WIRELESS MEDICAL DEVICE FOR RECORDING BIMODAL SKIN VIDEOS WITH LIGHT CONTROL

Description

[0001] The present invention relates to a medical device and a method for acquiring skin videos.

[0002] The need to have an image of chronic wounds treated in the context of telemedicine has been met for several years by the use of "general public" devices such as touch tablets, mobile phones, digital cameras and ceiling cameras by home nurses, coordinating doctors in EHPAD (Etablissement d'Hébergement pour Personnes Âlages Dépendes) and / or by doctors who remotely require a one-off consultant opinion as part of the chronic wound care pathway. A survey has highlighted the limitation of such devices because many photographs sent to experts are only partially usable: blurred images, with a low color rendering index or with insufficient lighting (some patients must provide their personal flashlight in order to send usable images to experts).Indeed, the surrounding lighting, which is the only lighting used (except when using a flash, which modifies the color rendering index and accentuates the brightness), is not constant in correlated color temperature (light from ceiling neon lights, incandescent bedside lamp, or sunlight if the patient is sitting near a window on a sunny day) or in intensity (sunlight varying according to cloud cover, season, time of day, and the equipment in the patients' homes being variable in number and orientation). The absence of polarization also negatively impacts the quality of the images generated because the brightness (specular reflection) often prevents remote expertise of the lesions concerned.

[0003] Currently, international recommendations for the management of chronic wounds in clinical settings include the measurement of PtcO 2: Transcutaneous Oxygen Pressure in some cases. However, the physiological parameter of cutaneous oxygenation level is almost never measured in clinical routine because: The devices for measuring it are expensive: at least 5,000 C, and the measurement is time-consuming: at least 30 minutes per patient, for limited information in terms of skin surface explored, most of the time, the devices being equipped with 3 electrodes of 1 cm 2< surface each. This means the measurement of PtcO 2 on a surface of 3 cm 2< in approximately 30 minutes.

[0004] Kong, L. et al., "Non-contact detection of oxygen saturation based on visible light imaging device using ambient light," Opt. Express 21, 17464-17471 (2013), is known for describing a device for measuring oxygenation levels using white light.

[0005] Also known is the paper Nitzan, M. et al. "Calibration-Free Pulse Oximetry Based on Two Wavelengths in the Infrared - A Preliminary Study." Sensors 14, 7420-7434 (2014), implementing the use of two wavelengths in the infrared.

[0006] Document US2004174525 describes a display device using parallel and crossed polarization.

[0007] Document US 2013 / 0071103 describes an apparatus capable of producing video sequences using several polarizers and light-emitting diodes emitting at different wavelengths.

[0008] Document US 2014 / 240468 is known, describing a bulky, floor-mounted imaging system that is not a portable device. This system allows an image to be produced using illumination of several different wavelengths, in particular, red, green and blue. Near infrared waves are also used.

[0009] Document US 2016 / 022181 describes an imaging apparatus for obtaining images from a near infrared sensor and images from a visible sensor. To do this, the apparatus comprises 12 near infrared diodes and 14 visible diodes. This document also describes two positioning lasers for positioning the apparatus relative to the imaged surface.

[0010] Documents US 2015 / 124067 and US 2015 / 124067 relate to a handheld device comprising at least one illuminator for projecting a beam of light and a video camera for capturing images of a region of interest.

[0011] US 2011 / 117025 describes a fluorescence-based imaging and monitoring device. This device comprises a light source for illuminating the target, the emitted light comprising at least one wavelength or wavelength band causing fluorescence of at least one biomarker associated with the target; and a light detector for detecting the fluorescence.

[0012] The present invention aims to provide a portable device capable of quickly producing images of two types: Providing good quality morphological information, i.e. with a high color rendering index, good resolution and good sharpness and Providing functional information relating to the level of skin oxygenation. The invention also aims to provide a device whose cost price is compatible with a sale price itself compatible with a purchase price defined during a survey as allowing sales to future target customers (home nurses, residential establishments for dependent elderly people (EHPAD), private doctors, health centers) and usable by the latter, that is to say adapting to their constraints in terms of mobility from the home or the room of one patient to another and therefore easily transportable (that is to say respecting the volume and weight constraints compatible with transport "by hand").

[0013] At least one of the aforementioned objectives is achieved with a portable device for acquiring images of a skin surface according to claim 1. This device comprises: an image acquisition camera, a memory medium for storing the images acquired by the camera, several light-emitting diodes or LEDs for illuminating a common area of ​​the skin surface, these light-emitting diodes comprising white and colored light-emitting diodes, a power supply.

[0014] The apparatus according to the invention further comprises a distance sensor for measuring the distance between the camera and the skin surface, as well as a processing unit connected to the distance sensor and configured to signal when the skin surface is within the depth of field of the camera.

[0015] Ideally, depth of field corresponds to a range of distances where the acquired image is sharp.

[0016] The apparatus according to the invention allows the acquisition of images which are used to determine the level of skin oxygenation.

[0017] This is non-contact imaging, meaning the device is positioned several centimeters from the skin's surface. It does not touch the skin's surface. It can be used handheld to capture a video sequence consisting of sharp images.

[0018] With the device according to the invention, a distance sensor allows the camera to be positioned at its focal distance, more generally in the depth of field. This ensures the sharpness of the acquired images.

[0019] The focal length depends on several parameters: the size of the camera sensor but for a given sensor, the "middle" or "center" of this "distance range" is given by the focal length specific to each lens, that is to say the lens located in front of the sensor; and for a given focal length, this depth of field finally depends on the aperture of the diaphragm, for example f / 11.

[0020] Advantageously, a diaphragm is placed in front of the camera to increase the depth of field. This diaphragm preferably has a small aperture, for example less than f / 8, preferably equal to f / 11.

[0021] The camera can be monochrome but it is preferably in color so as to obtain an image in real colors which alone allow an excellent color rendering index.

[0022] According to an advantageous characteristic of the invention, the distance sensor may be an ultrasonic rangefinder or an infrared radiation rangefinder. The latter is capable of sending a signal which is then reflected by the skin surface. The distance between the camera, on which the rangefinder is mounted, and the skin surface is determined from the time elapsed between the transmission and reception of the signal. Such a rangefinder is simple to use and inexpensive. According to an advantageous characteristic of the invention, the apparatus may comprise at least one diode or display device for generating a visible signal in response to an instruction from the processing unit when the skin surface is within the depth of field of the camera.

[0023] The visible signal may be the switching on or off of a diode, the display of an element such as a pattern, an image or the like on a camera display device or an attached display device.

[0024] Advantageously, the device according to the invention may comprise a loudspeaker capable of emitting an audible signal in response to an instruction from the processing unit when the skin surface is within the depth of field of the camera.

[0025] Whether it is an audible or visual signal, the device is able to indicate to the user that the distance between the camera and the skin surface is suitable for capturing a clear, high-quality image, in particular by using colored light-emitting diodes.

[0026] The presence of the colored light-emitting diodes and the ability to measure distance allows the single-handed portable device to acquire handheld (without the need to resort to the use of a spacer-type device to position the system at a fixed distance from the skin surface as found on certain viewing devices used in dermatology) video sequences lasting several seconds and consisting of clear images from the beginning to the end of the video sequence.

[0027] In order to further improve the image quality, the apparatus according to the invention may also comprise a sunshade to protect the camera lens from ambient light. This makes it possible to preserve the optimized color rendering index obtained by white lighting combining good lighting uniformity across the entire illuminated surface and an optimized correlated color temperature. By the color rendering index, or CRI, is meant the quantitative evaluation of the degree of agreement between the psychological color of an object illuminated by the test illuminant and that of the same object illuminated by the reference illuminant, the state of chromatic adaptation having been correctly taken into account (Commission Internationale de l'Eclairage, International Vocabulary of Illumination, CIE S 017 / E:2011, Vienna).

[0028] The CRI is quantitatively measurable and is expressed, for a given light, in relation to an ideal and for a given color temperature. The maximum index CRI=100 thus corresponds to an "ideal" white light such as natural light, while low indices CRI<20 correspond to the light emitted by a monochromatic lamp, such as a sodium vapor bulb, which allows little distinction between colors. For good quality lighting (as required for medical examinations), it is advisable to use lamps with a CRI greater than 90.

[0029] Furthermore, to obtain reliable colors across the entire measurement area, it is advantageous to have uniform illumination. Uniformity U can be defined as follows: U = I max − I min I max + I min

[0030] I max (respectively I min ) is defined as the maximum (respectively minimum) intensity found in the field of view (according to the grayscale values ​​evaluated using the software Matlab 2014, The Mathworks, Inc.). Smaller values ​​of U produce better illumination uniformity. Tests with the apparatus according to the invention have made it possible to obtain U values ​​equal to 0.17 while apparatuses according to the prior art had U values ​​up to 0.7, it is in this respect that the apparatus according to the invention is said to be optimized.

[0031] Thus, the sun visor limits the brightness coming from the surroundings, not just from sunlight. It contributes to the high color rendering index characterizing the image, which allows the morphology of the skin surface to be visualized.

[0032] This sun shield is a cover that can measure approximately 3 cm in length around the lighting ring and the camera in order to make the recorded image independent of ambient lighting; a problem that does not exist for devices with the camera placed in contact with the skin surface (such as dermoscopes for example). A characterization of the Color Rendering Index (CRI) made it possible to demonstrate the effectiveness of this technological solution compared to the CRI of devices placed in contact.

[0033] According to an advantageous characteristic of the invention, the processing unit can be configured to control the acquisition of images according to a video sequence of at least one image per second. The apparatus according to the invention makes it possible to effectively discriminate between different levels of skin oxygenation.

[0034] To obtain images usable for calculating the oxygenation level, an optimal duration of illumination of the skin surface by each group of LEDs (white or colored) was determined. This amounts to determining the duration of "pause" of the camera between two images for the accumulation of a sufficient number of photons to achieve sufficient sensitivity, all with the objective of finding the ideal compromise allowing a sufficiently fast acquisition to obtain a video rate, in the sense of at least 1 image per second.

[0035] This frame rate of one frame per second allows for a pause time long enough to accumulate enough photons but short enough to maintain a frame rate sufficient to be called "video." Ideally, a frame rate of ten frames per second is planned.

[0036] Advantageously, the processing unit can be configured to control the acquisition of the images by temporally multiplexing the lighting between the white light-emitting diodes and the color light-emitting diodes. This multiplexing is obtained in hardware from a multiplexer associated with the processing unit or in software by processing within the processing unit.

[0037] According to an advantageous characteristic of the invention, the colored light-emitting diodes comprise light-emitting diodes emitting in the red spectral band and light-emitting diodes emitting in the infrared spectral band.

[0038] The image acquisition camera can advantageously be optimized in the near-infrared spectral band. By optimized, we mean a gain of approximately 20 points, typically between 10 and 20, in sensitivity percentage (quantum efficiency) for wavelengths between 600 and 900 nm compared to a "non-optimized" camera.

[0039] Images obtained from white light provide access to morphological information. One or more white light-emitting diodes can be switched on on the same side to visualize the reliefs of the skin surface.

[0040] Images obtained from red light and infrared light provide access to functional information allowing the level of skin oxygenation to be assessed.

[0041] The device according to the invention makes it possible to acquire images according to three types of lighting: white, red and infrared.

[0042] The time multiplexing of a video sequence can then take place in white light (morphological information) and in red and infrared light (functional information).

[0043] According to another characteristic of the invention, the processing unit can be configured to alternately activate the light-emitting diodes emitting in the red spectral band and the light-emitting diodes emitting in the infrared spectral band. This amounts in particular to interposing a white light image (morphological information) between two images providing functional information, i.e. created from the red light illumination and the infrared light illumination.

[0044] Advantageously, each group of white, red or infrared light-emitting diodes can be positioned at an angle specific to each group relative to the optical axis so as to obtain homogeneous illumination on a common skin surface. In other words, the angle of implantation of the LEDs is specific to the optical characteristics of each type of LED and allows excellent homogeneity of illumination on the same common skin surface.

[0045] According to the invention, three different types of LEDs (different in wavelengths, irradiance and numerical aperture) are arranged in a sufficiently large number to achieve a sufficient irradiance level at the working distance (distance between the camera and the skin surface) but lower than the thresholds set by standard NF EN 62471:2008 according to the European directive relating to electro-medical devices 93 / 42 / EC.

[0046] The working distance can be, for example, 5 cm.

[0047] The number of LEDs for each group is constrained by the irradiance level of each group to reduce the camera's required dwell time and achieve a video-like frame rate. Typically, the light spot can be a 2 cm square.

[0048] The orientation of the LEDs is notably a function of the numerical aperture of the LEDs.

[0049] According to an advantageous characteristic of the invention, the processing unit is configured to calculate in real time the level of cutaneous oxygenation and display it in the form of a color code. Each color can correspond to a range of oxygenation level values.

[0050] Unlike prior art systems which provide information such as Hb, HbO2 concentrations, etc., the device according to the invention provides the user with information, PtcO2, validated by international clinical consensus as part of the parameters to be evaluated as part of a chronic wound management procedure.

[0051] According to the invention, the processing unit is configured to respect a pause time after each image acquisition, this pause time being a function of the desired sensitivity in determining the level of cutaneous oxygenation. The longer the pause time, the greater the sensitivity. A high sensitivity of the oxygenation level is the fact of being able to determine low values ​​of the transcutaneous partial pressure of oxygen, PtcO2.

[0052] With the apparatus according to the invention, it is possible to carry out an evaluation of the level of cutaneous oxygenation of an entire skin surface. For example, the apparatus can carry out a measurement of the PtcO2 on a skin surface of 4 cm 2< per second of video sequence, i.e. approximately 40 cm 2< per 10 seconds, and no longer punctually 3 cm 2< per 30 minutes as in current clinical practice. In addition, the time multiplexing of the 2 video streams in white light and in red / infrared light makes it possible to send at the same time with the same apparatus a conventional image (carrying the morphological information) and an image measuring the information on the level of cutaneous oxygenation for the same skin surface.

[0053] According to an advantageous characteristic of the invention, the apparatus may comprise a circular polarizing filter vertically polarizing the light coming from the skin surface, this circular polarizing filter being arranged between the lens of the camera and the skin surface to suppress light due to specular reflection coming from the skin surface.

[0054] According to an advantageous characteristic of the invention, the apparatus may comprise a linear polarizing filter horizontally polarizing the light generated by a portion of the white light-emitting diodes, this linear polarizing filter being arranged only facing said portion of white light-emitting diodes.

[0055] Preferably, the white light-emitting diodes are arranged along a circle of diameter D1, the color light-emitting diodes being arranged along a circle of diameter D2 such that D2>D1. The two circles may be concentric.

[0056] Advantageously, the light-emitting diodes can be held in place by a ring arranged around a camera lens. The ring is a solid, rigid element that carries the LEDs. Ideally, it is a circular ring, but it can be square, rectangular, oval, or other more complex shapes. The goal is to uniformly illuminate the skin surface.

[0057] Additionally, the lens hood may attach to the crown and may have a groove on its inner wall to hold the linear polarizing film.

[0058] According to an advantageous characteristic of the invention, the apparatus may comprise a linearity correction lens to limit distortions due to the use of different wavelengths among the light-emitting diodes.

[0059] A linearity correction lens ensures image sharpness in all three lighting modes. Since the diffraction angle depends on the wavelength, the diffraction angles of the radiation emitted by white, red, or infrared LEDs are very different from each other.

[0060] The apparatus according to the invention comprises a display screen and the processing unit is configured to simultaneously display a video stream acquired in white light to visualize the morphology of the skin surface and a graphical representation of the oxygenation level in color levels on the skin surface with display of the average oxygenation rate. This screen can therefore be integrated into the hand-held device or it can be a remote screen (computer screen, television, mobile phone, dedicated remote screen, etc.) to which the rest of the device connects with or without wires.

[0061] Preferably, the apparatus according to the invention comprises a wireless communication module for transferring images.

[0062] In addition in particular to the above, the apparatus according to the invention may comprise a main body having at one end an optical head in which at least the light-emitting diodes are located, and a handle fixed to a lateral side of the main body. For example, the power supply may be arranged in the handle, while the processing unit and the camera may be arranged in the main body.

[0063] According to another aspect of the invention, there is provided a method according to claim 20.

[0064] Of course, the various features, forms and variant embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive.

[0065] Other advantages and characteristics of the invention will appear on examining the detailed description of a non-limiting embodiment, and the appended drawings, in which: There figure 1 is a schematic view of a portable wireless device for acquiring skin videos according to the invention, The figure 2 is a schematic view of the optical head of the device according to the invention, The figure 3 is a schematic view of the filter and the sun visor covering the light-emitting diodes of the optical head according to the invention, The figure 4 is a very simplified schematic sectional view of the otic head, The figure 5 is a very simplified schematic view in functional blocks of the device according to the invention, The figure 6 is a flowchart illustrating an algorithm for calculating the oxygenation level according to the invention, The figure 7 is an image of a skin surface on a part of a hand using white light according to the invention, The figure 8 is a processed image of a skin surface on a portion of a hand using red and infrared illumination according to the invention, The figure 9 is another processed image of a skin surface on two fingers (one of the two fingers undergoing venous occlusion by the application of a tourniquet at the carpometacarpal joint to induce skin hypoxia) using red and infrared illumination according to the invention, and The figure 10 is a schematic view of the head of the device according to an exemplary embodiment.

[0066] On the figure 1 we distinguish a device 1 according to the invention intended to acquire videos of a skin surface. This device 1 comprises a main body designated in its entirety by the reference 2 and a handle 3.

[0067] The main body 2 comprises an optical head 4 equipped with optical means necessary for image acquisition. An electronic card is arranged in the rest of the main body. The latter has a cylindrical shape with a circular section. It is therefore an elongated cylinder of about ten centimeters and a radius of approximately four centimeters. The optical head is arranged on the front end, this is the part which comes in front of the skin surface to be imaged during use.

[0068] The handle 3 is hand-sized. It is attached to the main body on one side. When a user holds the handle, the main body is on the upper part. The overall shape of the device is that of a pistol. The handle has an elbow between an upper part and a lower part. The upper part is directly connected to the main body perpendicular to the outer wall of the main body. The lower part then curves out at an angle to facilitate gripping.

[0069] The device according to the invention is a portable device which weighs less than 1 kg and which can be transported in a small suitcase from one patient's home to another, as is the case for a home nurse, or from the room of an EHPAD resident to another.

[0070] In reference to the figures 2 à 4 , we can see some elements of the optical head 4.

[0071] Camera 5 is used for its optimized sensitivity in the visible - near infrared spectral band (470 - 850 nm). The camera includes a CMOS sensor 9 allowing a video sequence to be recorded on a memory card inserted into the camera.

[0072] This sensor 9 is covered with a circular polarizing filter 10, visible on the figure 4 , in the form of a disc placed in front of the sensor 9. This circular polarizing filter 10 is transparent blue, vertically polarizing the light coming from the skin surface to be imaged. It rests on a specific edge forming an integral part of the crown 6.

[0073] A crown 6 is arranged on the camera 5, on the outside and around the sensor 9. The crown carries eight white LEDs 7 surrounding the CMOS sensor. For reasons of simplification of the drawing, the colored LEDs are not shown on the figures 2 et 3 , but only on the figure 4 under reference 11. Each light-emitting diode is force-fitted into a hole oriented at 24° in the crown 6.

[0074] A circular power supply circuit 8 is inserted into the crown 6 from the rear, on the side of the camera 5. It connects each LED to the power supply and is controlled by the processing unit to sequentially light the LEDs.

[0075] The light-emitting diodes are oriented so as to evenly illuminate the skin surface. The disc 12 on the figure 2 fictionally illustrates the skin surface where the light beams from the light-emitting diodes overlap to form a homogeneous illumination surface.

[0076] A linear polarizing filter 13 is provided, in which holes have been drilled so as to provide: polarized lighting when four white LEDs are lit, these are LEDs in front of which the filter is actually present, not perforated, non-polarized lighting when the other four white LEDs are lit, those facing the holes drilled in the filter.

[0077] The linear polarizer filter horizontally polarizes the light generated by white light-emitting diodes.

[0078] Also provided is a lens hood 14 which attaches to the crown and has a rim to hold the linear polarizing filter in place.

[0079] On the figure 5 , the optical head is generally referenced in 4, which in association with the rest of the device, makes it possible to obtain a video sequence whose images present a high colorimetric rendering index.

[0080] A processing unit 15 makes it possible to control the lighting of the light-emitting diodes according to a predetermined rate. For example, with regard to the white LEDs, the processing unit can successively light four LEDs to provide polarized lighting, then four other LEDs to provide non-polarized lighting, and finally two LEDs located on the same side to provide lateral lighting aimed at providing better visualization of the skin reliefs. The last two LEDs are taken from among the set of white LEDs intended to produce polarized or non-polarized images, but it can also be two additional white LEDs.

[0081] According to the invention, the apparatus comprises a distance sensor 18 for measuring the distance between the camera and the skin surface. This distance sensor is an ultrasonic rangefinder which makes it possible to position the camera at its focal length, plus or minus the depth of field so as to ensure the sharpness of the image.

[0082] Advantageously, this distance sensor is connected to the processing unit which lights up an orange indicator light (see figure 10 ) placed on the device if the rangefinder detects a distance between the camera and the skin surface that is too small, in blue if the distance is too great and in green if the distance is between two extremes which correspond to the maximum and minimum depth of field.

[0083] This distance sensor 18 can be arranged on the crown as seen in the figure 2 , but it can also be arranged on the camera, integrated into the camera or arranged on an external wall of the main body. Preferably, the rangefinder is arranged as close as possible to the camera.

[0084] Preferably, the camera focal length is fixed with a depth of field (for example with an aperture of f / 11) allowing the working distance to be changed in real time within the limit of the depth of field. A variable focal length - autofocus - can also be considered.

[0085] The processing unit may comprise one or more microprocessors or microcontrollers associated with hardware and / or software components for the proper functioning of the device according to the invention. The software part is capable of interacting with the microprocessor, the camera, the power supply circuit, of processing the acquired images and of displaying two video streams.

[0086] On the figure 5 There is also a wireless communication module 16 for communication with a remote device such as a server, a router, a mobile phone, a computer, a tablet or other. This wireless communication module advantageously allows images and videos to be transferred from the device to the outside.

[0087] On the figure 5 we also distinguish a power supply 17.

[0088] According to the invention, the power supply can be in two parts: a battery that powers the processing unit, and a rechargeable battery that powers the LEDs.

[0089] The battery can be arranged in the handle 3 of the device. The rechargeable battery can be arranged in the main body 2.

[0090] The entire device fits in a single volume because all the elements are assembled and protected by plastic shells.

[0091] On the figure 6 A coded algorithm is illustrated to control the sequential switching on of the LED arrays, synchronize the video acquisition, and perform the calculations necessary for the time-multiplexed display of the two video streams of interest.

[0092] Step E1 of camera setup includes the following operations: Opening the camera, Configuring the bitmap display mode Configuring 8-bit colors Setting the range and offset Setting the exposure time, the number of frames per second Configuring the camera trigger Allocating memory for images Testing image acquisition by the camera

[0093] The E2 algorithm initialization step allows to define extinction coefficients of Hb (hemoglobin), HbO 2 (oxyhemoglobin) for the working wavelengths, 660 nm and 850 nm. This also allows to define light penetration depths in the skin, as well as to define specular and diffuse reflection rates. Then initialization during the same step, of five matrices of the same size as those of the images to be acquired: 2 optical density matrices at 660 nm and 850 nm, 2 matrices for Hb concentration and HbO 2 concentration, A matrix for the skin oxygenation level.

[0094] Then it is step E3 which allows the loop to be triggered for the representation of the oxygenation level.

[0095] Step E4 involves the acquisition of images at 660 nm and 850 nm.

[0096] In step E5, the specular reflection and the diffuse reflection are taken into account for each wavelength.

[0097] The calculation of optical densities (OD) is carried out in step E6.

[0098] The calculation of concentrations is carried out in step E7 according to the following formula in particular: C HbO 2 = OD λ 2 − ε Hb λ 2 . d λ 2 ε Hb λ 1 . d λ 1 . OD λ 1 ε HbO 2 λ 2 . d λ 2 − ε Hb λ 2 . d λ 2 . ε HbO 2 λ 1 ε Hb λ 1 C Hb = OD 1 ε Hb λ 1 . d λ 1 − ε HbO 2 λ 2 ε Hb λ 2 . C HbO 2

[0099] The calculation of the average oxygenation rate at the center of the target is carried out in step E8.

[0100] Then, in step E9, a graphic representation of the oxygenation level is produced in color levels with display of the average oxygenation rate.

[0101] THE figures 7 et 8 illustrate two images which respectively present two simultaneously displayed video streams produced by the apparatus according to the invention.

[0102] There figure 7 showing the video stream acquired in white light and which provides access to morphological information. figure 8 shows the video stream acquired by alternating red illumination (660 nm) and infrared illumination (850 nm) which, after data processing, allows an image to be displayed giving the levels of skin oxygenation also called functional information.

[0103] There figure 9 shows the ability of the device according to the invention to detect a variation in the level of cutaneous oxygenation by comparing the level of cutaneous oxygenation of two fingers of the same hand: the middle finger presenting a “normal” level of oxygenation (on the left in the figure with a dominant solid color) and the index finger to which a venous occlusion is applied at the level of the carpo-metacarpal joint presenting, as a consequence of the occlusion, a lower level of cutaneous oxygenation (on the right in the figure with a large shaded central part).

[0104] According to a particularly advantageous aspect of the invention, the apparatus: is portable and wireless, allowing it to be used more easily in certain telemedicine situations, allows handheld acquisition of images containing useful information because the images are very sharp thanks in particular to the rangefinder allowing the camera to be correctly positioned in the depth of field of the sensor, allows the acquisition of a classic image characterized by a high colorimetric rendering index thanks to the fact that the system integrates: bright lighting whose correlated color temperature is optimized (for example to discriminate pairs of colors of interest in clinical dermatology), and a sun visor which effectively isolates the sensor from the surrounding lighting.allows the simultaneous acquisition of two types of co-located information (morphological and functional) which can be transmitted remotely, is compatible with marketing because it has a controlled manufacturing cost, is compatible with clinical use because it meets the essential requirements of European directive 93 / 42 / EC relating to electro-medical devices, particularly in terms of electromagnetic compatibility and electrical and photobiological safety, and allows several viewing modes: Polarized mode, i.e. which eliminates the brightness which is often annoying for viewing skin lesions on a photo or video image (brightness being the common name used to designate the optical phenomenon of specular reflection), Classic mode without polarization in cases where this would be of interest, Lateral viewing in order to make reliefs more evident.

[0105] There figure 10 is a schematic view of the head of the device according to another exemplary embodiment of the device according to the invention. A sun visor 19 can be seen playing the same role as the sun visor 14 of the figures 3 And 4 An electronic card 20 carries a set of electronic components such as, for example, capacitors, resistors and control circuits.

[0106] The rangefinder 21 according to the invention is arranged near the camera 22 making it possible to detect the distance between the camera and the skin surface. Signaling diodes are arranged around the edge of the electronic card 20 so as to illuminate a circular strip 23, visible from the outside of the device and arranged between the sun visor 19 and the rest 24 of the head of the device.

[0107] It is also possible to consider having laser pointers (class 1 for example) in the head of the device.

[0108] Laser pointers could draw the corners of a viewing square so that the user can easily view the skin surface being imaged without having to move their gaze to a computer screen on which the video is simultaneously projected. This is an ergonomic way for the user to know exactly, and in real time, the skin surface being imaged.

[0109] In general, the invention relates to a portable apparatus for acquiring images of a skin surface, this apparatus comprising: an image acquisition camera, video or still images, a memory medium for storing the images acquired by the camera, several light-emitting diodes for illuminating in a time-multiplexed manner a common area of ​​the skin surface with optimized homogeneity. These light-emitting diodes include white light-emitting diodes with optimized correlated color temperature intended for the acquisition of real color images with a high color rendering index and color light-emitting diodes intended for the production of images providing information on the level of skin oxygenation.

[0110] An optimized correlated color temperature (CCT) means a CCT (measured, for example, by a spectroradiometer and expressed in Kelvin) included in the solar value range, i.e. between 5,000 and 6,000 K.

[0111] A high index means an IRC greater than 90, for example 94.4, knowing that the theoretical maximum is 100.

[0112] The irradiance levels can notably respect all the thresholds set by the NF EN 62471:2008 standard according to the European directive relating to electro-medical devices 93 / 42 / CE.

[0113] According to the invention, both types of images are displayed simultaneously on the screen.

[0114] The device also includes: a power supply, and a distance sensor to measure the distance between the camera and the skin surface, allowing freehand operation and thus enabling the acquisition of a video sequence made up of completely clear images.

[0115] The device may further include a sun visor (also contributing to the high color rendering index) a processing unit connected to the distance sensor and configured to signal when the skin surface is within the depth of field of the camera.

[0116] Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention.

Claims

1. A portable apparatus (1) for acquiring images of a skin surface, this apparatus comprising: - an image acquisition camera (5), - a storage medium for storing images acquired by the camera, - multiple light-emitting diodes (7, 11) for illuminating a common area (12) of the skin surface, these light-emitting diodes comprising white and colored light-emitting diodes, - a power supply (8), - a distance sensor (18) for measuring the distance between the camera (5) and the skin surface (12), - a processing unit (15) connected to the distance sensor (18) and configured to signal when the skin surface is within the depth of field of the camera (5), characterized in that it comprises a display screen and the processing unit (15) is configured to simultaneously display a video stream acquired in white light to visualize the morphology of the skin surface (12) and a graphic representation of the oxygenation level in color levels on the skin surface with a display of the average oxygenation rate.

2. The apparatus according to any one of the preceding claims, characterized in that the colored light-emitting diodes (17) comprise light-emitting diodes emitting in the red spectral band and light-emitting diodes emitting in the infrared spectral band.

3. The apparatus according to claim 2 characterized in that the processing unit (15) is configured to alternately activate the light-emitting diodes emitting in the red spectral band and the light-emitting diodes emitting in the infrared spectral band.

4. The apparatus according to claim 2 or 3, characterized in that each group of white, red or infrared light-emitting diodes is positioned at an angle specific to each group with respect to the optical axis so as to obtain homogeneous illumination on a common skin surface.

5. The apparatus according to any one of the preceding claims, characterized in that a diaphragm is placed in front of the camera (5) to increase the field depth.

6. The apparatus according to any one of the preceding claims, characterized in that it comprises a linearity correction lens to limit distortions due to the use of different wavelengths from the light-emitting diodes.

7. The apparatus according to any one of the preceding claims, characterized in that the distance sensor (18) is an ultrasonic or infrared rangefinder.

8. The apparatus according to any one of the preceding claims, characterized in that it comprises at least one diode or a display device for generating a visible signal in response to a command from the processing unit (15) when the skin surface is within the depth of field of the camera.

9. The apparatus according to any one of the preceding claims, characterized in that it comprises a loudspeaker capable of emitting a sound signal in response to a command from the processing unit when the skin surface is within the depth of field of the camera.

10. The apparatus according to any one of the preceding claims, characterized in that it comprises a lens hood (14, 19) to protect the camera lens from ambient lighting.

11. The apparatus according to any one of the preceding claims, characterized in that the processing unit (15) is configured to control the acquisition of images according to a video sequence of at least one image per second.

12. The apparatus according to any one of the preceding claims, characterized in that the processing unit (15) is configured to control the acquisition of images by time-multiplexed illumination between the white light-emitting diodes and the colored light-emitting diodes.

13. The apparatus according to any one of the preceding claims, characterized in that the processing unit (15) is configured to calculate the skin oxygenation level in real time and display it according to a color code.

14. The apparatus according to claim 13, characterized in that the processing unit (15) is configured to respect a pause time after each image acquisition, this pause time being proportional to a desired precision on the determination of the skin oxygenation level.

15. The apparatus according to any one of the preceding claims, characterized in that the white light-emitting diodes are arranged along a circle of diameter D1, the colored light-emitting diodes being arranged along a circle of diameter D2 such that D2>D1.

16. The apparatus according to claim 10, characterized in that the lens hood (14, 19) is attached to a ring (6) and comprises a groove on the inner wall thereof to hold the linear polarizing film (13).

17. The apparatus according to any one of the preceding claims, characterized in that it comprises a wireless communication module (16) for image transfer.

18. The apparatus according to any one of the preceding claims, characterized in that it comprises a main body (2) having at one end an optical head (4) wherein at least the light-emitting diodes are located, and a handle (3) attached to a lateral side of the main body.

19. The apparatus according to claim 18, characterized in that the power supply is arranged in the handle (3), while the processing unit (15) and the camera (5) are arranged in the main body (2).

20. A method of acquiring images of a skin surface from an apparatus (1), in which method the following steps are performed: - acquiring images from an acquisition camera (5), - storing acquired images on a storage medium, - illuminating a common area (12) of the skin surface from multiple light-emitting diodes (7, 11), these light-emitting diodes comprising white and colored light-emitting diodes, - measuring the distance between the camera and the skin surface by means of a distance sensor (18), and - emitting a signal using a processing unit (15) when the skin surface is within the depth of field of the camera, - characterized in that it comprises a step of simultaneously displaying a video stream acquired in white light to visualize the morphology of the skin surface (12) and a graphical representation of the oxygenation level in color levels on the skin surface with a display of the average oxygenation rate.