JP6713638B2 - Surface characteristic measuring method, surface characteristic measuring device, and surface characteristic measuring program - Google Patents

Description

The present invention relates to measurement of surface characteristics, and more particularly to measurement of physical characteristics of an object surface/surface layer using ultrasonic waves.

The evaluation of the properties of the object surface/surface layer is useful in various fields. For example, in the case of a living body, it is the skin that exists on the surface/surface layer of the living body, and by grasping the skin quality that is a characteristic of the skin, it is possible to perform skin care according to the skin quality and maintain healthy skin. it can. In the field of beauty/cosmetics, skin quality is generally evaluated through interviews with beauty engineers. It is also possible to objectively evaluate the condition and function of the skin by measuring mechanical properties of the skin (skin flexibility, elasticity, etc.) and optical properties (skin gloss and transparency, etc.) using a measuring device. Has been done.

Conventional measurement of physical properties of the skin using non-invasive measuring equipment is generally a method of applying stress to the skin from the surface layer under certain conditions or measuring reaction force and response after applying certain displacement. That value has been detected as an evaluation value of the physical properties of the entire skin. However, the characteristic value is detected as a value that includes all the contributions of each layer (stratum corneum, epidermis, dermis, subcutaneous tissue) constituting the skin. Since each layer constituting the skin has its own role and function, it is desirable that each layer can be individually measured and evaluated.

In particular, the stratum corneum, which is the outermost layer of the skin, has a barrier function and a moisturizing function necessary for maintaining vital activity, so accurate measurement of its characteristic values is an important issue in the fields of medicine and pharmaceuticals. is there. Further, since the object of appeal of skin care is limited to the stratum corneum in terms of pharmaceuticals, the evaluation of characteristics of the stratum corneum alone is also meaningful in the field of beauty and cosmetics. However, the conventional stress/displacement-type non-invasive skin measuring device cannot measure the physical properties of only the horny layer. When it is desired to measure the physical property values of each layer of skin, it is necessary to use an invasive method using excised skin pieces such as biopsy, instead of the non-invasive method. For example, the method of Patent Document 1 is a method of measuring the sound velocity distribution of the skin cross section by preparing a skin tomographic sample, and the sound velocity of each layer of the skin tomographic layer, that is, the physical characteristic value using the bulk elastic modulus as an index. It is possible to measure the hardness of each part of.

FIG. 1 is a sound velocity distribution image of a skin cross section cut by a conventional method. FIG. 1(A) is a young cheek skin section, and FIG. 1(B) is an elderly cheek skin section. As shown in Fig. 1, in the skin (cheek) exposed to ultraviolet rays, the sound velocity of the outermost stratum corneum becomes higher (harder), while the sound velocity of the middle dermis, that is, volume elastic modulus, decreases (becomes softer). It is known that complex changes can be seen. With respect to the measurement target that shows such complex changes, it is impossible to evaluate only the physical properties of the surface/surface layer with the conventional stress/displacement-added non-invasive skin measurement device. With the skin viscoelasticity measuring device by the suction method (a method to evaluate the height of the skin that rises when the skin is decompressed at a certain pressure), which is actually used as a non-invasive skin measurement device for the skin exposed to the UV When evaluated, the effect of softening the dermis is largely reflected, and it is not possible to capture the phenomenon that the surface/surface layer becomes hard.

In addition to the conventional non-invasive skin measuring device by applying stress/displacement, in recent years, a method of non-invasively obtaining hardness information at different depths of the skin has been proposed (Patent Reference 2). This method irradiates the skin with ultrasonic waves containing different frequency components and calculates the acoustic impedance of the reflected wave to measure the information of multiple layers at different depths. It is possible to separate from the information of the skin surface/surface layer, and it is possible to obtain the physical properties of only the skin surface/surface layer.

Japanese Patent Laid-Open No. 2007-271765 [Patent Document 1] JP-A-2006-271765

In the method of Patent Document 2 described above, the tip of the probe is pressed against the skin, the reflected waves of different frequencies are received from the skin, and the measurement is performed to acquire the information of each layer constituting the skin.

However, this method does not consider the effects of fine irregularities (skin grooves and crests) present on the skin surface. Actually, even if the tip of the probe is pressed against the skin, the skin groove portion is hard to contact the tip surface of the probe, and the accurate acoustic impedance of the stratum corneum cannot be acquired in the portion which is not in contact. This problem applies not only to skin measurement, but also to surface measurement of living bodies such as teeth and nails, and measurement of organic or inorganic surface/surface layer having fine irregularities.

Therefore, it is an object of the present invention to provide a surface property measuring method and a structure capable of accurately evaluating the surface property of a substance.

In order to solve the above-mentioned problems, mutual interaction between a reflection waveform from a measurement object and a reference waveform which is a reflection waveform from a reference substance (specifically, pure water used as an ultrasonic transmission medium (couplant)) The reflection component is extracted at the maximum point of the correlation function, and the acoustic impedance representing the surface characteristic is calculated according to the comparison result of this reflection component and the reference waveform.

Specifically, the surface characteristic measuring method is
Obtain a reflection signal from the measurement object by irradiating the measurement object with ultrasonic waves,
In the measurement device, the maximum value of the cross-correlation function of the reflection signal from the measurement object and the reference reflection signal from the reference material previously acquired,
Calculating the reflection component at the interface using the maximum value of the cross-correlation function,
Either the acoustic impedance of the measurement object or the acoustic impedance of the reference material is output as a measurement value according to the comparison result of the reflection component and the reference reflection signal.

By the above method, the surface characteristics of the substance can be measured with high accuracy.

It is a hardness distribution map of the skin section measured by the existing technology (the method of patent documents 1). It is a schematic diagram of a surface property measuring device of an embodiment. FIG. 3 is a block diagram of the surface characteristic measuring device of FIG. 2. It is a figure which shows the reflection state of an ultrasonic wave. It is a figure explaining the principle of the present invention. It is a figure explaining the cross correlation of the reflected waveform from a measuring object, and a reference waveform. It is a flowchart of the surface characteristic measuring method of embodiment. It is a figure which shows the measurement result when cross correlation with a reference wave is not taken. It is a figure which shows the measurement result at the time of taking the cross correlation with a reference wave. It is a processing flow when displaying a measurement result as an image. It is an image which shows the state of the skin surface actually measured using the surface property measuring device of an embodiment. It is a figure which shows the average acoustic impedance according to age based on the measurement data obtained in FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a schematic diagram of the surface characteristic measuring device 1 of the embodiment. The surface characteristic measuring device 1 has a probe 2 and an information processing device 3. The probe 2 has an acoustic window 5 that allows ultrasonic waves to pass therethrough. The material of the acoustic window 5 that is in contact with the measurement target has a known acoustic impedance different from that of the measurement target and is formed of a hard material (for example, a hard resin or the like) that can pass ultrasonic waves.

The probe 2 can communicate with the information processing device 3. In the example of FIG. 2, the cable 4 is used for connection, but wireless connection may be used. From the acoustic window 5 of the probe 2, an ultrasonic wave that is two-dimensionally scanned and transmitted is applied to the measurement object, and the reflected wave is received by the probe 2, converted into an electric signal, and output. The received reflected wave contains information about the measurement target.

The probe 2 can be held by hand, and when measuring the skin, for example, it can be held by hand and directly applied to the skin of the subject. Further, in order to perform highly accurate measurement without being affected by the movement of the body, it is possible to fix the probe 2 or fix the probe 2 and the cheek with double-sided tape before use.

The information processing device 3 analyzes the reflected wave received by the probe 2 to detect the surface characteristics of the measurement target. As the information processing device 3, any information processing device having an arithmetic processing function and a display function, such as a notebook computer and a tablet terminal, can be used. In the embodiment, the information processing device 3 obtains the maximum cross-correlation between the reflection waveform from the measurement target and the reference waveform, thereby interfering with the reflection waveform from the internal component of the measurement target and the surface morphology. Accurate acoustic impedance of the surface and surface layer is extracted by removing the effect of unevenness (effect on the reflected waveform due to contact with and non-contact with the acoustic window). For example, when the object to be measured is skin, it is possible to accurately measure the hardness of the skin surface layer (corneal layer) excluding the interference from the epidermis and dermis inside the skin and the influence of unevenness of the surface shape (texture, wrinkles, etc.) Acquire physical property information such as elasticity. When the object to be measured is a tooth, information such as the exact hardness of the enamel on the surface is measured, excluding the effects of the internal cementum and dentin, and the effects of unevenness of the surface shape (roughness). When the measurement target is a multi-layer film or a multi-layer coating material, the influence of the lamination inside and the influence of the unevenness of the surface shape are reduced, and the information such as the hardness and elasticity of the outermost layer is measured.

FIG. 3 is a block diagram of the surface characteristic measuring device 1 of FIG. The probe 2 has an ultrasonic sensor circuit 21 and an interface (I/F) 27. The interface 27 may be a wireless interface as described above or a physical interface.

The ultrasonic sensor circuit 21 includes a transmission unit 22, a reception unit 24, a transmission/reception wave separation circuit 25 for separating transmission/reception waves, and a transducer 28. The transmission unit 22 has a pulse generation circuit 23. The pulse generation circuit 23 generates a drive pulse at a predetermined timing. The transmitter 22 applies a drive pulse to the transducer 28 via the transmission/reception wave separation circuit 25. The transducer 28 converts the pulse (electrical) signal into mechanical vibration and outputs ultrasonic waves.

The transducer 28 receives the reflected wave reflected from the measurement object and converts the reflected wave into an electric signal. The received electric signal is supplied to the reception unit 24 by the transmission/reception wave separation circuit 25. The receiving unit 24 detects an analog electric signal and converts it into a digital signal by an analog/digital converter (ADC). The digital signal (reflected wave) is transmitted to the information processing device 3 via the interface 27.

The information processing device 3 includes a CPU 31, an interface (I/F) 32, a memory 33, a DSP (Digital Signal Processor) 34, an input device 35, a display device 36, and a storage device 37. The reflected wave signal transmitted from the probe 2 is input to the DSP 34 via the interface 32 and processed by the DSP 34.

The input device 35 is an input user interface such as a touch panel, a mouse, a keyboard. The display device 36 is a monitor display of liquid crystal, plasma, organic EL (electroluminescence), or the like. The storage device 37 is a hard disk drive such as a magnetic disk device or an optical disk device, and stores various programs and data. The memory 33 includes a RAM (random access memory) and a ROM (read only memory), and stores the reflection waveform of the reference substance and its acoustic impedance that are acquired in advance for ultrasonic measurement.

The DSP 34 determines the surface characteristics from the acoustic impedance of the measurement object based on the maximum cross-correlation between the reflection waveform from the measurement object and the reflection waveform from the reference material. In the embodiment, the DSP 34 is described as performing signal processing of ultrasonic reflected waves, but when using a surface characteristic measurement program described later, the CPU 31 reads the surface characteristic measurement program stored in the storage device 37 and performs signal analysis. May be executed.

FIG. 4 is a diagram showing a reflection state of ultrasonic waves. For example, consider the case of measuring the stratum corneum 51 on the skin surface. The skin is made up of multiple layers including an epidermis 52, a dermis 53, and a subcutaneous tissue (not shown). The outermost surface of the skin 52 is the horny layer 51. The surface of the skin has fine irregularities, that is, skin grooves 55 and cuticles 56. The skin groove 55 is a groove that divides the surface of the skin into fine skin ridges 56, but the skin groove 55 also includes wrinkles and pores where the skin groove is deep and rough. Even when the acoustic window 5 of the probe 2 is pressed against the skin, the skin groove 55 is not actually in contact with the acoustic window 5. A couplant (ultrasonic coupling medium) 10 such as water or gel exists between the acoustic window 5 and the skin groove 55. Since ultrasonic waves are almost 100% reflected in the air layer, ultrasonic measurements typically involve the couplant 10 to ensure the transfer of sound energy between the transducer 28 and the skin.

In the portion of the skin groove 55, the acoustic window 5 cannot directly contact the stratum corneum 51 but contacts the couplant 10. Therefore, the conventional method cannot acquire the accurate acoustic impedance of the stratum corneum 51. This is because, in reality, even the skin groove 55 is processed as the skin crest 56. When measuring the surface characteristics of the measuring object having fine irregularities, it is necessary to distinguish and evaluate the acoustic impedance acquired at the convex portion (for example, the crest 56) and the acoustic impedance at the concave portion (for example, the skin groove 55). is there.

FIG. 5 is a diagram illustrating the principle of the embodiment. In the embodiment, the reference signal representing the reflected waveform from the couplant 10 as the reference substance and its acoustic impedance are acquired in advance. By taking the maximum cross-correlation between the reflected waveform of the ultrasonic wave reflected by the measurement object (for example, skin) and the reference waveform, the reflected component from the layer deeper than the horny layer 51 on the surface is removed, and the acoustic The reflection information at the interface of the window 5 is extracted. By comparing this with the reference signal, it is determined whether the acoustic window 5 is in direct contact with the skin or the portion of the skin groove 55 in which the couplant 10 has entered.

In the portion where the acoustic window 5 is in direct contact with the stratum corneum 51, the reflected waveform st1 is obtained. The maximum peak is the component reflected at the interface between the stratum corneum 51 and the acoustic window 5. A plurality of small peaks appearing after the maximum peak are components reflected in a portion deeper than the stratum corneum 51. For example, it is a component reflected at the interface between the stratum corneum 51 and the epidermis 52, the interface between the epidermis 52 and the dermis 53 (see FIG. 4), the interface between the dermis 53 and the subcutaneous tissue, and the like.

On the other hand, in the portion where the acoustic window 5 does not contact the horny layer 51, a reflection waveform st2 different from the reflection waveform st1 is obtained. This includes a component reflected at the interface between the acoustic window 5 and the couplant 10 and a component reflected at the interface between the couplant 10 and the stratum corneum 51. Furthermore, similar to the reflection waveform st1, from a deeper portion of the skin. Also includes a reflection component.

In order to obtain the reference waveform of the reflected wave from the couplant 10, the acoustic window 5 or a substrate having the same quality and the same thickness as the acoustic window 5 is contacted only with the couplant 10, and the reflected wave from the interface between the acoustic window 5 and the couplant 10 is obtained. To get. This is the reference wave sr.

FIG. 6 is a diagram illustrating a cross-correlation function. In the embodiment, the cross-correlation function of each Fourier transform of the measured reflected wave and the reference wave is calculated, but in FIG. 6, the cross-correlation function is described with a waveform in the time domain before the Fourier transform for convenience of description.

The cross-correlation function is a value obtained by integrating the product of the reflected wave st from the measurement target (target) and the reference wave sr, and then dividing by the product of the effective value (rms: root mean square) of each waveform, It takes a value from -1 to 1. When the digitally sampled waveform is a multidimensional vector, the correlation between the reflected wave st from the target and the reference wave sr is a value obtained by dividing the inner product of the vector by the product of absolute values. The cross-correlation function is the result of calculating the correlation coefficient while changing the time difference between the waveforms.

Both the reference wave sr from the reference material and the reflected wave st from the target are most strongly reflected from the interface with the acoustic window 5. The reflection from the back (back) of the interface with the acoustic window 5 is smaller than the reflection from the interface of the acoustic window 5. Therefore, the point where the cross-correlation function between the reflected wave st from the target and the reference wave sr becomes maximum indicates the position of the interface with the acoustic window 5. The cross-correlation function at this time is Rmax.

By taking the maximum value of the cross-correlation function, the reflection component in the portion deeper than the interface of the acoustic window 5 is removed. When the acoustic window 5 or the substrate is curved in a convex shape, a position where Rmax is given in FIG. 7 is displaced. That is, the position Δt on the time axis when the cross-correlation function becomes maximum is not zero.

The reflected wave st in the time domain from the measuring object (target) is Fourier transformed to calculate the reflected signal St in the frequency domain. Further, the reference wave sr is Fourier transformed to calculate the reference signal Sr in the frequency domain. Using these, the magnitude of the reflection component St ⁽¹⁾ at the interface when the cross-correlation function becomes maximum is obtained. St ⁽¹⁾ is calculated from equation (1).

Here, Rm is the maximum value of the cross-correlation function of the Fourier-transformed reflection signal St and the reference signal Sr, |St| is the absolute value of the reflection signal St, and |Sr| is the absolute value of the reference signal Sr.

As described above, St ⁽¹⁾ is the reflection intensity at the interface where the acoustic window 5 directly contacts the substance. If the sizes of St ⁽¹⁾ and Sr are equal, it is possible to determine that the couplant 10 is in direct contact with the acoustic window 5 and corresponds to the skin groove 55. In this case, the acoustic impedance of the reference material (couplant 10) acquired in advance is output. In the present specification and claims, when the magnitudes of the reflected signal and the reference signal are “equal to each other,” it includes a slight error due to variations in the materials of the couplant and the acoustic window, variations in the measurement conditions, and the like. ..

When St ⁽¹⁾ is smaller than Sr (St ⁽¹⁾ <Sr), the acoustic impedance of the substance that is in direct contact with the acoustic window 5 is larger than the acoustic impedance of the couplant 10, which is the reference substance. You can tell that you are in contact with. In this case, the acoustic impedance of the stratum corneum 51 is calculated from the equation (2).

Here, Zt is the acoustic impedance of the keratin (skin) in contact with the acoustic window 5 (or the ultrasonic irradiation window), Zs is the acoustic impedance of the acoustic window, Zr is the acoustic impedance of the reference material, and St is the Fourier transformed Fourier transform. The reflected signal, Sr, is a reference signal after Fourier transform.

The obtained acoustic impedance may be converted into another mechanical characteristic such as bulk modulus. By imaging the acoustic impedance and the mechanical characteristics after conversion, it is possible to visually grasp the unevenness state and elasticity of the skin surface.

FIG. 7 is a flowchart of the surface characteristic measuring method of the embodiment. First, the reference signal Sr representing the component reflected from the reference substance and its acoustic impedance are acquired in advance (S101). The reference signal Sr and the acoustic impedance reflected from the reference material are stored in the memory 33. As the reference substance, water, gel, or the like may be used in addition to Couplant 10 described above. The reflection signal (reference signal) Sr from the reference substance is a value after Fourier transform.

Further, the reflection signal St from the measurement object (target) is acquired (S102). This reflection signal St is also a value after Fourier transform. Next, the maximum value Rm of the cross-correlation function of the reflected signal St and the reference signal Sr is calculated (S103).

The reflection component St ⁽¹⁾ at the interface of the acoustic window 5 is calculated using the measurement result and the calculated Rm (S104). It is determined whether the reflection component St ⁽¹⁾ at the interface is smaller than the reference signal Sr (S105). When the reflection component St ⁽¹⁾ at the interface is smaller than the reference signal Sr (YES in S105), it means that the acoustic window 5 is actually in contact with the measurement object. In this case, the acoustic impedance of the measurement object is calculated and output (S106).

When the reflection component St ⁽¹⁾ at the interface is not smaller than the reference signal Sr (NO in S105), it means that the acoustic window 5 is in direct contact with the reference substance. In the case of the skin surface, it means that the portion corresponding to the skin groove 55 is being measured. In this case, the acoustic impedance of the reference material is output (S107). When the acoustic impedance is obtained over the predetermined range, the surface characteristics are evaluated (S108), and the process is ended.

With the above method, it is possible to accurately measure and evaluate the fine irregularities and mechanical properties of the surface by measuring the surface properties using ultrasonic waves. For example, as the evaluation of the skin surface of a person, it is possible to evaluate whether it corresponds to the skin condition of several decades from the viewpoint of fineness of texture, smoothness, elasticity and the like.

FIG. 8 shows an ultrasonic image of living human skin in the case where the cross-correlation between the reflected wave from the target and the reference wave is not used, and the acoustic impedance at the line XX′. The horizontal axis of the image is the length (μm), and the vertical axis is the acoustic impedance (Pa·s/m ³ ).

FIG. 9 shows an ultrasonic image when the method of the above-described embodiment is applied to the same sample as that in FIG. 8 and acoustic impedance at the line XX′.

8 and 9 both show acoustic impedance images of a two-dimensional profile of the skin on the inside of the forearm (flexion side) of a healthy male in his 20s. The skin was measured after being washed and dried for a certain period of time. For the measurement, a transducer of 40 to 120 MHz was used, ultrapure water was used for couplant, and an acrylic plate was used for the substrate to contact the skin. Images were acquired at 200 x 200 pixels, focusing on the wavelengths most reflected at the surface.

In the conventional method of FIG. 8, the reflection from the internal layer becomes an interference at points A and B on the line XX′, which is a low value. On the other hand, in the method of FIG. 9, the reflection component from the inside is removed and the value of only the horny layer 51 is calculated. As described above, according to the method of the embodiment, the surface unevenness information can be accurately acquired.

FIG. 10 shows a processing flow when displaying the acquired acoustic impedance as image information. This processing can also be performed by the DSP 34 of the information processing device 3 or the CPU 31. The same steps as those in FIG. 7 will be described with the same reference numerals. First, the reflection signal (Fourier transform signal) Sr from the reference substance and its acoustic impedance are acquired in advance (S101). The coordinate data of the measurement point when the ultrasonic wave is relatively scanned with respect to the measurement object is acquired (S201). In the relative scanning, the probe 2 may be scanned with respect to a fixed measurement target, or the ultrasonic sensor circuit 21 may be fixed and the stage holding the sample may be two-dimensionally driven.

Next, the acoustic impedance at each measurement point is acquired (S202). The acoustic impedance is acquired by comparing the interface reflection intensity and the reference signal intensity based on the maximum of the cross-correlation function of the Fourier-transformed reference signal and the reflection signal from the target, as in S102 to S107 of FIG. Alternatively, the acoustic impedance of the reference substance is acquired. Image data is generated with gradation or color according to the acoustic impedance (S203).

It is determined whether there is another measurement point (S204), and if there is another measurement point (YES in S204), S201 to S203 are repeated. When the processes of S201 to S203 are completed for all the measurement points (YES in S204), the image is displayed (S205).

In the above flow, the acoustic impedance at each coordinate point may be calculated after temporarily storing the reflected wave and its Fourier transform value at each measurement point in association with the coordinate value in the memory 33 for all the measurement points. Also in this case, if the image data at all the coordinate points is generated, it is displayed on the display device 36. Alternatively, the acoustic impedance may be converted into another mechanical characteristic and displayed in gradation or color according to the converted value.

By the above method, the horny layer 51 that actually contacts the acoustic window 5 and the portion that abuts the skin groove 55 are distinguished, and the reflection component from the inner layer is eliminated, so that the accurate surface characteristic measurement is realized. ..

FIG. 11 is an image showing the state of the skin surface actually measured using the surface characteristic measuring device 1 of the embodiment. The skin surface of the cheek of 70 women in their 20s to 80s is measured. The breakdown of the 70 persons is 19 persons in their 20s (20 to 29 years old), 15 persons in their 40s (40 to 49 years old), 19 persons in their 60s (60 to 69 years old), 70s and 80s (70 to 70 years old) There are 17 people (86 years old).

As a measurement method, this time, the probe 2 is fixed vertically and the acoustic window 5 is arranged horizontally so as to obtain a more accurate value by eliminating the influence of body movement. The subject's cheek is placed horizontally in contact with the acoustic window 5, the tip of the probe 2 of the surface characteristic measuring device 1 is pressed against the cheek, and ultrasonic waves are applied to the skin of the measurement target site for measurement. The reflected signal from the target site was acquired and the acoustic impedance was calculated. The acoustic window 5 of the probe 2 is made of acryl having a thickness of 0.5 mm. A physiological saline solution was previously applied as couplant to the cheek of the subject. The measurement was performed under constant conditions of humidity of 45% and temperature of 25°C.

FIG. 11 shows the result of selecting a representative example of the acoustic impedance distribution in each measurement group. In the image, a portion with high acoustic impedance (white and light-colored portion) is skin, and a portion with low acoustic impedance (black or dark-colored portion) is air bubbles or couplant. The reflection signal from the measurement site is cross-correlated with the reference reflection signal of the reference substance (saline solution) acquired in advance, and the reflection component at the interface is calculated using the maximum value of the cross-correlation function as an index. Impedance is calculated. The calculated acoustic impedance shows an accurate measurement result in which the interference component due to internal reflection is removed.

It can be seen that the impedance in the image becomes whiter (higher impedance) as the age increases. The impedance distribution of the skin in its twenties in FIG. 11A is uniform throughout. This indicates that the skin mounds are elastic and evenly raised, and the texture is even. High-impedance parts increase as people age, in their 40s, 60s, and 80s. It is considered that this is because the horny layer becomes thicker and the texture becomes rougher with aging. Further, it is considered that the low impedance part locally exists in the 40s and 60s because the acoustic impedance is low because couplant enters the wrinkles and cracks due to the thickening of the stratum corneum. In this way, from the measurement results of the skin surface using acoustic impedance, not only the accurate acoustic impedance value of the stratum corneum, which excludes the influence of unevenness and the influence of the inside of the skin, but also about the fineness and smoothness of the skin Can also get information.

FIG. 12 shows the average acoustic impedance by age based on the measurement result of FIG. 11. Of the four groups divided into groups, the average acoustic impedance of the twenties (20 to 29 years old) is shown in age “20”. The average acoustic impedance of people in their 40s (40 to 49 years old) is shown in age “40”. The average acoustic impedance in the 60s (60 to 69 years old) is shown in age "60". The acoustic impedance in the 70s and 80s (70 to 86 years old) is shown in age "80". The acoustic impedance tends to increase as the age increases, and it is inferred that this may be related to the hardening of the stratum corneum with aging.

As shown in FIG. 11, the skin age of the measurement subject can be estimated by acquiring the average acoustic impedance distribution for each age in advance. The skin age may or may not match the actual age. If the measured skin age is higher than the actual age, measures depending on the degree of the chick can be recommended.

As described above, by using the surface characteristic measurement configuration and method of the embodiment, more accurate surface characteristic evaluation (step S108 in FIG. 7) can be realized.

When the above method is implemented by the surface characteristic measuring program, the surface characteristic measuring program is stored in the memory 33 or the storage device 37 in advance, and the CPU 31 reads and executes the surface characteristic measuring program. The surface characteristic measurement program is executed by the CPU 31.
(A) a procedure for acquiring a reflection signal of the ultrasonic wave applied to the measurement target;
(B) a step of calculating the maximum value of the cross-correlation function between the reflection signal from the measurement object and the reference reflection signal obtained from the reference substance, which is acquired in advance;
(C) A procedure of calculating a reflection component at the interface of the measurement object using the maximum value of the cross-correlation function,
(D) a step of outputting one of the acoustic impedance of the measurement object and the acoustic impedance of the reference substance as a measurement value in accordance with the comparison result of the reflection component and the reference reflection signal,
To run. Thereby, the surface characteristics can be measured with high accuracy.

According to the present invention, since the hardness information of the surface of the sample or the sample can be accurately measured, the mechanical properties of the surface of the living body such as skin, hair, nails and tooth pieces, the physical properties of the organic or inorganic surface/surface layer. It can be used to evaluate the presence or absence of defects.

1 Surface Characteristic Measuring Device 2 Probe 3 Information Processing Device 5 Acoustic Window 21 Ultrasonic Sensor Circuit 31 CPU (Processor)
33 memory 34 DSP (signal processing unit)
37 storage device

Claims (13)

Obtain a reflection signal from the measurement object by irradiating the measurement object with ultrasonic waves,
In the measurement device, the maximum value of the cross-correlation function of the reflection signal from the measurement object and the reference reflection signal from the reference material previously acquired,
Calculating the reflection component at the interface using the maximum value of the cross-correlation function,
Depending on the comparison result of the reflection component and the reference reflection signal, one of the acoustic impedance of the measurement object and the acoustic impedance of the reference material is output as a measurement value,
A method for measuring surface characteristics, which comprises: The surface characteristic measuring method according to claim 1, wherein when the intensity of the reflection component is smaller than the intensity of the reference reflection signal, the acoustic impedance of the measurement target is calculated and output. The surface characteristic measuring method according to claim 1, wherein when the intensity of the reflection component is not smaller than that of the reference reflection signal, the acoustic impedance of the reference substance is output. The reflection component is obtained by multiplying the reference reflection signal, a ratio of the reflection signal from the measurement object with respect to the reference reflection signal, and a maximum value of the cross-correlation function. 4. The method for measuring surface properties according to any one of 3 to 3. One-dimensionally or two-dimensionally scan the ultrasonic wave relative to the measurement object,
The surface characteristic measuring method according to claim 1, wherein the measured value is output for each coordinate point. The surface characteristic measuring method according to any one of claims 1 to 5, wherein the ultrasonic wave irradiation is performed by bringing an acoustic window of a probe of the measuring device into contact with the measurement object. 7. The surface characteristic measuring method according to claim 1, wherein the reference substance is water or a gel substance. The measurement object is skin,
The surface property measuring method according to claim 1, wherein at least one of elasticity, texture, pores, and wrinkles of the skin is evaluated based on the measured value. The measurement object is an organic or inorganic single-layer or laminated substance,
The surface property measuring method according to claim 1, wherein at least one of the surface roughness, elasticity, and defects of the outermost layer is evaluated based on the measured value. To the processor,
A procedure for acquiring the reflection signal of the ultrasonic wave irradiated to the measurement object,
A procedure for calculating the maximum value of the cross-correlation function of the reflection signal from the measurement object and the reference reflection signal from the previously acquired reference substance,
Calculating the reflection component at the interface using the maximum value of the cross-correlation function;
Depending on the comparison result of the reflection component and the reference reflection signal, a procedure for outputting one of the acoustic impedance of the measurement object and the acoustic impedance of the reference material as a measurement value,
A surface property measurement program that executes. An ultrasonic wave transmitting/receiving unit that irradiates the measurement object with ultrasonic waves and receives a reflection signal from the measurement object,
Intensity of the reference reflection signal from the reference material measured in advance, and a memory for storing the acoustic impedance of the reference material,
Calculate the reflection component at the interface based on the maximum value of the cross-correlation function of the reflection signal from the measurement object and the reference reflection signal, depending on the comparison result of the reflection component and the reference reflection signal, the measurement A signal processing unit that outputs one of the acoustic impedance of the object and the acoustic impedance of the reference material as a measurement value,
An apparatus for measuring surface characteristics, comprising: The surface characteristic measurement according to claim 11, wherein the signal processing unit calculates and outputs an acoustic impedance of the measurement target when the intensity of the reflection component is smaller than the intensity of the reference reflection signal. apparatus. The surface characteristic according to claim 11, wherein the signal processing unit reads out the acoustic impedance of the reference substance from the memory and outputs the acoustic impedance of the reference substance when the intensity of the reflection component is not smaller than that of the reference reflection signal. measuring device.