RU2785284C2 - Skin gloss measurement, using brewster angle - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: group of inventions relates to medicine; it can be used for skin gloss measurement. A system containing a machine-readable carrier is proposed for implementation of a method for detection of skin gloss, using a system containing a sensor, while the sensor contains n spatially spaced light sources made with the possibility of emission of unpolarized visible light of the source, wherein a value of n is at least three, a detector made at the first distance selected from a range of 10-80 mm from each of light sources and made with the possibility of detection of polarized light; and a polarizer made to the detector, wherein the polarizer contains one or more of a segmented polarizer and a polarizer of spatially changing polarization, the segmented polarizer contains a pixel polarizer of a wire mesh with n pixels having polarization orientations perpendicular to each other. Moreover, the system contains a case containing the sensor, and the case has the first hole providing a viewing field for the detector. In this case, the method includes subsequent emission of source light from the specified n spatially spaced light sources, wherein source light is emitted with optical axes at an angle of incidence, selected from a range of 50-60°, with the skin at the second distance set as a distance between the first hole and the detector or as a distance between the first hole and the last optical element in front of the detector, if viewed from the detector; detection of subsequently reflected source light subsequently generated by light sources; and generation of detector signals corresponding to the detected reflected light.

EFFECT: group of inventions provides for an increase in the efficiency of skin gloss measurement, using the Brewster angle.

11 cl, 24 dwg, 1 tbl

Description

The invention relates to a system containing a sensor for measuring skin gloss. In addition, the invention relates to a method for evaluating the gloss of the skin.

BACKGROUND OF THE INVENTION

Skin gloss problems are known in the art. US2015127071 (see also the equivalents of US9452113B2 or WO2013186716A2) refers to oily skin care and describes that the skin is rich in sebaceous glands and continuously regenerates. In addition, US2015127071 describes that sebum secretion is a normal phenomenon that is beneficial for both skin and hair. In general, sebum is an agent for moisturizing the epidermis. It is a natural product of the sebaceous gland, which is an outgrowth of the pilosebaceous complex. Essentially, it is a more or less complex mixture of lipids. Sebum protects the skin as well as the scalp and adds shine to the hair by lubricating the cuticle.

According to US2015127071, sebum hypersecretion or seborrhea can lead to appearance disorders. Thus, excess sebum secretion can lead to oily skin that looks shiny or iridescent, and it can also make the scalp look oily and dandruff, or greasy dandruff. This may be accompanied by an increase in pore size. For example, stress, fatigue, and winter can be factors that exacerbate these conditions in most people. Among people with oily skin, there may be subjects who have endocrine disorders or neurological disorders, or subjects suffering from obesity. In addition, oily skin can be found in teenagers, in people suffering from an excess of hormones (particularly male hormones), in women who are menstruating, or in women who have gone through menopause.

US2003045799 describes a portable body type monitoring device. For example, this device can be used to monitor at least one characteristic of the appearance of the skin or hair. The device may provide at least two images of the region of interest. The images differ from each other in a feature other than the magnification and intensity of the light source.

US2010249731 describes a method for measuring skin erythremia, which includes: a) obtaining a digital image of the skin under orthogonal polarization conditions with a white calibration standard included in the field of view of the image; b) identification of mean intensity values for red, green and blue channels for the white standard; c) calculating the skin reflectance values given by the red, green and blue intensities of each image pixel to the absorbance values by taking the logarithm of the ratio of the white standard values divided by the skin reflectance values in each of the red, green and blue channels, respectively where absorbance is: log(Iwhite(red, green, blue) / Iskin(red, green, blue)) for all pixels representing skin; d) subtracting the absorbance values of the red channel from the absorbance values of the green channel for all pixels representing the skin; e) subtracting the absorbance values of the red channel from the absorbance values of the blue channel for all pixels representing the skin; f) calculating the ratio of the value calculated in step (d) divided by the value calculated in step (e); g) building an intensity map for the ratio calculated in step (f).

US2014055661 describes an imaging apparatus comprising an optical system with lenses, an imaging apparatus comprising a plurality of first and second pixels, and an array optical device, the optical system with lenses comprising a first optical region that mainly transmits light oscillating through itself. in the direction of the first axis of polarization, and the second optical region, which passes through itself the light oscillating in any direction; and the matrix optical device ensures that the light that has passed through the first optical region is incident on the first pixels and the light that has passed through the second optical region is incident on the second pixels.

JPH07323013 describes a method for observing a skin surface by separating light reflected from a skin surface into two light paths and simultaneously receiving reflected light with different polarization components from a first light receiving filter and a second light receiving filter. The first polarized light filter for receiving light is built into the light path for light passing through the translucent mirror among the light reflected from the skin, and in addition to the light path for reflected light on the mirror, the second polarized light filter is installed to receive light with the polarized light direction, different from that of the first polarized light filter for receiving light. Then, the specific polarized light is emitted to the skin through the polarized light filter from the ring light, and the reflected light is received by the first CCD camera (Charge Coupled Device) through the first polarized light filter to receive the light. In addition, light reflected from the skin is received by the second CCD camera through a second polarized light filter to receive light, and these image signals are input to the same image processing part.

DISCLOSURE OF THE INVENTION

The appearance of the skin is strongly influenced by the presence of a thin emulsified film on the surface of the skin. Sebum, containing lipids from the sebaceous glands and epidermal keratinocytes, mixes with sweat and other lipids from cosmetics and the environment to form this emulsified film with a refractive index higher than that of the epidermis. Sebum makes the skin appear shinier due to the higher Fresnel reflectance and the smoother interface between air and sebum. The optimal balance between production and sebum requirements provides a feeling of lack of shine and healthy skin, and is also desirable from a dermatological and cosmetic point of view. Shiny and oily skin is considered unattractive and unpleasant, and is often associated with various dermatological disorders such as seborrhea, acne, and hormone imbalances. In conditions of sebum deficiency, the skin is prone to infections and there is a feeling of itching, dryness and looks dull, erythematous and scaly.

As a result, it is believed that strategies are needed to balance the needs of the skin with the optimal requirements for its lipids by controlling the rate of sebum secretion and/or monitoring the condition of the skin using non-invasive optical devices and methods.

Devices for measuring the degree of gloss of the skin are known from the prior art. However, they may, for example, have the disadvantage of depending on the position of rotation on the skin and/or may not be able to provide quantifiable results. Thus, it is an aspect of the invention to provide an alternative device (hereinafter, the more general term "system" is used herein) and/or method for determining skin luster, which preferably further at least partially eliminates one or more of the disadvantages described above. It may be an object of the present invention to overcome or eliminate at least one of the disadvantages of the prior art, or to provide a useful alternative.

Among other things, the invention provides a system ("system" or "skin sensor system") comprising a sensor for measuring a skin parameter, such as selected from one or more of the group consisting of skin luster and skin oiliness ("sensor" or “skin gloss sensor”), wherein the sensor comprises (i) a plurality of spatially separated light sources configured to output source light (“light”), and (ii) a detector configured at a first distance (d1) from each of the sources light, and the sensor is configured to output light source with optical axes (OL) at an angle (α) of incidence, in particular, selected from the range of 10-80°, with skin at a second distance (d2) and with the possibility of detecting the reflected light of the source ( reflected from the skin), and the sensor contains at least two light sources, in a more particular case, at least three light sources, and the light sources, in particular, are configured to issue unpolarized light source nick, in the more particular case - white light, and the first distance (d1), in particular, can be selected from the range of 1-100 mm, for example 5-80 mm, in particular 5-60 mm, in the more particular case - 5- 50 mm, for example, in particular 5-30 mm, and the detector is configured to detect polarized light.

With such a system, it is possible to determine the luster of the skin in a relatively reliable manner with reduced influence from the rotation of the sensor relative to the skin. In addition, thanks to such a system, it is possible to quantify the luster of the skin. As used herein, the term "skin luster" refers to the luster of the skin, but can also refer to "oily skin". Thus, as used herein, the term "skin luster" can also be defined as "a skin parameter that is specifically selected from one or more of the group consisting of skin luster and skin greasiness". The values that can be measured with the system described herein may reflect skin luster and skin greasiness, since skin luster may be related to skin greasiness. In this document, the term "skin luster" is sometimes used to refer to both the luster of the skin and the greasiness of the skin. Thus, in embodiments, the term "skin luster" may refer to the luster of the skin or the oiliness of the skin, or specifically to the luster of the skin.

As indicated above, the invention provides a system containing a sensor. The term "system" can refer to a single device, for example, having its own housing, but it can also refer to a plurality of functionally interrelated devices, such as, for example, a sensor and a control system, or a control system containing a device, such as a computer, smartphone etc. In embodiments, the term "sensor" can also refer to a plurality of sensors.

In particular, the system comprises a housing such that the system comprises a device comprising a housing. Essentially, the sensor may be in the housing. The body may have an opening. Such an opening may provide a field of view for the detector. In addition, the hole body can also provide a second distance, which can be defined as the distance between the hole (i.e. skin when the sensor is made on the skin) and the detector (or the last optical element, in particular a lens, in front of the detector (when viewed from the detector. The second distance can also be specified as the free working distance and can be given as the distance between the hole and the detector or, when optics are available, between the hole and the last optic (when viewed from the detector towards the hole). Thus, the second distance may also be indicated as the distance during operation between the skin and the detector or, when optics are available, between the skin and the last optic (when viewed from the detector towards the hole). It can be seen that the housing is designed as a distance-keeping device, since it determines the distance between the skin and the detector (or its last optical element). Such optical elements are made before the detector, i.e. the detector is made downstream of such (optional) optical elements. The second distance may be in the order of 10-45 mm, however it may even be up to 200 mm. Thus, in embodiments, the second distance may be selected from the range of 10-200 mm, such as 10-30 mm, or be in the range of 40-80 mm. The detector is configured to detect reflected light. Thus, the detector detects reflected light to form images during (successive) illumination by light sources (unpolarized). The detector essentially detects only polarized light, for example by means of a polarizer upstream of the detector. The optical axis of the detector and the optical axis of the sensor may be substantially the same. In addition, the optical axis of the sensor and the resulting optical axis of all light sources may substantially coincide.

In particular, the light sources are designed such that they are at a first distance from the detector which is less than the (relevant) field of view (dimensions). In addition, the plurality of light sources may particularly comprise sets of two (or more) light sources that are provided at the same distance from the detector. Such sets can be managed independently. In addition, the first distances are not necessarily the same for each of the light sources. Thus, the expression "the detector is made at a first distance (d1) from each of the light sources" and similar phrases can also be interpreted as "the light sources are made at first distances (d1) from the light sources, and the first distances for each of the light sources can be be identical, or there are two or more different first distances. As stated herein, the first distance may be selected in particular from the range of 1-100 mm.

Thus, the invention (in aspect (also)) provides a system comprising a sensor for measuring a skin parameter, comprising (i) a plurality of spatially separated light sources configured to output source light, and (ii) a detector configured at a first distance from each of the light sources, and the sensor is configured to output light source with optical axes at an angle (α) of incidence selected from the range of 10-80°, and during operation, the sensor (should be) installed on the skin, the hole in the sensor housing should be on the skin and is configured to detect the reflected light of the source (which is reflected by the skin), and the sensor contains at least three light sources, and the light sources are configured to output visible light of the source, and the visible light of the source is unpolarized, and the first distance is selected from range 10-80 mm, and the detector is configured to detect polarized light. The system may contain additional features as defined in the accompanying embodiments.

The system may include a memory, a processing device (or a "processor" or a "processor system" or a "controller" or a "control system"), a user interface, and a display unit for indicating a particular skin gloss value, such as an LED indicator (for example, suitable for indicating different values by switching to 0-n LEDs depending on the determined value, where n is the number of LEDs used to indicate the maximum determined value, with n generally greater than or equal to two, e.g. at least three) and/or display.

Examples of a user interface include, among others, a manually activated button, a display, a touch screen, a keyboard, a voice activated input device, an audio output device, an indicator (eg, lamps), a switch, a toggle switch, a modem, and a network card. In particular, the user interface may be configured to allow the user to instruct the device or apparatus with which the user interface is operatively interfaced, whereby the user interface is operable. In particular, the user interface may include a manually activated button, touch screen, keyboard, voice-activated input device, switch, toggle switch, etc., and/or, if necessary, a modem and network card, etc. The user interface may include a graphical user interface. The term "user interface" can also refer to a remote user interface, such as a remote control. The remote control may be a separate special purpose device. However, the remote control may also be a device with an application (App) configured to (at least) control the system or the device or apparatus.

The controller/processor and memory can be of any type. The processor may be configured to perform the various operations described and execute instructions stored in memory. The processor may be a specialized task or general purpose integrated circuit(s). In addition, the processor may be a special purpose processor for operation in accordance with the present system, or may be a general purpose processor in which only one of a plurality of functions for operation in accordance with the present system operates. The processor may operate using software, a plurality of software segments, or it may be a hardware device using an ASIC or multifunctional integrated circuit.

The sensor comprises (i) a plurality of spaced light sources configured to output source light ("light"). In particular, the sensor comprises at least three spatially separated light sources.

The term “light source” may include a semiconductor light emitting device such as a light emitting diode (LED), cavity cavity light emitting diode (CED), vertical cavity laser diode (VCR), edge emitting laser, etc. The term "light source" can also refer to an organic light emitting diode such as a passive matrix (PMOLED) or an active matrix (AMOLED). In a particular embodiment, the light source comprises a solid state light source (such as an LED or a laser diode). In an embodiment, the light source comprises an LED (light emitting diode). The term LED may also refer to a plurality of LEDs. In addition, in embodiments, the term "light source" can also refer to a so-called chip-on-board (COP) light source. The term "CNR" specifically refers to LED chips in the form of a semiconductor chip that is not enclosed or connected, but mounted directly on a substrate such as a printed circuit board. Thus, a plurality of semiconductor light sources can be installed on the same substrate. In embodiments, the CNR is a die with a plurality of LEDs arranged together as a single illumination module.

In addition, the light sources are configured to output unpolarized source light. This allows the sensor to obtain information from the direction of polarization of the reflected light.

In addition, the light sources are in particular designed to emit white light. As used herein, the term "white light" is known to those skilled in the art. In particular, it may refer to light having a correlated color temperature (CCT) of about 2000 to 20000 K, in particular 2700 to 20000 K, for general illumination, in particular in the range of about 2700 K to 6500 K, and for purposes backlight, in particular, in the range from 7000 K to 20000 K, and in particular, within about 15 SOTS (color alignment standard deviation) from the BBL (black body locus), in particular, within about 10 SOTS from the BBL , even more specifically, within about 5 SOCVs of the BRT. In particular, white light may be emitted by a blue LED with a yellow emitting luminescent material. Such a light source may produce white light that is substantially unpolarized.

The sensor contains a plurality of spatially separated light sources. This implies that there is some distance between the light sources. In particular, a detector is provided between the light sources. In addition, the maximum number of light sources is specifically about twelve, such as ten, eight, six, or four, or three. Up to about twelve, even more specifically up to about eight, such as up to about six, provides a configuration around the sensor, which also provides a spatial separation between adjacent light sources, which (also) can be on the order of about 1-100 mm, for example, at least at least 5 mm, for example at least 10 mm.

Thus, in embodiments, the system comprises at least three light sources. In still other embodiments, the sensor has an optical axis of the sensor, and the light sources are axisymmetric about the optical axis of the sensor. In embodiments, the light sources can be made relative to each other at angles with an optical axis of 360°/n, where n is the number of light sources. Thus, in embodiments in which the system contains at least three or four light sources, the mutual angles with the optical axis can be 120° and 90°, respectively.

Thus, as stated above, the system comprises, in particular, at least two light sources, more specifically, at least three light sources, and the light sources, in particular, are configured to emit unpolarized visible light of the source, more specifically , white light.

In embodiments, the system may in particular comprise a plurality of light sources emitting visible source light, wherein the source visible light is unpolarized, in particular substantially all of the source visible light is unpolarized. In particular, each of the light sources outputs substantially unpolarized visible source light. Thus, in these embodiments, unpolarized source light is radiated onto the skin, wherein the source light is not substantially partially polarized. Thus, the light sources are particularly adapted to emit visible light from the source, the visible light from the source being unpolarized.

As also noted above, the system also includes a detector located at a first distance (d1) from each of the light sources. Good results were obtained when the first distance (d1) was in the range of about 1-80 mm. Thus, in a specific embodiment, the first distance may be selected from the range of 1-80 mm, in particular from the range of 1-80 mm, in particular from the range of 2-60 mm, such as the range of 5-20 mm, for example the range of 6-14 mm.

In particular, the detector is configured to detect polarized light. To this end, the detector may include a polarizer which is provided prior to the detector. Thus, the detector can only receive polarized light, in particular S-polarized light. Some specific embodiments of the polarizer are also described below.

In particular, the detector is configured to detect polarized light. Thus, the sensor may include a polarizer upstream of the detector. The polarizer can filter the reflected light of the source (reflected from the skin) such that the detector receives polarized light, in particular S-polarized light, or alternatively in particular P-polarized light.

In specific embodiments, the sensor is configured to output light from a source with optical axes (OL) at an angle (α) of incidence, in particular selected from the range of 10-80°, with skin at a second distance (d2), and with the ability to detect reflected light source (reflected from the skin). Of course, the skin is not part of the system. However, the system is particularly configured to measure the skin at a second distance. For example, the system may include a spacing device or other element that allows the sensor to be mounted at a second distance. With this distance, the above angle of incidence, which is in the range of 10-80°, more specifically 20-80°, can be achieved. In specific implementations, which are further described below, the angle is selected from the range of 20-60°.

The distance keeping device is configured to be placed on the skin so that the skin is a second distance from the detector or the last optical element in front of the detector (when viewed from the detector). In particular, the distance maintaining device may be arranged to be positioned flat on the skin such that the skin is a second distance from the detector or the last optical element before the detector (when viewed from the detector). The distance maintaining device may be contained in the sensor housing. In particular, the system may comprise a housing which at least partially encloses the sensor, the housing comprising a spacing device. Alternatively, the system may comprise a housing and a (separate) spacing device; in such embodiments, the second distance may be further increased. In addition, the distance-keeping device other than the housing may have an opening.

The system, or at least part of it, such as the housing, may be configured to be pressed against the skin. Thus, "to the skin" may indicate that the system or at least part of it is pressed against the skin (during use), in particular, while maintaining a distance device, such as a housing, is pressed against the skin. Thus, the term "second distance" specifically refers to the distance between the detector or its last optical element (as viewed from the detector) and the skin during application of the system. The second distance is a non-zero distance between the hole/skin and the detector (or an optical element located before the detector, when such optical elements are available). In particular, the term "optical elements" here may refer to a lens.

In particular embodiments, the detector comprises a 2D camera such as a TD-Next 5620 M7_1A and TD-Next 5640 M12_3B CCD camera. Each pixel may consist of essentially three pixels for blue, green, and red, respectively. This can provide the detector with the blue, green, and red intensity channels separately.

In embodiments, the detector may have a detector area of about 10*10 mm ² . The detector may be of the order of 1 megapixel or more.

In still other embodiments, the sensor may also include a focusing lens upstream of the detector. The focusing lens can be configured such that the detector is in focus on one side and/or the skin is in focus on the other side of the lens. The lens can provide a good image of the skin on the detector.

In embodiments, the sensor may also have an opening upstream of the detector and upstream of the focusing lens. This may further add to the resolution. In embodiments, the hole diameter may be selected from the range of 0.1-5 mm, more specifically 0.1-2 mm, for example, in particular 0.1-0.8 mm.

The optical axis of the system can run perpendicular to the detector.

In particular embodiments, the system may also comprise an analysis system. The analysis system is configured to generate an appropriate skin sensor value depending on the signal from the sensor. The analysis system and the sensor may be in the same device, such as a skin cleansing device, a skin rejuvenation device, and so on. Thus, in embodiments, the system comprises a skin care device such as a skin cleanser, skin rejuvenation device, etc., the skin care device comprising a sensor and an analysis system. The analysis system may convert a signal from a sensor, more specifically a detector, into a signal that may contain useful user information, such as an indication of skin sheen on an indication unit (such as a display or a strip of LEDs). The skin sensor value may be a skin parameter or may be further processed into a skin parameter based on predetermined relationships between the skin sensor value and the skin parameter.

However, in other embodiments, the sensor may be contained in a separate device that is wired or wirelessly connected to the analysis system. For example, such an analysis system may be contained in a smartphone. For example, an application can be used to read a sensor and display a skin sensor value based on a sensor signal generated by the sensor. Thus, in still other embodiments, the system comprises (i) a skin care device, the skin care device comprising a sensor, and (ii) a second device operatively coupled to the skin care device, the second device comprising a system analysis. The term "analysis system" can also refer to a variety of interrelated systems. For example, a sensor may (also) include a processor and an external device may include a processor that can communicate with each other. The sensor processor may output a sensor signal, and the processor of the external device generates a skin sensor value indicative of the degree of gloss/oiliness of the skin based thereon.

The sensor signal may be a detector signal. In other embodiments, the sensor signal may be a processed detector signal. Thus, in embodiments, the expression "based on the detector signal" may also refer to the processed detector signal. Based on the sensor signal, i.e. essentially based on the detector signal, the analysis system can output the corresponding value of the skin sensor.

When the system includes a functional device such as a skin cleansing device or a skin rejuvenation device, the device may be configured to perform an action depending on a sensor signal (for gloss detection) (or a skin sensor value). For example, upon reaching a certain lower or upper threshold for skin luster (or skin oiliness), the functional device may provide a signal to the user, such as an audible or vibrating signal. Alternatively or in addition, the functional device may decrease or increase specific actions depending on the sensor signal, such as increased or decreased skin massage depending on the sensor signal.

Thus, in yet another aspect of the invention, there is also provided a method for detecting skin luster, comprising emitting source light using the system described herein onto skin and detecting source light reflected from the skin using the system described herein.

In particular, the method is carried out by placing the sensor on the skin, for example, with a housing having an opening, on the skin, and during operation there is a second distance between the skin and the detector or its last optical element.

In particular, the method is a non-medical method. In particular, the method is a cosmetic method.

In yet another aspect of the invention, a storage medium is provided on which program instructions are stored which, when executed by the system described herein, cause the system to perform the method described herein.

As stated above, the system may include a polarizer. The polarizer is configured to allow only one or more specific polarizations to enter the detector. Thus, in particular embodiments, the sensor comprises a polarizer upstream of the detector. More specifically, the polarizer comprises one or more of the following: (i) a segmented polarizer, and (ii) a spatially varying polarization polarizer. This makes it possible to reduce the influence of the position (rotation) of the detector, especially when the light sources are activated in series. Thus, the sensor can detect reflected light depending on the light source. With different polarizations of the polarizer, the sensitivity of the system can be higher.

Thus, in particular embodiments, the device has a detection mode in which the light sources are configured to sequentially output source light. In yet other specific embodiments, the detector may be configured to sequentially detect source reflected light produced by light sources in series and generate corresponding detector signals. As stated above, the system also comprises an analysis system, wherein the analysis system is configured to generate a corresponding skin sensor value depending on the sensor signal, and in specific embodiments, the skin sensor value is based on the average of the respective detector signals.

In embodiments, the segmented polarizer comprises a wire mesh polarizer pixel with two or more pixels having different polarization orientations. In this document, the term "pixels" can also refer to areas. Specifically, the sensor comprises n light sources, such as four lights, and wherein the segmented polarizer comprises a wire mesh polarizer pixel with n pixels having polarization orientations that are perpendicular to each other, such as two sets of two pixels (in the case of four light sources). As stated above, the value of n is in particular equal to at least 2, such as 3 or 4 or more.

In embodiments, the spatially varying polarization polarizer comprises one or more of an azimuthally varying polarization polarizer and a radially varying polarization polarizer, which, in particular, allows more emitters to be arranged very close together.

Best results can be obtained around the Brewster angle. Thus, in embodiments, the sensor is configured to output light from a source with optical axes (OL) at an angle (α) of incidence with the skin at a second distance (d2), wherein the angle (α) of incidence is selected from the range of 50-60°, even more specifically, the angle (α) of incidence is selected from the range of 52-56°.

Thus, inter alia, systems and methods for measuring skin glare are provided herein using sequential illumination from a plurality of unpolarized light emitters illuminating the skin at an incidence angle that is (substantially) equal to the Brewster angle or polarization, and a segmented polarizer or spatially variable polarizer. polarization in the detection path.

Particularly good results can be (thus) obtained when the light sources are activated sequentially. Since the light sources are made in different positions, the reflection behavior and polarization behavior, as well as the angular dependence of the reflected light, thus may provide additional information (which may result from skin structure and/or illumination unevenness) and/or may allow the sensor dependence to be reduced. from the position of rotation on the skin.

Thus, in particular embodiments, the device has a detection mode in which the light sources are configured to sequentially output source light.

For example, sensors may have a measurement frequency in the range of 0.1*n-100*n Hz, where n is the number of light sources. For example, at 1*n Hz, every second of all the lights sequentially illuminated the skin, and the detector (sequentially) measured the possible reflections based on the respective light sources.

Of course, the use of multiple lights may also allow subsets of two or more lights to be activated. For example, this may be possible when four lights are used to provide two sets of two lights that are opposite each other (with a detector in between) with the sets of lights alternately turned on and off.

In addition, combinations of such methods may be used, where, for example, the arrangement of a set of light sources may change over time. For example, in the timed mode, the lights are activated sequentially, and at the subsequent specified time, the lights are activated as a group. Such a mode may include the repetition of these successive predetermined moments. All types of lighting schemes can be used to further create a more accurate skin gloss measurement.

The detector signal may be an average between the signals generated by the respective light sources. Thus, in still other embodiments, the detector is configured to sequentially detect source reflected light generated by the light sources in series and to generate corresponding detector signals, the system also comprising an analysis system configured to generate an appropriate skin sensor value depending on the signal from the sensor, and wherein the value of the skin sensor is based on the average value of the respective detector signals. Thus, the detector signals, in particular, are first processed and then averaged. Thus, the detector signal may be an average of the signals generated by the respective light sources.

As stated above, the system may include at least three light sources. In addition, as mentioned above, in embodiments, the sensor has an optical axis (O2) of the sensor, and moreover, the light sources are made axisymmetrically around the optical axis (O2) of the sensor.

In still other specific embodiments, as also discussed above, the system may also comprise an analysis system, wherein the analysis system is configured to generate an appropriate skin sensor value depending on the sensor signal. There can be a number of ways to generate a signal from a sensor. Even though low cost devices are known for home use, gloss measurement using these devices does not appear to be quantitative and may also not correlate with subjective perception and device reference measurements. Methods for estimating gloss can be based on counting the number of white pixels above a certain threshold in camera images taken using non-polarized light. However, it seems that the gloss score based on the number of white pixels depends on the intensity levels of the incident light (and its fluctuations), the threshold value, and the variation in the optical properties of the skin (inter- and intra-individual variations), which is less desirable.

This document describes below some specific implementation options that may provide more reliable results.

Thus, in embodiments, the system is particularly configured to create a skin image by means of a detector, wherein the skin image comprises a first region in which the maximum intensity is determined and a second region located at a first image distance from the first region, the first region and the second area does not overlap, and the system is also configured to generate a skin sensor value based on the intensity depending on the reflected light of the source along the path between the first area and the second area. An image may have an image region. The first and second regions may be regions, eg 0.05-30%, eg 0.05-15%, eg 0.1-10%, of the image area. In addition, the first image distance, i.e. the distance between the first region and the second region, more specifically the shortest distance between the boundaries of the two regions, may be at least of the order of the size of the first region or the second region. In general, the first region and the second region may be substantially the same. If necessary, the areas may also differ, but a correction factor must be applied. In addition, in general, these areas are chosen to be square or rectangular, in particular square. The region in which the maximum intensity is determined may be the region of the image where essentially a mirror reflection takes place, i.e. where the source light is reflected as from a mirror and is detected by the detector.

Thus, the first image distance may be in the range of the square root of 0.05-30% of the image area, eg, the square root of 0.05-15% of the image area, eg, the square root of 0.1-10% of the image area. In particular, the distance between the first region and the second region is at least 5% of the square root of the image region. It should be noted that the image area may not have a fixed value, but may, for example, depend on the magnification.

In addition, it should be noted that the term "imaging" and similar terms may not necessarily include the creation of a real image at a point in time, but may also refer to reading values from a detector at various positions on the surface of the detector.

It appears that the information that can be obtained from two areas and/or from a (straight) line, or the area between these two areas, can provide information regarding the degree of sheen, which can allow the quantification of skin gloss (including skin oiliness). ), especially when the system has been calibrated (see also below).

Thus, in embodiments, the system may be configured to generate a skin sensor value based on the slope of the curve given by the reflected light intensity of the source along the path between the first region and the second region. Thus, it appears that useful skin gloss values can be generated based on the slope of the curve or the angle of the curve.

Alternatively or in addition, the system may be configured to generate a skin sensor value based on the area below the curve given by the reflected light intensity of the source along the path between the first area and the second area. Thus, it appears that also useful skin gloss values can be generated based on the area under the curve or the angle of the curve. A path can also be designated as a straight path or a line.

As yet another alternative or addition, the system may be configured to generate a skin sensor value based on the number of image pixels above a predetermined threshold. Thus, it appears that useful skin gloss values can also be generated based on the number of pixels above the threshold.

Furthermore, alternatively or in addition, the system may be configured to generate a skin sensor value based on the average number of image pixels above predetermined thresholds, weighted with the respective pixel intensity, respectively. Thus, also based on the weighted number of pixels above the threshold value, useful skin gloss values can be generated.

As yet another alternative or addition, the system may be configured to generate a skin sensor value based on the ratio between the integrated intensity of the first region and the second region. Thus, a ratio mirrored to the diffusion intensity of these respective ratios can also be used to generate skin gloss values. For example, when the system is calibrated with a substantially specularly reflective area and a substantially diffuse reflective area, the skin gloss parameters can be obtained from a relationship mirrored to the diffusion intensity of these respective relationships.

In addition, as an alternative or addition, the system is configured to determine binary large objects (Binary Large Object, BLOB) in the image, and moreover, the system is configured to generate a skin sensor value based on one or more of the average size and maximum size of the large binary objects in the image. Thus, useful skin gloss values can also be generated based on the number of BLOBs and/or the sizes of the BLOBs. Thus, in this implementation, the number of white pixels is not used by itself, but is determined by BLOBs. Thus, a threshold value can also be defined for these BLOBs, eg at least the number k of adjacent pixels beyond a particular intensity threshold.

In the above embodiments, the number of calibration procedures was indicated. In particular, for quantifying skin gloss or skin oiliness, it may be useful to calibrate the system, more precisely, the sensor (and thus, in fact, the detector). This calibration can be performed after the sensor has been manufactured. Alternatively or in addition, the calibration may be implemented in software for each sensor based on one or more earlier calibrations of the sample sensors. Calibration may also be part of the measurement process or may be scheduled on a regular basis. In a specific implementation, the calibration is applied immediately after the manufacture of the sensor. In addition, the system may contain control routines that may update the calibration based on the parameters of the reference sensor or based on, for example, a shift in the signal, etc.

In particular embodiments, the analysis system is configured to generate an appropriate skin sensor value depending on the sensor signal after flat field correction. Flat field correction is a technology used to improve the quality of digital imaging. In particular, flat field correction is used to compensate for artifacts from 2D images that are caused by illumination and detection inhomogeneities, pixel-to-pixel changes in detector sensitivity, and/or distortions in the optical path. As stated above, the flat field correction can be based on a measurement with only a diffusion reference value, for example a diffusion standard such as a Spectralon. Based on such measurements, a flat field correction can be provided that can be used in any measurement (as described herein).

In still other embodiments, the system is configured to generate a corresponding skin sensor value depending on the sensor signal based on an average of the respective red, green, and blue channel signals in the detector.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which the respective reference numerals indicate the respective parts, and in which:

in FIG. 1a-1b schematically depict some aspects of the system;

in FIG. 2a-2b: optical diagram of the system model used for the simulation and some aspects regarding the field of view;

in FIG. 3a-3c. Power distribution on the sensor obtained for different brightness values. The gray values are the logarithm of the power density;

in FIG. 4. Relationship between specular power and diffuse background power as calculated from ray tracing as a function of gloss value varying from 0% (diffusion standard) to 100% (mirror).

in FIG. 5: Schematic representation of detected polarization states when multiple emitters are used for illumination in an annular configuration and a polarizer with uniform polarization properties is used in the detection path;

in FIG. 6: Reflection and transmission of unpolarized light on the surface;

in FIG. 7: Schematic representation of polarization circuits for illumination and detection to minimize the dependence of the brightness value on sensor rotation;

in FIG. 8a-b are schematic representations of some spatially varying filters or phase plates;

in FIG. 9: The configuration of the nanowire polarizing filter array used for the CMOS polarizing image sensor consists of 4 sub-pixels with a reference and three grid-covered pixels at 0°, 45° and 90° orientations;

in FIG. 10: Schematic representation of a possible polarization scheme for illumination and detection;

in FIG. 11: Change in the number of white pixels measured in-vivo , depending on the angle of rotation of the sensor for a different threshold;

in FIG. 12. Professional gloss meter calibration based on measurements by calibration standards, diffusion standard and reflective mirror;

in FIG. 13: Comparison of different methods (by angle, tilt/diffusion ratio, number of weighted pixels) of estimating the gloss value in the lower gloss range;

in FIG. 14: Comparison of different methods (by angle, tilt/diffusion ratio, number of weighted pixels) of estimating the gloss value in the higher gloss range;

in FIG. 15a-d: Illustration of image processing steps for tilt (angle) based gloss estimation.

The schematic drawings are not necessarily drawn to scale.

IMPLEMENTATION OF THE INVENTION

FIG. 1a schematically depicts a system 1 comprising a sensor 100 for measuring a skin parameter (selected from one or more of the group consisting of skin gloss and skin oiliness). The sensor 100 includes a plurality of spaced light sources 110 configured to output source light 111, and a detector 120 configured at a first distance d1 from each of the light sources 110. Sensor 100 is configured to output source light 111 with optical axes OL at an incidence angle α selected from the range of 10-80°, with skin at a second distance d2, and to detect reflected source light 111. In particular, the sensor 100 here may comprise at least three light sources 110, only two are shown for purposes of understanding, the light sources 110 being configured to output unpolarized visible source light 111. For example, the first distance d1 may be selected from the range of 10-80 mm, and wherein the detector 120 is configured to detect polarized light.

The detector 120 may include, for example, a 2D camera 101. In addition, the sensor 100 may include a focusing lens 102 upstream of the detector 120 and an aperture 103 upstream of the detector 120 and upstream of the focusing lens 102. The aperture 103 has a diameter D1 selected from range 0.1-0.8 mm. The focusing lens may be, for example, a 5-15 mm lens, such as a 10 mm lens. In addition, the system may contain a second focusing lens, and the combination of this lens with the first lens can provide the desired field of view and depth of focus for the entire system (see, for example, FIG. 2a). The light sources 110 are configured to output unpolarized white light 111 from the source.

As indicated in FIG. 1a, system 1 may also include an analysis system 2 configured to generate an appropriate skin sensor value depending on the signal from sensor 100.

The analysis system 2 may be contained in a device that also contains the sensor 100 (see also FIG. 1b) or may be contained in a separate device. FIG. 1a also schematically depicts such an implementation in which the system 1 comprises a skin care device 3, the skin care device 3 comprising a sensor 100, and a second device 200 operatively connected to the skin care device 3, the second device 200 contains system 2 analysis.

Sensor 100 has an opening 107. This opening may in particular be flat, i.e. its periphery may have an edge that is substantially flat. In this way, the sensor can be placed flat on the skin. The opening 107 may have a diameter D2 or an equivalent diameter D2 which may be in the range of about 10-30 mm.

The designation O2 refers to the optical axis of the sensor 100. When the sensor 100 is placed on the skin, this axis may be substantially normal to the skin.

The designation TS refers to the top surface of the sensor. It may be a flat surface. The term LB refers to a direct light barrier designed to prevent that light from light sources from possibly reaching the detector without a single reflection and/or which can reduce light reaching the detector 120 that was not reflected by the skin but was reflected by other internal surfaces of the sensor. The designation 104 refers to the polarizer.

The O2 axis may substantially coincide with the normal to the skin.

In particular, TS may indicate the upper surface of the housing 105. In fact, the upper surface TS may define the second distance d2 from the skin to the detector 102 or its last lens. Here, the top surface of the TS has a hole 107. The size of the hole can also be specified as a field of view (FOV). The field of view is also referred to here as FV. It should be noted that the slot or opening 107 may be round, but may also be square or rectangular, or may have a different shape. The designation FVA refers to the angle of the field of view. The designation TT refers to the total length, which is the distance from the opening 107 (i.e. the skin in use) and the top side of the support on which the light source 110 is mounted, this distance being substantially the same as the distance to the top of the source. 110 light, as is the case in commonly used solid state light sources such as LEDs. The overall length may be in the range of 10-200 mm, eg in the range of 10-80 mm, eg in the range of 10-30 mm, or in the range of 40-200 mm, eg in the range of 40-80 mm. The total length of the CT is greater than the second distance d2. The detector 120 and optional optical elements may have a height in the range of about 1-50 mm, such as 1-20 mm. As can be understood from the drawings, when the sensor 100 is mounted on the skin, a second distance d2 is guaranteed. Thus, the sensor 100 may comprise a distance maintaining device, such as a housing 105 (as shown) or, if desired, a housing and a separate distance maintaining device. As indicated above, the visible light 111 of the source is, in particular, unpolarized. Thus, the source light 111 is, in particular, unpolarized source light. It should be noted that the optical axis of the O2 sensor 100 and the optical axis of the detector 120 may substantially coincide. In addition, the optical axis of the O2 sensor and the resulting optical axis of all light sources 110 may be the same.

In general, the distance d2 can be defined as the distance between the hole to be located on the skin and the detector or its last optical elements as viewed from the detector.

FIG. 1b schematically shows an embodiment of a system 1 in which the system 1 comprises a skin care device 3 such as a skin cleansing device, a skin rejuvenation device, the skin care device 3 comprising a sensor 100 and an analysis system 2. The skin care device 3 may comprise a display unit IU and/or also a user interface UI. The designation FA refers to a functional area, such as an area that can be used to massage or exfoliate the skin.

To study the claimed system for capturing the shine of the skin, the authors of the invention used Monte Carlo ray tracing with special software. The simulation computes photometric and radiometric scores to perform a complete illumination and detection analysis. A schematic representation of a camera prototype and a system diagram are shown in FIG. 2a. FIG. 2a schematically depicts another embodiment of system 1. Here, an additional lens 102b is used, made up to hole 103. The size of the sensor determines the size of the box so that light from the corner of the box will hit the sensor at the edge for specular reflection. The authors used a black box around the transducer to prevent signals from the walls and diaphragm from reaching the transducer directly without interacting with the skin. The skin sample was modeled using a surface having a reflectivity of 17%. Part of this reflected light is specularly reflected, meaning that the angle of reflection is the same as the angle of incidence, and part of the light is diffusely reflected, meaning that there is no relationship between the direction of the incoming light and the reflected light. Thus, the gloss property of the sample was changed by choosing how much of the reflected light is specular and how much is diffuse. The authors investigated the entire range from 100% specular (mirror) to 0% specular or 100% diffuse (diffusion standard). In order to be able to obtain information about the degree of gloss of the sample, the authors require that the specular reflection from the LED light can reach the surface of the sensor. Thus, the previously determined size of the box ensures that we can use only significant distances between the LED and the sensor.

The LED that was used has a color temperature of 4000 K and a CRI of 70 and has also been modeled as a Lambert surface emitter. The LED package itself was modeled as having a diffuse reflectivity of 90%. The LED goes out as a 70% reflective surface. The PCB is modeled as having a diffuse reflectance of 60%. The body walls, as well as the STOP blocking surface, were modeled as black, but not completely black, but having a diffuse reflectance of 5%. The lenses are modeled as having refractive indices corresponding to N-LASF9 and N-BK7 glass for the larger and smaller glass, respectively.

Examples of power density distributions on the sensor for three different brightness values are shown in FIG. 3. The figure shows the logarithm of gray values. As can be seen in the graphs, changes in the sample luster value from the reflective mirror (100%) to the diffusion standard (0%) correspond to changes in the amplitude of the specularly reflected light. It falls while the diffuse background signal increases. Basically, what happens is that in the case of a mirror, the LED is imaged on the surface of the sensor, and the image becomes more and more blurred as the degree of gloss decreases.

FIG. 2b is a schematic plan view (without housing) showing detector 120 as a crosshatched rectangle in the middle. A rectangular detector is used here, for example having an aspect ratio of 4:3. The field of view FV is the area at the opening of the housing (not shown) or the spacing device if applicable (not shown) that the detector 120 can see. In particular, this field of view, hence the opening, is chosen such that it has the same symmetry as the detector 120, although the hole may also have, for example, circular symmetry. Here, the rectangular field of view FV has a length FVL and a width FVW, and a diagonal FVD. If the field of view is circular, then the diameter will be provided (FVL=FVW=FWD). In particular, the light sources 110 are configured such that the edge-to-edge distance between the light source 110 and the detector 120 is smaller than the size of the relevant field of view parallel to the first distance d1 from the corresponding light source 110 to the detector 120. Here, the distances d1 of the light sources 110 , which are denoted s2 and s7, in particular less than FVW; the distances d1 of the light sources 110, which are designated s4 and s5, are in particular smaller than FVL. In addition, in particular, the distances d1 of the light sources 110, which are indicated by s1, s, s6 and s8, in particular, are smaller than the FVD (diagonal).

As an alternative to the edge-to-edge distance, the distance from the center of the light source, such as in particular the LED, to the center of the detector 120 can also be applied, which in turn should be less than the size of the relevant field of view, including the size light source 0.5 and detector size 0.5.

FIG. 3a shows the image obtained with the image after measuring the surface with 100% gloss. FIG. 3b shows the image obtained with the image after measuring the surface with 50% gloss and the surface with 50% diffusion. FIG. 3c shows an image taken with the image after measuring the surface with 100% diffusion.

FIG. 4 information from the graphs shown in FIG. 3 was presented in a different way. The power density was integrated into a box and centered around the mirror image position. This gives the amount of light that is reflected specularly. From the total amount of light hitting the sensor, the authors can then calculate the power contained in the diffuse background. The ratio of these two numbers, specular power divided by background power, is plotted in FIG. 4. As expected, the ratio increases with the degree of gloss. This plot implies that the authors can derive the sample shininess value from a single prototype camera image by using various methods such as the number of pixels above the threshold weighted with intensity, the slope of the intensity transition from specular to diffuse, and the ratio of specular background to background. diffuse in the selected study area. The gloss value estimated using these new simulation-based methods is described elsewhere in this document. Details of the new methods that have been developed by the authors for estimating the gloss value, and the physical principles underlying these methods, are described elsewhere in this document.

FIG. 4 on the x-axis is the percentage of the degree of gloss, while at 0% is the diffuse surface, and on the right at 100% is the mirror surface. The y-axis represents the ratio of specular to diffuse (specular/diffuse).

Among other things, the following provides a method and system based on successive illumination of a plurality of unpolarized light emitters illuminating the skin at an illumination angle that is substantially equal to the Brewster angle or polarization and using segmented or spatially variable polarization detection.

A possible approach could be based on estimating the number of white pixels above some threshold value as an indicator of skin luster. However, the number of white pixels on the sensor changes as the prototype/sensor is rotated for measurement. The dependence of the gloss value on the angle of rotation of the sensor becomes more pronounced when higher threshold values are used to estimate the number of white pixels, skin structures are present, and a single emitter is used for illumination. Thus, the luster characteristics of skin with spatially variable surface and structural properties can only be partially obtained using a single light source in imaging with a polarization-sensitive camera. This dependency is a critical issue because consumers will randomly place the sensor camera on the skin and this will lead to a non-quantitative evaluation of the gloss value and therefore degrade the quality of the information that can potentially be offered to consumers.

To overcome this limitation and reduce the dependence of the brightness value on the angle of rotation of the sensor, the authors propose, among other things, a variety of non-polarized light sources (N > 2) that provide sequential illumination and S-polarized detection using an inexpensive camera sensor. However, in this approach, the detection of the preferred S-polarized state, which is a specular reflection/shine indicator, can only be realized for one pair of two unpolarized light sources (U1 with U3 combination or U2 with U4 combination) that are diametrically opposed to each other (FIG. . 5). This implies that when a polarizer with uniform polarization properties is used, the maximum number of light sources in the optical path to detect that can provide the optimum polarization state is two. FIG. 5a shows the sensor in the middle, and U1-UV denote unpolarized light sources. FIG. 5a shows the detection circuit, and FIG. 5b shows a detection circuit assuming a uniform polarizing filter.

Among other things, the present document proposes the use of a camera system and methods for quantitative measurement of skin gloss, which is essentially independent of the angle of rotation of the sensor. Among other things, sequential illumination from more than three light sources (non-polarized) and sequential detection using a cheap camera sensor (S-polarized detection) can be used. A schematic representation of the optical layout of the camera prototype is shown in FIG. 2a.

Aspects that were also used for the prototype, for example, may include:

1) White light LED lighting; 2) Non-polarized lighting (number of LEDs > 3); 3) The angle of incidence, in particular ~ 54° (i.e. in the range of 50-60°), is equal to the Brewster angle; 4) LED-sensor distance > 5mm (range 6-14mm); 5) Sensor-camera (inexpensive) with a focusing lens and a hole (aperture size 0.2-0.6 mm); and 6) Segmented polarizer or spatially variable polarization polarizer in front of the camera.

The image processing algorithms used to estimate the gloss value may be based on the number of white pixels or the slope of the change in intensity along the optical axis, normalized to the maximum value after flat field correction. Other methods are also described in this document.

When unpolarized light is reflected by the skin surface, the polarization properties of the reflected light depend on the illumination angle (FIG. 6). The two orthogonal linear polarization states important for reflection and transmission are called p- and s-polarization. P-polarized light (from German parallel ) has an electric polarized field parallel to the plane of incidence, while s-polarized light (from German senkrecht ) is perpendicular to that plane. The designation N refers to the normal (to the surface), the designation PI refers to the plane of incidence. In addition, the designation SK refers to a fall surface such as a skin surface. The designations S and P refer to polarizations.

Reflected light will be unpolarized for an illumination angle that is 0° or 90°, partially polarized (preferably S) for illumination angles between 0° and 90°, and plane polarized ( S ) for a single illumination angle that is the polarization angle or Brewster angle. .

The angle of incidence (0° and 90°) at which the reflection coefficient for light that has an electric field parallel to the plane (P) of incidence tends to zero, and the reflected light at this angle is linearly polarized, while its electric field vectors are perpendicular to the plane (S) incidence is called the polarization angle or Brewster angle. The polarization angle or Brewster angle (θB) can be calculated based on the Fresnel equations. The Fresnel equations predict that p-polarized light (the electric field is polarized in the same plane as the incident beam and the surface normal) will not be reflected if the angle of incidence is θ _B = 1/tan(n ₂ /n ₁ ), where n ₁ is the refractive index of the primary medium through which the light propagates (the "incident medium"), and n ₂ is the coefficient of the other medium. For a glass medium (n ₂ ≈ 1.5) in air (n ₁ ≈ 1), the Brewster angle for visible light is approximately 56°. For the optical design disclosed in the present invention, light falls on the interface between air and skin, and the Brewster angle is approximately 54°. The preferred range is 50-60°.

Thus, implementations may use a segmented (for fewer emitters from four to eight) or spatially varying polarization polarizers (for more emitters, eg more than 12) in the detection path. In particular, the number of segments equals the number of emitters.

When the illumination angle is between 0 and 90°, detection of partially polarized (preferably S) specularly reflected light, which is a measure of gloss, can be improved by filtering this component using an S -polarizer in front of the camera. In the case of an illumination scheme using multiple light sources, a segmented polarizer or a spatially varying polarization polarizer may be used, as shown in FIG. 7. This implies that when four emitters are used for illumination, the orientation of the polarizer in front of the sensor for the pair of light sources (U2 and U4) must be orthogonal ( H ) to the orientation of the polarizer (V) that is used in the optical path for the light determined from U1 and U3. These segments can be cut from a standard inexpensive polarization sheet and can be placed in the appropriate orientation by rotating the individual segments to form a segmented polarizer. The designation 104 refers to the polarizer. In addition, the designation 1041 refers to a segmented polarizer.

FIG. 8A-b show spatially varying polarization polarizers 1042, which they vary azimuthally or radially, respectively.

The segmented polarizer can be placed in the optical path for detection, or it can also be imprinted on the camera sensor itself by fabricating wire mesh polarizers using a standard CMOS process. A high-speed polarization image sensor with a pixel size of 6 µm for polarization mapping has already been reported, which consists of 4 sub-pixels with a reference and three grid-coated pixels with 0°, 45° and 90° orientations.

FIG. 9 is a schematic of an embodiment of a segmented polarizer 1041 comprising a wire mesh pixel polarizer 1043 with two sets of two pixels 1044 having polarization orientations perpendicular to each other.

As mentioned above, measurement of the gloss characteristics of skin with spatially variable surface and structure properties using an optical sensor may depend on the rotation angle of the sensor when one or two light sources are used. This can lead to a non-quantitative evaluation of the gloss value and therefore degrade the quality of gloss information that can potentially be offered to consumers.

Thus, the present document also provides systems and methods for quantitative measurement of skin gloss, which are less dependent on the angle of rotation of the sensor. Alternatively or in addition, the proposed invention may be based on the use of sequential illumination and detection using more than three light sources (non-polarized illumination) and a camera sensor (polarization detection).

Among other things, the authors analyzed changes in the number of white pixels compared to the rotation angle of the sensor when adjusting the polarizing camera for imaging. Among other things, the authors found that the dependence of the brightness value on the angle of rotation of the sensor becomes more pronounced at a high threshold value, when structure is present and when a single emitter is used for illumination.

Thus, inter alia, the present document proposes the use of camera systems and methods for quantitative measurement of skin gloss, which is less dependent on the angle of rotation of the sensor. In embodiments, among other things, the proposed invention may be based on the use of sequential illumination from more than three light sources (non-polarized illumination) and sequential detection using a single low-cost camera sensor (polarization detection). The gloss value is estimated based on the average number of pixels estimated from a plurality of independent images taken along different directions. A schematic representation of the optical layout of the camera prototype is shown in FIG. 2a. The image processing method(s) used to estimate the gloss value may be based on the number of white pixels or the slope of the change in intensity along the optical axis, normalized to the maximum value after flat field correction, although other options may also be possible (see also below). ).

Aspects that were also used for the prototype, for example, may include: 1) white light LED lighting; 2) non-polarized sequential illumination with multiple emitters (number of LEDs > 3); 3) an angle of incidence, in particular > 45° (in general, in particular in the range of 40-80°); 4) LED-sensor distance > 5mm (range 6-14mm); 5) sensor-camera (inexpensive) with a focusing lens and a hole (boundary size 0.2-0.6 mm); and 6) Polarizer in front of the camera.

The authors investigated the dependence of the gloss value (the number of white pixels above a certain threshold value) on the sensor rotation angle (0-360° in 30° increments). Measurements were performed using a prototype camera using one and two emitters with sequential illumination.

• Spectralon (diffusion standard with uniform optical properties);

• Skin ex-vivo (for controlled experiments); and

• Skin in-vivo (forehead, skin type II).

Based on experimental data measured on Spectral, ex-vivo and in-vivo skin, the authors have shown by example that the underestimation of gloss content resulting from rotation-related effects associated with the use of a single emitter can be minimized by using sequential illumination. using more than three emitters (triangular configuration for N=3 and rectangular configuration for N=4, etc.) that are arranged symmetrically in an annular lighting configuration (FIG. 10). When multiple emitters are used independently, the brightness value depends on the rotation angle, this effect is predominantly contributed by the number of white pixels in areas where the intensity distributions from the multiple emitters overlap. Here, under A, B and C are light sources that are arranged in an annular configuration.

In order to quantify the dependence of gloss on the angle of rotation of the sensor, the number of white pixels was estimated depending on the angle of rotation of the sensor for another threshold value (FIG. 11). FIG. 11, the x-axis represents the rotation angle RA of the sensor, and the y-axis represents the number N of white pixels (in relative units). The number of POL_L pixels is displayed depending on the angles for a series of thresholds, where 110 indicates a threshold value of 110, and 200 indicates a threshold value of 200. The designations MX and MN refer to the maximum and minimum, respectively.

For a given threshold value, the dependence of gloss on rotation angle is expressed as the maximum relative difference in the number of pixels: (ΔGloss)= (max-min)/(average (max,min).

Based on these experiments, the following conclusions can be drawn:

- the number of pixels estimated using the Spectralon, with uniform optical properties, showed less dependence on the angle of rotation of the sensor;

- the number of pixels, estimated using ex-vivo and in-vivo skin measurements, showed dependence on the angle of rotation;

- this dependence of the gloss value on the angle of rotation is the result of the heterogeneity of the properties of the structures and the surface of the skin. This angle dependence becomes more pronounced when skin structures are present and in particular after cleaning; and

- dependence on the angle of rotation of the sensor can be minimized using multiple sources of illumination compared to a single emitter. This dependency is further reduced when multiple emitters are used in series (L_R) rather than simultaneously (L, R):

- ∆Glare (Nonpolar)(L_R) ∆Glare (Nonpolar)(L, R) < ∆Glare (Nonpolar)L, ∆Glare (Nonpolar)R and/or

- ΔGlitter (Polar)(L_R) < ΔGlitter (Polar)(L, R) < ΔGlitter (Polar)L, ΔGlitter (Polar)R

Here,

- L: One non-polarized emitter on the left side;

- R: One non-polarized radiator on the right side;

- L, R: 2 emitters (L and R) are used simultaneously and one image is captured; and

- L_R: 2 emitters (L and R) are used in series and the brightness value is estimated based on the average value (emitters L and R are diametrically opposed to each other in a ring configuration).

The results are summarized in the table below:

Spectralon ex vivo skin type 2
(before cleaning) skin type 2
(after cleaning) terms maximum relative change in the number of pixels due to rotation (0-360) maximum relative change in the number of pixels due to rotation (0-180) maximum relative change in the number of pixels due to rotation (0-360) maximum relative change in the number of pixels due to rotation (0-360) non-polar_R 0.03 1.29 0.57 1.87 non-polar_L 0.05 1.48 0.62 1.62 non-polar_LR 0.01 0.96 0.42 1.81 non-polar_L_R 0.33 1.65 polar_R 0.05 2 0.94 1.81 polar_L 0.1 2 1.29 2.0 polar_LR 0.02 2 0.85 1.83 polar_L_R 0.77 1.81

Thus, inter alia, systems and methods for measuring skin gloss using sequential illumination from more than three light sources (unpolarized illumination, equal-angle separation) and one low-cost camera sensor (polarized detection) are presented herein to minimize gloss value dependency. on the orientation of the sensor.

Below, the authors present experiments performed on calibration samples (mirror, calibration tiles, glossy paper, diffusion standard) with a range of gloss values from 0 to 100 gloss units. The authors compared the gloss values measured with a camera and other professional devices known from the prior art. FIG. 12 shows the DR of the device in GU units, where DS is the diffusion standard, RM is the reflective mirror, and S is the gloss calibration standards. The x-axis shows the gloss in GU calibration standards.

Measurements were performed using a professional industrial Gardner gloss meter (G85) to set the measurement scale in the range from 0 to 100 gloss units (GU). The performance and linearity of a professional gloss meter (Gardner 85) over a higher range of gloss units was measured using three highly polished black glass reference standards (Novo Gloss) with a given refractive index in known gloss reference units of 50, 60, 90 GU. They were used as "calibration tiles" or "calibration standards". There is no such material that would provide a wide range of gloss values with the same surface properties and with a sufficient number of samples. The first calibration tiles cover medium high gloss values, while the glossy paper covers low gloss values. Thus, we used glossy paper with a gloss range in the lower gloss range after calibrating the device using these calibration tiles. These calibration standards have assigned gloss values for the measurement angle and can be analyzed against the BIN standard for material studies. The authors observed a good correlation between the brightness value measured with the Gardner 85 and the reference value of the brightness of the calibration brightness standards. The authors performed additional experiments on the mirror and diffusion standard to establish an upper calibration point of 100 on the mirror and with the lower endpoint set to 0 on the diffusion standard. The authors observed a shift of 10 GU on the mirror and the diffusion standard. Measurements made at other illumination angles, such as 20° and 65°, in the Gardner device could not provide a wide range from 0 to 100 GU and, therefore, the authors used a specific illumination angle of 85° as a reference angle for next measurements.

Shown are the performance and linearity of the camera prototype and the gloss measurement algorithms in the low and high gloss range using glossy paper (FIG. 13) and calibration tiles (FIG. 14), respectively. A description of the various methods used to estimate camera image gloss and determine flat field correction can be found in Section 6. Gloss units measured with a professional device, Gardner 85, were used as a reference value on the horizontal axis. Camera performance is normalized to the maximum value. The authors observed that the accuracy of measurement in different ways depends on the range of brightness of the samples. For lower gloss values, the accuracy of tilt measurements and the number of weighted pixels are higher than those of the specular-to-diffuse ratio approach. In the case of samples with higher gloss values, the number of weighted pixels and the specular-diffuse ratio are superior compared to the slope/angle method. These observations are consistent with the simulation results. FIG. 13, the x-axis represents gloss units, and the y-axis represents device performance in random units. The notation S/D refers to the respective values of the slope/diffusion ratio; S/A refers to the respective slope/angle ratio values; and NWP denotes the corresponding value of the number of weighted pixels. FIG. 14 uses the same notation as in FIG. 13 for various curves; in addition, the designation R refers to reference units of brightness.

Currently, different illumination angles are used, depending on the gloss levels. The 85° incidence angle (AOI) gloss meter is more sensitive to gloss differences below 10 GU@ 60º, while the 20º AOI has higher resolution on high gloss coatings above 70 GU@ 60º. This indicates that a single camera device with different algorithmic approaches can be used to measure gloss values in the range of 0 to 100 GU without any hardware modification, and significantly good accuracy can be achieved for all samples using the series method. weighted pixels.

The gloss levels of the sample were measured and the performance of the method was evaluated on calibration standards with other professional gloss meters. The measurement accuracy of the surface properties of both the calibration tiles and the glossy paper is uniform. Results may differ when measurements are made on leather with expected non-homogeneous surface properties and expected low gloss values.

In addition, the measurement of skin gloss using a camera can be influenced by a number of factors, such as skin color, degree of skin swelling depending on applied pressure and amount of sebum, sweat, etc. on the surface of the skin It is likely that the color of the skin will only give the effect of a difference in intensity in the blue, green or red channels, and this can be compensated for by automatic intensity correction in the final system. The brightness differences that can be detected depend on the brightness level, and the relevance of these differences that can be detected depends on how many units of brightness can be subjectively perceived as significantly different. When measured at a 60° angle, these differences that can be detected depend on the gloss level of the sample, for example a difference of 3.0 GU measured on a very matte surface (maybe 5 GU) will be seen by the human eye, however when coated with stronger gloss (perhaps 60 GU), the difference will be very difficult to notice.

Described below are some possible (pre-)processing steps based on RGB imaging (red, green, blue) to grayscale and flat field correction that can be used as pre-processing steps for the methods described. below (or above). It is assumed that the resulting images are not saturated. Saturated images increase the overall intensity of the image and therefore irrelevant (background) information may be taken into account.

Each camera capture produces four images taken by four unpolarized light sources, which are located at the bottom right - BR, bottom left - BL, top left - TL and top right - TR. Then, these images are used to perform signal averaging and to minimize the relationship between gloss value and sensor rotation.

From RGB to Greyscale: The SensorTech camera image is a 24-bit RGB image. Each color has 8 bits. The color value for each pixel in an RGB image is a 24-bit value. For each pixel, the color intensity tree can be divided by using parts of a 24-bit number (bits 0-7 are BLUE (B), bits 8-15 are GREEN (G), bits 16-23 are RED (R)) . The grayscale image is an average of the information obtained from the R, G and B channels, and when testing an RGB image for saturation, individual channels must be tested. In the algorithms implemented in LabVIEW, a grayscale image is obtained by adding three channels (R, G and B), i.e. the maximum image intensity can be 3 x 255 = 765.

Flat Field Correction: The purpose of Flat Field Correction (FFC) is to remove image artifacts caused by pixel-to-pixel changes in camera sensitivity and general intensity distortions in the optical path. Also, the authors use FFC to compensate for the gradient change in pixel intensity in an image as a result of unpolarized light. To perform FFC, a diffusion standard image, such as a Spectralon, is used. Since there are many light sources on the SensorTech camera, different images are taken, i.e. FFC is performed for each emitter separately.

Flat field correction (FFC) of an image is performed by dividing the image into a reference image (spectralon) and then multiplying each pixel by the average pixel intensity of the reference image.

Some of the methods that can be used for measurements (quantitative) are described below.

Number of Pixels Above Threshold: This method relies on the fact that specular light appears brighter in an image than a diffuse background. It is important that the images are not saturated: 1) the authors use images from 4 unpolarized light sources in the camera (BR, TL, BL and TR). Each image is processed separately; 2) convert the image from RGB to grayscale; 3) apply FFC to the grayscale image; 5) counting the number of pixels with an intensity that is higher and lower than half of the maximum intensity; 6) The result is: (#pixels above)/(#pixels below); 7) average = (#pixels above)/(#pixels below result of 4 images). With more or less light sources, n images can be used instead of 4 images, with n referring to the number of lights.

Slope (angle) calculation: This method uses the slope (angle) of the intensity distribution in the region of interest defined in a window around the transition from specular reflection to diffusion in the direction of the optical axis, and also uses unpolarized light sources. An ideal mirror will give a 100% specular reflection of the emitter, concentrated on a small area on the sensor, with zero hum (noise), while an ideal diffusion standard will give a nearly uniform intensity distribution on the sensor after FFC. Tilt (angle) gives an indication of how quickly the intensity falls off as a function of distance along the optical axis. The following actions may be included (see also FIG. 15).

1. Each of the four images taken from the unpolarized light sources in the camera (BR, TL, BL and TR) is processed separately;

2. Convert image from RGB to grayscale;

3. Reduce image resolution by a factor of 8 to remove backscattered light caused by skin structure. Applying a median filter with a kernel size of 15 to additionally remove any skin structures and re-enhance the image resolution in the direction of the original size;

4. Now the search for the intensity of the glare in the image will be carried out. It is represented by the area with maximum intensity. This is done through the following steps:

a. Search for maximum intensity on a 16x image with reduced resolution;

b. Definition of threshold values for the image with this intensity;

c. Create a binary image (0 = lower threshold, 1 = upper threshold);

d. Using the connectivity of 8 devices to create BLOBs (Binary Large Objects).

e. Getting the center of mass of the largest BLOB;

5. Determination of a line between a certain glare intensity and the center of the image.

6. Create (#160) rectangles (width 75, height 50) with rectangle centers that are evenly spaced along the line;

7. If a flat field correction is applied, then steps 5, 6, 7 are then repeated on the reference image and divided by the flat field results;

8. Plotting the results on the X, Y coordinate axes, where X corresponds to the range [1, 160], and Y is the average intensity.

Specific parameters (steps 6-8) were selected in relation to the images acquired by the present system. It is possible that these settings may require further adjustment for images received by other devices.

9. Obtaining the average intensity in each rectangle;

10. If the maximum of this graph is not X=1, then the part is removed until the maximum value of Y is reached. Divide the remaining graph into 3 parts;

11. Calculation of the slope on the graph according to the first graph. This is always a negative value.

a. A high specular reflection should result in a high negative number.

b. Diffuse reflection should result in low negative numbers.

12. Averaging the result of the slope obtained for the four images.

FIG. 15 is a schematic of the raw image of FIG. 15a; in FIG. 15b shows a processed image such as after FFC. FIG. 15c shows the region with the maximum MI intensity, with the region indicated by reference symbol 1001. Reference symbol 104 indicates a line connecting the first region 1001 and the second region 1002, which is made at some distance. The movement from the first region 1001 to the second region 1002 along the line 104 may be substantially the same as the movement of the window along the optical axis. FIG. 15d shows the intensity profile along this line. The slope 1005 and/or the area under the curve 1006 may be used as a measure for the skin parameter.

The ratio of specular and diffuse intensity: Directly reflected light (directed by a mirror at the same angle into the reflection channel) and diffusely reflected (scattered) light are received by two separate measurement channels. Scattered/diffuse reflected light is measured at 0° (fully vertical above the surface being measured), assuming the light scatters in the same way at all angles (diffuse channel). These specular and diffuse components are spatially separated but are detected on the same sensor plane and use broadband wavelength illumination and a wide range of illumination and detection angles. The method is based on calculating the ratio of the intensity in the area under study around the place of specular reflection relative to that of diffuse light. These regions of interest are similar to those used for tilt (angle) based gloss estimation. Thus, the ratio of specular to diffuse intensity gives maximum values for specimens with high gloss values such as a mirror (~1).

In particular, in this method, the average intensities of the region with the strongest reflection are compared with the average intensities of the region of diffuse reflection.

1. Average intensities are calculated over the region of the rectangle with the strongest specular reflection;

2. Similarly, average intensities are calculated over the region of the rectangle with maximum diffuse reflection; and

3. The calculated ratio is the intensity ratios (step 1/step 2).

Polarization difference imaging method (similar to SAMBA): This method can use polarization channel information in addition to the unpolarized illumination channel. The skin was illuminated with polarized and unpolarized light sequentially and detected using a polarizing sensor-camera. In general, the principle of measurement in this method is based on the formation of images with a polarization difference and is similar to that used in a professional gloss measurement device such as SAMBA. However, here the authors used unpolarized light and a polarizing filter. For calculation in a way similar to SAMBA, the authors use sources of polarized and unpolarized light. Unpolarized light sources have specular and diffuse components, while polarized light has only diffuse components. To obtain the specular component, the polarized image is subtracted from the non-polarized image.

1. Polar_BR and polar_TL images are processed together with non-polar_BR and non-polar_TL images.

2. Convert image from RGB to grayscale.

3. Applying FFC to a grayscale image.

4. For further processing, the authors transformed the image through its symmetry, i.e. maximum reflection should be top right (TR).

Polar_BR and non-polar_BR images are transformed via horizontal symmetry, while polar_TL and non-polar_TL images are transformed via vertical symmetry.

5. For every four images, the average intensity is calculated within the 200x200 rectangle that is in the center of the image. The rectangle is chosen such that there is only diffuse reflection. With these intensity values, it seems possible to compensate for the light intensity between images. The size of the rectangle is predetermined for the present system.

6. Calculation of 2 ratios

a. Ratio_BR = polar_BR intensity / non-polar_BR intensity

b. Ratio TL = polar_TL intensity/non-polar_TL intensity.

7. Division of non-polarized images into their ratios.

8. Adding polarized images, resulting in only 1 polarized image.

9. Adding non-polarized images, resulting in only 1 non-polarized image.

10. Subtraction: Unpolarized - Polarized.

11. Calculation of the average intensity and its standard deviation in the entire resulting image.

12. Samba / stdev average result.

Average BLOB size and maximum BLOB size; This method is based on the average size and maximum size of the BLOB (Large Binary Object) present in the image, and is more relevant for quantifying skin characteristics related to oiliness rather than glossiness. The relationship between luster and oiliness of the skin still needs to be well understood. A BLOB can be seen as a group of pixels that follow each other with the same characteristics. The intensity of the pixels must be above a certain level. The method is based on the visual representation of fat in the image. The following steps can be performed:

1. The authors use only images from unpolarized light (BR, TL, BL and TR).

2. Convert image from RGB to grayscale.

3. Applying FFC to a grayscale image.

4. Determining the maximum intensity of a pixel in an image.

a. Definition of image thresholds, for example with 80% or 90% or 95% of the maximum value. And creating a binary image (Above threshold = 1; Below threshold = 0).

5. BLOB calculation using the connectivity of 8 devices.

6. Calculation of the average size over all BLOBs.

7. Calculate the maximum BLOB size.

8. Calculation of average values for 4 images (obtained using four light sources, which are arranged in a ring configuration).

Number of Pixels Above Threshold: This method is based on the difference in intensity between specular and diffuse reflected light. The specular reflection is brighter and therefore can be used to quantify the degree of gloss after image thresholds have been determined. Here, the authors use a range of thresholds to facilitate better discrimination of skin color and also to provide a more sensitive way to account for additional information when FFC is not performed. This information may be discarded when only pixel intensities above a particular threshold are taken into account. The main disadvantage of this algorithm is that the thresholds must be customized for specific cases.

1. Four images (BR, TL, BL and TR) are processed separately.

2. For each such image: the R, G, and B channels are flat-field corrected by the R, G, and B channels, respectively, of the reference image using a spectralon.

3. Using a set of thresholds {110, ..... 180, ....., 220} for the equalized B channel and {120} for the equalized R and G channels to determine image thresholds.

4. Count the number of pixels with intensity above the selected threshold.

5. The resulting number of pixels is obtained by averaging the number of pixels calculated for each image BR, TL, BL and TR.

Weighted Number of Pixels Above Threshold: This method is also based on differences in specular and diffuse reflected light intensity. The authors choose some RGB intensity values by defining image thresholds and based on that, perform the following steps. All pixels above a certain threshold yield the same value (1) regardless of the actual pixel intensity levels. Since brighter specular reflections correspond to higher gloss values, in this method, the authors weight a preselected pixel by its intensity values. The following steps describe the details of the algorithm:

1. BR, TL, BL and TR images are processed separately.

2. For each such image: the R, G and B channels are flat-field corrected by the channels of the reference RGB image (spectralon) if FFC is used.

3. Convert RGB image to grayscale.

4. Using a set of threshold values {110, ..... 180, …. 220} for the equalized B channel and {120} for the equalized R and G channels to determine the image thresholds.

5. Multiply each pixel above the threshold by its grayscale intensity and sum them.

6. Normalization of the result by the number of pixels.

7. The resulting weighted number of pixels is obtained by averaging the weighted number of pixels calculated for each image BR, TL, BL and TR.

Number of BLOBs/Average BLOB Size/Largest BLOBs: Here, the authors use a variety of thresholds to select the number of pixels (to form a BLOB) where the image is converted to grayscale and 95% of the maximum intensity value is selected. As mentioned above, lower thresholds can introduce additional important information, in particular in the case of uneven illumination.

The main steps of the algorithm are as follows:

1. BR, TL, BL and TR images are processed separately.

2. For each such image: the R, G and B channels are flat-field corrected by the channels of the reference RGB image (spectralon) if FFC is used.

3. Using a set of thresholds {110, ....., 180, ….., 220} for the equalized B channel and {120} for the equalized R and G channels to determine image thresholds.

4. Search for connected pixels and their approximation by contours - BLOB.

5. Number of BLOBs: The resulting number of BLOBs (edges) is obtained by averaging the number of edges of the BR, TL, BL, and TR images.

6. BLOB Size: Calculate the size of the rectangles and take the average / take the largest. Again, the resulting average BLOB size/largest size is obtained by averaging the average outline sizes/largest of the images BR, TL, BL, and TR.

The term "multiple" refers to two or more.

As used herein, the term "substantially", for example, "essentially consists", will be understood by a person skilled in the art. The term "substantially" can also include implementations with "completely", "completely", "all", etc. Thus, in embodiments, the word "substantially" may also be deleted. Where applicable, the term "substantially" may also refer to 90% or more, such as 95% or more, in particular 99% or more, even more specifically 99.5% or more, including 100%. The term "comprise" also includes embodiments in which the term "comprises" means "consists of". The term "and/or", in particular, refers to one or more elements specified before and after "and/or". For example, the expression "element 1 and/or element 2" and similar phrases may refer to one or more of element 1 and element 2. In an embodiment, the term "comprising" may refer to "consisting of", but in another implementation it may also refer to "comprising at least certain species and optionally one or more other species".

In addition, the terms first, second, third, and the like in the specification and claims are used to distinguish between like elements and not necessarily to describe sequence or chronological order. It should be understood that the terms used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein may operate in other sequences than those described or illustrated here.

Among other things, the devices presented here are described during operation. As will be clear to a person skilled in the art, the invention is not limited to methods of operation or functioning devices.

It should be noted that the above embodiments are illustrative and not limiting of the present invention, and a person skilled in the art will be able to implement a wide range of alternative implementations without departing from the scope of the appended claims. In claims, any parenthetical references are not to be considered as limiting the claim. The use of the verb "comprises" and its conjugations does not preclude the presence of elements or steps other than those specified in a claim. Unless the context clearly indicates otherwise, in the description and claims, the words "comprise", "comprising" and the like should be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, in the sense of "including but not limited to". The grammatical indicator of the singular before an element does not exclude the presence of a plurality of such elements. The present invention may be implemented by hardware comprising several different elements, as well as by a suitably programmed computer. In a device claim that lists multiple features, multiple of those features may be implemented by the same piece of hardware. The fact that some measures are listed in mutually distinct dependent claims does not in itself indicate that a combination of these measures cannot be successfully used.

The invention also provides a control system that can control an apparatus or device or system, or that can execute a method or process as described herein. In addition, the invention also provides a computer program product running on a computer that is operatively connected to or contained in an apparatus or device or system controls one or more controllable elements of such apparatus or device or system.

The invention is also applicable to a device containing one or more of the distinguishing features described in the description and/or shown in the accompanying drawings. The invention also relates to a method or process comprising one or more of the features described in the description and/or shown in the accompanying drawings.

Various aspects described in this patent may be combined to provide additional benefits. In addition, one skilled in the art will appreciate that embodiments may be combined, and also that more than two embodiments may be combined. In addition, certain features may form the basis for one or more divisional applications.

Claims (41)

1. System (1) for determining the gloss of the skin, containing a sensor (100) for measuring a skin parameter, while the sensor (100) contains (i) n spatially separated light sources (110) configured to output unpolarized visible light (111) source, and the value of n is not less than three; (ii) a detector (120) made at a first distance (d1) selected from the range of 10-80 mm from each of the light sources (110) and configured to detect polarized light; and (iii) a polarizer (104) upstream of the detector (120), wherein the polarizer (104) contains one or more of (i) segmented polarizer (1041) and (ii) a polarizer (1042) of spatially varying polarization, moreover, the system (1) contains a housing (105) containing a sensor (100), the housing (105) has a first opening (107) providing a field of view for the detector (120), the sensor (100) is made, when used, with the possibility of issuing light (111) of a source directed towards the skin, with optical axes (OL) at an angle (α) of incidence selected from the range of 50-60°, with the skin at a second distance (d2 ) given as the distance between the first hole (107) and the detector (120) or as the distance between the first hole (107) and the last optical element in front of the detector (120) as viewed from the detector (120) and detection, when used, reflected light (111) source, characterized in that the device has a discovery mode, light sources (110) are configured to sequentially output light (111) of the source, the detector (120) is configured to sequentially detect the reflected light of the source, sequentially generated by the light sources (110), and with the possibility of generating the corresponding detector signals, the segmented polarizer (1041) comprises a wire mesh pixel polarizer (1043) with n pixels (1044) having polarization orientations perpendicular to each other. 2. The system (1) according to claim 1, which also comprises an analysis system (2) configured to generate an appropriate skin sensor value depending on the signal from the sensor (100). 3. System (1) according to claim 2, which comprises a skin care device (3), wherein the skin care device (3) comprises a sensor (100) and an analysis system (2). 4. The system (1) according to claim. 2, which contains (i) a device (3) for skin care, wherein the skin care device (3) comprises a sensor (100) and (ii) a second device (200) operably connected to the skin care device (3), and the second device (200) contains the system (2) analysis. 5. System (1) according to any one of the preceding claims, wherein the segmented polarizer (1041) comprises a wire mesh pixel polarizer (1043) with two or more pixels (1044) having different polarization orientations. 6. The system (1) of claim 1, wherein the spatially varying polarization polarizer (1042) comprises one or more of an azimuthally varying polarization polarizer and a radially varying polarization polarizer. 7. System (1) according to claim 2, wherein the value of the skin sensor is based on the average value of the respective detector signals. 8. The system (1) according to claim 2, which is configured to create an image (1000) of the skin using a detector (120), and the image (1000) of the skin contains the first area (1001), in which the maximum intensity is detected, and the second area (1002) at the first distance (1003) of the image from the first area (1001), the first region (1001) and the second region (1002) do not overlap, and the system (1) is also configured to generate a skin sensor value based on the intensity depending on the reflected light (111) of the source along the path (1004) between the first area (1001) and the second area (1002). 9. System (1) according to any one of the preceding claims, wherein the sensor (100) has an optical axis (O2) of the sensor, and the light sources (110) are axisymmetric around the optical axis (O2) of the sensor. 10. A method for detecting skin gloss using a system (1) containing a sensor (100), while the sensor (100) contains (i) n spatially separated light sources (110) configured to output unpolarized visible light (111) source, and the value of n is not less than three; (ii) a detector (120) made at a first distance (d1) selected from the range of 10-80 mm from each of the light sources (110) and configured to detect polarized light; and (iii) a polarizer (104) upstream of the detector (120), wherein the polarizer (104) contains one or more of (i) segmented polarizer (1041) and (ii) a polarizer (1042) of spatially varying polarization, the segmented polarizer (1041) comprises a wire mesh pixel polarizer (1043) with n pixels (1044) having polarization orientations perpendicular to each other; moreover, the system (1) contains a housing (105) containing a sensor (100), and the housing (105) has a first opening (107) providing a field of view for the detector (120), wherein the method includes - sequential output of light (111) of the source from the specified n spatially separated light sources (110), and the light (111) of the source is output with optical axes (OL) at an angle (α) of incidence selected from the range of 50-60°, with skin on a second distance (d2) defined as the distance between the first hole (107) and the detector (120) or as the distance between the first hole (107) and the last optical element in front of the detector (120) as viewed from the detector (120); - detection of sequentially reflected source light, sequentially generated by light sources (110); and - generating detector signals corresponding to the detected reflected light. 11. A data carrier for determining skin gloss, which stores program instructions that, when executed by the system (1) according to any of the previous paragraphs. 1-9 cause system (1) to execute the method of claim 10, system (1) comprising a processor.

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