Method for estimating skin viscoelasticity index
By estimating skin viscoelasticity using facial imaging parameters, the method addresses the limitations of expensive and skill-dependent devices, enabling affordable and frequent skin viscoelasticity assessments.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- FUAN KERU
- Filing Date
- 2024-12-06
- Publication Date
- 2026-06-18
AI Technical Summary
Existing methods for measuring skin viscoelasticity, such as those using devices like the CUTOMETER, are expensive, require specialized skills, and are limited to specific facilities, making it difficult to obtain skin viscoelasticity indices easily and affordably.
Estimate skin viscoelasticity using numerical parameters derived from facial imaging, employing facial shape parameters and skin viscoelasticity indices calculated from these parameters, which can be determined visually or through machine learning, and corrected for tilt and distortion.
Enables easy and cost-effective estimation of skin viscoelasticity, allowing frequent monitoring of skin changes and improving the accuracy of assessing skin health.
Smart Images
Figure 2026098937000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a method for estimating a skin viscoelasticity index from an image obtained by imaging a face.
Background Art
[0002] The health state of the skin is evaluated using various indices. For example, the presence or absence of the "firmness" feeling of the skin is regarded as one of the evaluation indices for the health state and the degree of aging. "Firmness" can be divided into two types: firmness derived from the stratum corneum and epidermis, and firmness derived from the dermis. In particular, the firmness derived from the dermis has elasticity such that when the skin is pressed with a finger, it rebounds, and when the finger is released, it quickly returns to its original state, which is also physically referred to as viscoelasticity. And this viscoelasticity exhibited by the skin also decreases due to factors such as age, ultraviolet exposure, and skin exposure to chemical substances. Therefore, the firmness of the skin can also be an index of skin aging.
[0003] Regarding regarding considering the skin as an elastic body, methods and measuring devices have been developed to measure the viscoelastic modulus of the skin and use it in place of the sensory evaluation method of "firmness". As a typical skin viscoelasticity measuring device, there is CUTOMETER (trade name) (manufactured by Courage & Khazaka). This device draws the skin surface into the probe opening in a negative pressure state, measures the skin length drawn into the opening with a prism, then releases the suction, and similarly measures the displacement length (return) when the suction is released, and obtains a skin viscoelasticity index from this measurement result (see Non-Patent Document 1). Using the viscoelastic modulus measured by this device as an index, the evaluation of the degree of skin aging and the evaluation of the effects of cosmetics have been widely popularized in the cosmetics industry and the beauty-related medical field. However, the technology for measuring skin viscoelasticity using a skin viscoelasticity measuring device is such that the probes and devices used for measurement are expensive and require skill in use. Therefore, the facilities where measurement is possible are limited to specialized salons and medical institutions, etc., and it is difficult to know the skin viscoelasticity index cheaply, simply, and quickly.
[0004] The applicant of the present application has proposed an estimation method for estimating a skin viscoelasticity index from a stratum corneum image in Patent Document 1. The method described in Patent Document 1 allows for the numerical evaluation of the length, diameter, linearity, etc., of fibrillin, which is the skeletal fiber of elastic fibers. [Prior art documents] [Patent Documents]
[0005] [Patent Document 1] Japanese Patent Publication No. 2024-19957 [Non-patent literature]
[0006] [Non-Patent Document 1] Integral Co., Ltd., "CUTOMETER MPA580 Skin Viscoelasticity Measurement Device Manual," Revised May 2007. [Overview of the Initiative] [Problems that the invention aims to solve]
[0007] The method described in Patent Document 1 requires the collection of stratum corneum cells, imaging of the collected stratum corneum cells, and analysis of those cells, making it difficult to implement easily. The object of this invention is to provide a simple method for estimating the skin viscoelasticity index. [Means for solving the problem]
[0008] This invention was made after diligent research to solve the above problems, and it was discovered that the skin viscoelastic index can be estimated using numerical parameters obtained from facial imaging images as indicators. Specifically, the means for solving the problems of the present invention are as follows: 1. An estimation method characterized by estimating a skin viscoelastic index using facial shape parameters obtained from facial imaging images as indicators. 2. The estimation method according to 1, characterized in that the facial shape parameter is one or more selected from the group consisting of (1) to (14) below. (1) The length from the center of the nose to the point where a line extended horizontally touches the contour. (2) Within the contour, in the area between the line extended horizontally from (1) and the line extended straight down from the corner of the lips, the longest length from the center of the nose (3) The length from the point where a line drawn straight down from the center of the nose touches the tip of the chin (the point where the line drawn straight down from the center of the nose intersects with the contour). (4) The angle formed by a line drawn horizontally from the center of the mouth and a line connecting the point of contact between this line and the contour and the central tip of the chin. (5) The line extending horizontally from (1) and the line connecting the point of contact with the contour to the central tip of the chin, and the area of the arc formed by the contour. (6) The length from the center of the mouth downwards to the tip of the center of the chin. (7) The angle formed by the line extended horizontally from (1) and the line extended from the point of contact between this line and the contour to the highest point of the cheekbone. (8) Length from the highest point of the cheekbone to the outer corner of the eye (9) Ratio of face shape parameters (1) to (2) (1 / 2) (10) Ratio of face shape parameters (1) to (3) (1 / 3) (11) Ratio of face shape parameters (2) and (3) (2 / 3) (12) Ratio of face shape parameters (8) to (1) (8 / 1) (13) Ratio of face shape parameters (8) to (3) (8 / 3) (14) Maximum value of the differential curve of the brightness value in the nasolabial fold area 3. The estimation method according to 1. or 2., characterized in that the skin viscoelastic index is one or more selected from the group consisting of R1 to R8 below. R1 = Uf - Ua: The amount of skin that did not instantly return to its original shape after being deformed by suction. R2 = Ua / Uf: The ratio of total displacement to total recovery when the skin is deformed by suction (total recovery amount / total displacement amount) R3: Height of the final waveform when the skin is deformed by suction. R4: The portion of the final waveform that did not return to its original shape after the skin was deformed by suction. R5 = Ur / Ue: The ratio of instantaneous recovery amount to instantaneous displacement amount when the skin is deformed by suction (instantaneous recovery amount / instantaneous displacement amount) R6 = Uv / Ue: Ratio of the amount of delayed displacement to the amount of instantaneous displacement when the skin is suctioned and deformed (delayed displacement amount / instantaneous displacement amount) R7 = Ur / Uf: Ratio of the amount of instantaneous recovery to the total displacement amount when the skin is suctioned and deformed (instantaneous recovery amount / total displacement amount) R8 = Ua: Amount of delayed recovery when the skin is suctioned and deformed (Ue: Instantaneous deformation during suction, Uv: Deformation over time during suction, Uf: Maximum suction height, Ur: Instantaneous return after negative pressure release, Ua: Final return after release)
Advantages of the Invention
[0009] By the estimation method of the present invention, skin viscoelasticity indexes can be estimated very easily and at low cost. By estimating skin viscoelasticity indexes more frequently than before using the estimation method of the present invention, the state changes of skin viscoelasticity indexes can be grasped, so that the influence of daily life on skin viscoelasticity indexes can be grasped more accurately.
Brief Description of the Drawings
[0010] [Figure 1] Diagram for explaining face shape parameters. [Figure 2] Diagram for explaining face shape parameters.
Embodiments for Carrying Out the Invention
[0011] The estimation method of the present invention estimates skin viscoelasticity indexes using face shape parameters obtained from captured images of the face as indicators. The captured image of the face may be a still image captured from the front or a moving image captured from various angles.
[0012] In the estimation method of the present invention, the combination of the face shape parameters used as indicators and the skin viscoelasticity indexes to be estimated is not particularly limited as long as they have a correlation. For example, the following (1) to (14) can be mentioned as face shape parameters, and the following R1 to R8 can be mentioned as skin viscoelasticity indexes.
[0013] 「Face Shape Parameters」 The facial shape parameters (1) to (8) are shown in Figures 1 and 2. (1) The length from the center of the nose to the point where a line extended horizontally touches the contour. (2) Within the contour, in the area between the line extended horizontally from (1) and the line extended straight down from the corner of the lips, the longest length from the center of the nose (3) The length from the point where a line drawn straight down from the center of the nose touches the tip of the chin (the point where the line drawn straight down from the center of the nose intersects with the contour). (4) The angle formed by a line drawn horizontally from the center of the mouth and a line connecting the point of contact between this line and the contour and the central tip of the chin. (5) The line extending horizontally from (1) and the line connecting the point of contact with the contour to the central tip of the chin, and the area of the arc formed by the contour. (6) The length from the center of the mouth downwards to the tip of the center of the chin. (7) The angle formed by the line extended horizontally from (1) and the line extended from the point of contact between this line and the contour to the highest point of the cheekbone. (8) Length from the highest point of the cheekbone to the outer corner of the eye (9) Ratio of face shape parameters (1) to (2) (1 / 2) (10) Ratio of face shape parameters (1) to (3) (1 / 3) (11) Ratio of face shape parameters (2) and (3) (2 / 3) (12) Ratio of face shape parameters (8) to (1) (8 / 1) (13) Ratio of face shape parameters (8) to (3) (8 / 3) (14) Maximum value of the differential curve of the brightness value in the nasolabial fold area
[0014] In this specification, the vertical and horizontal (left-right) directions of the face are based on the state of the face when a person is standing upright, that is, with the top of the head pointing upwards and the chin pointing downwards. The center of the nose is the highest point on the midline between the left and right sides of the nose. In (2), the area of the contour between the line extended horizontally in (1) and the line extended straight down from the corner of the lips is the part of the contour shown in Figure 2 where the darker lines overlap. In (14), the point where the differential curve of the luminance value is at its maximum is the position where the nasolabial fold is deepest.
[0015] The facial features used to identify the facial shape parameters described above may be determined visually by a human from the captured image, mechanically, or using machine learning-trained AI. Furthermore, points determined by AI may be manually corrected by a human. When determined mechanically, for example, the point with the highest brightness value within a specific area of the captured image, i.e., the point where light is most strongly reflected, can be determined as the highest point. Additionally, before identifying the facial features, the tilt and distortion of the facial image can be corrected, for example, so that the central tip of the chin is directly downwards. Face shape parameters can be defined using only one side of the face, or both sides. When using both sides, the average of the values obtained from each side is used.
[0016] "Skin viscoelasticity index" R1 = Uf - Ua: The amount of skin that did not instantly return to its original shape after being deformed by suction. R2 = Ua / Uf: The ratio of total displacement to total recovery when the skin is deformed by suction (total recovery amount / total displacement amount) R3: Height of the final waveform when the skin is deformed by suction. R4: The portion of the final waveform that did not return to its original shape after the skin was deformed by suction. R5 = Ur / Ue: The ratio of instantaneous recovery amount to instantaneous displacement amount when the skin is deformed by suction (instantaneous recovery amount / instantaneous displacement amount) R6 = Uv / Ue: The ratio of delayed displacement to instantaneous displacement when the skin is deformed by suction (delayed displacement / instantaneous displacement) R7 = Ur / Uf: Ratio of instantaneous recovery amount to total displacement amount when the skin is deformed by suction (instantaneous recovery amount / total displacement amount) R8 = Ua: Delayed recovery amount when the skin is deformed by suction. (Ue: instantaneous deformation during suction, UV: deformation over time during suction, Uf: maximum suction height, Ur: instantaneous return after negative pressure release, Ua: final return after release) The skin viscoelastic index can be measured, for example, using a skin viscoelasticity measuring device (CUTOMETER, manufactured by Courage & Khazaka).
[0017] In the estimation method of the present invention, the method for estimating the skin viscoelastic index using facial shape parameters as indicators is not particularly limited, and known methods can be used. For example, facial shape parameters may be subjected to simple linear regression analysis or multiple linear regression analysis. The multiple linear regression analysis may be linear multiple linear regression analysis or nonlinear multiple linear regression analysis. When performing multiple linear regression analysis, the number of facial shape parameters used as indicators is not particularly limited and can be 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, 10 or more, 11 or more, 12 or more, 13 or more, or 14. In the estimation method of the present invention, the absolute value (|r|) of the correlation coefficient between the estimated skin viscoelastic index and the facial shape parameter, which is an index, is preferably 0.2 or higher, more preferably 0.3 or higher, even more preferably 0.4 or higher, even more preferably 0.5 or higher, even more preferably 0.6 or higher, even more preferably 0.7 or higher, and even more preferably 0.8 or higher. [Examples]
[0018] "Acquisition of facial shape parameters" For 40 Japanese women (ages 32-58), frontal still images of their faces were captured using a full-face camera (Visia), and one expert visually identified the position of each image to determine the facial shape parameters (1) to (14) described above.
[0019] "Skin viscoelasticity index" For the same 40 Japanese women, after washing their faces and resting for 10 minutes, the viscoelasticity of the skin on their cheeks was measured using a Cutometer® (manufactured by Courage + Khazaka Electronic GmbH (Cologne, Germany)).
[0020] "Simple linear regression analysis" Simple regression analysis was performed on each facial shape parameter and the skin viscoelasticity index. For those where a correlation was found, the correlation coefficient r, p-value, and the equation of the simple regression line (Y=aX+b, where X is the facial shape parameter value and Y is the skin viscoelasticity index) are shown in Tables 1 and 2.
[0021] [Table 1]
[0022] [Table 2]
[0023] The facial shape parameters and skin viscoelasticity index shown in Tables 1 and 2 showed a correlation (|r|≧0.2).
[0024] Multiple Regression Analysis 1 Multiple regression analysis was performed on the skin viscoelasticity index using 3 to 6 facial shape parameters as explanatory variables. For those for which a correlation was found, the equation of the multiple regression line (Y = a1X1 + a2X2 + ... + b, where Xn is the facial shape parameter value and Y is the skin viscoelasticity index) is shown in Table 3. [Table 3] The skin viscoelasticity indices R2, 3, and 5-8 showed a high correlation (|r|≧0.4) with 3-6 facial shape parameters as explanatory variables.
[0025] Multiple Regression Analysis 2 Multiple regression analysis was performed on the skin viscoelasticity index using 14 facial shape parameters as explanatory variables. The equation of the multiple regression line (Y = a1X1 + a2X2 + ... + b, where Xn is the facial shape parameter value and Y is the skin viscoelasticity index) is shown in Tables 4 and 5. [Table 4] [Table 5]
[0026] As shown in Tables 4 and 5, a higher correlation (|r|≧0.5) with the skin viscoelasticity index was observed by combining facial shape parameters.
Claims
1. An estimation method characterized by estimating a skin viscoelastic index using facial shape parameters obtained from facial imaging images as indicators.
2. The estimation method according to claim 1, characterized in that the facial shape parameter is one or more selected from the group consisting of (1) to (14) below. (1) The length from the center of the nose to the point where a line extended horizontally touches the contour. (2) Within the contour, in the area between the line extended horizontally in (1) and the line extended straight down from the corner of the lips, the longest length from the center of the nose (3) The length from the point where a line drawn straight down from the center of the nose touches the tip of the center of the chin (the point where the line drawn straight down from the center of the nose intersects with the contour). (4) The angle formed by a line drawn horizontally from the center of the mouth and a line connecting the point of contact between this line and the contour and the central tip of the chin. (5) The line connecting the point of contact between the horizontally extended line of (1) and the contour to the central tip of the chin, and the area of the arc formed by the contour. (6) The length from the center of the mouth downwards until the line touches the tip of the center of the chin. (7) The angle between the line drawn horizontally from (1) and the line drawn from the point of contact between this line and the contour to the highest point of the cheekbone. (8) The length from the highest point of the cheekbone to the outer corner of the eye (9) Ratio of facial shape parameters (1) to (2) (1 / 2) (10) Ratio of face shape parameters (1) to (3) (1 / 3) (11) Ratio of face shape parameters (2) and (3) (2 / 3) (12) Ratio of facial shape parameter (8) to (1) (8 / 1) (13) Ratio of facial shape parameters (8) to (3) (8 / 3) (14) Maximum value of the differential curve of the brightness value in the nasolabial fold area
3. The estimation method according to claim 1 or 2, characterized in that the skin viscoelastic index is one or more selected from the group consisting of R1 to R8 below. R1 = Uf - Ua: The amount of skin that did not instantly return to its original shape after being deformed by suction. R² = Ua / Uf: The ratio of total displacement to total recovery when the skin is deformed by suction (total recovery / total displacement) R3: The height of the final waveform when the skin is deformed by suction. R4: The portion of the final waveform that did not return to its original state after the skin was deformed by suction. R5 = Ur / Ue: The ratio of instantaneous recovery amount to instantaneous displacement amount when the skin is deformed by suction (instantaneous recovery amount / instantaneous displacement amount) R6 = UV / Ue: The ratio of delayed displacement to instantaneous displacement when the skin is deformed by suction (delayed displacement / instantaneous displacement) R7 = Ur / Uf: The ratio of the instantaneous recovery amount to the total displacement amount when the skin is deformed by suction (instantaneous recovery amount / total displacement amount) R8 = Ua: Delayed recovery amount when the skin is deformed by suction. (Ue: instantaneous deformation during suction, UV: deformation over time during suction, Uf: maximum suction height, Ur: instantaneous return after negative pressure release, Ua: final return after release)