WO2020156296A1

WO2020156296A1 - Measuring method and device for measuring thickness of substrate

Info

Publication number: WO2020156296A1
Application number: PCT/CN2020/073094
Authority: WO
Inventors: Haifeng Chen
Original assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Current assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Priority date: 2019-01-29
Filing date: 2020-01-20
Publication date: 2020-08-06
Anticipated expiration: 2021-07-29
Also published as: AR117862A1; CN111426273A

Abstract

Provided is a measuring method and device for measuring a thickness of a substrate (102). The substrate (102) has a first surface (102a) and a second surface (102b) opposite to the first surface (102a). The measuring method comprises providing a detection beam and a reference beam (S410); obtaining a sample beam (S420); obtaining an interference signal varying with a wavelength of a light source (S430); obtaining a two-dimensional image or a three-dimensional image (S440); in the two-dimensional image or the three-dimensional image, determining a position of the interface between the substrate (102) and external environment according to a variation of the light intensity information with axial depth (S450); and in the two-dimensional image or the three-dimensional image, obtaining the thickness of the substrate (102) according to the determined position of the interface (S460).

Description

Measuring Method and Device for Measuring Thickness of Substrate

Technical Field

Provided is a measuring technology, in particular a measuring method and device for measuring a thickness of a substrate.

Background

In the conventional measuring field, thickness measurement is basically performed based on a contact measurement implemented by a caliper, a micrometer and so on. However, for the thickness measurement of products such as glass, the contact measurement will cause problems such as surface scratches, inaccurate measurements, etc.

In order to solve the above problems, optical devices are used to perform a non-contact measurement in some solutions in the prior art. For example, in Chinese patent publication CN103175837B, it is discussed a solution of using an OCT technology to implement a non-contact measurement so as to detect defects in a substrate. However, the patent does not relate to any technical solutions of how to use an OCT technology to measure a thickness of a substrate. In the article "Windshield Wedge Angle and Layer Thickness Measurements" of Lumetrics, Inc., it is described a technical solution of using time domain OCT (TD-OCT) optical equipment to implement a non-contact measurement so as to obtain a thickness of a substrate. Although as described in this article, TD-OCT optical devices can realize non-destructive measurements of thickness for products such as glass, however, according to the solution in this paper, during the measurement process of using a TD-OCT optical device, the optical device needs to use a driving mechanism to drive a reference arm of TD-OCT optical device to move, so as to realize a point-by-point scanning in the axial direction. In other words, the solution needs a driving mechanism to assist an axial scanning so as to obtain the optical information of each point in the axial direction. For this reason, the device has problems of structures being complex, measurement speed being slow, etc.

Therefore, it is desirable to provide a technical solution with a simple structure and fast measurement speed when measuring a thickness of a substrate.

Summary of the Invention

In view of the above problems found in the prior art, provided in the invention is a technical solution of measuring a thickness of a substrate. According to the technical solution of the invention, the structure of the measuring device is simple and the measuring speed is fast.

According to one aspect of the present invention, there provides a measuring method for measuring thickness of a substrate, the substrate having a first surface and a second surface opposite to the first surface, wherein the measuring method comprises: providing a detection beam and a reference beam; obtaining a sample beam which is generated at points along an optical detection path through which the detection beam is incident from multiple incident points distributed on the first surface to reflection points on the second surface, wherein the reflection points correspond to the incident points respectively; obtaining an interference signal based on an interference beam formed by the interference between the sample beam and the reference beam, wherein the interference signal varies with a wavelength of a light source; calculating light intensity information of each of the points along the optical detection path, and obtaining a two-dimensional image or a three-dimensional image of the substrate according to information of a plurality of light intensities associated with the multiple incident points; in the two-dimensional image or the three-dimensional image, determining a position of the interface between the substrate and external environment according to a variation of light intensity information with axial depth; and in the two-dimensional image or the three-dimensional image, obtaining the thickness of the substrate according to the determined position of the interface.

According to a possible embodiment, the substrate is a multi-layer structure comprising two or more dielectric layers, and the measuring method further comprises: in the two-dimensional image or the three-dimensional image, determining a position of physical interface between adjacent dielectric layers of the dielectric layers according to the variation of the light intensity information with axial depth; and in the two-dimensional image or the three-dimensional image, obtaining thickness of each of the two or more dielectric layers according to the determined position of the physical interface and the refractive index of each dielectric material relative to the detection beam.

According to a possible embodiment, the step of providing the detection beam and the reference beam comprises: providing a single beam from the light source; and splitting the single beam into the detection beam and the reference beam.

According to a possible embodiment, the light source has a center wavelength in a range of about 800nm-1550nm, preferably about 840nm-135nm; and/or the light source has a bandwidth in a range of about 30nm-160nm, preferably about 35nm-110nm.

According to a possible embodiment, the light source has a center wavelength of about 860nm and a bandwidth equal to or greater than about 35nm, or the light source has a center wavelength of about 1310nm and a bandwidth equal to or greater than about 100nm, preferably, the center wavelength is about 860nm and the bandwidth is about 40nm, or the center wavelength is about 1310nm and the bandwidth is about 105 nm.

According to a possible embodiment, the measuring method comprises one or more of the following: the measuring method has an axial resolution which is less than or equal to about 10μm and is greater than or equal to about 1 μm; the measuring method has a minimum axial imaging depth in the air of about 8mm; the measuring method has a transversal resolution of about 0.1mm-0.6 mm, preferably about 0.2mm-0.5mm; the measuring method has a longitudinal resolution of about 0.1mm-0.6 mm, preferably about 0.2mm-0.5mm.

According to a possible embodiment, the light source is a broadband light source having a center wavelength in a range of about 800nm-1400nm, and the interference signals are obtained by an imaging spectrometer having a resolution in a range of about 0.015nm-0.035nm; or the light source is a swept source having a wavelength interval between adjacent wavelengths in a range of about 0.015nm-0.035nm and having a center wavelength in a range of about 800nm-1400nm.

According to a possible embodiment, the substrate or dielectric material is transparent or translucent, optionally, the substrate or dielectric material is one or more of glass, PVB, PET or plastic.

According to another aspect of the present invention, there provides a measuring device for measuring thickness of a substrate, the substrate having a first surface and a second surface opposite to the first surface, the measuring device comprising: a light source for providing a single beam; a split unit for splitting the single beam into a detection beam and a reference beam; a first obtaining unit for obtaining a sample beam which is generated at points along an optical detection path through which the detection beam is incident from multiple incident points distributed on the first surface to reflection points on the second surface, wherein the reflection points correspond to the incident points respectively; a second obtaining unit for obtaining an interference signal based on an interference beam formed by the interference between the sample beam and the reference beam, wherein the interference signal varies with a wavelength of a light source; and an execution unit for executing the steps of: calculating light intensity information of each of the points along the optical detection path, and obtaining a two-dimensional image or a three-dimensional image of the substrate according to information of a plurality of light intensities associated with the multiple incident points; in the two-dimensional image or the three-dimensional image, determining a position of the interface between the substrate and external environment according to a variation of light intensity information with axial depth; and in the two-dimensional image or the three-dimensional image, obtaining the thickness of the substrate according to the determined position of the interface.

According to a possible embodiment, the substrate is a multi-layer structure comprising two or more dielectric layers, and the measuring device is configured to further execute the steps of: in the two-dimensional image or the three-dimensional image, determining a position of a physical interface between adjacent dielectric layers of the dielectric layers according to the variation of the light intensity information with axial depth; and in the two-dimensional image or the three-dimensional image, obtaining the thickness of each of the two or more dielectric layers according to the determined position of the physical interface and the refractive index of each dielectric material relative to the detection beam.

According to a possible embodiment, the light source has a center wavelength being about 860nm and a bandwidth being equal to or greater than about 35nm, or the light source has a center wavelength being about 1310nm and a bandwidth being equal to or greater than about 100nm, preferably, the center wavelength is about 860nm and the bandwidth is about 40nm, or the center wavelength is about 1310nm and the bandwidth is about 105 nm.

According to a possible embodiment, the measuring device comprises one or more of the following items: the measuring device has an axial resolution being less than or equal to about 10μm and being greater than or equal to about 1 μm; the measuring device has a minimum axial imaging depth in the air being about 8mm; the measuring device has a transversal resolution being about 0.1mm-0.6 mm, preferably about 0.2mm-0.5mm; the measuring device has a longitudinal resolution being about 0.1mm-0.6 mm, preferably about 0.2mm-0.5mm.

According to a possible embodiment, the light source is a broadband light source having a center wavelength in a range of about 800nm-1400nm, and the second obtaining unit comprises an imaging spectrometer having a resolution in a range of about 0.015nm-0.035nm; or the light source is a swept source having a wavelength interval between adjacent wavelengths in a range of about 0.015nm-0.035nm and having center wavelength in a range of about 800nm-1400nm.

According to a possible embodiment, the substrate or the dielectric material is transparent or translucent, optionally, the substrate or dielectric material includes one or more of glass, PVB, PET or plastic.

Brief Description of the Drawings

The invention, as well as principles, features and advantages thereof, will be well understood by reference to the following detailed description when read in conjunction with the accompanying drawings, wherein:

Fig. 1 is a schematic block diagram illustrating a measuring device for measuring a thickness of a substrate in accordance with the present invention;

Figs. 2 and 3 are schematic diagrams illustrating processes of obtaining a sample beam by means of using the measuring device illustrated in Fig. 1;

Fig. 4 is a flow chart illustrating a measuring method for measuring a thickness of a substrate in accordance with a feasible embodiment of the present invention;

Fig. 5 is a schematic block diagram illustrating an embodiment of the measuring device illustrated in Fig. 1;

Fig. 6 is a schematic block diagram illustrating another embodiment of the measuring device illustrated in Fig. 1; and

Fig. 7 is a graph illustrating a measuring result of measuring a glass product by means of using the measuring device illustrated in Fig. 5.

Description of Embodiments

In the specific description of the following embodiments, reference will be made to the accompanying drawings which form part of the present invention. The accompanying drawings show, by way of example, specific embodiments which can implement the present invention. The exemplary examples are not intended to exhaust all the examples according to the invention. It can be understood that other examples can be utilized and structural or logical modifications can be made without departing from the scope of the invention. Therefore, the following specific description is not restrictive, and the scope of the invention is limited by the appended claims.

Technologies, methods and equipment known to those skilled in the art may not be discussed in detail, but, where appropriate, the technologies, methods and equipment shall be considered as part of the specification. For the connection between the units in the attached drawings, it is only for explanation, which means that at least the units at both ends of the connection are coupled with each other, and it is not intended to limit that there is no interrelationship between the units that are not connected.

The terms "about" when used in conjunction with a numerical variable, generally refers to the values of the variable and all values of the variable within the experimental error (e.g., within a 95%confidence interval of the mean) or within ±10%of the specified value, or broader.

The term "one or more" means one, two, three, four, five, six or more. The term "two or more" means two, three, four, five, six or more.

Fig. 1 shows a measuring device 100 for measuring a thickness of a substrate according to the present invention. In this embodiment, the measuring device 100 is a measuring device implemented by means of using the frequency domain OCT (FD-OCT) technology. Figs. 2 and 3 show processes of obtaining a sample beam by means of using the measuring device 100 illustrated in Fig. 1. Referring to Figs. 2 and 3, a substrate 102 has a first surface 102a and a second surface 102b opposite to the first surface 102a. The first surface 102a and the second surface 102b are the interfaces between the substrate 102 and the external environment, respectively. A plurality of

incident points

104a and 106a are distributed on the first surface 102a.

Although it is illustrated in Figs. 2 and 3 that the substrate 102 is a monolayer structure, the substrate 102 may also include a multilayer structure (not shown) composed of two or more dielectric layers, such as two or three layers. The multiple dielectric layers may include the same dielectric material or different dielectric materials. For example, the substrate 102 may include a single-layer or multi-layer structure comprising one or more of glass, PVB, PET, plastic. The substrate or dielectric material is transparent or translucent so that incident light can penetrate.

Although Fig. 2 and Fig. 3 illustrate that the first surface 102a and the second surface 102b of the substrate 102 are nearly flat surfaces and are substantially parallel to each other, the first surface 102a may be an arc surface, and the second surface 102b may also be an arc surface, and the arc of the first surface 102a and the second surface 102b may be the same or may be different. It should be understood that the pattern of the first surface 102a and the second surface 102b may include any combination according to specific implementations, for example, the first surface 102a and the second surface 102b are both substantially flat surfaces, and the extension lines of the first surface 102a and the second surface 102b have an included angle; or the first surface 102a is substantially flat surface and the second surface 102b is arc surface; or the first surface 102a is an arc surface and the second surface 102b is a substantially flat surface, and so on.

Referring to Fig. 1, the measuring device 100 includes a light source 110, a split unit 120, a first obtaining unit 130, a second obtaining unit 140 and an executing unit 150. Each unit will be described in detail below with reference to the attached drawings.

The light source 110 is used to provide a single beam. In the measuring device 100, the light source 110 may use, for example, a broadband light source or a swept source.

The split unit 120 is coupled with the light source 110 to divide the single beam provided by the light source 110 into a detection beam and a reference beam.

The first obtaining unit 130 is coupled with the split unit 120 and is used to obtain a sample beam based on the detection beam. The first obtaining unit 130 obtains back scattered light, as a sample beam corresponding to the incident point 104a, which is generated at points in an optical detection path 104c through which the detection beam is guided to reflection points 104b on the second surface 102b from multiple incident points 104a on the first surface 102a, and the reflection points 104b corresponding to the incident points 104a respectively.

In this embodiment, the optical detection path will be different according to different incident angles of detection beams. As shown in Fig. 2, in the case that the detection beam is vertically incident onto the first surface 102a of the substrate 102, the detection beam is vertically guided to the second surface 102b along the optical detection path 104c from the incident point 104a of the first surface 102a. As shown in Fig. 3, when the detection beam is obliquely incident onto the first surface 102a of the substrate 102, the detection beam is guided to the second surface 102b with a corresponding angle along the optical detection path 104c from the incident point 104a of the first surface 102a.

The second obtaining unit 140 is coupled with the split unit 120 and the first obtaining unit 130 and is used to obtain an interference signal based on a sample beam from the first obtaining unit 130 and a reference beam from the split unit 120. In the second obtaining unit 140, the sample beam and the reference beam interfere with each other to form an interference beam, and the second obtaining unit 140 obtains, based on the interference beam, an interference signal varying with the wavelength of the light source 110. The interference signal includes light intensity information, which varies with the wavelength of the light source 110, of each point on the detection path 104c.

The execution unit 150 is coupled with the second obtaining unit 140 and is used to perform the following steps. The execution unit 150 calculates, according to the light intensity information varying with the wavelength of the light source 110, light intensity information varying with the axial depth of the substrate 102, and obtains, according to the light intensity information varying with the axial depth of the substrate 102 at a plurality of

incident points

104a and 106a, a two-dimensional image or a three-dimensional image of the substrate 102.

The external environments around the first surface 102a and the second surface 102b of the substrate 102 respectively may be the same dielectric material or may be different dielectric materials. In the case that they are the same dielectric material, the external environments around the first surface 102a and the second surface 102b respectively may be air or water or non-corrosive gas or non-corrosive liquid. In the case that they are different dielectric materials, the external environment around the first surface 102a may be air or water or non-corrosive gas or non-corrosive liquid. The second surface 102b may be in contact with a supporting platform, and the external environment around the second surface 102b may be a supporting platform made of metal or plastic.

In the case that the substrate 102 is a single-layer structure, in the two-dimensional image or the three-dimensional image, the execution unit 150 determines the position of the interface between the substrate 102 and the external environment, and obtains the thickness of the substrate 102 according to the determined position and the refractive index of the dielectric material of the substrate 102 relative to the detection beam. When the substrate 102 is a multilayer structure composed of multiple dielectric layers, in the two-dimensional image or three-dimensional image, the execution unit 150 determines the location of the physical interface between different dielectric layers according to the light intensity information varying with the axial depth, and calculates the thickness of each dielectric layer according to the location of the determined physical interface and the refractive index of each dielectric layer relative to the detection beam. In the case that the substrate 102 is a multi-layer structure comprising two or more dielectric layers, in the two-dimensional image or the three-dimensional image, the execution unit 150 determines the positions of physical interfaces between different dielectric layers of the dielectric layers according to the variation in the light intensity information as a function of axial depth, and calculates the thickness of each of the dielectric layers according to the determined positions of the physical interfaces and the refractive index of each dielectric material relative to the detection beam.

Based on the above description, it can be seen that the measuring device 100 of the invention can detect the light intensity information of the back scattering light at the position of each depth in the substrate 102 at one time, without obtaining the light intensity information at the position of each depth one by one by means of performing a point-by-point scanning in the axial direction with the help of a driving mechanism as described in the prior art. Therefore, the measuring device 100 of the invention does not need the driving mechanism for the point-by-point scanning, and thus the device structure is simplified, the time for the point-by-point scanning is saved, and the measuring speed is greatly improved.

In the case of using the measuring device 100 to measure the thickness of the substrate 102, a minimum axial imaging depth and an axial resolution of the measuring device 100 are needed to be considered comprehensively. In the disclosure, the minimum axial imaging depth refers to the minimum imaging depth in the Z direction as shown in Fig. 2 and Fig. 3. That is to say, in the case of using the measuring device 100 to measure the thickness of the substrate 102, in order to realize the thickness measurement of the substrate, the minimum axial imaging depth of the measuring device 100 should be at least about greater than the thickness of the substrate to be measured. In the disclosure, the axial resolution refers to the resolution in Z direction as shown in Fig. 2 and Fig. 3. In the case of using the measuring device 100 to measure the thickness of the substrate 102, according to the specific application scenario of the substrate 102, the axial resolution should meet the requirement of the axial resolution of the specific application scenario.

The axial resolution (in air) of the measuring device 100 can be determined by means of the following formula (1) :

wherein δz is the axial resolution, lc is the coherent length, λ0 is the central wavelength of the light source 110, and Δλ is the bandwidth of the light source 110.

The axial maximum imaging depth of the measuring device 100 can be determined by means of the following formula (2) :

wherein Z _max is the maximum axial imaging depth and λ0 is the central wavelength of the light source 110. In some examples, the light source 110 is implemented with a wide-band light source and the second obtaining unit 140 includes a spectrometer having a grating for light splitting, and δλ is the resolution of the grating. In other examples, the light source 110 is implemented with a swept source, and δλ is the adjacent wavelength interval of the light source 110.

It can be seen that the axial imaging depth and axial resolution of the measuring device 100 are both related to the parameters of the light source 110. For example, the longer the central wavelength of the light source 110, the greater the imaging depth and the greater the axial resolution. Therefore, setting the center wavelength of the light source 110 may cause the imaging depth of the measuring device 100 to increase, but may also cause the axial resolution of the measuring device 100 to decrease, and when the axial resolution is too low, it cannot reach an appropriate accuracy even if a scanning process is repeated multiple times and then an averaging process of the results of the multiple scanning processes is performed. That is to say, although the advantage of increasing the imaging depth is obtained, the problem of reducing the axial resolution is caused. Therefore, it is necessary to select and set the parameters of the light source 110 so as to balance the axial imaging depth and the axial resolution of the device 100.

The inventor finds that by means of selecting and setting the performance parameters of the light source 110, for example, the center wavelength and bandwidth of the light source 110, both the axial maximum imaging depth and the axial resolution of the measuring device 100 can meet the requirement of the substrate to be measured in a specific application scenario.

The central wavelength of the light source 110 is the main factor affecting the axial imaging depth of the measuring device 100. The light source has a center wavelength in a range of about 800nm-1550nm, preferably about 840nm-135nm. The bandwidth of the light source 110 is the main factor affecting the axial resolution of the measuring device 100. The light source 110 has a bandwidth in a range of about 30nm-160nm, preferably about 35nm-110nm. In some preferred examples, the light source 110 has a center wavelength being about 860nm and a bandwidth being equal to or greater than about 35nm, or the light source 110 has a center wavelength being about 1310nm and a bandwidth being equal to or greater than about 100nm. In other preferred examples, the center wavelength of the light source 110 is about 860nm and the bandwidth is about 40nm, or the center wavelength is about 1310nm and the bandwidth is about 105 nm. The light source 110 with the above described parameters has a minimum axial imaging depth in the air being about 8mm (in the air) and an axial resolution being less than or equal to about 10μm and being greater than or equal to about 1 μm.

In the present embodiment, the lateral resolution and the longitudinal resolution of the measuring device 100 may also be controlled by means of setting the distance between the incident points. For example, the linear distance in the X direction between any two of the incident points is set to be about 0.1mm-0.6 mm, preferably about 0.2mm-0.5mm, and thus the transversal resolution of the measuring device 100 of the invention is about 0.1mm-0.6 mm, preferably about 0.2mm-0.5mm. The linear distance in the Y direction between any two of the incident points is set to be about 0.1mm-0.6 mm, preferably about 0.2mm-0.5mm, and thus the longitudinal resolution of the measuring device 100 of the invention is about 0.1mm-0.6 mm, preferably about 0.2mm-0.5mm.

In the disclosure, the transversal resolution of the measuring device 100 refers to the resolution in the X direction shown in Fig. 2 or Fig. 3, and the longitudinal resolution of the measuring device 100 refers to the resolution in the Y direction shown in Fig. 2 or Fig. 3. Of course, the resolution in the X direction shown in Fig. 2 or Fig. 3 may also be set as the longitudinal resolution, while the resolution in the Y direction shown in Fig. 2 or Fig. 3 may also be set as the transversal resolution.

In the case of using the measuring device 100 with the light source 110 having the above performance parameters to measure a specific substrate, for example, the specific substrate comprises a multilayer structure composed of glass and PVB film, the minimum axial imaging depth of the measuring device 100 can reach about 5mm in the substrate, and the axial resolution is less than or equal to about 10μm and greater than or equal to about 1μm. Therefore, the measuring device 100 with the light source 110 having the above described performance parameters is particularly suitable for measuring thickness of each layer of a multilayer glass product composed of glass and PVB film, for example, the multilayer glass product is a glass of a vehicle front windshield.

Fig. 5 is an embodiment of the measuring device 100 according to the present invention. As shown in Fig. 5, the measuring device 100 includes a broadband light source 510, a spectroscopic coupling member 520, a reference arm 530, a sample arm 540, a spectrometer 550, a photo-detector 560 and a computing device 570. In this embodiment, the measuring device 100 is a measuring device realized by means of using a spectrum domain OCT (SD-OCT) technology. In this embodiment, the broadband light source 510 implements the light source 110 illustrated in Fig. 1. The l spectroscopic coupling member 520 implements the split unit 120 illustrated in Fig. 1. The sample arm 540 implements the first obtaining unit 130 illustrated in Fig. 1. The spectroscopic coupling section 520, the reference arm 530, the sample arm 540, the spectrometer 550 and the photo-detector 560 together realize the second obtaining unit 140 illustrated in Fig. 1. The computing device 570 implements the execution unit 150 illustrated in Fig. 1. The process of measuring thickness using the measuring device 100 according to this embodiment is described below.

The light source 510 emits a low coherent beam. The low coherence beam enters the beam splitting coupling member 520 through a light source arm 512 (e.g., an optical fiber) . The spectroscopic coupling member 520 divides the low coherence beam into a detection beam and a reference beam. The detection beam is guided onto the first surface 102a of the substrate 102 through the sample arm 540. The detection beam is guided to the second surface 102b from the incident points 104a of the first surface 102a, and the back scattering light generated at points through which the detection beam passes the substrate 102 is taken as the sample beam corresponding to the incident point 104a. The reference beam enters the reference arm 530. The reference beam from the reference arm 530 combines with the sample beam from the sample arm 540 in the light splitting coupling section 520 and interferes with each other to form an interference beam. The interference beam is transmitted to the spectrometer 550 through a detection arm 552, such as an optical fiber. The spectrometer 550 has a grating (not shown) , which is used to divide light to obtain an interference spectra of different wavelengths. The interference spectrum includes light intensity information of each point at each depth position of the substrate 102. After the interference spectrum is collected by the photo-detector 560, Fourier transform is performed in the computing device 570 to obtain the light intensity information varying with the depth of the substrate 102. Next, the computing device 570 obtains a two-dimensional image or a three-dimensional image of the substrate 102 based on the light intensity information, which varies with depths, of

incident points

104a, 106a. In the two-dimensional or the three-dimensional images, the computing device 570 determines the interface position between the substrate 102 and the external environment according to the light intensity information varying with the axial depth, and obtains the thickness of the substrate 102 according to the determined interface position. Further, in the case that the substrate 102 is a multilayer structure composed of two or more dielectric layers, in the two-dimensional image or the three-dimensional image, the computing device 570 determines the position of the physical interface between different dielectric layers according to the light intensity information varying with the axial depth, and calculates the thickness of each dielectric layer according to the determined position of the physical interface and the refractive index of each dielectric material relative to the detection beam.

When the thickness measurement is performed by means of the measuring device 100 according to this embodiment, the center wavelength of the broadband light source 510 is 860nm, the bandwidth is 45nm, and the resolution of the imaging spectrometer is 0.02nm.

The measuring device 100 of this embodiment splits the interference signal to obtain the interference spectrum be means of a spectrometer based on a grating, and the measuring device 100 of this embodiment can obtain the interference spectrum signal of all the position points along the detection path at one time, without moving the reference arm 530 to realize the axial scanning. The measuring device 100 according to this embodiment has simple structure and fast measuring speed. Moreover, the measuring device 100 with the broadband light source 510 having the above described performance parameters is particularly suitable for measuring the thickness of each layer of the multilayer glass product composed of glass and PVB film.

In one example, the thickness of the glass product is measured with the measuring device 100 illustrated in Fig. 5. In this example, the glass product is a laminate structure composed of two dielectric layers, namely, PVB layer and glass layer laminated with the PVB layer. In the measuring process, the thicknesses of the PVB layer and the glass layer are measured by means of selecting eleven measuring areas on the surface of the glass product. The measuring results are shown in Table 1 and Figure 7.

Table 1

Areas	The thickness of the glass layer (μm)	The thickness of the PVB layer (μm)
1	1578.8	668.2
2	1577.5	670.4
3	1576.3	671.3
4	1579.5	671.4
5	1576.2	664.8
6	1579.1	664.0
7	1592.4	668.8
8	1582.8	670.1
9	1586.2	666.9
10	1579.1	672.0
11	1577.0	691.7

Fig. 6 is another embodiment of the measuring device 100 according to the present invention. As shown in Fig. 6, the measuring device 100 includes a swept light source 610, a spectroscopic coupling member 620, a reference arm 630, a sample arm 640, a photo-detector 650, and a computing device 660. In this embodiment, the measuring device 100 realizes a measuring device by means of using a swept-source OCT (SS-OCT) technology. In this embodiment, the swept light source 610 realizes the light source 110 illustrated in Fig. 1. The spectroscopic coupling member 620 implements the split unit 120 illustrated in Fig. 1. The sample arm 640 implements the first obtaining unit 130 illustrated in Fig. 1. The spectroscopic coupling member 620, the reference arm 630, the sample arm 640 and the photo-detector 650 together implement the second obtaining unit 140 illustrated in Fig. 1. The computing device 660 implements the execution unit 150 illustrated in Fig. 1. The process of measuring the thickness using the measuring device 100 according to this embodiment is described below.

Compared with the measuring device 100 in Fig. 5, in this embodiment, the measuring device 100 in Fig. 6 uses the swept light source 610 to replace the broadband light source 510, and thus omits the spectrometer. The other portions of the measuring device 100 in this embodiment can be realized in a similar way with the measuring device 100 as described by referring to Fig. 5, and thus corresponding description is also applicable in this embodiment.

In this embodiment, the measuring device 100 obtains an interference spectrum based on a swept light source 610. In particular, the measuring device 100 uses a swept light source 610 with an output wavelength scanning at a high speed over time, and then records the signal of each wavelength by means of the photo-detector 650 to obtain the interference spectrum. After obtaining the interference spectrum, the computing device 660 performs the steps, which are similar to those of the computing device 570, to perform a data processing on the interference spectrum so as to obtain the thickness of each dielectric layer of the substrate 102.

In the case of using the measuring device 100 of this embodiment for a thickness measurement, the swept light source 610 has a center wave being 1310nm, a bandwidth being 105nm, and an adjacent wavelength interval being 0.025nm.

In the case of using the measuring device 100 illustrated in Fig. 6, in addition to the advantage of the measuring device 100 described above with reference to Fig. 5, the measuring device 100 according to this embodiment introduces the swept light source 610 and thus the measurement speed is faster.

In an example, the thickness of the glass product is measured with the measuring device 100 illustrated in Fig. 6. In this example, the glass product is a laminate structure composed of three dielectric layers, namely, a first glass layer, a second glass layer, and a PVB layer laminated between the two glass layers. From some testing measurement, the thickness of the first glass layer is about 2099.5 μm, the thickness of the PVB layer is about 694.0 μm and the thickness of the second glass layer is about 2097.2 μm.

Provided is also a measuring method for measuring a thickness of a substrate. Fig. 4 is a flowchart illustrating a measuring method 400 for measuring the thickness of the substrate 102 according to a feasible embodiment of the present invention. Optionally, the measuring method 400 is implemented by the above described measuring device 100. However, it should be noted that the principle of the present invention is not limited to the measuring devices of specific types and structures. As shown in Fig. 4, in step 410, a detection beam and a reference beam are provided. In step 420, a sample beam is obtained. The sample beam is generated at points in an optical detection path through which the detection beam is guided to reflection points on the second surface from multiple incident points on the first surface, and the reflection points correspond to the incident points respectively. In step 430, an interference signal is obtained by means of an interference beam is formed by the interference between the sample beam and the reference beam, and the interference signal varies with a wavelength of a light source. In step 440, light intensity information of each of the points along the optical detection path is calculated based on the interference signal, and a two-dimensional image or a three-dimensional image of the substrate is obtained according to information about a plurality of light intensities associated with the multiple incident points. In step 450, in the two-dimensional image or the three-dimensional image, the position of the interface between the substrate and the external environment is determined according to the variation in the light intensity information as a function of axial depth. In step 460, in the two-dimensional image or the three-dimensional image, the thickness of the substrate is obtained according to the determined position of the interface.

It should be understood that the operating process of the measuring device 100 is also applicable to the measuring method 400. Therefore, the related features described above with respect to the measuring device 100 are also applicable to the measuring method 400.

While the present invention has been described with reference to various technical features thereof, it will be understood that many modifications and improvements are possible to be made by those skilled in the art, and these modifications and improvements may fall within the scope of the present invention. The implementations which have been described are illustrative and the scope of the present invention is not limited to them. The scope of the present invention is defined by the appended claims.

Claims

A measuring method for measuring a thickness of a substrate, the substrate having a first surface and a second surface opposite to the first surface, wherein the measuring method comprises:

providing a detection beam and a reference beam;

obtaining a sample beam which is generated at points along an optical detection path through which the detection beam is incident from multiple incident points distributed on the first surface to reflection points on the second surface, wherein the reflection points correspond to the incident points respectively;

obtaining an interference signal based on an interference beam formed by the interference between the sample beam and the reference beam, wherein the interference signal varies with a wavelength of a light source;

calculating light intensity information of each of the points along the optical detection path, and obtaining a two-dimensional image or a three-dimensional image of the substrate according to information of a plurality of light intensities associated with the multiple incident points;

in the two-dimensional image or the three-dimensional image, determining a position of the interface between the substrate and external environment according to a variation of light intensity information with axial depth; and

in the two-dimensional image or the three-dimensional image, obtaining the thickness of the substrate according to the determined position of the interface.
The measuring method according to claim 1, wherein the substrate is a multi-layer structure comprising two or more dielectric layers, and the measuring method further comprises:

in the two-dimensional image or the three-dimensional image, determining a position of physical interface between adjacent dielectric layers of the dielectric layers according to the variation of the light intensity information with axial depth; and

in the two-dimensional image or the three-dimensional image, obtaining thickness of each of the two or more dielectric layers according to the determined position of the physical interface and the refractive index of each dielectric material relative to the detection beam.
The measuring method according to claim 1 or 2, wherein the step of providing the detection beam and the reference beam comprises:

providing a single beam from the light source; and

splitting the single beam into the detection beam and the reference beam.
The measuring method according to claim 3, wherein

the light source has a center wavelength in a range of about 800nm-1550nm, preferably about 840nm-135nm; and/or

the light source has a bandwidth in a range of about 30nm-160nm, preferably about 35nm-110nm.
The measuring method according to claim 3, wherein

the light source has a center wavelength being about 860nm and a bandwidth being equal to or greater than about 35nm, or the light source has a center wavelength being about 1310nm and a bandwidth being equal to or greater than about 100nm,

preferably, the center wavelength is about 860nm and the bandwidth is about 40nm, or the center wavelength is about 1310nm and the bandwidth is about 105 nm.
The measuring method according to any one of claims 1-5, wherein the measuring method comprises one or more of the following:

the measuring method has an axial resolution which is less than or equal to about 10μm and is greater than or equal to about 1 μm;

the measuring method has a minimum axial imaging depth in the air of about 8mm;

the measuring method has a transversal resolution of about 0.1mm-0.6 mm, preferably about 0.2mm-0.5mm;

the measuring method has a longitudinal resolution of about 0.1mm-0.6 mm, preferably about 0.2mm-0.5mm.
The measuring method according to any one of claims 1-6, wherein

the light source is a broadband light source having a center wavelength in a range of about 800nm-1400nm, and the interference signals are obtained by an imaging spectrometer having a resolution in a range of about 0.015nm-0.035nm; or

the light source is a swept source having a wavelength interval between adjacent wavelengths in a range of about 0.015nm-0.035nm and having a center wavelength in a range of about 800nm-1400nm.
The measuring method according to any one of claims 1-7, wherein the substrate or dielectric material is transparent or translucent, optionally, the substrate or dielectric material is one or more of glass, PVB, PET or plastic.
A measuring device for measuring a thickness of a substrate, the substrate having a first surface and a second surface opposite to the first surface, wherein the measuring device comprises:

a light source for providing a single beam;

a split unit for splitting the single beam into a detection beam and a reference beam;

a first obtaining unit for obtaining a sample beam which is generated at points along an optical detection path through which the detection beam is incident from multiple incident points distributed on the first surface to reflection points on the second surface, wherein the reflection points correspond to the incident points respectively;

a second obtaining unit for obtaining an interference signal based on an interference beam formed by the interference between the sample beam and the reference beam, wherein the interference signal varies with a wavelength of a light source; and

an execution unit for executing the steps of:

calculating light intensity information of each of the points along the optical detection path, and obtaining a two-dimensional image or a three-dimensional image of the substrate according to information of a plurality of light intensities associated with the multiple incident points;

in the two-dimensional image or the three-dimensional image, determining a position of the interface between the substrate and external environment according to a variation of light intensity information with axial depth; and

in the two-dimensional image or the three-dimensional image, obtaining the thickness of the substrate according to the determined position of the interface.
The measuring device according to claim 9, wherein the substrate is a multi-layer structure comprising two or more dielectric layers, and the measuring device is configured to further execute the steps of:

in the two-dimensional image or the three-dimensional image, determining a position of a physical interface between adjacent dielectric layers of the dielectric layers according to the variation of the light intensity information with axial depth; and

in the two-dimensional image or the three-dimensional image, obtaining the thickness of each of the two or more dielectric layers according to the determined position of the physical interface and the refractive index of each dielectric material relative to the detection beam.
The measuring device according to claim 9 or 10, wherein the light source has a center wavelength in a range of about 800nm-1550nm, preferably about 840nm-135nm; and/or

the light source has a bandwidth in a range of about 30nm-160nm, preferably about 35nm-110nm.
The measuring device according to any one of claims 9-11, wherein the light source has a center wavelength being about 860nm and a bandwidth being equal to or greater than about 35nm, or the light source has a center wavelength being about 1310nm and a bandwidth being equal to or greater than about 100nm,

preferably, the center wavelength is about 860nm and the bandwidth is about 40nm, or the center wavelength is about 1310nm and the bandwidth is about 105 nm.
The measuring device according to any one of claims 9-12, wherein the measuring device comprises one or more of the following items:

the measuring device has an axial resolution being less than or equal to about 10μm and being greater than or equal to about 1 μm;

the measuring device has a minimum axial imaging depth in the air being about 8mm;

the measuring device has a transversal resolution being about 0.1mm-0.6 mm, preferably about 0.2mm-0.5mm;

the measuring device has a longitudinal resolution being about 0.1mm-0.6 mm, preferably about 0.2mm-0.5mm.
The measuring device according to any one of claims 9-13, wherein

the light source is a broadband light source having a center wavelength in a range of about 800nm-1400nm, and the second obtaining unit comprises an imaging spectrometer having a resolution in a range of about 0.015nm-0.035nm; or

the light source is a swept source having a wavelength interval of adjacent wavelengths in a range of about 0.015nm-0.035nm and having center wavelength in a range of about 800nm-1400nm.
The measuring device according to any one of claims 9-14, wherein the substrate or the dielectric material is transparent or translucent, optionally, the substrate or dielectric material includes one or more of glass, PVB, PET or plastic.