WO2004056262A1

WO2004056262A1 - Apparatus and method for the reproduction of measuring conditions based on the body surface or surface veins and the contacting pressure

Info

Publication number: WO2004056262A1
Application number: PCT/CN2003/000813
Authority: WO
Inventors: Kexin Xu; Xiaodong Hu; Jingying Jiang
Original assignee: Tianjin Sunshine Optics Technologies Co., Ltd.
Priority date: 2002-11-22
Filing date: 2003-09-24
Publication date: 2004-07-08
Also published as: CN1416780A; CN1203809C; AU2003272847A1

Abstract

The present invention relates to an apparatus and a method for reproduction of measuring conditions based on the body surface or surface veins and the contacting pressure. The apparatus comprises an optical fiber measuring head, servo positioning devices for straight displacements in the x, y, z directions and angle around the z-axis, an object stage, a lighting device, a camera, an image collecting card, a spectrum detecting system and a computer processing system; the apparatus is simultaneously mounted with a contacting pressure sensor, a temperature sensor and a processing and collecting device for pressure and temperature signals. The steps of the method are as follows: (1) collecting, matching and positioning the image of body surface or surface veins; (2) performing the positioning for measuring position of the xy plane displacement and the rotating angle around z-axis and the like according to the result of the image matching; (3) performing the positioning in z direction according to the contacting pressure of the position of the measuring element and the body surface or surface veins; (4) during the operation of the measuring element, collecting the image of the body surface or surface veins characters, monitoring and measuring the movement state of the measured position.

Description

Based on human body surface or surface texture features and contact pressure

Measuring condition reproduction device and method

Technical field

The present invention relates to a measurement device and method, and in particular to a device and method for reproducing measurement conditions based on human body surface or surface texture features and contact pressure. Background technique

During the non-invasive infrared spectrum detection of human body components (such as blood glucose concentration, etc.), due to differences in human tissue structure such as skin tissue and thickness, blood vessel distribution, fat composition and thickness, and fluctuations in the external environment, It is required to keep the measurement conditions such as the measurement site and the contact pressure constant.

In a detection system based on infrared spectroscopy, even if the content of a component to be measured in the human body is basically constant, the spectral measurement data of different human bodies or different parts of the same human body may show a large difference. Therefore, the currently available methods are: (1) measuring multiple groups of infrared absorption spectra for a specific part of a specific individual; (2) measuring the component content of each group of spectra at a corresponding time using an invasive method; (3) using the above steps to obtain Establish a mathematical model of the infrared absorption spectrum and component content data; (4) Use this mathematical model to analyze the component content corresponding to the infrared absorption spectrum obtained from subsequent actual measurements. In order to ensure the reusability of the data model and the reliability of the final measurement results, certain restrictions must be placed on the measurement locations and conditions, that is, the actual measurement conditions of the subsequent component content are consistent with the measurement conditions established by the mathematical model.

In order to keep the measurement conditions constant, the current implementation methods can be roughly divided into two categories: One is the use of specific limit devices, such as: hand molds, finger cots, limit stops, etc., so that the measurement location of the measured object can basically be It is limited to a certain area. The second is to make specific marks at or near the measurement site, use image acquisition and processing methods to calculate the relative position, and move the measurement device to the corresponding position. The following problems exist in the prior art:

'(1) It is not possible to automatically and effectively identify whether the measured object is the same individual, and human intervention is required; (2) The reproduction accuracy of the measurement position is low, and it can only reach the pixel level; (4) There is no effective solution to the rotation phenomenon of the measurement site;

(5) The measurement error caused by the movement of the measurement site during the measurement process cannot be considered and resolved. Summary of the Invention

In order to overcome the above-mentioned shortcomings in the prior art, the present invention establishes a measurement condition reproduction device based on human body surface layer or surface texture features and contact pressure, and proposes a corresponding implementation method.

The method steps of the present invention are as follows:

(1) Image pickup, matching and positioning of human body surface or surface texture features;

(2) Positioning of measurement positions such as xy plane displacement and z-axis rotation angle according to the results of surface or surface texture image matching;

(3) Positioning in the z direction according to the contact pressure between the measuring element and the surface layer or surface of the human body;

(4) During the operation of the measuring element, continue to collect images of human body surface or surface texture features, and monitor the movement status of the measurement part.

among them:

Image collection of the surface layer or surface texture of the human body measurement surface. The surface texture features are the surface texture of the skin such as fingerprints and palm prints. The surface layer refers to the texture features reflected by blood vessels, bones and pores near the surface of the skin. The measurement position will be the saved image as a template image, and the contact pressure information will be attached.

After the human body measurement part is repositioned, first collect the surface layer or surface texture image of the measurement part, and then match and identify the current image and the template image by image processing to obtain the displacement of the measurement part in the xy plane and Offset of the z-axis rotation angle.

Drive the servo device according to the XY plane displacement and the z-axis rotation angle deviation obtained above to make the measuring element reach the corresponding position, and then adjust the position of the measuring element in the z-axis direction according to the contact pressure between the measuring element and the measurement part;

Start the measurement element into the working state, continue to collect the surface layer or surface texture image of the measurement part, and obtain the movement state of the measurement part by image subtraction operation.

The image is matched with the template image using the following method: (1) The wavelet transform and exhaustion method are used to determine the rotation angle. The wavelet transform reduces the data amount of the texture image at the measurement site and accelerates the process of rotation angle correction;

(2) Use phase correlation to detect displacement changes of pixel accuracy to reduce the impact of image distortion and light unevenness on image matching;

(3) Use surface fitting technology to detect displacement changes of sub-pixel accuracy, so that the accuracy of image matching reaches sub-pixel level.

According to a method for reproducing the measurement conditions based on human body surface or surface texture features and contact pressure, we have designed a specific spectrum measurement device: as shown in Figure 1: It consists of fiber optic probes in the x, y, and z directions. Linear displacement and z-axis angle servo positioning device, stage, lighting device, camera, frame grabber, spectrum detection system and computer processing system; contact pressure sensor and temperature sensor are set at the measurement site and the probe, and the pressure, Temperature signal processing and acquisition device.

The work of the device includes the following steps:

(1) Establish a template model, the steps are shown in Figure 2: Drive the camera to the initial position, collect the texture information of the human body surface or surface, save the image to the template image library, drive the optical fiber probe to the image center, and drive the optical fiber probe Make contact with the measurement site, maintain the set contact pressure, and measure the temperature of the contact site;

(2) Perform spectral measurement under the conditions of step (1), and create a specific mathematical model of spectral measurement for the measurement location based on the spectral data;

(3) After the human body measurement part is repositioned, first drive the camera to the initial position, collect the surface or surface texture image of the human body measurement part, and then judge whether the template image exists. If there is no error message displayed and end, otherwise select the corresponding template image Then, the current image and the template image are matched and identified through image processing to obtain the current measurement position and the offset of the measurement position in the xy plane and the z-axis rotation angle and the amplitude of the maximum correlation peak when the template image is established If the amplitude of the maximum correlation peak exceeds the limit, it prompts the template image to be selected incorrectly and ends. Otherwise, it continues to determine whether the offset of the xy plane exceeds the displacement of the drive mechanism. If it exceeds the limit, it ends after prompting the limit information, otherwise it drives the servo. The device makes the optical fiber probe reach the corresponding position, and then adjusts the position of the measuring element in the z-axis direction according to the contact pressure between the optical fiber probe and the measurement part, and measures the temperature of the contact part, as shown in FIG. 3;

(4) Use optical fiber probe and spectral detection system to perform spectral detection, and measure the measurement contact at that time Perform temperature analysis on the temperature of the part, the measured spectral data and the mathematical model of spectral measurement established in step (2);

(5) During the spectrum detection process, continue to collect the surface layer or surface of the measurement site. The texture image is obtained by the subtraction operation of the measurement site. If the movement of the measurement site is found during the measurement process, the spectrum detection is terminated and the device is restarted. Enter the measurement condition reproduction process.

The invention has the following advantages:

(1) Repetitive positioning of the probe in the xy plane displacement and rotation angle according to the texture features of the human body surface or surface;

(2) The surface texture or surface texture of the human body can be the texture of the skin surface, such as fingerprints and palm prints, or the texture features of blood vessels, bones and pores near the surface of the skin, which are fixed under certain conditions;

(3) According to the contact pressure between the optical fiber probe and the measurement site, the probe is repeatedly positioned in the vertical z-axis;

(4) Collect the temperature information of the measurement site and introduce it into the infrared spectrum analysis process;

(5) Monitor the movement status of the body measurement part during the acquisition of the infrared spectrum to ensure the accuracy of the spectrum measurement;

(6) The wavelet transform is used to reduce the data amount of the texture image at the measurement site and accelerate the process of rotation angle correction;

(7) Use phase correlation technology to achieve image matching, reduce the impact of image distortion and uneven illumination on image matching;

(8) Use surface fitting technology to make the image matching accuracy reach sub-pixel level

(9) Simplify the collection of texture images by means of ring-shaped edge lighting and direct front camera;

(10) The servo system is used to realize the automatic positioning of the optical fiber probe. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1: Block diagram of measurement condition reproduction system;

Figure 2: Initial measurement condition determination process;

Figure 3: Measurement condition reproduction processing flow;

Figure 4: Structure of an image positioning system based on palmprint recognition;

Figure 5: A schematic diagram of the structure of an image positioning system based on fingerprint recognition; Figure 6a _{: a} front view of the structure of a ring-shaped edge lighting device;

Figure 6b: Side view of the structure of the ring-shaped edge lighting device;

Figure 7: Schematic diagram of position shift between two images;

Figure 8: Image matching processing flow;

Figure 9: Template palm print image;

Figure 10: The palmprint image is currently collected;

Figure 11: Phase correlation results of the currently acquired image after rotation correction processing with the template image; Figure 12: Superposition results of the current acquisition image after rotation and translation correction with the template image; Figure 13a: Fiber optic probe in contact with the measurement site Schematic diagram of pressure detection;

Figure 13b: Top view of the contact pressure detection between the optical fiber probe and the measurement site;

Figure 14: Schematic diagram of the contact temperature between the optical fiber probe and the measurement site;

Figure 15: Motion state discrimination processing flow;

Figure 16: Comparison of the CV values of the spectral measurement results before and after the system is reproduced using the measurement conditions; Figure 16- (1) Test object 1;

Figure 16- (2) Test object 2;

Figure 16- (3) Test object 3. detailed description

The present invention is discussed in further detail below with reference to the drawings and specific embodiments.

1. Structure of measurement condition reproduction system

A lighting device is installed below the stage with a hole, the device is provided with a hole attached to the stage, and the axis coincides; the servo positioning device is composed of four parts: an X-axis servo positioning device, a y-axis servo positioning device, z-axis servo positioning device, z-axis rotation servo positioning device; z-axis rotation servo positioning device is installed on z-axis servo positioning device; optical fiber probe is installed on _Z- axis rotation servo positioning device, and the center axis coincides with its rotation axis; servo The displacement mechanism in the positioning device is driven by a stepper motor and controlled by a servo controller, which is controlled by a computer.

Among the texture features of the human body's surface layer or surface, the texture features of fingerprints and palm prints are relatively obvious, and the location is convenient for non-invasive infrared spectrum detection. According to the characteristics of the measurement parts on the fingers and palms, the structure of the measurement condition reproduction system is also different.

As shown in Figure 4: In an image positioning system based on palmprint recognition, the optical fiber probe 8 and the CCD The camera 1 is located at the same location 2 as the inside of the palm, that is, the image matching information is the texture of the palm area, and the measurement position of the infrared spectrum is the palm of the hand. The stage 3 is driven by the X-axis servo positioning device 4 and the y-axis servo positioning device 5. The X-axis servo positioning device is fixed on the base plate 7. The y-axis servo positioning device is orthogonally fixed to the X-axis servo positioning device on the X-axis servo positioning device. The stage is fixed on the y-axis servo positioning device. The servo positioning device for driving the optical fiber probe 8 is composed of two parts step by step: a z-axis servo positioning device 6 and a z-axis rotary servo positioning device 9. The z-axis servo positioning device is fixed on the base plate by a vertical connection. The z-axis servo positioning device is installed on the z-axis servo positioning device. The optical fiber probe is mounted on the _Z- axis rotary servo positioning device, and the center axis coincides with its rotation axis. The displacement mechanism in the servo positioning device is driven by a stepping motor and controlled by a servo controller, which is controlled by a computer. .

As shown in Figure 5: In an image positioning system based on fingerprint recognition, the optical fiber probe 8 and the CCD camera 1 are located at the measured part 2 such as both sides of a finger, that is, the information of image matching is the fingerprint, and the measurement position of the infrared spectrum is The back of the finger, such as the nail area, is fixed on the stage 3. The servo positioning device driving the optical fiber probe is composed of four parts step by step: X-axis servo positioning device 4, y-axis servo positioning device 5, _Z- axis servo positioning device 6, z-axis rotary servo positioning device 9. The X-axis servo positioning device is connected to the bottom plate 7. The y-axis servo positioning device is orthogonally fixed to the X-axis servo positioning device on the X-axis servo positioning device. The z-axis servo positioning device is mounted on the y-axis servo positioning device through a vertical connection, and the _Z- axis rotates. The servo positioning device is mounted on the z-axis servo positioning device. The optical fiber probe 8 is mounted on the z-axis rotation servo positioning device 9, and the center axis thereof coincides with its rotation axis. The displacement mechanism in the servo positioning device is driven by a stepping motor and controlled by a servo controller, which is controlled by a computer.

In the image positioning system of the above two applications, the palm and fingers are placed on a carrier with the front side facing down, and a through hole 10 is provided on the carrier to facilitate the collection of palm prints or fingerprint images. A ring-shaped edge lighting device 11 is installed under the carrier. The device also has a through hole, the same size as the hole of the carrier, and the axes coincide.

2. Lighting realization ''

Illumination of the measurement site is achieved by means of circular edge illumination. In order to facilitate the image collection of palm prints and fingerprints, there are circular holes 10 under the palms and fingers, as shown in FIGS. 4 and 5. A light emitting diode (LED) light source fixing structure is fixed below the palm and finger bearing surface, as shown in Figs. 6a and 6b. The material of the fixing structure is plexiglass, and the circumference of the circular hole 10 is 24 grooves 12 are evenly arranged, and each groove can be embedded with a light emitting diode (LED). The bottom surface of the groove 12 is an inclined surface, which is higher near the center to ensure that the LED is illuminated obliquely upward. The plexiglass on the side of the center hole is roughened, so that the diffuse reflection of the LED illuminates the measurement site.

3. Implementation of image acquisition

In order to avoid image distortion caused by oblique imaging and the subsequent positioning errors, the CCD camera 1 is installed directly below the center axis of the circular hole, as shown in Figs. 4 and 5.

In the fingerprint positioning system, because the optical fiber probe is above the nail and does not conflict with the position of the CCD camera, the CCD camera is fixedly installed on the bottom plate directly below the fingerprint.

In the palmprint positioning system, it is required that the optical fiber probe should be directly under the palm in the test state, which conflicts with the front image of the palmprint. In order to solve this contradiction, the optical fiber probe is mounted on the z-axis rotary servo positioning device, and the CCD camera is mounted on the _z- axis servo positioning device. As the servo positioning device is combined step by step, the _Z axis servo positioning device can be translated to different positions under the drive of the X axis servo positioning device and the y axis servo positioning device, that is, the CCD camera is moved to the stage during the image acquisition stage. Just below the circular hole, move the fiber-optic probe directly under the circular hole of the stage in the spectrum measurement stage.

The CCD camera outputs a standard video signal and inputs it to a frame grabber in a computer system.

4. Image processing flow and algorithm

Before repeating the positioning of the optical fiber probe, the offset between the currently acquired image and the template image needs to be determined. Figure 7 is a schematic diagram of the offsets of the two images. The origins of the two coordinate axes in the figure are the centers of the two images. It can be seen that there is a displacement offset and a rotational offset of the xy plane in the two images. After the image capture card collects palm print and fingerprint images, it needs to enter the image processing process to determine the position offset of the two images, and then drive the servo positioning system with the position offset to make the optical fiber probe reach the corresponding position. The image processing flow is divided into three stages: (1) the determination of the rotation angle using wavelet transform and exhaustion method; (2) the use of phase correlation to detect the displacement change of pixel accuracy; (3) the use of quadratic surface fitting for sub- Pixel-precision displacement change detection.

FIG. 8 is an image processing flowchart, which is described in detail below:

4.1 Determination of rotation angle using wavelet transform and exhaustion method

Under multiple measurement conditions, it is difficult to ensure that the position of the body measurement site is completely consistent, including rotation angle and plane displacement. Because image matching based on phase correlation is more sensitive to the angle of rotation, it is necessary to determine the current acquired image and template before determining the xy plane displacement. The rotation angle of the image.

In order to make the image positioning system have higher accuracy, the resolution of the set image is

768x582. There are simple limit devices on the stage of the palms and fingers. The displacement of the palms and fingers is within a small range, which makes it possible to meet the positioning requirements by capturing images with a central resolution of 256x256 and performing image matching. However, image matching based on phase correlation requires a Fourier transform, which is computationally intensive, and the exhaustive method requires multiple phase correlation operations. Even if the image resolution is 256x256, the amount of data is still very large, and it takes a long time to directly perform the exhaustive phase correlation on the image with this resolution. In order to reduce the amount of data in the phase-dependent image matching operation, wavelet transform is performed on the currently acquired image and the template image before determining the rotation angle of the exhaustion method, reducing the image resolution to 32x32, which greatly reduces the time of this image processing stage. . The wavelet multi-scale of the image represents a pyramid-like structure, which is very beneficial for fast image matching from coarse to fine. According to the theory of wavelet transform, after the image is transformed by wavelet, the overall characteristics of the image are basically maintained in the scale space, that is, the low-frequency portion, and the amount of data in the scale space portion after extraction is significantly reduced compared to the original image.

The specific steps of using the exhaustive method to determine the rotation angle offset of the two images are as follows: (1) Assume that the range A of the rotation change of the current set image relative to the template image is [Amin, Am _aX ]. It is required to determine the step angle ΔΑ where the angle is exhausted; (2) Rotate the current acquired image by Amin, find its Fourier transform, and perform phase correlation with the template image, find the corresponding peak-to-noise ratio of the relevant peak, and save it to a list; (3) Rotate the current acquired image by Amin + ΔΑ, find its Fourier transform, and perform phase correlation with the template image, find the corresponding peak-to-noise ratio of the relevant peak, and save it in the list described above; (4) use the step size Gradually increase the rotation angle of the currently acquired image for ΔΑ until the rotation angle reaches Amax, find its Fourier transform at each step, and perform phase correlation with the template image to obtain the corresponding correlation peak signal-to-noise ratio, which is also stored in the above-mentioned In the list; (5) traverse the list, compare the correlation peak signal-to-noise ratio corresponding to each rotation angle, and the rotation angle corresponding to the maximum correlation peak signal-to-noise ratio Offset angle of the two images.

4.2 Detection of pixel-accurate displacement changes using phase correlation

After using the wavelet transform and exhaustion method described in 4.1 to determine the rotation angle of the current set image and template image, it is necessary to use phase correlation processing again for image matching to determine the displacement offset of the xy plane of the two images. Phase correlation is an image matching algorithm with little geometric distortion. Law. Because the geometric distortion has a large impact on the high-frequency components of the image and a small impact on the low-frequency components, a phase correlation algorithm based on the Fourier spectrum with a low-pass filter characteristic is used in this device, which can greatly reduce the geometric distortion on the matching performance Impact.

The following formula is the basic formula of the phase correlation operation. '

F ξ, η) Όξ, η)

Among them, ^ and are the results of Fourier transform of two images (currently acquired image and template image), respectively. According to the formula (1) and the theory of Fourier transform, the phase spectrum contains the position shift information of the two images, and it is a power spectrum whose spectral amplitude is 1 in the full frequency domain. According to the inverse Fourier transform of (1), it can be seen that the phase correlation function is a delta pulse function located at the position offset (x0, yO) of the two figures, which is also called the correlation peak. When the two images are completely similar, the value is 1, otherwise it is 0. Therefore, the phase correlation calculation results of the two images are used in this device to determine the displacement amount of the images.

In this device, phase matching is used for image matching to determine the displacement offset with the following characteristics: (1) Large displacement detection range. When there is only a displacement change between the two images, the maximum displacement offset of the xy plane can be detected to reach half the image width. (2) Sharp related peaks. When the two images are completely correlated, the calculated δ pulse function has a very sharp correlation peak, which can achieve an accurate matching of the positions of the center points of the two images. (3) Little dependence on image gray. When there is a gray level difference between the two images, the position of the calculated δ pulse function does not change, but there is a difference in amplitude, so it has a strong ability to resist image occlusion. (4) The amount of rotation offset between the two images has a greater impact on the results of image matching. When there is a rotation angle offset between the two images, the spectrum of the Fourier transform is also rotated. When the rotation angle offset is greater than 5 °, even if the two images are identical, the correlation peak attenuation is zero, that is, the displacement offset of the two images in the xy plane cannot be determined based on the correlation peak. Therefore, in the previous step, the rotation angle is determined by judging the size of the correlation peak, and the image is rotated by this angle to perform phase correlation, and finally the position offset of the two images is obtained.

Through the above image processing process, the position offset of the currently acquired image and the template image can be determined, and the minimum unit of the offset is 1 pixel. To further accurately determine the position offset To improve the positioning accuracy of the system, the following sub-pixel matching algorithm based on quadric surface fitting is used.

4.3 Sub-pixel precision displacement change detection using quadric surface fitting

In this system, a surface fitting method is adopted. This method has the advantages of fast and easy calculation, and the accuracy can reach sub-pixels. The idea of the surface fitting method is: take the best matching point at the pixel level as the center, perform surface fitting according to the similarity measure, and then calculate the exact position of the extreme point by corresponding mathematical methods. This device uses the correlation coefficient of phase correlation as the similarity measurement feature, selects the quadric surface as the fitting function, and uses the multivariate least squares regression method in the calculation to determine the exact location of the extreme point.

The quadric fitting function uses the formula:

PC (x, y) = ax + by + cxy + dx + ey + f

Among them, PC (x, y) is a phase correlation value corresponding to the position (x, y). The above function can be written as:

AX = B where,

The device adopts the multivariate least squares regression method in the fitting calculation, which makes the calculation simple and accurate. In the calculation process, the vector X is used as the regression coefficient, and it is assumed that the value of the random variable B depends on the independent variable in the matrix A. The regression coefficient is obtained as the coefficient of the fitting function. After the coefficients of the fitting function are obtained, the precise position of the image offset with sub-pixel accuracy can be obtained using the following formula.

2db-ce 2ae― dc

X =-y

c ^² - 4ab c ² - ab FIG. 9 as a template palmprint image 10 is currently acquired palmprint, the resolution of the image is two 256 X 256. It can be seen that there is a significant angular and displacement shift in the two images. Increase angle The amount is set to 0.1 degree, and the rotation angle is detected by applying wavelet transform and exhaustion method, and the rotation angle of the palm image of the current set relative to the template palm image is 13.9 degrees counterclockwise. After the currently collected palm print image is rotated counterclockwise by 13.9 degrees, phase correlation matching processing is performed with the template palm print image. Figure 11 is a flat distribution map of the correlation function obtained by processing, and the horizontal offset of the two images is obtained according to the position of the maximum correlation peak. The amount is -20 pixels, and the vertical offset is 64 pixels. Rotate the currently collected palm print image map 13.9 degrees counterclockwise, and translate -20 pixels and 64 pixels in the horizontal and vertical directions, respectively, and then superimpose the template palm print image. As shown in FIG. 12, it can be seen from the superimposed image that the above-mentioned detection of the rotation angle and displacement offset using phase correlation is correct and effective. On the basis of using phase correlation to detect displacement changes in pixel accuracy, and then using quadric surface fitting to detect displacement changes in sub-pixel accuracy, the horizontal offset of the two images is -20.08 pixels, vertical The offset in the direction is 64.20 pixels. Through further evaluation, the rotation detection accuracy of the measurement condition reproduction device can reach 0.1 degrees, and the translation detection accuracy can reach 1/50 of a pixel.

5. Measurement of contact parameters and adjustment of the z-direction position of the optical fiber probe

After the image processing process is completed, the relative position of the measurement site in the xy plane, that is, the offset and rotation angle of the xy axis, and then rely on the xy plane servo positioning device to drive the optical fiber probe so that the probe axis coincides with the center point of the measurement site. The optical fiber probe is rotated by a certain angle through the z-axis rotation positioning device, which is the rotation angle obtained by the image processing process. Finally, the optical fiber probe is driven by the z-direction approaching servo device to bring the optical fiber probe into contact with the measurement site.

After the optical fiber probe contacts the measurement part, the pressure sensor will output the contact pressure signal and input it into the signal acquisition card. The computer compares the collected contact pressure signal with a preset value, and then adjusts the relative position of the optical fiber probe in the z direction. Position, so that the contact pressure between the optical fiber probe and the measurement site is basically maintained near a preset pressure value. The measurement of contact pressure is shown in Figure 13. A circular-shaped gas path bracket 13 is fixed on the top of the cylindrical optical fiber probe, and a silicone tube 14 is installed in the annular area between the bracket and the optical fiber probe 8. The inside of the silicone tube is filled with air and connected with a The silicon pressure sensor is connected to form a closed gas path. Repeated positioning of the probe in the vertical z-axis is achieved based on the contact pressure between the probe and the measurement location. When the measurement part of the human body is in contact with the optical fiber probe, the pressure in the closed gas path changes due to the pressure of the inflatable silicone tube at the measurement part, and the contact pressure of the human measurement part and the optical fiber probe can be obtained.

After the optical fiber probe is in contact with the measurement site, the computer can The card collects the contact temperature of the two, and uses the data as parameters for mathematical model establishment and infrared spectrum analysis. The temperature sensor 15 is a thin-film thermistor, and is attached to the measurement surface of the optical fiber probe, as shown in FIG. 14. There are two bundles of optical fibers installed in the optical fiber probe, one bundle is distributed in the center area of the probe, and the other bundle is distributed in a ring area of the probe. Four temperature sensors are evenly pasted in the middle area between the two optical fibers, and ten temperature sensors are evenly pasted along the circumference in the peripheral area of the optical fiber bundle 16. The signal acquisition card collects the temperature of the 14 detection points into the computer system and performs average processing to ensure the accuracy of the temperature measurement.

6. Exercise state discrimination

When the optical fiber probe moves to the corresponding position and comes into contact with the measurement site, the infrared optical path detection system starts to work. In the process of infrared spectrum detection, the relative position of the measurement site is required to be kept basically fixed. In order to achieve this, while driving the optical fiber probe to the calculated position and starting the spectral measurement, the CCD camera collects an image of the contact area of the optical fiber probe and the measurement site-the position of the round hole on the stage, and uses it as a motion state to determine In the process of spectral measurement, the computer collects an image of the same area after every five wavelengths of spectral measurement, and performs a subtraction operation with the template image discriminated by the motion state. Whether the measurement site has moved during the process. If the result of the subtraction of the two images during the spectrum measurement process is basically zero, it indicates that the relative position of the measurement site has not changed. Continue the spectrum measurement cycle until the end of the spectrum measurement and display the end of measurement prompt message, otherwise it indicates that the measurement site is detected The relative position has changed, and the spectrum measurement was suspended, indicating that the measurement data is invalid, and requiring the user to re-enter the measurement condition reproduction process to ensure the accuracy of the spectrum measurement. Fig. 15 is a processing flow for judging a motion state.

7. Infrared spectrum measurement and analysis results

After the relative position of the optical fiber probe is determined by using the above-mentioned measurement condition reproduction method, the spectrum measurement can be entered. In order to compare the results of the spectral measurements before and after using the measurement condition reproduction system, a series of tests were performed on the palm area. There are two kinds of test schemes: (1) Measurement conditions: The measurement of the spectral data when the reproduction device is not working: First, adjust the center axis of the optical fiber probe and the center axis of the round hole of the stage to coincide, and then manually adjust the optical fiber probe to be vertical The orientation position makes the optical fiber probe have a certain contact pressure with the palm. At the same time, the z-axis rotary servo positioning mechanism is reset to the zero position. The palm of the measured object is lifted after each spectrum measurement is completed, and the servo is reset when it is placed on the stage. The positioning device does not work, that is, the position of the optical fiber probe is fixed; the palm is repeatedly placed on the carrier 10 times, each time 10 sets of spectral data were obtained. (2) Measurement conditions Measurement of the spectral data during the operation of the reproduction device: Determine and save the measurement conditions before the measurement of the first group of spectral data, such as: template palm print image, contact pressure, and the palm of the measured object remains after each spectral measurement is completed. Lift up, but after each relocation, before entering the spectral data measurement, use the measurement condition reproduction device to reproduce the measurement conditions saved before the first set of spectral data measurement, and finally perform the measurement of the spectral data; also place the palm repeatedly Go to the carrier 10 times and obtain 10 sets of spectral data.

Using the above test scheme, the spectral data of three different humans were measured. The statistical results are shown in Figure 16- (1), Figure 16- (2), and Figure 16- (3). The evaluation index of the statistical graph is the ratio of the maximum fluctuation of the light intensity corresponding to each wavelength point in the 10 sets of spectral data to the light intensity, which is abbreviated as CV. The dashed line in the figure indicates the statistical result of the spectral data when the measurement condition reproduction device is not working, and the solid line in the figure indicates the statistical result of the spectral data when the measurement condition reproduction device is in operation.

By comparing the CV values of different human bodies, the following conclusions can be drawn: (1) The change in the position of the measurement site has a greater impact on the spectral measurement, and corresponding measures must be adopted to limit the change in position; (2) The present invention is based on The human body surface layer or surface texture feature and contact pressure measurement condition reproduction device can greatly reduce the influence of the change of the position of the measurement location on the spectrum measurement, and improve the measurement stability and repeatability of the spectrum.

Claims

Rights request

1. A method for reproducing measurement conditions based on human body surface or surface texture features and contact pressure, which is characterized in that it mainly includes the following steps:

(2) positioning of measurement positions such as xy plane displacement and z-axis rotation angle according to the results of surface layer or surface texture image matching;

(4) During the operation of the measuring element, collect images of human body surface or surface texture features, and monitor the movement state of the measurement part.

2. A method of reproducing measurement conditions based on human body surface or surface texture features and contact pressure according to claim 1, wherein the steps are:

(1) Image collection of the surface layer or surface texture of the body measurement site. The surface texture is characterized by the surface texture of the skin such as fingerprints and palm prints. The surface layer refers to the texture features reflected by blood vessels, bones and pores near the surface of the skin. The preset measurement position will save the image as a template image and attach the contact pressure information;

(2) After the human body measurement part is repositioned, first collect the surface layer or surface texture image of the measurement part, and then match and identify the current image and the template image through image processing to obtain the measurement part at xy when the current measurement part and the template image are established. Offset of plane displacement and z-axis rotation angle;

(3) Drive the servo device according to the displacement of the xy plane displacement and the _Z axis rotation angle obtained in step (2) to make the measuring element reach the corresponding position, and then adjust the measuring element in the z axis direction according to the contact pressure between the measuring element and the measurement part position;

(4) Start the measuring element into the working state, continue to collect the surface layer or surface texture image of the measurement part, and obtain the movement state of the measurement part through the image subtraction operation. -

3. The method for reproducing the measurement conditions of human body surface layer or surface texture features and contact pressure according to claim 1, 2, wherein the method of matching the current image with the template image is: (1) The wavelet transform and exhaustion method are used to determine the rotation angle. The wavelet transform reduces the data amount of the texture image at the measurement site and accelerates the process of rotation angle correction;

(2) Use phase correlation to detect pixel-accurate displacement changes to reduce the effects of image distortion and uneven illumination on image matching;

4. A spectroscopic measuring device based on a method for reproducing the conditions of a human body's surface layer or surface texture and a measurement condition of a contact pressure, which is a fiber-optic probe, a linear displacement in the x, y, and z directions and a z-axis angle servo positioning device. It consists of a table, a lighting device, a camera, an image acquisition card, a spectrum detection system, and a computer processing system. It is characterized in that a contact pressure sensor, a temperature sensor, and a processing and acquisition device for pressure and temperature signals are provided at the measurement site and the probe.

The spectrum measurement device based on the method for reproducing the measurement conditions of the human body surface layer or surface texture and the contact pressure according to claim 4, wherein the device is installed below a carrier with holes. Lighting device, the device is provided with a hole attached to the stage, and the axis coincides; the servo positioning device is composed of four parts: X-axis servo positioning device, y-axis servo positioning device, _Z- axis servo positioning device, z-axis rotation Servo positioning device; The z-axis rotary servo positioning device is installed on the z-axis servo positioning device; the optical fiber probe is installed on the z-axis rotary servo positioning device, and the central axis coincides with its rotation axis; The displacement mechanism in the servo positioning device consists of steps The input motor is driven and controlled by a servo controller, which is controlled by a computer.

.

6. A spectrum measurement device based on a method for reproducing the measurement conditions of human body surface or surface texture features and contact pressure according to claim 4, characterized in that said illumination device is realized by means of ring-shaped edge illumination. : A fixed structure of light emitting diode light source is arranged below the stage. The material of the fixed structure is plexiglass. 24 grooves are evenly arranged on the circumference of the circular hole, and each groove can be embedded with a light emitting diode (LED). The bottom surface of the groove is an inclined surface, which is higher near the center to ensure that the LED is illuminated obliquely upwards; the plexiglass on the side of the center hole is roughened so that the LED diffuse reflection irradiates the measurement site.

7. A spectrum measurement device based on a method for reproducing the measurement conditions of human body surface or surface texture features and contact pressure according to claim 4, wherein in the device, a CCD camera is installed below the stage, Adopt direct front camera; when the probe is on the same side as the camera, the optical fiber probe is installed in the _Z- axis rotation servo positioning device, and the CCD is taken. The camera is mounted on the z-axis servo positioning device.

The spectrum measurement device based on the method for reproducing the measurement conditions of the human body surface layer or surface texture and the contact pressure according to claim 4, wherein the contact pressure sensor is fixed at the top of the optical fiber probe. An annular gas path bracket is installed with a flexible silicone tube in the annular area between the bracket and the optical fiber probe. The tube is filled with air and connected to a pressure sensor to form a closed gas path. The contact pressure of the measurement site enables repeated positioning of the probe in the vertical z-axis.

The spectrum measurement device based on the method for reproducing the measurement conditions of human body surface layer or surface texture characteristics and contact pressure according to claim 4, wherein the temperature sensor is a thin film thermistor and is attached to an optical fiber Measuring surface of the probe.

10. A spectrum measurement device based on a method for reproducing a measurement condition of a human body surface layer or surface texture feature and contact pressure according to claim 4, characterized in that it comprises the following steps:

(1) Create a template model, the steps are as follows: drive the camera to the initial position, collect the texture information of the human body surface or surface, save the image to the template image library, drive the optical fiber probe to the image center, and drive the optical fiber probe to contact the measurement site , And maintain the set contact pressure, and measure the temperature of the contact area;

(3) After the human body measurement part is repositioned, first collect the surface layer or surface texture image of the human body measurement part, and then match and identify the current image and the template image through the image processing method, and obtain that the measurement part is located when the current measurement part and the template image are established. xy plane displacement and z axis rotation angle offset, then drive the servo device to make the optical fiber probe reach the corresponding position, and then adjust the position of the measuring element in the z axis direction according to the contact pressure between the optical fiber probe and the measurement part;

(4) Use optical fiber probes and spectral detection systems to perform spectral detection, measure the temperature of the measurement contact site at that time, and substitute the measured spectral data into step (2) The mathematical model of spectral measurement established for data analysis;

(5) During the spectrum detection process, continue to collect the surface or surface texture image of the measurement part, and obtain the movement state of the measurement part through the image subtraction operation. If the measurement part is found to move during the measurement process, the spectral detection is terminated, and the device re-enters Measurement condition reproduction process.