Method and device for monitoring thickness of optical thin film on line and coating system

Abstract

The invention provides a method and a device for monitoring the thickness of an optical thin film on line and a coating system, belongs to the field of optical thin film thickness monitoring, and is suitable for high-difficulty optical filters such as optical communication GFF and the like. The optical signals with different wavelengths are emitted to the film thickness monitoring area of the optical substrate, and the optical thicknesses corresponding to the optical signals with different wavelengths are obtained, so that the thickness monitoring precision of the optical film plated on the optical substrate can be improved, and the physical thickness calculation deviation of the optical film is reduced. Laser with multiple wavelengths penetrates through a film thickness monitoring area of an optical substrate in a time-sharing mode and is received by a photoelectric probe, optical signals with multiple wavelengths in different time periods can be obtained, the optical signals with different wavelengths are processed respectively, optical thicknesses corresponding to the optical signals with different wavelengths can be obtained, and therefore the physical thickness of the thin film is obtained through calculation. The switching speed of lasers with different wavelengths is high, optical signal values of two wavelengths can be obtained in a very short time, the difference is small, and it can be ensured that the calculated optical thickness and physical thickness of the film are kept consistent.

Description

Technical Field

[0001] The present invention relates to the technical field of optical thin film thickness monitoring, and particularly to a method, device and coating system for on-line monitoring of the thickness of an optical thin film. Background Art

[0002] During vacuum coating, in order to ensure the coating quality and the coating success rate, it is often necessary to on-line monitor the thickness of the optical thin film during the coating process. Most of the existing monitoring methods are single-wavelength monitoring, which cannot meet the monitoring requirements of complex film systems, resulting in insufficient monitoring accuracy for some film layers, large physical thickness deviation of the formed thin film, and ultimately coating failure. Based on this, the present invention proposes a method, device and coating system for on-line monitoring of the thickness of an optical thin film to overcome the above problems. Summary of the Invention

[0003] The object of the present invention is to provide a method, device and coating system for on-line monitoring of the thickness of an optical thin film, which can improve the thickness monitoring accuracy of the optical thin film coated on an optical substrate, reduce or eliminate the calculation deviation of the physical thickness of the optical thin film by emitting optical signals with different wavelengths to the film thickness monitoring area of the optical substrate and obtaining the optical thickness corresponding to the optical signals with different wavelengths, so as to solve the problems of insufficient monitoring accuracy of the existing single wavelength, large physical thickness deviation of the thin film, inability to meet the monitoring requirements of complex film systems, and insufficient coating success rate.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] The present invention provides a method for on-line monitoring of the thickness of an optical thin film, including:

[0006] Emitting an optical signal λ1 to the film thickness monitoring area of the optical substrate during the coating process, and receiving the optical signal λ1 transmitted through the film thickness monitoring area to obtain a transmittance array T1 corresponding to the optical signal λ1;

[0007] Emitting n - 1 optical signals λ n to the film thickness monitoring area of the same optical substrate, and receiving each optical signal λ n transmitted through the film thickness monitoring area to obtain n - 1 transmittance arrays T n corresponding to different optical signals λ n ; where n is a positive integer not less than 2, and the wavelength of each optical signal λ n is different from the wavelength of the optical signal λ1; when n is not less than 3, the wavelengths of any two different optical signals λ n are different;

[0008] Processing the transmittance array T1 and the transmittance arrays T n, the film optical thickness M corresponding to optical signals of different wavelengths is obtained m ; where m is a positive integer not less than 1.

[0009] Preferably, both m and n are equal to 2, so as to obtain the film optical thickness M1 and the film optical thickness M2 corresponding to the optical signal λ1 and the optical signal λ2 respectively after processing the transmittance array T1 and the transmittance array T2.

[0010] Preferably, the optical signal λ1 and the optical signal λ n are simultaneously emitted to the film thickness monitoring area of the optical substrate.

[0011] Preferably, the optical signal λ1 and the optical signal λ n are emitted to the film thickness monitoring area of the optical substrate at different times, and the emission time interval between any two adjacent emitted optical signals is 15 ms to 30 ms.

[0012] Preferably, the optical signal λ1 and the optical signal λ n are both vertically emitted to the film thickness monitoring area.

[0013] The present invention also provides a device for on-line monitoring of the thickness of an optical thin film, which can implement the above method for on-line monitoring of the thickness of an optical thin film, including:

[0014] A workpiece disk, which is used to be installed in a vacuum coating machine and is rotationally drivenly connected to the vacuum coating machine, and the workpiece disk is used to place an optical substrate; a monitoring hole group for film thickness monitoring of the optical substrate is arranged on the workpiece disk, the monitoring hole group includes a through hole one, a through hole two and an interval shielding area located between the through hole one and the through hole two, the through hole one and the through hole two are located on the same circumference, and a coating monitoring film is arranged in one of the through hole one and the through hole two;

[0015] A laser group, including a collimator and at least two lasers, the collimator is used to be arranged above the workpiece disk, any one of the lasers is connected to the collimator through an optical fiber, and the collimator is used to emit the optical signal emitted by the laser to the monitoring hole group; the wavelengths of the optical signals emitted by any two of the lasers are different;

[0016] A receiving component, which is used to be arranged below the workpiece disk, and the receiving component can receive the optical signal passing through the monitoring hole group and calculate the transmittance array corresponding to the optical signal.

[0017] Preferably, the receiving component includes a control terminal and an optical probe disposed below the workpiece disk. The optical probe is configured to receive the optical signal passing through the monitoring hole group. The optical probe is communicatively connected to the control terminal through an analog-to-digital converter. The control terminal is capable of calculating the transmittance array corresponding to the optical signal based on the optical signal.

[0018] Preferably, the device for on-line monitoring of the optical film thickness further includes an optical switch. The collimator is connected to the output end of the optical switch through a main optical fiber. Each laser is respectively connected to the input end of the optical switch through a branch optical fiber. The optical switch is communicatively connected to the control terminal. The control terminal is capable of controlling the optical switch to switch different lasers to emit the optical signal to the collimator.

[0019] Preferably, the first through hole, the second through hole, and the spaced-apart shielding region have the same arc length on the circumference.

[0020] The present invention also provides a coating system for on-line monitoring of the optical film thickness, including a vacuum coating machine and the above-mentioned device for on-line monitoring of the optical film thickness. The workpiece disk is installed in the vacuum coating machine and is rotationally drivenly connected to the vacuum coating machine. The rotational drive is configured to drive the workpiece disk to perform in-situ rotation with the center of the circle of the circumference as the center.

[0021] A light-transmitting window one and a light-transmitting window two are respectively provided at the top and bottom of the vacuum coating machine. The collimator is disposed outside the light-transmitting window one. The receiving component is disposed outside the light-transmitting window two. The input end of the receiving component is aligned with the output end of the collimator, and the connection line between the input end of the receiving component and the output end of the collimator vertically penetrates the monitoring hole group.

[0022] The present invention has achieved the following technical effects compared with the prior art:

[0023] The method, device, and coating system for on-line monitoring of the optical film thickness proposed by the present invention can improve the thickness monitoring accuracy of the optical film deposited on the optical substrate, reduce or even eliminate the calculation deviation of the physical thickness of the optical film, by emitting optical signals of different wavelengths to the film thickness monitoring area of the optical substrate and obtaining the optical thickness corresponding to the optical signals of different wavelengths, so as to solve the problems of insufficient monitoring accuracy of a single wavelength in the prior art, large deviation of the physical thickness of the film, inability to meet the monitoring requirements of complex film systems, and low coating success rate. It is applicable to the monitoring of high-difficulty filters such as optical communication GFF and multi-band filters.

[0024] Lasers of multiple wavelengths pass through the film thickness monitoring area of the optical substrate and are received by the optoelectronic probe, so that optical signals at different time periods of multiple wavelengths can be obtained. By separately processing the optical signals of different wavelengths, the optical thickness corresponding to the optical signals of multiple different wavelengths can be obtained, and thus the physical thickness of the thin film can be calculated.

[0025] In addition, the switching speed of lasers of different wavelengths is fast. Generally, the switching can be completed at the level of 20 ms, so that the optical signal values of two wavelengths can be obtained in a very short time. The difference is small, which can ensure that the calculated optical thickness and physical thickness of the thin film are consistent. Brief Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0027] Figure 1 It is a schematic flow chart of the method for on-line monitoring of the thickness of an optical thin film disclosed in an embodiment of the present invention;

[0028] Figure 2 It is a schematic diagram of the structure and installation of the device for on-line monitoring of the thickness of an optical thin film disclosed in an embodiment of the present invention;

[0029] Figure 3 It is a top view of a set of monitoring hole groups arranged on the workpiece disk disclosed in an embodiment of the present invention;

[0030] Figure 4 It is a top view of multiple sets of monitoring hole groups arranged on the workpiece disk disclosed in an embodiment of the present invention.

[0031] In the figure, the reference numerals are: 100, device for on-line monitoring of the thickness of an optical thin film;

[0032] 1, workpiece disk;

[0033] 2, vacuum coating machine; 21, first light-transmitting window; 22, second light-transmitting window;

[0034] 3, rotation drive;

[0035] 4, monitoring hole group; 41, first through hole; 42, second through hole; 43, spaced occlusion area; 44, coating monitoring film;

[0036] 5, collimator; 51, collimator bracket;

[0037] 6, circumference;

[0038] 7, first laser;

[0039] 8. Laser two;

[0040] 9. Main optical fiber;

[0041] 10. Branch optical fiber;

[0042] 11. Optical switch;

[0043] 12. Control terminal;

[0044] 13. Electron gun;

[0045] 14. Optical probe;

[0046] 15. Analog-to-digital converter. Specific embodiments

[0047] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0048] One of the purposes of the present invention is to provide a method for on-line monitoring of the thickness of an optical thin film, which can improve the thickness monitoring accuracy of the optical thin film deposited on an optical substrate and reduce or even eliminate the physical thickness calculation deviation of the optical thin film by emitting optical signals of different wavelengths to the film thickness monitoring area of the optical substrate and obtaining the optical thickness corresponding to the optical signals of different wavelengths, so as to solve the problems of insufficient monitoring accuracy of a single wavelength in the prior art, large physical thickness deviation of the thin film, inability to meet the monitoring requirements of complex film systems, and low coating success rate.

[0049] Another purpose of the present invention is to provide a device for on-line monitoring of the thickness of an optical thin film, which can implement the above method for on-line monitoring of the thickness of an optical thin film.

[0050] Still another purpose of the present invention is to provide a coating system including the above device for on-line monitoring of the thickness of an optical thin film.

[0051] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0052] Embodiment 1

[0053] As Figure 1As shown in the figure, this embodiment provides a method for online monitoring of the thickness of an optical thin film, which mainly includes: emitting an optical signal λ1 to the film thickness monitoring area of an optical substrate during the film coating process, and receiving the optical signal λ1 that passes through the film thickness monitoring area to obtain a transmittance array T1 corresponding to the optical signal λ1. The aforementioned film coating process refers to the process of coating an optical thin film on the surface of an optical substrate using a vacuum coater, which is common knowledge in the art and will not be elaborated here. After obtaining the transmittance array T1, n - 1 optical signals λ n are emitted to the film thickness monitoring area of the same optical substrate, and each optical signal λ n that passes through the film thickness monitoring area is received to obtain n - 1 transmittance arrays T n corresponding to different optical signals λ n respectively; where n is a positive integer not less than 2, and the wavelength of each optical signal λ n is different from the wavelength of the optical signal λ1; when n is not less than 3, the wavelengths of any two different optical signals λ n are also different. That is to say, the essence of the above method for online monitoring of the thickness of an optical thin film is to emit at least two optical signals with different wavelengths to the film thickness monitoring area of the optical substrate. After obtaining the transmittance array T1, each time an optical signal is emitted to the film thickness monitoring area of the same optical substrate, it corresponds to 1 different optical signal λ n . For example: if n = 2, then the method mainly emits two optical signals with different wavelengths, namely optical signal λ1 and optical signal λ2, to the film thickness monitoring area of the optical substrate during the film coating process; if n = 3, then the method mainly emits three optical signals with different wavelengths, namely optical signal λ1, optical signal λ2, and optical signal λ3, to the film thickness monitoring area of the optical substrate during the film coating process; if n = N (N is a positive integer not less than 4), then the method mainly emits N optical signals with different wavelengths, namely optical signal λ1, optical signal λ2, optical signal λ3...... and optical signal λ N N, and so on. The optical signal λ n and the transmittance array T n are in one-to-one correspondence, that is, each group of optical signals λ n corresponds to a group of transmittance arrays T n . Finally, the obtained transmittance array T1 and transmittance arrays T n are processed to obtain the film optical thickness M m corresponding to different wavelength optical signals, where m is a positive integer not less than 1. Among them, the optical signal λ1, the transmittance array T1, and the film optical thickness M1 correspond, the optical signal λ2, the transmittance array T2, and the film optical thickness M2 correspond,......, and so on.

[0054] In some embodiments, the optical signal λ1 and the optical signal λn It can be emitted to the film thickness monitoring area of the optical substrate simultaneously, or can be emitted to the film thickness monitoring area of the optical substrate at different times (i.e., at different moments), that is, each optical signal is emitted to the film thickness monitoring area of the optical substrate in batches and at different times. When the optical signal λ1 and the optical signal λ n When emitted to the film thickness monitoring area of the optical substrate at different times, it is preferably that the emission time interval between two adjacent emitted optical signals is 15 ms to 30 ms, and about 20 ms is optimal among them.

[0055] In some embodiments, m and n are both preferably equal to 2, that is, the aforementioned method for on-line monitoring of the optical film thickness preferably emits two optical signals with different wavelengths, optical signal λ1 and optical signal λ2, to the film thickness monitoring area of the optical substrate during the coating process, and the emission time interval between the optical signal λ1 and the optical signal λ2 is preferably 20 ms. After obtaining and processing the transmittance arrays T1 and T2, the film optical thickness M1 and the film optical thickness M2 corresponding to the optical signals λ1 and λ2 can be obtained respectively.

[0056] In some embodiments, it is preferably that during the monitoring process, the optical signals λ1 and the optical signal λ n are both perpendicularly emitted to the film thickness monitoring area, which can improve the optical reception efficiency.

[0057] The aforementioned method for on-line monitoring of the optical film thickness uses lasers with multiple wavelengths to pass through the film thickness monitoring area of the optical substrate in different time periods and is received by the photoelectric probe, so that optical signals with different wavelengths at different time periods can be obtained. By separately processing the optical signals with different wavelengths, the optical thicknesses corresponding to multiple optical signals with different wavelengths can be obtained, and thus the physical thickness of the thin film can be calculated.

[0058] In addition, the switching speed of lasers with different wavelengths is fast. Generally, the switching can be completed at the 20 ms level, so that the optical signal values of two wavelengths can be obtained in a very short time, with small differences, which can ensure that the calculated optical thickness and physical thickness of the thin film are consistent. It is applicable to the monitoring of high-difficulty filters such as optical communication GFF and multi-band filters.

[0059] Example 2

[0060] Such as Figures 2 to 4As shown in the figure, in this embodiment, a device 100 for on-line monitoring of the thickness of an optical thin film is proposed, which is used to be installed on a vacuum coating machine 2 for use; the vacuum coating machine 2 is a finished product with a mature coating function. The specific structure and coating principle of the vacuum coating machine 2 will not be elaborated here. The device 100 for on-line monitoring of the thickness of an optical thin film can perform real-time thickness monitoring on the optical thin film coated on the optical substrate on the upper surface of the workpiece disk 1 during the coating process of the coating machine. The device 100 for on-line monitoring of the thickness of an optical thin film includes a workpiece disk 1, a laser group and a receiving component. Among them, the workpiece disk 1 is used to be installed in the coating chamber of the vacuum coating machine 2 and is connected to the rotation drive 3 of the vacuum coating machine 2. The rotation drive 3 generally uses a drive motor, and the motor shaft penetrates through the coating chamber and extends into the coating chamber. The workpiece disk 1 is coaxially connected to the end of the motor shaft. The workpiece disk 1 is used to place the optical substrate, so that the workpiece disk 1 can be driven by the motor to rotate in situ around the motor shaft, so that the vapor ejected by the electron gun 13 in the coating chamber is evenly coated on the surface of the optical substrate to achieve coating. The workpiece disk 1 is a common coating component in the field of optical coating and can be in the shape of a flat plate or Figure 2 the umbrella shape shown in the figure (also known as "coating umbrella"); the difference is that in this solution, a monitoring hole group 4 is also opened on the workpiece disk 1, as Figure 3 shown in the figure. The monitoring hole group 4 includes a through hole one 41, a through hole two 42 and an interval shielding area 43 located between the through hole one 41 and the through hole two 42. The interval shielding area 43 is actually the unopened area of the workpiece disk 1, and the through hole one 41 and the through hole two 42 are separated by this area. Considering that the workpiece disk 1 is in a continuous rotation state during the coating process, preferably, the through hole one 41 and the through hole two 42 are located on the same circumference 6, and the circumference 6 and the circular workpiece disk 1 are concentric structures. A coating monitoring film 44 is arranged in one of the through hole one 41 and the through hole two 42, and the other remains unobstructed; as a preferred solution, the coating monitoring film 44 is inlaid in the through hole one 41. The coating monitoring film 44 can be an optical lens with a certain refractive index, such as a transparent glass sheet, etc. The position of the optical substrate corresponding to the monitoring hole group 4 is the film thickness monitoring area of the optical substrate. The through hole one 41, the through hole two 42 and the interval shielding area 43 in the same monitoring hole group 4 are arranged adjacent to each other, and multiple groups of monitoring hole groups 4 can be opened at intervals on the circumference 6 according to needs to improve the monitoring frequency, as Figure 4As shown, it is a schematic diagram of five sets of monitoring hole groups 4 opened on the circumference 6. The laser group includes a collimator 5 and at least two lasers. The wavelengths of the optical signals emitted by any two lasers are different. The collimator 5 is used to be arranged on the vacuum coating machine 2 and is located above the workpiece disk 1. Any one laser is located outside the vacuum coating machine 2, and any one laser is connected to the collimator 5 through an optical fiber. After the collimator 5 is installed, its position is fixed and is used to emit the optical signal emitted by the laser to the monitoring hole group 4. Each time the monitoring hole group 4 rotates to the exit area of the collimator 5, a signal will pass through the monitoring hole group 4 for the receiving component to receive. The receiving component is used to be arranged outside the vacuum coating machine 2 and is located below the workpiece disk 1. The receiving component can receive the optical signal passing through the monitoring hole group 4 and calculate the transmittance array corresponding to the optical signal.

[0061] In some embodiments, preferably, the receiving component includes a control terminal 12 and a light probe 14 arranged below the workpiece disk 1. The light probe 14 is used to receive the optical signal passing through the monitoring hole group 4. The light probe 14 is communicatively connected to the control terminal 12 through an analog-to-digital converter 15. The control terminal 12 can calculate the transmittance array corresponding to the optical signal according to the optical signal. Among them, the control terminal 12 is preferably a computer, the light probe 14 is preferably a photodetector, and the analog-to-digital converter 15 is preferably an A / D converter.

[0062] In some embodiments, the device 100 for on-line monitoring of the optical film thickness further includes an optical switch 11. The collimator 5 is connected to the exit end of the optical switch 11 through a main optical fiber 9. Each laser is respectively connected to the entrance end of the optical switch 11 through a branch optical fiber 10. The optical switch 11 is communicatively connected to the control terminal 12. The control terminal 12 can control the optical switch 11 to switch different lasers to emit optical signals to the collimator 5, thereby realizing the time-division emission of optical signals with different wavelengths.

[0063] Taking the case where there are two sets of lasers as an example, as Figure 2 shown, the two sets of lasers are laser one 7 and laser two 8 respectively. The paths of the laser beams emitted by laser one 7 and laser two 8 are as Figure 2 shown by the black arrows in. Correspondingly, the optical switch 11 is preferably a 2×1 optical switch, that is, the optical switch 11 has two entrance ports and one exit port; laser one 7 and laser two 8 are respectively connected to the two entrance ports of the optical switch 11 through a branch optical fiber 10, and the exit port of the optical switch 11 is connected to the collimator 5 through the main optical fiber 9. The optical switch 11 is a finished product, such as a common mechanical optical switch, and its specific structure and working principle will not be elaborated here.

[0064] In some embodiments, in order to further improve the monitoring accuracy, it is preferred that the arc lengths of the first through hole 41, the second through hole 42, and the spaced-apart shielding region 43 of each monitoring hole group 4 on the circumference 6 are the same. The first through hole 41 and the second through hole 42 can both be circular holes or both be rectangular holes, and can also be both set as fan-shaped holes. The specific hole shape can be flexibly adjusted according to needs. In each monitoring hole group 4, the first through hole 41, the second through hole 42, and the spaced-apart shielding region 43 are arranged adjacent to each other seamlessly. The central angle occupied by each monitoring hole group 4 on the workpiece disk 1 is preferably 5° to 80°. Generally, the larger the outer diameter of the workpiece disk 1, the relatively smaller the central angle corresponding to each monitoring hole group 4.

[0065] In some embodiments, the collimator 5 can be fixed to the outer wall of the coating chamber through the collimator bracket 51. The coating chamber of the vacuum coating machine 2 is respectively provided with a first light-transmitting window 21 and a second light-transmitting window 22 at the top and bottom. The first light-transmitting window 21 and the second light-transmitting window 22 can both be glass windows, which can ensure light transmission and can also ensure the vacuum degree and airtightness of the coating chamber. The collimator 5 can be installed on the top of the coating chamber through the collimator bracket 51 and is located outside the first light-transmitting window 21. The optical probe 14 of the receiving component is preferably arranged outside the second light-transmitting window 22. The incident end of the optical probe 14 is aligned with the exit end of the collimator 5, and it should be ensured that the line connecting the incident end of the optical probe 14 and the exit end of the collimator 5 (such as Figure 2 the dotted line shown, this dotted line is not a structural component of the coating system for on-line monitoring of the thickness of the optical film, but is only an auxiliary indication line) vertically penetrates the monitoring hole group 4. Taking the workpiece disk 1 as Figure 2 the flat plate shown as an example, it is preferred that the collimator 5, the first light-transmitting window 21, the second light-transmitting window 22, and the optical probe 14 are arranged vertically and aligned. The line connecting the exit end of the collimator 5 and the incident end of the optical probe 14 vertically penetrates the workpiece disk 1 and the monitoring hole group 4 thereon.

[0066] Taking the device 100 for on-line monitoring of the thickness of the optical film as an example, in which two sets of lasers, namely the first laser 7 and the second laser 8, are simultaneously provided, the monitoring method and monitoring principle will be specifically described below.

[0067] A set of monitoring hole groups 4 are provided on the workpiece disk 1. Each time the monitoring hole group 4 rotates between the collimator 5 and the optical probe 14, the collimator 5 sequentially irradiates the through-hole 41, the interval shielding area 43, and the through-hole 42. The optical probe 14 sequentially collects the optical signals passing through the through-hole 41, the interval shielding area 43, and the through-hole 42. The optical signals corresponding to the through-hole 41, the interval shielding area 43, and the through-hole 42 are the test signal S, the dark signal B, and the reference signal R respectively. The transmittance T of the thin film can be expressed as: T = (S - B) / (R - B). It should be noted that the optical signal emitted by the collimator 5 should be perpendicular to the workpiece disk 1. For example, when the workpiece disk 1 uses a coating umbrella, since the coating umbrella has a spherical structure, the through-hole 41, the interval shielding area 43, and the through-hole 42 all have a certain curvature. At this time, the collimator 5 is arranged obliquely so that the optical signal emitted by the collimator 5 is always located on the spherical radial direction of the through-hole 41, the interval shielding area 43, and the through-hole 42. However, considering the actual deviation, during actual installation, it is ensured that the collimator 5 is aligned with the receiving end face of the optical probe 14, and the connection line between the center of the receiving end face of the collimator 5 and the optical probe 14 is perpendicular to the through-hole 41 (monitoring film), the interval shielding area 43, and the through-hole 42.

[0068] The laser 7 and the laser 8 respectively emit optical signals λ1 and λ2. The two optical signals with different wavelengths are respectively coupled into two different branch optical fibers 10; the two branch optical fibers 10 are connected to two input ports of the optical switch 11, and the output port of the optical switch 11 is connected to the collimator 5.

[0069] The rotation drive 3 rotates to drive the workpiece disk 1 to rotate; the control terminal 12 issues an instruction to the optical switch 11 to make the optical signal λ1 output in parallel through the collimator 5 and approximately perpendicularly projected onto the workpiece disk 1. The workpiece disk 1 rotates, and after the optical signal λ1 sequentially passes through the through-hole 41 (monitoring film), the interval shielding area 43, and the through-hole 42, it is received by the optical probe 14 and the transmittance array T1 corresponding to the optical signal λ1 is obtained after computer processing. The control terminal 12 issues an instruction to the optical switch 11 to make the optical signal λ2 output in parallel through the collimator 5 and approximately perpendicularly projected onto the workpiece disk 1. The workpiece disk 1 rotates, and after the optical signal λ2 sequentially passes through the through-hole 41 (monitoring film), the interval shielding area 43, and the through-hole 42, it is received by the optical probe 14 and the transmittance array T2 corresponding to the optical signal λ2 is obtained after computer processing.

[0070] The control terminal 12 processes the transmittance array T1 and the transmittance array T2 respectively to obtain the thin-film optical thickness corresponding to the optical signals λ1 and λ2, thereby calculating the physical thickness of the thin film. Since the change in the thin-film thickness will cause the change in the transmittance T, therefore, according to the change law of the optical signal and some software algorithms, the thin-film phase thickness corresponding to the two wavelengths can be obtained respectively, and the physical thickness of the same thin film corresponding to the two wavelengths can be calculated, and the accuracy is higher than that of the single-wavelength thin-film thickness monitoring. Selecting the physical thickness of the thin film corresponding to the wavelength with a fast-changing optical signal can improve the monitoring accuracy.

[0071] The above device 100 for on-line monitoring of the optical thin-film thickness has the following advantages:

[0072] 1. By adding an optical switch, two monitoring wavelengths are obtained, thereby obtaining the transmittance values at different wavelengths; compared with a single monitoring wavelength, dual-wavelength monitoring can select the wavelength with the fastest-changing optical signal as the monitoring wavelength, and the monitoring accuracy is high; it avoids the situation where the optical signal changes slowly and the monitoring accuracy is poor for a single-wavelength monitoring.

[0073] 2. It can simultaneously monitor the transmittance of two specific wavelengths, improving the film system monitoring accuracy, such as in the coating occasion of a dual-channel filter.

[0074] 3. High accuracy. Optical thin films with the same physical thickness have different optical thicknesses for different wavelengths. By calculating the optical thicknesses of the two wavelengths, the monitoring error can be excluded and higher monitoring accuracy can be obtained.

[0075] 4. Flexible monitoring. During the coating process, the optical signal changes with the thin film. For a certain wavelength, the optical signal changes very little near the extreme value, while the optical signal of another wavelength may change very fast. Therefore, the wavelength with a fast-changing optical signal can be selected as the basis for judgment.

[0076] 5. In some special film systems, the monitoring wavelength can be set within a certain specific wavelength range to monitor the optical signal of the specific wavelength to meet the design requirements.

[0077] 6. The optical switch has a fast switching speed. Generally, the switching can be completed at the 20ms level. Therefore, the optical signal values of the two wavelengths can be obtained in a very short time, with small differences, ensuring that the calculated thin-film optical thickness and physical thickness are consistent. It is applicable to the monitoring of high-difficulty filters such as optical communication GFF and multi-band filters.

[0078] Example 3

[0079] This embodiment provides a coating system for on-line monitoring of the thickness of an optical thin film, which includes a vacuum coating machine 2 and a device 100 for on-line monitoring of the thickness of an optical thin film disclosed in Embodiment 2. Based on this, the coating system has both coating and real-time and accurate monitoring functions of the film thickness. The vacuum coating machine 2 is a finished product and has a mature coating function. The specific structure and coating principle of the vacuum coating machine 2 will not be elaborated here. The device 100 for on-line monitoring of the thickness of an optical thin film can perform real-time thickness monitoring on the optical thin film coated on an optical substrate during the coating process of the coating machine. Combining Figure 2 As can be seen, the workpiece disk 1 is installed in the coating chamber of the vacuum coating machine 2 and is connected to the rotation drive 3 of the vacuum coating machine 2. The rotation drive 3 generally uses a drive motor, and the motor shaft penetrates through the coating chamber and extends into the coating chamber. The workpiece disk 1 is coaxially connected to the end of the motor shaft. The workpiece disk 1 is used to place an optical substrate, so that the workpiece disk 1 can be driven by the motor to rotate in place with the motor shaft as the axis (that is, the workpiece disk 1 is driven to rotate in place with the center of the circle 6 as the center of the circle), so that the vapor ejected by the electron gun 13 in the coating chamber is evenly coated on the surface of the optical substrate to achieve coating. The workpiece disk 1 is a common coating component in the field of optical coating, and can be umbrella-shaped (also known as "coating umbrella") or Figure 2 the flat shape shown in

[0080] At the top and bottom of the coating chamber of the vacuum coating machine 2, a first light-transmitting window 21 and a second light-transmitting window 22 are respectively provided. The first light-transmitting window 21 and the second light-transmitting window 22 can both be glass windows, which can ensure light transmission, and can also ensure the vacuum degree and sealing performance of the coating chamber. The collimator 5 can be installed on the top of the coating chamber through a collimator bracket and is located outside the first light-transmitting window 21. The optical probe 14 of the receiving component is preferably arranged outside the second light-transmitting window 22. The incident end of the optical probe 14 is aligned with the exit end of the collimator 5, and it should be ensured that the connection line between the incident end of the optical probe 14 and the exit end of the collimator 5 (such as Figure 2 the dotted line shown in Figure 2 perpendicularly penetrates through the monitoring hole group 4. Taking the flat shape of the workpiece disk 1 shown in

[0081] as an example, it is preferred that the collimator 5, the first light-transmitting window 21, the second light-transmitting window 22 and the optical probe 14 are arranged vertically and aligned. The connection line between the exit end of the collimator 5 and the incident end of the optical probe 14 perpendicularly penetrates through the workpiece disk 1 and the monitoring hole group 4 thereon. During the coating process of the above coating system for on-line monitoring of the thickness of an optical thin film, the device 100 for on-line monitoring of the thickness of an optical thin film can monitor the optical signals of two or more specific wavelengths, so that the actual physical or optical thickness of the thin film can be accurately calculated, the coating success rate of a complex film system can be improved, and it is applicable to the monitoring of high-difficulty filters such as optical communication GFF and multi-band filters.

[0082] It should be noted that the structures, proportions, sizes, etc. depicted in the accompanying drawings of this specification are only used to cooperate with the content disclosed in the specification for those skilled in this technology to understand and read, and are not used to limit the conditions under which the present invention can be implemented. Therefore, they do not have any substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope covered by the technical content disclosed in the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle", and "one" cited in this specification are also only for the convenience of clear description and are not used to limit the scope in which the present invention can be implemented. The change or adjustment of their relative relationships, without substantial change in the technical content, should also be regarded as the scope in which the present invention can be implemented.

[0083] In the present invention, specific examples are used to elaborate on the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for on-line monitoring of the thickness of an optical thin film, characterized in that, Comprising: Emitting an optical signal λ1 to a film thickness monitoring area of an optical substrate during the film coating process, and receiving the optical signal λ1 that passes through the film thickness monitoring area to obtain a transmittance array T1 corresponding to the optical signal λ1; n-1 optical signals λ are emitted to the film thickness monitoring area of ​​the same optical substrate. n , and receiving each optical signal λ passing through the film thickness monitoring area n , to obtain n-1 optical signals with different n The corresponding transmittance array T n Wherein, n is a positive integer not less than 2, and each of the optical signals λ n The wavelengths of the optical signal λ1 are all different from the wavelength of the optical signal λ1; when n is not less than 3, any two different optical signals λ n The wavelengths are different; Processing the transmittance array T1 and the transmittance array T n , to obtain the film optical thickness M corresponding to optical signals of different wavelengths m ; where m is a positive integer not less than 1.

2. The method for on-line monitoring of the thickness of an optical thin film according to claim 1, characterized in that, Both m and n are equal to 2, so as to obtain a film optical thickness M1 and a film optical thickness M2 corresponding to the optical signal λ1 and the optical signal λ2 respectively after processing the transmittance array T1 and the transmittance array T2.

3. The method for on-line monitoring of the thickness of an optical thin film according to claim 1 or 2, characterized in that, The optical signal λ1 and the optical signal λ n are simultaneously emitted to the film thickness monitoring area of the optical substrate.

4. The method for online monitoring of the thickness of an optical thin film according to claim 1 or 2, characterized in that, The optical signal λ1 and the optical signal λ n are alternately emitted to the film thickness monitoring area of the optical substrate, and the emission time interval between two adjacent emitted optical signals is 15 ms to 30 ms.

5. The method for on-line monitoring of the thickness of an optical thin film according to claim 1 or 2, characterized in that, The optical signal λ1 and the optical signal λ n are both perpendicularly emitted towards the film thickness monitoring region.

6. An apparatus for on-line monitoring of the thickness of an optical thin film, which is capable of implementing the method for on-line monitoring of the thickness of an optical thin film according to any one of claims 1 to 2 and 4, characterized in that, Comprising: A workpiece disk, which is used to be installed in a vacuum coating machine and is rotationally drivenly connected to the vacuum coating machine, and the workpiece disk is used to place an optical substrate; a monitoring hole group for film thickness monitoring is arranged on the workpiece disk, and the monitoring hole group includes a through hole one, a through hole two and an interval shielding area located between the through hole one and the through hole two, the through hole one and the through hole two are located on the same circumference, and a coating monitoring film is arranged in one of the through hole one and the through hole two; A laser group, including a collimator and at least two lasers, the collimator is used to be arranged above the workpiece disk, any one of the lasers is connected to the collimator through an optical fiber, and the collimator is used to emit the optical signal emitted by the laser to the monitoring hole group; the wavelengths of the optical signals emitted by any two of the lasers are different; A receiving component, which is used to be arranged below the workpiece disk, and the receiving component can receive the optical signal passing through the monitoring hole group and calculate a transmittance array corresponding to the optical signal.

7. The device for on-line monitoring of the thickness of an optical thin film according to claim 6, characterized in that, The receiving component includes a control terminal and an optical probe arranged below the workpiece disk, the optical probe is used to receive the optical signal passing through the monitoring hole group, the optical probe is communicatively connected to the control terminal through an analog-to-digital converter, and the control terminal can calculate the transmittance array corresponding to the optical signal according to the optical signal.

8. The device for on-line monitoring of the thickness of an optical thin film according to claim 7, characterized in that, It further includes an optical switch, the collimator is connected to the output end of the optical switch through a main optical fiber, each laser is respectively connected to the input end of the optical switch through a branch optical fiber, the optical switch is communicatively connected to the control terminal, and the control terminal can control the optical switch to switch different lasers to emit the optical signal to the collimator.

9. The device for online monitoring of the thickness of an optical thin film according to any one of claims 6 to 8, characterized in that The arc lengths occupied by the through hole one, the through hole two and the interval shielding area on the circumference are the same.

10. A coating system for online monitoring of the thickness of an optical thin film, comprising a vacuum coater and the device for online monitoring of the thickness of an optical thin film according to any one of claims 6 to 9, characterized in that, The workpiece disk is installed in the vacuum coating machine and is rotationally drivenly connected to the vacuum coating machine, and the rotational drive is used to drive the workpiece disk to rotate in place with the center of the circumference as the center; A light-transmitting window one and a light-transmitting window two are respectively arranged at the top and the bottom of the vacuum coating machine, the collimator is arranged outside the light-transmitting window one, the receiving component is arranged outside the light-transmitting window two, the input end of the receiving component is aligned with the output end of the collimator, and the connection line between the input end of the receiving component and the output end of the collimator vertically penetrates the monitoring hole group.

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