cosmetic product has   kills! Lets be applied, vis-à-vis the solar radiation characterized by the fact that one lights a zone rfh? of the skin to be examined with UVA radiation and that the intensity of the U! VA rf! lchi radiation is measured at an angle Cr? different from the specular reflection angle so as to eliminate as much as possible !! specular reflection and to appreciate essentially diffuse reflection.   7. Procedure according to claim 1, characterized in that the beam is directed   radiation incident I! VA in a normal direction   However, I have to examine the area (4) 3 and measure the intensity of the reflected UVA radiation according to a   direction of 45- with respect to a. incident management.   3. Method according to claim 1 or 2, characterized in that the area (4) of 92 skin is illuminated. study for a limited time, less than! minute. 4. Apparatus for implementing the   process according to one of claims 1 b 3,   characterized by the fact that it includes a source (1)   of UVA radiation arranged so that its   c-thirsty directed to the area (4) of skin f to study and at least one reflexion photoreceptor (1!) arranged so as to receive the UiVA radiation reflected by! skin following an angle (r) making it possible to eliminate Ru   3g maximum specular reflection and appreciate essen- so diffuse reflection.   5. Apparatus according to claim 4, charac + ris by the fact that the axis (X) of the light source is disposed orthogonally to the area (4) of -9 the skin to be studied while the or each reflection photoreceptor ( 11) is oriented along 18R an angle of about 45- with respect to the axis (XI of the light source.   6. Apparatus according to claim 4 or 5, characterized in that the light source (! S is constituted by a halogen lamp (23, whose spectrum is wide and the high efficiency for a small footprint, the above halogen lamp (2 ? producing diffuse lighting.   7. Apparatus according to claim 6, 1P characterized in that the halogen lamp (2) is combined with a UVA filter (3) suitable for leaving pass that LIVA radiation.   8. Apparatus according to any one of   Claims 4 to 7, characterized in that   ! 5 several, in particular eight, reflection photoreceptors (11) are provided for measuring the reflected intensity, these photoreceptors (11) being arranged around the axis of the light source, with regular angular spacings.   9. Apparatus according to any of the   Claims 4 to 8, characterized in that it   includes incident photoreceptor means (7) capable of measuring the intensity of the light emitted by the source 1 B. 92 10. Apparatus according to any one of the   Claims 4 to 8, characterized in that it   comprises a head comprising a cylindrical case 9 (2) equipped, in the upper part with a halogen lamp (21 and, in its lower half, with a support (22) for incident photoreceptors (7) embedded in a   cylindrical wall of said support (22) and oriented radially   Also, for the UVA filter (3) disposed against a throttle (293) of the support (22) and for a sleeve <24) having inclined cylindrical passages (96) regularly distributed corresponding to the   reflection photoreceptors (11).   1g 11. Apparatus according to one that!   Claims 4 to 1, characterized in that i!   includes a timer (6), in particular controlled by a push button (5), suitable for a. turn on the source   S bright (1) for a relatively short time.   12. Apparatus according to claim 11, characterized in that it includes storage means, provided with digital displays (32, 33):   suitable for storing and displaying related information   on the one hand, the emitted intensity and, on the other hand, the reflected intensity, before extinguishing the source and the calculation means to establish, from this information, by comparison with a defined scale.   beforehand, a reflection percentage of the ray- IJVA ment.   13. Application of a procedure according to one of the   claims 1. to. the establishment of a classification   quantified cation of the skin linked to phototypes.   14. Application of a procedure + according to one of claims 1 to 3, to the quantification of the protective power against solar radiation of a product applied to the skin, of its persistence and of its persistence t5 Application of a method according to !'one of the   claims 1 to 3 ,. determining the index   protection of a product with respect to UJVA.