Optical film thickness control method for vacuum coating

Abstract

The invention relates to an optical film thickness control method for vacuum coating, which is characterized in that the thickness of an optical film of a product sheet is monitored by using light control sheets, one light control sheet or the same coating monitoring position on the light control sheet only monitors one material, and the thicknesses of optical films of different materials are monitored by different light control sheets or different coating positions on the light control sheets; the monitoring comprises the following steps: in the coating process, detecting the current thickness of the optical thin film on the optical control sheet in real time by using a single-layer film thickness measuring method, and judging whether the thickness of the optical thin film on the product sheet is reached or not according to the current thickness. By adopting the optical coating method provided by the invention, the thickness of each dielectric layer can be accurately controlled, so that an optical product with more accurate film thickness control is obtained.

Description

Technical Field

[0001] The invention relates to a method for controlling optical film thickness of vacuum coating. Background Art

[0002] Optical thin films are usually made of a series of high and low refractive index materials of different thicknesses, which are alternately coated. The film thickness of optical thin films is a key factor affecting the final performance of the product, especially the spectral performance, so it is necessary to monitor it accurately.

[0003] Optical film thickness control is a commonly used film thickness monitoring method. Conventional optical film thickness control methods are divided into single wavelength method and wide spectrum method according to the wavelength range.

[0004] The single-wavelength control method is to compare the light curve of the light control film during the coating process with the light curve of the original design process to determine whether the film thickness has been reached. This feature comparison method has some difficulties, such as the thickness of the feature pair is not necessarily equal. In addition, no matter how accurate the monitoring process is, it is impossible to completely match the design, that is, there must be errors. According to the principle of optical thin films, the shape of the subsequent process curve will inevitably change. However, since the single-wavelength light control only measures the light at a single wavelength position, it does not know how the overall spectrum has changed, that is, it does not know how to correct the monitoring process. The monitoring process is still monitored according to the characteristics of the original design process curve, and new deviations will occur. This phenomenon of deviation in the monitoring target of the subsequent layer due to the deviation of the previous film layer is called error transmission. Moreover, the influence of this error transmission on the subsequent layer is very random and sometimes divergent. Due to the existence of error transmission, the reliability of thickness judgment is lower for the later film layer. Therefore, usually after a certain number of layers are monitored by a light control film, the transmission error is cut off by switching the light control film.

[0005] At present, the conventional practice of wide-spectrum light control is to compare the collected spectral data with the target spectrum of the current layer design. When the deviation value is the smallest, that is, the lower extreme value is reached, and the film thickness is considered to have been reached. In this thickness judgment method, there is no mathematical expression for the relationship between the deviation value and the film thickness, and the extreme value changes are difficult to judge. There are also problems such as multiple extreme values. In addition, in this wide-spectrum method, the contribution of each band spectrum to thickness judgment is different, and it changes with the film layer. For example, in the band that has been cut off, it is difficult for the new coating to make the spectrum change significantly and resolvably. Obviously, this has different effects on different film systems. In addition, the wide-spectrum spectrometer itself has problems such as large stray light and poor signal-to-noise ratio. These have increased the difficulty of using conventional wide-spectrum light control. Summary of the invention

[0006] The main purpose of the present invention is to provide an optical film thickness control method for vacuum coating with high film thickness control accuracy.

[0007] In order to achieve the above-mentioned purpose, the present invention provides a method for controlling the thickness of an optical film of a vacuum coating, which still uses a light control sheet to monitor the thickness of an optical film of a product sheet. However, unlike the conventional method, a light control sheet or the same coating monitoring position on the light control sheet only monitors the thickness of an optical film of one material, and the thickness of optical films of different materials are monitored by different light control sheets or different coating positions on the light control sheets.

[0008] The monitoring includes: in the coating process, using a single-layer film thickness measurement method to detect the current total thickness of the film layer on the current material light control sheet in real time. The current thickness of the optical film layer is obtained by subtracting the total thickness at the beginning of coating of the optical film layer from the total thickness at the current moment.

[0009] The single-layer film thickness measurement method is as follows: the spectrum of the optical film on the light control sheet is detected in real time by a wide-spectrum spectrometer, and the spectrum is converted from a wavenumber spectrum to an optical thickness spectrum by Fourier transform. The maximum peak position after conversion is the total optical thickness of the current single-layer film. The total thickness of the optical film at the current moment is obtained by dividing the optical thickness by the refractive index of the material.

[0010] In an embodiment of the present invention, the light control plate is pre-plated with an optical film of a monitoring material, and the pre-plating thickness satisfies: at least one interference peak appears within the spectral range.

[0011] In an embodiment of the present invention, the spectrum is a relative spectrum or an absolute spectrum.

[0012] In an embodiment of the present invention, the spectrum is a transmission spectrum or a reflection spectrum.

[0013] In an embodiment of the present invention, the light control sheet is located close to the product sheet and rotates together with the product sheet. The real-time detection is to detect the current thickness of the optical film on the light control sheet once every rotation of the light control sheet.

[0014] In an embodiment of the present invention, the light control sheet remains stationary during the coating process.

[0015] In an embodiment of the present invention, the light control plate is arranged in a switching mechanism. Before coating optical films of different materials, the coating position of the light control plate used for monitoring or the corresponding light control plate is switched to a position where the film can be coated through the switching mechanism, and the light control plate or the coating position not used for monitoring is switched to a position where the film cannot be coated.

[0016] In an embodiment of the present invention, the light control plate is arranged near a deposition source of the material it monitors, and a baffle is arranged near the deposition source so that the light control plate can only be plated by the material it monitors.

[0017] In an embodiment of the present invention, the deposition rate is calculated by the thickness at different moments.

[0018] In an embodiment of the present invention, the refractive index of the light control sheet is different from the refractive index of the optical film material monitored by the light control sheet, so that the transmittance or reflectance of the single-layer film has a spectral fluctuation amplitude that can be resolved by the spectral monitoring unit.

[0019] The above-mentioned film thickness control method of the present invention monitors the film thickness of multi-layer optical films according to the materials and single-layer films, and determines whether the optical film has reached the designed thickness by the film thickness detected in real time. Compared with the curve shape comparison method of the prior art, its control principle and method are completely different. The method of the present invention can more accurately control the thickness of each layer of optical film, thereby obtaining an optical product with more accurate film thickness control. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the framework of optical film thickness control of vacuum coating in Example 1.

[0021] Figure 2 A schematic diagram showing that the light control sheet of the rotating workpiece holder and the product sheet are placed at the same position.

[0022] Figure 3 This is a schematic diagram of the framework of optical film thickness control of vacuum coating in Example 2.

[0023] Figure 4 This is a schematic diagram of the framework of optical film thickness control of vacuum coating in Example 3.

[0024] In the figure: a-rotating axis, 1-light source, 2-rotating workpiece holder, 3-light-passing window, 4-light-collecting lens group, 51-first light-guiding optical fiber, 52-second light-guiding optical fiber, 6-fast wide spectrometer, 7-film changing mechanism, 8-thickness monitoring software, 91-crystal control probe, 92-oscillation package, 93-crystal controller, 94-evaporation controller, 10-baffle, 11-evaporation mechanism, 12-evaporation material, 13-coating chamber, 14-power supply, 15-switching mechanism, 16-shielding mechanism, 21-light-controlled film, 22-white film, 23-black film, 24-product film, 25-crystal-controlled film. DETAILED DESCRIPTION

[0025] The term "product sheet" in this article is used to refer to various products to be coated, and their shape is not necessarily required to be sheet-shaped.

[0026] The term "light control film" in this article refers to a substrate used for optical film thickness control. The substrate can be of any material and any shape. However, optical use requires certain conditions to be met. The thickness of the substrate used as a light control film is generally in the order of millimeters.

[0027] The term "white film" in this article refers to a piece that does not block light. Figure 2 No sheet is placed in the workpiece holder, and the light beam can pass through completely.

[0028] The term "black film" in this article refers to the light blocking position. Figure 2 In the workpiece rack, a substrate is often wrapped in opaque aluminum foil and placed here to block the light beam.

[0029] The term "optical thin film" in this article refers to the film layer coated on the product sheet or light control sheet. The thickness of the film is in the order of tens of nanometers to tens of micrometers.

[0030] In view of the problem that the monitoring accuracy of the method of using a light control sheet to monitor the thickness of a multilayer film in the prior art is not high, the present invention provides a method for controlling the thickness of an optical film of a vacuum coating with a different technical concept. In the method, a light control sheet is used to monitor the thickness of an optical film of a product sheet, wherein:

[0031] A light control sheet or the same coating monitoring position on the light control sheet only monitors the thickness of an optical film of one material, and the thickness of optical films of different materials are monitored by different light control sheets or different coating positions on the light control sheets.

[0032] The monitoring includes: in the coating process, using a single-layer film thickness measurement method to detect the current total thickness of the film layer on the current material light control sheet in real time. The current thickness of the optical film layer is obtained by subtracting the total thickness at the beginning of coating of the optical film layer from the total thickness at the current moment.

[0033] The present invention uses the idea of ​​monitoring only one material with one light control sheet, and transforms multilayer films of different materials into single-layer films corresponding to several materials (referring to a film layer composed of only a single material, and a film layer formed by coating the same material multiple times is still a single-layer film) and monitors them separately. For example, when two materials, high H and low L, are used on a product sheet to coat optical thin film layers alternating in an HLHLH manner, the light control sheets corresponding to monitoring the two materials are an H light control sheet and an L light control sheet. All H materials are monitored by the H light control sheet. All L materials are monitored by the L light control sheet. When monitoring the first H layer, switch to the H light control sheet. For the second L layer, switch to the L light control sheet for monitoring. The third H layer is switched to the H light control sheet again. The fourth L layer is switched to the L light control sheet again. The fifth H layer is switched to the H light control sheet again. Switching is performed between the two light control sheets in this way. There is only a single layer of film of H material on the H light control plate, and there is only a single layer of film of L material on the L light control plate. When monitoring the film thickness, the thickness measurement method of the single layer film can be used to measure the thickness changes of the two single layers of film. Compared with the original method of multi-layer film by curve comparison, the monitoring method of the present invention is to monitor the film thickness by measuring the film thickness of the light control plate, which has the advantages of high precision and accurate film thickness control, and avoids the problem of cumulative error in curve comparison monitoring of film thickness.

[0034] Among them, a specific and feasible method for measuring the thickness of a single-layer film can be: using a wide-spectrum spectrometer to detect the spectrum of the optical film on the light-control sheet in real time, and converting the spectrum from a wavenumber spectrum to an optical thickness spectrum through Fourier transform. The maximum peak position after conversion is the total optical thickness of the current single-layer film. Dividing the optical thickness by the material refractive index gives the total thickness of the optical film at the current moment. (If the spectrum of a multilayer film is converted, this feature is not available and the thickness cannot be measured in this way.)

[0035] The method of monitoring the spectrum of the wide spectrometer is the same as the conventional one, and can be used for transmission measurement or reflection measurement. The light source bright reference and dark background need to be calibrated. The dark background here refers to the original light spectrum measured when the light path is blocked during transmission measurement; the original light spectrum measured when there is no mirror-reflecting object or a completely black object (with a very low reflectivity, close to 0) during reflection measurement. The bright reference is usually the original light spectrum when there is no object blocking the transmission measurement; when reflecting, the original light spectrum under reflection can be made by using glass or aluminum mirrors without a film layer and other objects with a reflectivity that is relatively flat within the spectrum range of the spectrometer. The bright reference and dark background can be measured once in advance and saved as data archives for automatic call when calculating the transmittance or reflectance later. In some embodiments of the present invention, the bright reference and dark background are calibrated once every rotation. (Current spectrum-dark background) / (bright reference-dark background) is the transmittance spectrum or the reflectance spectrum.

[0036] This method uses the spectrum of a single-layer film to convert it into an optical thickness spectrum through Fourier transform. The maximum peak position after conversion is the total optical thickness of the current single-layer film. The result of the calculation is the thickness itself. The current thickness of the optical film can be obtained by dividing the optical thickness by the refractive index of the material. The refractive index of the material can be measured by traditional methods and then introduced into this method. In the Fourier transform result, the optical thickness corresponding to the single-layer film only requires the peak position, and there is no requirement for the absolute amplitude. In addition, since a piece of light control film is only plated with a single material, the peak amplitude of the reflectivity or transmittance of its single-layer film is unchanged in principle, but as the film thickness increases, the peak value increases. Since all wavelengths in the spectral band are involved in the calculation, the method has strong anti-noise ability. Therefore, when converting thickness, the method does not require absolute spectral transmittance or reflectance. In some cases, using relative transmittance or relative reflectance can obtain a higher spectral fluctuation amplitude and further enhance the anti-interference ability. This reduces the application requirements of this method. Because in monitoring, the current thickness of this layer of optical film is obtained by subtracting the total thickness at the beginning of the coating of this layer of optical film from the total thickness at the current moment. The thickness at the beginning can be arbitrary in principle, that is, the error of the previous layer does not affect the thickness judgment of the current layer, that is, there is no error transmission effect. The theoretical thickness resolution of this method is very high. The simulation using a conventional 2048-unit 400-1100nm wide spectrometer shows that its thickness resolution can reach 0.1nm.

[0037] In the above method, the light control sheet needs to be pre-plated with a certain basic thickness of the optical film of the monitored material, and the pre-plated thickness must meet the following requirements: at least one interference peak appears in the spectrum range. Only after reaching this thickness can the thickness of the optical film be calculated.

[0038] The refractive index of the substrate material of the light control plate and the optical film to be monitored should have a certain difference, so that the transmittance or reflectance spectrum has certain fluctuations. The refractive index of the light control plate can be selected to be higher than that of the monitored optical film, or it can be lower than that of the monitored optical film. For example, when coating an optical film of SiO2, the refractive index of the SiO2 optical film is around 1.44, and a high-refractive-index glass with a refractive index of around 1.7 can be selected as the light control plate, and its light fluctuation reaches 5%, which is conducive to accurately analyzing the thickness of the optical film. For example, for high-refractive optical films, conventional glass with a lower refractive index can be selected as the light control plate. It can be seen that the present invention selects a light control plate material that is conducive to monitoring according to the optical properties of each layer of the film material, so that the amplitude of the light fluctuation monitored by the spectrometer has a more significant difference, which can solve the problem that the amplitude of the light change is small and difficult to monitor, and improve the accuracy of monitoring. The light control plate substrate mentioned above is usually required to be transparent within the monitoring spectrum range. However, in the case of reflectivity monitoring, even a material that is opaque to the monitored spectrum but has a very high refractive index can be selected as the light control film substrate to obtain a larger refractive index difference and thus a larger reflectivity spectrum.

[0039] The light control sheet is arranged in a switching mechanism, and before coating optical films of different materials, the light control sheet or the coating position of the light control sheet is switched to the corresponding light control sheet through the switching mechanism. The structure of the switching mechanism is known.

[0040] The present invention converts various multilayer films into single-layer films that are easy to handle during the coating thickness monitoring process to overcome the various shortcomings of traditional light control. This is essentially a method of simplifying the complex. The present invention is further described in detail below through examples. The vacuum coating device used in the present invention and its operation method are known.

[0041] Embodiment 1

[0042] This embodiment uses a transmissive direct light control method. Figure 1 The vacuum coating device includes a coating chamber 13 for evaporation coating, an umbrella-shaped rotating workpiece rack 2 is arranged at the upper part of the coating chamber, and the rotating workpiece rack 2 can rotate around the axis a in the figure, and the light control sheet 21, the white sheet 22, the black sheet 23 and the product sheet 24 can be pressed. Figure 2The evaporation mechanism 11 is arranged in a circular manner on the rotating workpiece rack 2. The structure of the evaporation mechanism is known, and it mainly includes a heating mechanism for evaporation. The heating mechanism is provided with an evaporation boat for placing the evaporation material 12. When evaporation is performed, the evaporation material 12 is heated and vaporized by the evaporation mechanism 11. The rotating workpiece rack 2 drives the light control sheet, white sheet, black sheet and product sheet placed thereon to rotate together. The vaporized evaporation material is deposited on the surface of the light control sheet, white sheet, black sheet and product sheet to form an optical film with uniform thickness. A light-transmitting window 3 for light transmission is provided on one side of the top of the coating chamber 13. The light-transmitting window 3 is a lens sealed and connected to the coating chamber shell, so that light can pass through the light-transmitting window. The position of the light-transmitting window 3 can ensure that the light control sheet 21, white sheet 22, black sheet 23 and product sheet 24 can pass under it when rotating.

[0043] The switching device 16 is arranged on the rotating workpiece rack 2. The structure of the switching mechanism 16 is known and is only briefly illustrated in the attached figure. The switching device includes a tray, a light control sheet is placed on the tray, and a coating hole is eccentrically opened below the tray. The tray can rotate around the center, and there is a structure for shifting and shifting on the top. When replacing the light control sheet, the cylinder drives the straight rod to extend above the workpiece rack and shift and shift.

[0044] The optical monitoring device includes a light source 1, a group of light-collecting lens groups 4, a wide spectrometer 6 and a computer 8, wherein the light-collecting lens group 4 is connected to the wide spectrometer through a light-guiding optical fiber 51, and the spectrometer 6 is connected to the computer 8 through a signal line. The light source 1 is arranged in the coating chamber 13 and below the rotating workpiece rack 2, and the light-collecting lens group 4, the wide spectrometer 6 and the computer 8 are arranged outside the coating chamber 13. The light source is arranged below one side of the rotating workpiece rack 2. When the rotating workpiece rack 2 rotates, the light control sheet, white sheet, black sheet and product sheet placed thereon can pass above the light source during rotation and be illuminated by the light emitted by the light source. The light emitted by the light source 1 passes through the light control sheet, white sheet, black sheet and product sheet passed by the above-mentioned rotation, and then is emitted from the light-transmitting window above, emitted into the light-collecting lens group 4, and then transmitted to the wide spectrometer 6 by the light-guiding optical fiber 51 at the rear end of the light lens group 4 for monitoring and analysis. The wide spectrometer transmits data to the computer 8 through the signal line. The computer is installed with thickness monitoring software.

[0045] Each time the product rack rotates, the spectra of the light control sheet, black, and white are measured once. The order of measurement is not important. The light control sheet, black, and white are measured in sequence according to custom. The wide spectrometer measures the transmittance spectrum of the light control sheet through transmission. Then, through Fourier transformation, the total thickness of the single-layer film coated on the light control sheet at the current moment can be obtained. The current thickness of the optical film layer is obtained by subtracting the total thickness at the beginning of the coating of the optical film layer from the total thickness at the current moment.

[0046] The optical film thickness monitoring of the coating process of this embodiment mainly includes the following steps:

[0047] Prepare a light control sheet, and select the material of the light control sheet according to the material of the optical film to be monitored, so that there is a sufficient difference between the transmittance of the light control sheet and the optical film.

[0048] Pre-plating the light control sheet, according to the material of the optical film to be monitored, pre-plating an optical film of the same material with a certain initial thickness on the light control sheet, the initial thickness satisfies: at least one interference peak appears in the spectrum range of the spectrum monitoring unit. The initial film thickness of the pre-plating light control sheet is measured in advance.

[0049] Place the product sheet, white sheet, black sheet and the light control sheet that participates in this layer of plating according to Figure 2 The method is circumferentially placed on the surface of the rotating workpiece rack, and the light control sheet is arranged in the switching device.

[0050] The switching mechanism is controlled to switch to the corresponding light control sheet. The vacuum evaporation coating device is controlled to start coating the first layer of optical thin film. The optical monitoring system monitors the thickness of the light control sheet and controls the vacuum coating device to stop coating when the thickness requirement is reached.

[0051] Afterwards, before each layer of optical film is deposited, the switching mechanism is controlled to switch to the corresponding light control sheet, and then the deposition of the optical film layer is started. The optical monitoring system monitors the thickness of the light control sheet and controls the vacuum coating device to stop coating when the thickness requirement is reached.

[0052] Embodiment 2

[0053] This embodiment uses the back-reflective indirect light control method. Figure 3 Based on the structure of the vacuum coating device described in Example 1, a baffle 10 is provided on the evaporation device 11.

[0054] The switching mechanism of this embodiment is arranged on the top of the umbrella-shaped rotating workpiece frame 2. The switching device comprises a tray, a hole for receiving coating is eccentrically exposed below the tray, a motor drives the rotating tray from outside the vacuum chamber, and a limit switch is used to realize the rotation positioning.

[0055] The main equipment of the optical monitoring device includes a light source power supply 14, a light source 1, a group of light-collecting lens groups 4, a wide spectrometer 6 and a computer 8, wherein the light-collecting lens group is connected to the wide spectrometer through a light-guiding optical fiber 51, and the spectrometer 6 is connected to the computer 8 through a signal line. The light source 1 is connected to a light-guiding optical fiber 52, and the light transmitted by the light source through the light-guiding optical fiber 52 is irradiated to the light control plate from the front end of the light-guiding optical fiber. The light-collecting lens group 4 is arranged in the coating chamber, and the wide spectrometer 6 and the computer 8 are arranged outside the coating chamber 13. Specifically, the front end of the optical fiber is arranged above the switching mechanism. When the rotating workpiece rack 2 rotates, the light source can irradiate the light control plate switched by the switching mechanism, and after being reflected by the light control plate rotated above, it is emitted into the light-collecting lens group 4, and then transmitted to the wide spectrometer 6 by the light-guiding optical fiber 51 at the rear end of the optical lens group 4 for monitoring and analysis. The wide spectrometer transmits the optical data including the refractive index to the computer 8 through the signal line. The computer is installed with thickness monitoring software. The wide spectrometer measures the transmittance spectrum of the light control plate by reflection. Then, through Fourier transformation, the total thickness of the single-layer film deposited on the light control plate at the current moment can be obtained. The current thickness of the optical film layer is obtained by subtracting the total thickness at the beginning of the coating of the optical film layer from the total thickness at the current moment. The time to stop the coating of the optical film layer is predicted according to the preset thickness, and the vacuum coating equipment is controlled to stop coating.

[0056] This embodiment also includes a crystal control system for monitoring the deposition rate, and the crystal control system includes a crystal control probe 91, an oscillation package 92, a crystal control instrument 93, and an evaporation source control mechanism 94. The crystal control probe is installed at the center of the rotating workpiece rack. When the rotating workpiece rack 2 rotates, the crystal control probe remains stationary and can always detect. The crystal control probe transmits the detected crystal control data to the crystal control instrument 93 through the oscillation package 92. The crystal control instrument 93 controls the evaporation of the coating material by the evaporation mechanism 11 through the evaporation mechanism control device 94. The crystal control instrument also transmits the data to the computer 8 of the optical monitoring device.

[0057] The optical film thickness monitoring of the coating process of this embodiment mainly includes the following steps:

[0058] Referring to the first embodiment, a pre-plated annular light control plate is prepared.

[0059] The product sheets are divided into Figure 3 The described method is placed circumferentially in the switching mechanism.

[0060] The control switching mechanism is switched to monitor the light control sheet corresponding to the first layer of optical thin film material to be exposed in the coating chamber. The vacuum evaporation coating device is controlled to start coating the first layer of optical thin film, and the optical monitoring system monitors the film thickness of the light control sheet, and controls the vacuum coating device to stop coating when the thickness requirement is reached.

[0061] Afterwards, before each layer of optical film is deposited, the switching mechanism is controlled to switch to the corresponding light control plate, and then the deposition of this layer of optical film begins. The optical monitoring system monitors the film thickness of the light control plate, and controls the vacuum coating device to stop coating when the thickness requirement is reached.

[0062] Embodiment 3

[0063] This embodiment uses the back-reflective indirect light control method. Figure 4 Based on the structure of the vacuum coating device described in Example 1, the vacuum coating device includes a plurality of evaporation mechanisms 11, each evaporation mechanism 11 is used to vaporize a different coating material, and a baffle mechanism is arranged between each evaporation mechanism, and the baffle mechanism is used to shield the light control plate 21 near any evaporation mechanism from being coated by other evaporation mechanisms. Figure 4 Only one of the evaporation mechanisms is shown in the figure. In practice, the light control plate 21 can be placed near each evaporation mechanism used for evaporation. The placement method can refer to Figure 4 In this embodiment, the light control sheet is fixed near the evaporation mechanism by placing a bracket, and is located below the shielding mechanism, so that the light control sheet will not be affected when the evaporation mechanism on the other side is working.

[0064] The main equipment of the optical monitoring device of this embodiment includes a light source power supply 14, a light source 1, a group of light receiving lens groups 4, a wide spectrometer 6 and a computer 8, wherein the light receiving lens group 4 is connected to the wide spectrometer 6 through a light guide fiber 51, and the spectrometer 6 is connected to the computer 8 through a signal line. The light source 1 is connected to a light guide fiber 52, and the light transmitted by the light source through the light guide fiber 52 is irradiated from the front end of the light guide fiber to the light control plate. The light receiving lens group 4 is arranged in the coating chamber, and the wide spectrometer 6 and the computer 8 are arranged outside the coating chamber 13. The front end of the light guide fiber 51 is arranged below the light control plate 21. When the rotating workpiece rack 2 rotates, the light source can irradiate the light control plate switched by the switching mechanism, and after being reflected by the light control plate rotated by the above-mentioned light, it is emitted into the light receiving lens group 4, and then transmitted by the light guide fiber 51 at the rear end of the light lens group 4 to the wide spectrometer 6 for monitoring and analysis. The wide spectrometer is used to measure the spectrum. The wide spectrometer transmits data to the computer 8 through the signal line. The computer is installed with thickness monitoring software.

[0065] The wide-spectrometer measures the transmittance spectrum of the light control film through reflection. Then, through Fourier transform, the total thickness of the single-layer film coated on the light control film at the current moment can be obtained. The current thickness of the optical film layer is obtained by subtracting the total thickness at the beginning of the coating of the optical film layer from the total thickness at the current moment. The time to stop the coating of the optical film layer can be predicted based on the preset thickness, and the vacuum coating equipment can be controlled to stop coating.

[0066] This embodiment includes a crystal control system, and its configuration is the same as that of the second embodiment, and some of its equipment is in Figure 4 For details on how to set it, please refer to Figure 3 The difference from the second embodiment is that, since the light control sheet of this embodiment is arranged near the evaporation mechanism, a switching mechanism is no longer arranged on the top of the rotating workpiece frame 2, but a crystal control sheet 25 is placed, combined with Figure 3 and Figure 4 The crystal control probe 91 is arranged above the crystal control sheet 25. When the rotating workpiece frame 2 rotates, the crystal control probe can always detect the crystal control sheet. The crystal control probe transmits the detected crystal control data to the crystal control instrument 93 via the oscillation package 92. The crystal control instrument 93 controls the evaporation of the coating material by the evaporation mechanism 11 through the evaporation mechanism control device 94. The crystal control instrument also transmits the data to the computer 8 of the optical monitoring device.

[0067] The optical film thickness monitoring of the coating process of this embodiment mainly includes the following steps:

[0068] A light control plate and a pre-plated light control plate are prepared with reference to Example 1. In this embodiment, a crystal control plate is also prepared.

[0069] The product sheets are divided into Figure 2 Place the light control sheet on the surface of the rotating workpiece holder in an annular direction in the manner described above. Figure 4 The crystal control piece is placed on top of the rotating workpiece holder.

[0070] The vacuum evaporation coating device is controlled to start coating the optical film, and the optical monitoring system monitors the thickness of the light control sheet. In this process, since the light control sheet is only affected by the evaporation mechanism on its own side, it can only monitor the thickness of one layer of optical film and is not affected by the deposition coating of other evaporation materials. When the thickness requirement is reached, the vacuum coating device is controlled to stop coating.

[0071] The embodiments of the present invention are only used to illustrate the present invention and do not constitute a limitation on the scope of the claims. Other substantially equivalent substitutes that can be thought of by those skilled in the art are all within the protection scope of the present invention.

Claims

1. A method for controlling optical film thickness of vacuum coating, characterized in that: Use light control sheets to monitor the thickness of the optical film on the product sheet, where: A light control sheet or the same coating monitoring position on the light control sheet only monitors the thickness of an optical film of one material, and the thickness of optical films of different materials are monitored by different light control sheets or different coating positions on the light control sheets. The monitoring includes: during the coating process, using a single-layer film thickness measurement method to real-time detect the current total thickness of the film layer on the current material light control sheet, and subtracting the total thickness of the optical film at the beginning of coating of the optical film at the current moment from the total thickness at the current moment to obtain the current thickness of the optical film.

2. The optical film thickness control method according to claim 1, characterized in that The single-layer film thickness measurement method is as follows: the spectrum of the optical film on the light control plate is detected in real time by a wide spectrometer, and the spectrum is converted from a wavenumber spectrum to an optical thickness spectrum by Fourier transform. The maximum peak position after conversion is the total optical thickness of the current single-layer film, and the total thickness of the optical film at the current moment is obtained by dividing the optical thickness by the refractive index of the material.

3. The optical film thickness control method according to claim 2, characterized in that The light control sheet is pre-plated with an optical film of the monitoring material, and the pre-plating thickness satisfies: within the spectral range, at least one interference peak appears.

4. The optical film thickness control method according to claim 2, characterized in that The spectrum described is a relative spectrum or an absolute spectrum.

5. The optical film thickness control method according to claim 2, characterized in that The spectrum is a transmission spectrum or a reflection spectrum.

6. The optical film thickness control method according to claim 1, characterized in that The light control sheet is located close to the product sheet and rotates with the product sheet. The real-time detection is to detect the current thickness of the optical film on the light control sheet once every rotation of the light control sheet.

7. The optical film thickness control method according to claim 1, characterized in that The light control sheet remains stationary during the coating process.

8. The optical film thickness control method according to claim 1, characterized in that The light control plate is arranged in a switching mechanism. Before coating optical films of different materials, the coating position of the light control plate used for monitoring or the corresponding light control plate is switched to a position where the film can be coated through the switching mechanism, and the light control plate or the coating position not used for monitoring is switched to a position where the film cannot be coated.

9. The optical film thickness control method according to claim 1, characterized in that The light control plate is arranged near a deposition source of the material it monitors, and a baffle is arranged near the deposition source so that the light control plate can only be plated by the material it monitors.

10. The optical film thickness control method according to claim 1, characterized in that The deposition rate was calculated from the thickness at different times.

11. The optical film thickness control method according to claim 1, characterized in that The refractive index of the light control plate is different from the refractive index of the optical film material monitored by the light control plate, so that the transmittance or reflectance of the single-layer film has a spectral fluctuation amplitude that can be resolved by the spectral monitoring unit.

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