CN110763159A - Optical deflection microscopic surface measuring device and method - Google Patents

Abstract

The invention discloses an optical deflection microscopic surface measurement method. The method comprises: using a three-coordinate measuring device to measure and calibrate a structural position parameter S of the optical deflection microscopic surface measuring device; S. Calculate the phase distribution of the deformed fringe optical signal, where the deformed fringe optical signal includes the feature information of the microscopic surface profile of the element to be tested; according to the phase distribution, obtain the actual light spot distribution corresponding to the microscopic surface of the element to be tested; The actual light spot distribution is compared with a preset ideal light spot distribution to obtain the microscopic surface profile of the element to be tested. Correspondingly, the invention also discloses an optical deflection microscopic surface measuring device. The invention realizes a technical solution for microscopic measurement with high precision, low cost, high spatial resolution and fast measurement speed.

Description

A kind of optical deflection microscopic surface measurement device and method

technical field

The invention relates to the technical field of measurement, in particular to an optical deflection microscopic surface measurement device and method.

Background technique

In recent years, with the development of micro-nano technology, the demand for measuring the micro-deformation of components has gradually increased, and the requirements of measurement accuracy and speed have also been continuously improved. In the prior art, the microscopic measurement of the reflective surface is usually realized by technical solutions such as optical interferometer measurement method and scanning microscope measurement method. However, the optical interferometer measurement method has the disadvantages of small measurement dynamic range, easy to be disturbed by the environment, and high detection cost. Scanning microscopy methods, such as projection electron microscopy (STEM), have extremely high horizontal and vertical resolution, but their small measurement ranges and high inspection costs limit their use in engineering surface measurements.

等，Microdeflectometry-a novel tool to acquire three-dimensional microtopographywith nanometer height resolution,"Optics Letters 33(4),396-398)中实现了对反射面面形误差的检测，通过条纹相位与面形斜率的关系来求解面形误差，测量精度低，并且该装置的视场范围小，使测量范围受到限制。Chinese Patent Application Publication No. CN107560564A is an invention patent for a free-form surface detection method and system. The patent uses a traditional optical deflection measurement device, which uses a projection screen, a component to be measured, and a CCD detector to form a reverse Hartmann optical detection. Although the system can achieve rapid measurement of the surface of the component, its spatial resolution is low and it cannot achieve accurate microscopic measurement. A device for microscopic measurement of optical deflection (see Gerd

et al., Microdeflectometry-a novel tool to acquire three-dimensional microtopography with nanometer height resolution, "Optics Letters 33(4), 396-398) realized the detection of the surface shape error of the reflecting surface, through the relationship between the fringe phase and the surface shape slope To solve the surface shape error, the measurement accuracy is low, and the field of view of the device is small, which limits the measurement range.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an optical deflection microscopic surface measurement device and method, which realizes a technical solution for microscopic surface measurement with high precision, low cost, high spatial resolution and fast measurement speed.

In order to achieve the above object, the present invention provides an optical deflection microscope surface measurement device, the measurement device includes a projection screen, a beam splitting prism, a component to be measured, a microscope objective lens, an imaging lens, a CCD detector and a computer, wherein, The element to be tested is placed under the beam splitter prism, the projection screen is arranged on the left side of the beam splitter prism and the two are parallel, and the microscope objective lens, imaging lens and CCD detector are arranged in sequence on the beam splitter prism. Above the beam splitting prism, the computer generates a sinusoidal fringe light signal, the sinusoidal fringe signal light passes through the beam splitting prism and projects to the component to be measured, and returns to the beam splitting prism through the surface of the component to be measured. After the microscope objective lens and the imaging lens are converged into a converging beam, the converging beam presents a deformed fringe light signal in the CCD detector, and the computer analyzes the deformed fringe light signal to obtain the The microscopic surface profile information of the measuring element.

In order to achieve the above object, the present invention provides a method for measuring an optical deflection microscopic surface, the method comprising:

S1, using three-coordinate measuring equipment to measure and calibrate the structural position parameter S of the optical deflection microscopic surface measuring device;

S2. Calculate the phase distribution of the deformed fringe optical signal according to the measured and calibrated structural position parameter S, where the deformed fringe optical signal includes the feature information of the microscopic surface profile of the element to be measured;

S3. According to the phase distribution, obtain the actual light spot distribution corresponding to the microscopic surface of the element to be tested;

S4. Comparing the actual light spot distribution with a preset ideal light spot distribution to obtain the microscopic surface profile of the element to be tested.

Preferably, the step S1 includes: structural position parameters S={(x _i , y _i , z _i ), (α _i , β _i , γ _i )}, where i represents the number of labels of components, (x _i y _{i zi} ) represents the three-dimensional spatial position coordinates of the element marked i, and (α _i , β _i , γ _i ) represents the inclination angle of the i-th element with respect to the x-axis, the y-axis and the z-axis, respectively.

Preferably, the step S2 includes:

Using computer modulation to generate four sinusoidal fringe optical signals in the x direction and four sinusoidal fringe optical signals in the y direction with phases of 0, π/2, π, and 3π/2 respectively;

According to the four-step phase shift in the x and y directions, the CCD detector collects four x-direction deformed fringe light signals with a phase difference of π/2 and four y-direction deformed fringe light signals with a phase difference of π/2.

Preferably, the step S2 further includes:

Calculate the light intensity of the sinusoidal fringe light signal according to formula (1);

Set δ _n to be π/2, and use the four-step phase-shifting method to obtain the light intensities of the four groups of deformed fringe light signals as I ₁ (x,y), I ₂ (x, y), I ₃ (x, y), I ₄ (x, y).

Preferably, the step S2 further includes:

According to the phase shift calculation formula (2), the phase distribution of the deformed fringe optical signal is obtained;

Preferably, the step S2 further includes:

Using the phase shift technology and the phase unwrapping algorithm, the deformed fringe optical signal collected by the CCD detector is calculated to obtain the corresponding phase distribution; the phase distribution relationship and the phase unwrapping method satisfy the formula (3);

Among them, Φ(i) is the unwrapped phase, and k(i) is the translation function.

Preferably, the step S3 includes:

The phase values in the x horizontal direction and the y vertical direction in the deformed fringe light signal respectively correspond to the abscissa and ordinate values of the pixel projected on the CCD detector;

According to formula (4), the coordinates of the light-emitting pixel points on the x-axis and y-axis corresponding to each bright spot in the deformed fringe light signal are obtained as:

Wherein, p _x and p _y are the projection fringe widths of the projection screen in the x-direction and the y-direction, respectively, acquired by the CCD detector.

Preferably, the step S4 includes:

According to the structural position parameter S, establish an ideal optical microscopic deflection model in which the optical path from the CCD detector sequentially passes through the imaging lens, the microscope objective lens, the beam splitter prism, the component to be measured, and the projection screen;

In the ideal optical microscopic deflection model, the small hole of the CCD detector is used as a point light source, and the reflective surface of the element to be measured is set as an ideal surface;

An ideal spot coordinate value corresponding to the actual spot coordinate value is generated according to the ray tracing method

Preferably, the step S4 further includes:

According to the difference between the actual spot coordinate value and the ideal spot value, obtain the wavefront slope distribution of the micro-surface profile;

Use the integral method to obtain the microscopic surface profile information of the component to be tested.

Compared with the prior art, an optical deflection microscopic surface measuring device and method of the present invention has the following beneficial effects:

(1) The present invention improves the problem of low spatial resolution of the traditional optical deflection measurement system, and does not require additional compensation optical elements and standard optical elements;

(2) The calibration of the measurement system is simplified, and the ideal optical deflection microscopic measurement model is built through computer software to realize ray tracing, which effectively improves the measurement accuracy without increasing the cost;

(3) In view of the damage of contact measurement, the harsh measurement environment of interferometry, the low spatial resolution of traditional deflection measurement devices and the technical problems of low measurement accuracy, the present invention provides a high-precision, low-cost, Microscopic measurement device and method with high spatial resolution and high measurement speed.

Description of drawings

FIG. 1 is a system schematic diagram of an optical deflection microscopic surface measurement apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic flowchart of a method for optically deflected microscopic surface measurement according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of deformed fringe optical signals in the x-direction and the y-direction according to a specific embodiment of the present invention.

FIG. 4 is a schematic diagram of the phase distribution in the x-direction and the phase distribution in the y-direction according to a specific embodiment of the present invention.

FIG. 5 is a schematic diagram of a microscopic surface profile in a specific embodiment of the present invention.

Detailed ways

The present invention will be described in detail below with reference to the specific embodiments shown in the accompanying drawings, but these embodiments do not limit the present invention, and those of ordinary skill in the art can make structural, method, or functional transformations according to these embodiments. All are included in the protection scope of the present invention.

As shown in an embodiment of the present invention as shown in FIG. 1 , the optical deflection microscopic surface measurement device includes a projection screen 1 , a beam splitting prism 2 , an element to be measured 3 , a microscope objective lens 4 , an imaging lens 5 , and a CCD detector 6 and a computer, wherein the component to be tested 3 is placed under the beam splitting prism 2, the projection screen 1 is placed on the left side of the beam splitting prism 2 and the two are parallel, and the microscope objective lens 4, imaging The lens 5 and the CCD detector 6 are sequentially arranged above the dichroic prism 2 . The computer generates a sine fringe light signal, and the sine fringe signal light is projected to the element to be measured 3 through the beam splitting prism 2, returns to the beam splitter prism 2 through the surface of the element to be measured, and passes through the beam splitting prism 2. The microscope objective lens 4 and the imaging lens 5 are converged into a converging beam, and the converging beam presents a deformed fringe light signal in the CCD detector 6, and the computer analyzes the deformed fringe light signal to obtain the The microscopic surface profile information of the measuring element. The projection screen 1 , the beam splitting prism 2 , the microscope objective lens 4 , the imaging lens 5 , and the CCD detector 6 constitute a deflection microscopic measurement system based on reverse Hartmann optical detection. The projection screen 1 and the CCD detector 6 establish a communication connection with the computer respectively. Computer modulation generates a sinusoidal fringe light signal, which is projected onto the projection screen. The sinusoidal fringe light signal is incident on the beam splitting prism 2 through the projection screen 1 , and the sinusoidal fringe light signal is reflected to the element to be measured 3 via the beam splitter 2 , and passes through the surface of the element to be measured 3 . The reflection passes through the beam splitter prism 2 and is transmitted to the microscope objective lens 4, where it becomes a condensed beam at the microscope objective lens 4, and the condensed beam is condensed to the CCD detector 6 through the imaging lens 5, and the CCD detects The device 6 presents a deformed fringe light signal according to the condensed beam signal. The optical axis of the microscope objective 4 , the optical axis of the imaging lens 5 , and the center of the CCD detector 6 and the center of the dichroic prism 2 are on the same straight line, and the CCD detector 6 is perpendicular to the optical axis of the imaging lens 5 . The microscope objective 4 is a long working distance microscope objective, and the surface of the component to be tested 3 is located on the focal plane of the microscope objective 2 . The beam-splitting prism 2 is a square cube beam-splitting prism whose inclined surface is coated with a beam-splitting film and the remaining surfaces are coated with an anti-reflection film. Fine-tuning is achieved by relatively moving or rotating the element to be tested 3 up and down to ensure that the surface of the element to be tested 3 is located on the focal plane of the microscope objective 4, and then the projection screen 1 is moved relatively left and right, so that the element to be tested 3 is positioned on the focal plane of the microscope objective 4. 3. The light emitted from the projection screen 1 can be captured by the CCD detector 6 to obtain a clear and complete image. The measuring device has the advantages of simple structure, convenient adjustment, strong versatility, high resolution and detection accuracy, and can realize high-precision microscopic measurement of the surface of the component to be measured.

In an embodiment of the present invention as shown in FIG. 2, the present invention provides a method for measuring an optical deflection microscopic surface, the method comprising:

S201, using three-coordinate measuring equipment to measure and calibrate the structural position parameter S of the optical deflection microscopic surface measuring device;

S202. Calculate the phase distribution of the deformed fringe optical signal according to the measured and calibrated structural position parameter S, where the deformed fringe optical signal includes the feature information of the microscopic surface profile of the element to be measured;

S203, according to the phase distribution, obtain the actual light spot distribution corresponding to the microscopic surface of the element to be tested;

S204 , comparing the actual light spot distribution with a preset ideal light spot distribution to obtain the microscopic surface profile of the element to be tested.

In the step S201, the installation of the optical deflection microscope surface measuring device is performed. The element to be tested 3 is placed under the beam splitter prism 2, the projection screen 1 is placed on the left side of the beam splitter prism 2 and the two are parallel, and the microscope objective lens 4, the imaging lens 5 and the CCD detect The device 6 is sequentially arranged above the beam splitting prism 2 . The projection screen 1 , the beam splitting prism 2 , the microscope objective lens 4 , the imaging lens 5 , and the CCD detector 6 constitute a deflection microscopic measurement system based on reverse Hartmann optical detection.

The structure and position parameters of the reverse Hartmann refraction circuit including the projection screen, beam splitting prism, component to be measured, microscope objective lens, imaging lens and CCD detector are measured by using a three-coordinate measuring device with a measurement accuracy of the order of microns. S is measured and calibrated, and its structural position parameters S={(x _i , y _i , z _i ), (α _i , β _i , γ _i )}, where i represents the label number of the element, (x _i y _i z _i ) represents the three-dimensional spatial position coordinates of the element marked i, and (α _i , β _i , γ _i ) represents the inclination angle of the i-th element with respect to the x-axis, the y-axis and the z-axis, respectively.

According to a specific embodiment of the present invention, the step S202 includes: using computer modulation to generate a sinusoidal fringe optical signal, configuring parameters for the sinusoidal fringe optical signal, and setting the phases to be 0, π/2, π, 3π/ 2 4 sinusoidal fringe optical signals in the x direction and four sinusoidal fringe optical signals in the y direction. According to the four-step phase shifting in the x and y directions, the projection screen projects the sinusoidal fringe light signal, which is reflected by the element to be measured and then converged by the microscope objective lens, and then imaged by the imaging lens, so that the CCD detector collects four images with a phase difference of π/2 The x-direction deformed fringe light signal and four y-direction deformed stripe light signals with a phase difference of π/2.

Calculate the light intensity of the sinusoidal fringe light signal according to formula (1):

The light intensity of the sinusoidal fringe optical signal is adjusted by adjusting the value of δ _n ; the value of δ _n is π/2, and using the four-step phase shifting method, the light intensities of the four groups of deformed fringe optical signals are obtained as I ₁ (x, y), I ₂ (x, y), I ₃ (x, y), I ₄ (x, y).

According to the phase shift calculation formula (2), the phase distribution of the deformed fringe optical signal is obtained:

For the deformed fringe optical signal collected by the CCD detector, the corresponding phase distribution is obtained by using the phase shift technology and the phase unwrapping algorithm, and the deformed fringe optical signal includes the characteristic information of the microscopic surface profile of the element to be tested. The phase distribution relationship and the phase unwrapping method satisfy formula (3):

Among them, Φ(i) is the unwrapped phase, and k(i) is the translation function.

According to the phase distribution, the actual light spot distribution corresponding to the microscopic surface of the element to be tested is obtained. Specifically, the phase values in the x horizontal direction and the y vertical direction in the deformed fringe optical signal correspond to the abscissa and ordinate values of the pixel projected on the CCD detector, respectively; according to formula (4), the The coordinates of the x-axis and y-axis light-emitting pixel points corresponding to each bright spot in the deformed stripe light signal are:

Wherein, p _x and p _y are the projection fringe widths of the projection screen in the x-direction and the y-direction, respectively, acquired by the CCD detector. According to formula (4), the actual light spot distribution corresponding to the microscopic surface of the element to be measured is obtained.

The actual light spot distribution is compared with a preset ideal light spot distribution to obtain the microscopic surface profile of the element to be tested. Specifically, according to the structural position parameter S, an ideal optical microscopic deflection model in which the optical path passes through the imaging lens, the microscope objective lens, the beam splitting prism, the element to be measured, and the projection screen in sequence from the CCD detector is established; In the micro-deflection model, the small hole of the CCD detector is used as a point light source, and the reflective surface of the element to be measured is set as an ideal surface; Ideal spot coordinates.

Through the difference between the actual spot coordinate value and the ideal spot value obtained from the actual measurement data, the wavefront slope distribution of the micro-surface profile is obtained, and the micro-surface profile information of the component to be measured is obtained by the integration method, so as to complete the measurement of the component to be measured. High-precision microscopic measurement.

和

根据式(4)求得对应相位值的像素点投影在CCD探测器上的横坐标和纵坐标值，即实际光斑坐标值。根据参数S在计算机软件中建立光学偏折显微测量模型，并模型中将待测元件的反射面置为理想面，根据光线追迹法可获得与实际光斑坐标值相对应的理想光斑坐标值。图4为对用四步移相算法求解的CCD探测器采集到的四步移相正弦条纹相位展开后得到的x方向的相位分布(左图)和y方向的相位分布图(右图)。根据上述实际测量数据得出的实际光斑坐标值与检测系统模型光线追迹结果的理想光斑值差异进行分析，可得出微观面形的波前斜率分布，最终对波前斜率积分可得到金属表面的微观面形轮廓信息，如图5所示。The present invention will be further described below through a specific embodiment. The beam splitter prism in the optical deflection microscope surface measurement device adopts a broadband square beam splitter prism with a side length of 25.4mm, and the microscope objective adopts a long working distance microscope objective with a magnification of 10× and a working distance of 34mm, and a CCD detector. A CCD detector with a resolution of 1328 (H) × 1048 (V) and a pixel size of 3.63 μm × 3.63 μm was used. The entire measuring device was measured and calibrated with a three-coordinate instrument with an accuracy of 5.0 μm and a resolution of 0.078 μm. Circular metal surfaces with a diameter of 50.02 mm were subjected to optical deflection microscopic surface measurements. The metal surface is relatively moved up and down or rotated to achieve fine-tuning to ensure that the metal surface is located on the focal plane of the microscope objective lens, and then the projection screen is moved relatively left and right, so that the metal surface reflects the light emitted from the projection screen to present a clear and complete image on the CCD detector. . The optical deflection microscopic surface measuring device was calibrated with a three-coordinate instrument, and the structure parameter S of the structure position was obtained. The parameters are configured through the pre-stored program of the computer, so that the projection screen can display the four-step π/2 phase-shifted sinusoidal fringe optical signals in the x-direction and the y-direction respectively. The number of horizontal stripes is controlled to be 90 and the number of vertical stripes is 160 by computer program. According to the parameter calculation of the projection screen, the fringe spacing is 17.1mm. The CCD detector collects the deformed fringe optical signals in the x and y directions after the four-step phase-shifted sinusoidal stripes are reflected by the metal surface in real time. Deformed fringe light signal. Using the four-step phase-shifting algorithm, the phase distribution corresponding to the four-step phase-shifting sinusoidal fringes collected by the CCD detector is calculated according to equation (2).

and

According to formula (4), the abscissa and ordinate values of the pixel point corresponding to the phase value projected on the CCD detector are obtained, that is, the actual spot coordinate value. According to the parameter S, an optical deflection microscopic measurement model is established in the computer software, and the reflective surface of the element to be measured is set as the ideal surface in the model, and the ideal spot coordinate value corresponding to the actual spot coordinate value can be obtained according to the ray tracing method. . Figure 4 shows the phase distribution in the x-direction (left image) and the phase distribution in the y-direction (right image) obtained after the phase unwrapping of the four-step phase-shifted sinusoidal fringe acquired by the CCD detector solved by the four-step phase-shift algorithm. According to the difference between the actual spot coordinate value obtained from the above actual measurement data and the ideal spot value of the detection system model ray tracing result, the wavefront slope distribution of the micro-surface shape can be obtained, and finally the wavefront slope can be integrated to obtain the metal surface. The microscopic surface profile information is shown in Figure 5.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those of ordinary skill in the art will appreciate that various Improvements, additions and substitutions are possible.

Claims (10)

1. An optical deflection microscopic surface measuring device is characterized in that the measuring device comprises a projection screen, a beam splitter prism, a component to be measured, a microscopic objective, an imaging lens, a CCD detector and a computer, wherein the component to be measured is arranged below the beam splitter prism, the projection screen is arranged on the left side of the beam splitter prism and enables the component to be measured and the microscopic objective, the imaging lens and the CCD detector to be parallel, the microscopic objective, the imaging lens and the CCD detector are sequentially arranged above the beam splitter prism, the computer generates a sinusoidal fringe optical signal, the sinusoidal fringe optical signal is projected to the component to be measured through the beam splitter prism, returns to the beam splitter prism through the surface of the component to be measured and is converged into a convergent light beam through the microscopic objective and the imaging lens, the convergent light beam presents a deformed fringe optical signal in the CCD detector, and the computer analyzes the deformed fringe optical signal, and acquiring the microcosmic surface profile information of the element to be detected.

2. A method of measuring an optical deflection microscopy surface measurement device as defined in claim 1, the method comprising:

s1, measuring and calibrating a structural position parameter S of the optical deflection microscopic surface measuring device by adopting three-coordinate measuring equipment;

s2, calculating the phase distribution of the deformed stripe optical signal according to the measured and calibrated structure position parameter S, wherein the deformed stripe optical signal comprises the micro surface profile characteristic information of the element to be measured;

s3, acquiring actual light spot distribution corresponding to the microscopic surface of the element to be measured according to the phase distribution;

and S4, comparing the actual light spot distribution with a preset ideal light spot distribution to obtain the micro surface profile of the element to be detected.

3. The optical deflection microscopy surface measurement method according to claim 2, wherein the step S1 includes: structure position parameter S { (x)_i,y_i,z_i),(α_i,β_i,γ_i) Where i denotes the number of the element (x)_iy_iz_i) Three-dimensional spatial position coordinates of the element denoted by the reference character i, (α)_i,β_i,γ_i) Reference is made to the inclination of the ith element with respect to the x, y and z axes, respectively.

4. The optical deflection microscopy surface measurement method according to claim 3, wherein the step S2 includes:

modulating and generating 4 sinusoidal stripe optical signals in the x direction and four sinusoidal stripe optical signals in the y direction with phases of 0, pi/2, pi and 3 pi/2 respectively by using a computer;

according to the four-step phase shift in the x direction and the y direction, the CCD detector collects four x direction deformation stripe optical signals with phase difference of pi/2 and four y direction deformation stripe optical signals with phase difference of pi/2.

5. The optical deflection microscopy surface measurement method according to claim 4, wherein the step S2 further comprises:

calculating the light intensity of the sinusoidal fringe light signal according to formula (1);

setting delta_nIs pi/2, and four steps of phase shifting method are utilized to obtain four groups of deformed stripe optical signals with light intensity I₁(x,y)、I₂(x,y)、I₃(x,y)、I₄(x,y)。

6. The optical deflection microscopy surface measurement method according to claim 5, wherein the step S2 further comprises:

obtaining the phase distribution of the deformed fringe optical signal according to a phase shift calculation formula (2);

7. the optical deflection microscopy surface measurement method according to claim 6, wherein the step S2 further comprises:

calculating the deformed fringe optical signals collected by the CCD detector by utilizing a phase shift technology and a phase expansion algorithm to obtain corresponding phase distribution;

the phase distribution relation and the phase expansion method satisfy the formula (3);

where Φ (i) is the unwrapped phase and k (i) is the translation function.

8. The optical deflection microscopy surface measurement method according to claim 7, wherein the step S3 includes:

phase values in the x horizontal direction and the y vertical direction in the deformed stripe optical signal respectively correspond to abscissa and ordinate values of pixel points projected on the CCD detector;

obtaining the coordinates of the luminous pixel points of the x axis and the y axis corresponding to each bright spot in the deformed stripe optical signal according to the formula (4);

wherein p is_xAnd p_yAnd acquiring projection fringe widths of the projection screen in the x direction and the projection screen in the y direction respectively for the CCD detector.

9. The optical deflection microscopy surface measurement method according to claim 1, wherein the step S4 includes:

establishing an ideal optical micro-deflection model of a light path passing through an imaging lens, a micro objective lens, a beam splitter prism, a component to be measured and a projection screen in sequence from a CCD detector according to the structural position parameter S;

in the ideal optical microscopic deflection model, the small hole of the CCD detector is used as a point light source, and the reflecting surface of the element to be measured is set as an ideal surface;

and generating an ideal light spot coordinate value corresponding to the actual light spot coordinate value according to a light ray tracing method.

10. The optical deflection microscopy surface measurement method according to claim 9, wherein the step S4 further comprises:

obtaining the wave front slope distribution of the microcosmic profile according to the difference between the actual spot coordinate value and the ideal spot value;

and obtaining the microcosmic surface profile information of the element to be detected by using an integration method.

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