KR100459014B1 - Method and apparatus for distribution analysis of surface color - Google Patents

Abstract

The present invention discloses a method for analyzing surface color and a color analysis device.

According to the present invention, in the method for analyzing the color of the surface, the light source for supplying light to the color analysis target, the image data to be obtained by means of acquiring reflected light reflected on the surface of the analysis target and the surface of the color analysis target Standardizes the state of the light source, obtains the reflected light by reflecting the standardized light source on the standardized surface to analyze the color, obtains the reflected light having the wavelength value of the predetermined region among the reflected light in the unit of the predetermined wavelength, and obtains the obtained wavelength Extracting the parameters for analyzing the color of the surface in units of pixels or in the area of the surface to be observed from the star images, the skin color can be efficiently analyzed regardless of the skin measurement environment. Therefore, there is an advantage that the diagnosis and treatment associated with human skin can be efficiently performed.

Description

Method and apparatus for distribution analysis of surface color

TECHNICAL FIELD The present invention relates to surface state measurement and analysis, and more particularly, to a method and apparatus for observing a surface of a living body such as skin and analyzing the color thereof.

Conventional devices that measure the color of the surface are measured only by the average value of the observation site, so it is difficult to compare the normal and lesion areas at the same time as the skin color or to analyze the distribution of the skin color at the normal area. The development of a new skin color measurement method that can be used is an urgent setting.

In the case of the spectrophotometer which is conventionally used for analyzing the color of the skin surface of the human body, since only the average value of the entire observation surface is calculated, it is difficult to observe the exact skin surface because it is impossible to measure the difference in the colors of the observation surface. There is a lack of reliability even when extracting the parameters for. In addition, color analysis is possible as an average value only within the observation surface, and color distribution analysis is impossible. And since these instruments are based on the assumption that the sample to be analyzed is a completely horizontal surface, accurate analysis of curved surface colors such as living surfaces is impossible.

In addition, conventional color analysis requires the use of standard light sources such as D65 or D50, so when using a light source that is easy to obtain, for example, a halogen, the radiant spectrum is different from the standard light source. Can't get it. In the color analysis, research on the standardization of devices (eg, CCD devices) capable of detecting information for each wavelength should be preceded as the result of judging the image may vary depending on the state of the observer of the colors. do.

The technical problem to be achieved by the present invention, to solve the above problems, can correct the light source and the acquired image even without using a standard light source, and is not affected by the state of the surface of the object or sensing elements such as CCD elements To provide a standardization method for color analysis.

Another technical problem to be achieved by the present invention is to provide a method and a color analysis device for analyzing the surface color that can obtain the surface state accurately and obtain the parameters for analyzing the skin color in the standardized state.

Figure 1 illustrates the flow of a standardization method for analyzing the color of a surface in accordance with the present invention.

2 is a spectral distribution diagram in the visible light region of a halogen lamp, which is a light source for observing a surface, and a standard light source D65, which are already known.

FIG. 3 shows the reflectance spectral distribution of a white reference measured with a halogen light source and under a light source normalized to a standard light source D65.

4 shows the flows of a method for analyzing the color of a surface according to the invention.

5 is a block diagram showing the configuration of an apparatus for analyzing the color of the surface according to the present invention.

FIG. 6 illustrates an example of a configuration when the configuration of FIG. 5 is implemented.

7 conceptually illustrates a layer of an image obtained through LCTF.

According to the present invention for solving the above technical problem, the standardization method for analyzing the color of the surface by acquiring the image by means of reflecting the light from the light source and obtaining the reflected light as an image, Normalizing the light source by comparing the radial spectrum of the light source with the radial spectrum of a predetermined standard light source and comparing and correcting the difference for each wavelength band; The white reference of the radiant spectrum of the light source is compared with the white reference of the radiant spectrum of a predetermined standard light source for each wavelength band, and according to the difference, the inherent reflectance of the surface color analysis target Standardizing the image acquisition means by correcting the image data acquired by the image acquisition means by adjusting a white balance for each wavelength; And standardizing the surface state by using a three-dimensional measurement parameter according to the enlargement or reduction of the area of the surface to be analyzed for color or the bending of the surface state.

According to the present invention for solving the other technical problem, the method of analyzing the color of the surface, (a) the radial spectrum of the light source for supplying light to the color analysis target radiant of the predetermined standard light source Standardize the light source by correcting the spectral value of the light source by using the difference for each wavelength band compared to the spectrum, and by using the three-dimensional measurement parameters according to the enlargement or reduction of the area of the surface that is the color analysis target or the bending of the surface state Standardizing; (b) illuminating the standardized light source in step (a) on a standardized surface to be analyzed for color to obtain reflected light; (c) acquiring the reflected light having a wavelength value of a predetermined region among the reflected light in units of a length of a predetermined wavelength; And (d) extracting parameters for analyzing the color of the surface from the obtained wavelength-specific images in pixel units or area units of the observation target surface.

In accordance with another aspect of the present invention, there is provided a device for analyzing the color of a surface, the light source for shining light on the surface to be analyzed; A reflected light acquisition unit configured to determine a color analysis area of the surface by enlarging or reducing the light source reflected on the surface according to a predetermined magnification; A wavelength-specific image acquisition unit configured to acquire images of the reflected light having a wavelength value of a predetermined region among the obtained reflected light in units of a length of a predetermined wavelength; A parameter extraction unit for extracting parameters for analyzing the color of the surface from the obtained wavelength-specific images in units of pixels or areas of the observation target surface; And standardizing the light source by comparing the radiant spectrum of the light source with the radiant spectrum of a predetermined standard light source, comparing and correcting the difference for each wavelength band, and whitening the radiant spectrum of the light source. The white reference is compared with the white reference of the radiant spectrum of a predetermined standard light source by wavelength band, and the white balance of each wavelength is measured by measuring the inherent reflectance of the surface color analysis target according to the difference. And a standardization unit for standardizing image state obtained by the image acquisition unit for each wavelength using three-dimensional measurement parameters according to the curvature of the surface state of the color analysis target. The unit extracts the data normalized by the standardization unit when extracting parameters. Characterized in that for.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 illustrates the flow of a standardization method for analyzing the color of a surface in accordance with the present invention.

This standardization method for analyzing the color of the surface by acquiring the image by means of the surface of the object reflecting light from the light source and acquiring the reflected light as an image, uses the radial spectrum of the light source. Standardize the light source by comparing and correcting the difference for each wavelength band in comparison with the radial spectrum of a predetermined standard light source (step 100), and white reference of the radiant spectrum of the light source is predetermined. The white reference of the radiant spectrum of the standard light source is compared with the wavelength band, and the inherent reflectance of the surface color analysis object is measured according to the difference, and the white balance is obtained by each wavelength to obtain the image acquisition means. Standardize the image acquisition means by correcting the image data (step 110), and The enlarged or reduced to the zone, or by using a three-dimensional measurement parameter according to the curvature of the surface state standardize the surface state (step 120).

Examples of the need to standardize, for example, for light sources, observations under daylight and artificial light may have different results, and if the observer is color blind or aging deteriorates vision or other visual function, accurate results will not be obtained. This is because the analysis result may vary depending on whether the surface state of the object to be observed is flat or irregular.

2 is a spectral distribution diagram in the visible light region of a halogen lamp, which is a light source for observing a surface, and a known standard light source D65.

The radial spectrum of a light source, which is a halogen lamp, is compared with the radial spectrum of a standard light source, and the difference is compared for each wavelength band. The spectral value of the light source of the halogen lamp is corrected using the difference value to normalize the light source (step 100).

Light is reflected on the surface of an object to obtain reflected light and color analysis using the image. At this time, it is the task of the human eye to acquire or view the light as an image, but in the present invention, the image is acquired using the CCD element of the CCD camera. By standardizing this and obtaining objective and quantitative data, you can obtain more accurate measurements.

The CCD camera to be used as the image acquisition means may use a general B / W (black / white) CCD element, and standardizes in a manner similar to the above standardization method.

By measuring the reflectance of the white reference and adjusting the white balance based on the value, the inherent characteristic reflectance of the object can be known. Therefore, through this standardization process, it is possible to convert the measured values under various kinds of standard light sources in one measurement by using known spectral values of standard light sources (e.g. D65, D50, etc.) even when using other light sources as well as halogen lamps. There is a meaning of standardization.

The difference occurring for each wavelength between the radial spectrum of the desired light source and the radial spectrum of the light source currently used (halogen lamp in this embodiment) is defined as a white reference. The value corresponding to this difference is normalized by correcting pixel by pixel in the image data obtained through the CCD camera (step 110). This method allows you to measure the unique reflectance value of an object even if the light source is different. In addition, at this time, a glare on the surface of the skin may be prevented by using a polarizing filter.

FIG. 3 shows the reflectance spectral distribution of a white reference measured at a halogen light source and under a light source normalized with a standard light source D65.

The surface state that is the subject of color analysis is the surface of the human skin. At this time, if the arm, hand, back, etc., which are not very curved, are flat and there is no severe movement or trembling during measurement, there will be no problem in obtaining necessary data. However, it is necessary to observe the color even in the wrinkles in minute areas such as wrinkled areas. Also, the part where the color changes, for example, the normal part and the abnormal part, will have the wrong color of the skin. Therefore, there is a need to observe necessary parts.

To this end, the area of the area to be measured may be selected by enlarging or reducing the magnification by using a means such as a macro lens. In this case, therefore, it is possible to standardize the surface to be observed, including a zoomable lens.

Also, in the case of wrinkled parts, three-dimensional standardization is required. This is described in detail in the inventor's invention (0286434) of the present invention. Thus, the techniques described in the known invention can be used to obtain three-dimensional skin measurement parameters including surface irregularities, bone cross-sectional areas of skin wrinkles, three-dimensional surface areas, and three-dimensional volumes, which are used to determine the state of the surface. Normalize (step 120).

Figure 4 shows an example of the flow of the method for analyzing the color of the surface according to the present invention. This method compares the radial spectrum of a light source that supplies light to a color analysis target with the radial spectrum of a predetermined standard light source, and corrects the spectral value of the light source using the difference for each wavelength band to normalize the light source. Standardize the surface state by expanding or reducing the area of the surface to be analyzed by color or by using three-dimensional measurement parameters according to the curvature of the surface state (step 400), and reflecting the standardized light source on the standardized surface to be analyzed for color. Obtaining reflected light (step 410), obtaining reflected light having a wavelength value of a predetermined region among the reflected light in units of a predetermined wavelength (step 420), and obtaining a pixel or a target surface from the obtained wavelength-specific images. Extract the parameters to analyze the color of the surface in the unit of area (step 430). You will be seated. At this time, the image obtained by standardizing the image capturing means may be normalized as in step 400 to 110.

5 is a block diagram showing the configuration of an apparatus for analyzing the color of the surface according to the present invention.

The apparatus includes a light source 500 that shines light on a surface to be analyzed for color, and a reflected light acquisition unit 510 which is obtained by determining a color analysis region of the surface by enlarging or reducing the light source reflected on the surface according to a predetermined magnification. A wavelength-specific image acquisition unit 520 for acquiring the reflected light having a wavelength value of a predetermined region among the acquired reflected light in units of a length of a predetermined wavelength, and a region of a pixel unit or an observation target surface from the obtained wavelength-specific images It includes a parameter extraction unit 530 for extracting parameters that can analyze the color of the surface in units. The radiant spectrum of the light source 500 is compared with the radiant spectrum of a predetermined standard light source to compare and correct the difference for each wavelength band, thereby standardizing the light source and radiant spectrum of the light source. The white reference is compared with the white reference of the spectral spectrum of a predetermined standard light source and the difference between wavelength bands, and according to the difference, the inherent reflectance of the surface color analysis object is measured and the white balance of each wavelength is measured. standardization unit 540 that standardizes the surface state by standardizing the image data acquired through the image acquisition unit 520 for each wavelength using three-dimensional measurement parameters according to the curvature of the surface state of the color analysis target. Also includes.

FIG. 6 illustrates an example of a configuration when the configuration of FIG. 5 is implemented. The halogen lamp 600 was used as the light source 500, the macro lens 610 was used as the reflected light acquisition unit 610, and the reflected light having a wavelength value of a predetermined region among the reflected light in the wavelength-specific image acquisition unit 520. The LCTF 620, which is a Liquid Crystal Tunable Filter, is used for dividing the signal into a unit of a predetermined wavelength, and the respective images are obtained by using a CCD camera 625. An image grabber board was used.

Since the parameter extraction unit 530 and the standardization unit 540 are implemented in a hardware or suitable program in a computer including an image grabber board connected to the LCTF 620 or the CCD camera 625, It is not shown in FIG.

Hereinafter, the operation of the present invention will be described based on the configuration of FIG. 6.

The standardization unit 540 standardizes through steps 100 to 120 as described in FIG. 1. That is, even if the surface of the light source or the object is changed, the preparation work is performed to obtain the same result. This can be done by controlling the operation as in the description of FIG. 1 through a program, and the result will be used in the parameter extraction unit 530.

The wavelength of the reflected light to be observed in the present invention is preferably between 400nm and 720nm. It would be desirable to observe in the region of visible light, since the above wavelength band is the wavelength of visible light.

LCTF (Liquid Crystal Tunable Filter) is a Lyot-type birefringent filter that filters light wavelengths between 400 nm and 720 nm in 10 nm units. And RS-232C, serial interface, can be used to communicate with PC. Therefore, control is possible through a computer program. By using the appropriate program, commands can be sent to the LCTF to control its operation in software.

In the halogen lamp 600, when light emitted from the polarization filter described through the standardization process is reflected to the object and enters the macro lens 610 (step 410), the LCTF 620 is transferred through the RS-232C port of the computer. Drive by control.

As a result, 33 images of 400 to 720 nm are received through the CCD camera 625 through the reflected light in units of 10 nm, and are stored as images using an image grabber board mounted on a PC (step 420).

The LCTF 620 and the image grabber board are synchronized through a program to operate the LCTF 620 at 10 nm intervals, and store each image frame as an image on the image grabber board, for example, 640 × 480, 256 gray levels (gray). 33 pieces of image data having a level) resolution are obtained. Each image is an 8-bit gray level image and may be composed of 256 levels of data of 0-255 for each pixel.

7 conceptually illustrates a layer of an image obtained through LCTF. Divided by 10 nm of the visible light region, the reflectance value of each image can be obtained as data.

The stored images are used as reflectance values for each wavelength. Image data for each wavelength stored as an image can be analyzed for each pixel, so that measurement of a normal region and a lesion region can be simultaneously performed with a single measurement. In addition, the measurable area may be variably changed by adjusting the magnification of the macro lens 610.

The parameters extracted by the parameter extractor 530 include XYZ components of the rectangular coordinate system of the surface color, L * a * b * components in the CIELAB color gamut, RGB components, HSI components in the HSI color gamut, erythema index, and It is preferred to include a melanin index.

At this time, the XYZ component is extracted by using the reflectance value of the image for each wavelength acquired in step 420 and the spectral value of the light source, and from this, L * a * b *, RGB, HSI, erythema index and It is preferable to extract the melanin index.

An example of obtaining each parameter is described below.

It calculates by changing the level data 0-255 of video data into the value of the level 0-100 of an actual reflectance.

To calculate the XYZ value Using the value of The value uses the 10 ° observer value established by the CIE, and the value to be measured is the spectral value of the light source. And the reflectance value of the object Value. The following equations in the CIE 1964 system can be used to calculate the XYZ values to analyze colors and medically study the results.

From the calculated XYZ values, L * a * b * is obtained from the following equation.

here, = lightness, = chroma coordinates in the CIELAB color space, = tristimulus values of ideal white.

At this time, CIELAB color difference is expressed by the following equation.

In order to calculate RGB, we need an XYZ value. However, here is an example of calculating RGB using image data obtained directly through the CCD camera 625.

The wavelength of each RGB used here is R = 650nm, G = 530nm, B = 460nm, and RGB values are calculated by taking an average of the image data before and after each wavelength.

The method of obtaining the HSI value is as follows.

The erythema index and the melanin index are obtained by the following equation.

Where IR and IG represent the intensity of RED and GREEN, respectively.

The present invention has a difference from the present invention in determining the wavelength of the red value and the green value in a commercial device. For example, in the conventional DermaSpectrometer, G: 568 nm, R: 655 nm, and Erythema Meter use wavelengths of G: 546 nm and R: 671 nm. However, the present invention is characterized in that the wavelength range suitable for the characteristics of the LCTF is selected to use values of R: 680 to 700 nm and G: 560 to 580 nm, not wavelengths having a single value.

Such calculation for parameter extraction can be calculated through a program implemented in a computer. In calculating the above values, more reliable values can be obtained using standardized values.

Table 1 shows the results for comparison between the skin analysis method according to the invention and the CV of the xyz value of normal skin measured by a conventional spectrophotometer.

CV of x CV of y CV of z mean SD mean SD mean SD SCDA 1.39 0.76 0.94 0.31 2.25 1.09 Spectrophotometer 2.19 0.55 2.01 0.42 4.10 1.05 p-value <0.05 <0.05 <0.05

Table 1 shows the CV (Coefficient Variation) values measured by the measured values for each site. In both cases, the T-test result showed statistically significant values. At this time, the CV of the color value of normal skin measured according to the present invention has a lower value than the spectrophotometer. This proves that the skin analysis method according to the present invention has higher reproducibility and reliability than the conventional spectrophotometer.

The visual grade of dermatitis induced after topical application of sodium lauryl sulfate (SLS) and the measurement results of skin color by the method proposed in the present invention were expressed and analyzed in various color models. Results The results of analysis of the xyz color model showed that the z value was most correlated with the visual grade of inflammation. In the L * a * b * color model, the a * value increased statistically as the degree of inflammation increased. In the RGB color model, the R value was statistically significant. In the HSI color model, the H and I values increased with visual grade.

As described above, the erythema index and melanin index are measured using the reflectance of a particular wavelength. Comparing the results of calculating the erythema index and melanin index, which are the parameters of the conventional commercialized skin color measuring instrument, and the erythema index and melanin index extracted according to the present invention, the results measured by the method according to the present invention more accurately determine the severity of dermatitis. It can be seen that the expression.

The difference between the color analysis method according to the present invention and the conventional method using the spectrophotometer is that the method using the spectrophotometer uses a reflectance at a specific wavelength, which is the same method as other color measuring instruments, In the apparatus, it measured within the range of a predetermined specific wavelength. The result of the color analysis method according to the present invention is more meaningful than the result using the spectrophotometer. This is because the method or apparatus according to the present invention can measure the spectral distribution data of reflectance for each wavelength for each pixel of each image.

Comparing the difference between the spectrometer used in the prior art and the apparatus or method according to the present invention, the method according to the present invention has a difference that the measuring part is variable unlike the conventional method. Spectrophotometer is not possible to analyze the color of small part because the area taken by the sensor is constant, but the color analysis method according to the present invention varies the measurement area according to the magnification of the macro lens, and the analysis of each pixel unit in the image obtained by measuring once It is possible.

In addition, since the wavelength spectrum distribution data of each pixel unit can be obtained, color analysis for efficient skin color distribution is possible. This allows for pixel-by-pixel and region-by-region comparisons and simultaneous comparisons between normal and lesion sites in color analysis of the area to be measured.

Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. Examples included in the above description are introduced for the understanding of the present invention, and these examples do not limit the spirit and scope of the present invention. The scope of the present invention is shown not in the above description but in the claims, and all differences within the scope will be construed as being included in the present invention.

In addition, it can be easily understood by those skilled in the art that each of the above steps according to the present invention can be variously implemented in software or hardware using a general programming technique.

And some steps of the invention may also be embodied as computer readable code on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, CD-RW, magnetic tape, floppy disks, HDDs, optical disks, magneto-optical storage devices, and carrier wave (eg, Internet It also includes the implementation in the form of). The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

According to the present invention, in the method for analyzing the color of the surface, the light source for supplying light to the color analysis target, the means for acquiring the reflected light reflected on the surface of the analysis target and the state of the surface of the color analysis target To obtain the reflected light reflected from the standardized surface to analyze the color of the standardized light source, to obtain the reflected light having a wavelength value of a predetermined area among the reflected light in the unit of a predetermined wavelength, the pixels from the obtained wavelength-specific images Extracting parameters for analyzing the color of the surface in units of units of the unit or the surface to be observed, it is possible to efficiently analyze the skin color regardless of the skin measurement environment. Therefore, there is an advantage that the diagnosis and treatment associated with human skin can be efficiently performed.

Claims (8)

In the standardization method for analyzing the color of the surface by obtaining the image by means of the surface of the object reflects the light from the light source and obtains the reflected light as an image, Normalizing the light source by comparing the radial spectrum of the light source with the radial spectrum of a predetermined standard light source and comparing and correcting the difference for each wavelength band; The white reference of the radiant spectrum of the light source is compared with the white reference of the radiant spectrum of a predetermined standard light source for each wavelength band, and according to the difference, the inherent reflectance of the surface color analysis target Standardizing the image acquisition means by correcting the image data acquired by the image acquisition means by adjusting a white balance for each wavelength by measuring a); And A standardization method for analyzing the color of the surface comprising the step of normalizing the surface state by using the three-dimensional measurement parameters according to the expansion or reduction of the area of the surface to be analyzed color. In the method of analyzing the color of the surface, (a) Comparing the radial spectrum of the light source that supplies light to the color analysis target with the radial spectrum of a predetermined standard light source and correcting the spectral value of the light source using the difference for each wavelength band to normalize the light source And standardizing the surface state by using a three-dimensional measurement parameter according to an enlargement or reduction of an area of the surface to be analyzed for color or a surface state bending; (b) illuminating the standardized light source in step (a) on a standardized surface to be analyzed for color to obtain reflected light; (c) acquiring the reflected light having a wavelength value of a predetermined region among the reflected light in units of a length of a predetermined wavelength; And and (d) extracting parameters for analyzing the color of the surface from the obtained wavelength-specific images in pixel units or area units of the observed surface. The method of claim 2, In the step (c), the predetermined region of the wavelength value is a visible light region of 400nm to 720nm method for analyzing the color of the surface. The method of claim 2, The parameters extracted in step (d) include the XYZ component of the rectangular coordinate system of the surface color, the L * a * b * component in the CIELAB color region, the RGB component, the HSI component in the HSI color region, the erythema index, and melanin. A method for analyzing surface color comprising a melanin index. The method of claim 4, wherein In the step (d), the XYZ component is calculated using the reflectance value of the wavelength-specific image obtained in the step (c) and the spectral value of the light source, from which L * a * b *, RGB , HSI, erythema index, and melanin index, When calculating the erythema index and melanin index, a wavelength value of 680 to 700 nm as the R component, 560 to 580 nm as the G component is used. In the device for analyzing the color of the surface, A light source illuminating a surface to be analyzed for color; A reflected light acquisition unit configured to determine a color analysis area of the surface by enlarging or reducing the light source reflected on the surface according to a predetermined magnification; A wavelength-specific image acquisition unit configured to acquire images of the reflected light having a wavelength value of a predetermined region among the obtained reflected light in units of a length of a predetermined wavelength; A parameter extraction unit for extracting parameters for analyzing the color of the surface from the obtained wavelength-specific images in units of pixels or areas of the observation target surface; And The radiant spectrum of the light source is compared with the radiant spectrum of a predetermined standard light source to compare and correct the difference for each wavelength band, thereby normalizing the light source, and a white reference of the radiant spectrum of the light source. The white reference is compared with the white reference of the radial spectrum of a predetermined standard light source and the wavelength band, and the white balance of each wavelength is measured by measuring the intrinsic reflectance of the surface color analysis target according to the difference. And a standardization unit for standardizing image state obtained by standardizing image data acquired through the image acquisition unit for each wavelength by using three-dimensional measurement parameters according to the curvature of the surface state of the color analysis target. And the parameter extracting unit uses data normalized by the standardizing unit when extracting a parameter. delete The method of claim 6, The wavelength-specific image acquisition unit is an apparatus for analyzing the color of the surface, characterized in that it comprises a LCTF (Liquid Crystal Tunable Filter) for passing the wavelength of light between 400nm to 720nm in 10nm units.