Fresnel membrane processing methods, Fresnel membranes, PPG modules and electronic equipment

Abstract

This application provides a method for processing a Fresnel membrane, characterized in that the method includes: applying a surface crystallizing agent to the surface of the Fresnel membrane to form a first region, the surface crystallizing agent being used to promote the absorption of ultraviolet laser by the Fresnel membrane; irradiating the first region with ultraviolet laser to form a first tank, the sidewalls of the first tank comprising carbon black, the carbon black including carbon black generated by the reaction of the Fresnel membrane under ultraviolet laser irradiation, the position of the first tank corresponding to the position of the first region. The method provided by this application can reduce the number of processing steps for the Fresnel membrane and improve processing efficiency.

Description

Technical Field

[0001] This application relates to the field of optical device technology, and more specifically, to a method for processing a Fresnel film, a Fresnel film, a PPG module, and an electronic device. Background Technology

[0002] The development of smart wearable devices has brought new means and channels for health monitoring, enabling people to obtain their own physiological information more conveniently and promptly. Heart rate monitoring modules, as an important monitoring sensor in wearable devices, are experiencing a surge in demand, with increasingly stringent requirements for measurement accuracy.

[0003] The heart rate monitoring module mainly consists of a light-emitting diode (LED) and a photodetector (PD). The LED emits light of different wavelengths, and the PD monitors heart rate and blood oxygen by receiving the useful light signal emitted by the LED and reflected through the skin. To improve the aesthetics and light intensity of the design, a Fresnel membrane is added for device shielding and optical focusing. Because the Fresnel membrane has a toothed structure, the light emitted by the LED is constantly reflected within the membrane, causing multiple light rays to be emitted into the PD without being reflected by the skin. This results in significant light leakage within the membrane, i.e., optical noise.

[0004] In existing technologies, a photothermal processing method is typically used to create grooves on a Fresnel membrane, followed by screen printing ink on the sidewalls of the grooves to prevent light leakage. However, this method of cutting grooves before printing ink involves many steps and is relatively complex. Therefore, it is necessary to provide a more convenient Fresnel membrane processing method to achieve the light-blocking effect of the Fresnel membrane. Summary of the Invention

[0005] This application provides a method for processing a Fresnel membrane, a Fresnel membrane, a PPG module, and an electronic device, which can reduce the processing steps of the Fresnel membrane.

[0006] In a first aspect, a method for processing a Fresnel membrane is provided, comprising: applying a surface crystallizing agent to the surface of the Fresnel membrane to form a first region, the surface crystallizing agent being used to promote the absorption of ultraviolet laser by the Fresnel membrane; irradiating the first region with ultraviolet laser to form a first tank, the sidewall of the first tank comprising carbon black, the carbon black comprising carbon black generated by the reaction of the Fresnel membrane under the ultraviolet laser irradiation, the position of the first tank corresponding to the position of the first region.

[0007] In the embodiments provided in this application, ink is applied to the surface of the Fresnel membrane, and then a groove is created on the Fresnel membrane using ultraviolet laser processing. This allows the Fresnel membrane to undergo a depolymerization reaction, and the depolymerization products, such as carbon black, can be directly retained on the surface of the groove, achieving the light-blocking effect of the Fresnel membrane. This eliminates the need to achieve the light-blocking effect by screen printing ink on the sidewalls of the groove after it has been created. Furthermore, since the depolymerization products are directly retained on the surface of the groove, there is no need for waste removal processing, thereby reducing processing steps, improving processing efficiency, and increasing product yield.

[0008] In conjunction with the first aspect, in some implementations of the first aspect, the surface crystallizer is also used to promote the recrystallization of the Fresnel film.

[0009] In the embodiments provided in this application, the Fresnel membrane undergoes a depolymerization reaction under the action of ultraviolet laser, and the polymerized long-chain molecules gradually break down and eventually decompose into carbon black, that is, elemental carbon. The surface crystallizer is also used to promote the recrystallization of the Fresnel membrane, that is, to promote the crystallization of the carbon black.

[0010] In conjunction with the first aspect, in some implementations of the first aspect, the carbon black also includes the carbon black in the surface crystallizer.

[0011] In the embodiments provided in this application, the surface crystallizer may include carbon black, which may remain on the surface of the Fresnel membrane as a light-shielding material, or may be used to promote the absorption of ultraviolet laser by the Fresnel membrane and promote the crystallization of carbon black generated by the reaction of the Fresnel membrane under the action of ultraviolet laser.

[0012] In conjunction with the first aspect, in some implementations of the first aspect, the sidewall of the first tank further includes iron(III) oxide, which is contained in the surface crystallizer.

[0013] In the embodiments provided in this application, the surface crystallizer may also include iron(III) oxide, which is black in color and can be left on the side wall of the tank after grooving as a light-shielding material. Furthermore, the iron(III) oxide can also increase the absorption of the Fresnel film to ultraviolet laser and promote the crystallization of carbon black generated by the reaction of the Fresnel film under the action of ultraviolet laser.

[0014] In conjunction with the first aspect, in some implementations of the first aspect, the first region is a region surrounding the center of the Fresnel membrane and located on the surface of the Fresnel membrane.

[0015] In the embodiments provided in this application, ink is applied around the center of the Fresnel membrane, that is, a groove is opened around the center of the Fresnel membrane. This can achieve a light-blocking effect around the center of the Fresnel membrane, that is, the Fresnel membrane in a 360° direction, thereby facilitating the practical application of the Fresnel membrane in devices.

[0016] In conjunction with the first aspect, in some implementations of the first aspect, the photon energy of the ultraviolet laser is greater than the bond energies of the C-C bonds and CO bonds in the Fresnel film.

[0017] In conjunction with the first aspect, in some implementations of the first aspect, the wavelength of the ultraviolet laser is 280nm to 400nm.

[0018] In the embodiments provided in this application, when the photon energy of the ultraviolet laser is greater than the bond energies of the C-C and CO bonds in the Fresnel membrane, the ultraviolet laser can break the C-C and CO bonds in the Fresnel membrane, causing the Fresnel membrane molecules to break, i.e., undergoing a depolymerization reaction. This ultimately generates light-shielding materials such as carbon black, which remain on the surface of the tank, achieving the light-shielding effect of the Fresnel membrane. When the wavelength of the ultraviolet laser is between 280 nm and 400 nm, the corresponding photon energy is relatively high, which can break the chemical bonds such as the C-C and CO bonds in the Fresnel membrane.

[0019] In conjunction with the first aspect, in some implementations of the first aspect, the processing method further includes: determining the pulse width of the ultraviolet laser based on the thickness of the Fresnel film and the absorption rate of the Fresnel film on the ultraviolet laser.

[0020] In conjunction with the first aspect, in some implementations of the first aspect, the pulse width of the ultraviolet laser is on the picosecond level.

[0021] In the embodiments provided in this application, the pulse width of the ultraviolet laser is determined based on the thickness of the Fresnel film and the absorption rate of the Fresnel film to the ultraviolet laser, so that a suitable pulse width can be obtained, and the pulse width is in the picosecond range, for example, 1 to 1000 ps. This can reduce the heat-affected zone of ultraviolet laser processing, that is, reduce the melting phenomenon of the Fresnel film, improve the product yield, and make the product more aesthetically pleasing.

[0022] In conjunction with the first aspect, in some implementations of the first aspect, the processing method further includes: determining the processing power, processing frequency, and processing speed of the ultraviolet laser based on at least one of the following parameters: the pulse width, the total heat consumed by the ultraviolet laser processing, the path length of the ultraviolet laser processing, and the thickness of the Fresnel film, wherein the total heat is determined based on the absorption rate of the Fresnel film of the ultraviolet laser.

[0023] In the embodiments provided in this application, the power, frequency, and speed of the ultraviolet laser are calculated and determined based on the pulse width, the total heat consumed by the ultraviolet laser processing, the path length of the ultraviolet laser processing, and the thickness of the Fresnel film. This allows for the acquisition of suitable processing parameters, thereby enabling the Fresnel film to form a tank primarily through photochemical corrosion, i.e., a depolymerization reaction, reducing melting and improving product yield.

[0024] In conjunction with the first aspect, in some implementations of the first aspect, the spot diameter of the ultraviolet laser is 0.01 mm to 0.1 mm.

[0025] In the embodiments provided in this application, when the spot diameter of the ultraviolet laser is 0.01mm to 0.1mm, the size of the first groove in the radial direction is smaller, which improves the accuracy of the grooving position and thus improves the product yield.

[0026] In a second aspect, a Fresnel membrane is provided, which is manufactured by the method described in the first aspect or any implementation thereof.

[0027] In conjunction with the second aspect, in some implementations of the second aspect, the first groove includes a first curved groove and a second curved groove, the first curved groove and the second curved groove being spaced apart around the center of the Fresnel membrane, and the projections of the ends of the first curved groove and the ends of the second curved groove in the radial direction of the Fresnel membrane at least partially overlap.

[0028] In conjunction with the second aspect, in some implementations of the second aspect, the first groove further includes a third bend and a fourth bend, the third bend and the fourth bend being located on the periphery of the first bend and the second bend in the radial direction, and the third bend and the fourth bend being spaced apart around the center of the Fresnel membrane, and the projections of the ends of the third bend and the ends of the fourth bend in the radial direction at least partially overlap.

[0029] In conjunction with the second aspect, in some implementations of the second aspect, the dimension of the first groove in the radial direction is 0.01 mm to 0.1 mm.

[0030] Thirdly, a PPG module is provided, the PPG module including a Fresnel membrane as described in the second aspect or any implementation thereof; the PPG module further includes: a light-emitting diode (LED) and a photodetector (PD), the LED and the PD being located on the toothed surface of the Fresnel membrane, the LED being used to emit light signals, and the PD being used to receive the light signals emitted by the LED and reflected by the skin to achieve heart rate monitoring; wherein, the first groove is located on the Fresnel membrane at a position corresponding to the connection area of ​​the PD and the LED.

[0031] Fourthly, an electronic device is provided, including a PPG module as described in the third aspect. Attached Figure Description

[0032] Figure 1 This is a schematic diagram illustrating the working principle of a PPG module.

[0033] Figure 2 This is a schematic diagram of the structure of a Fresnel membrane.

[0034] Figure 3 This is a schematic diagram of the optical path of a PPG module.

[0035] Figure 4 This is a schematic flowchart of a Fresnel membrane processing method provided in an embodiment of this application.

[0036] Figure 5 This is a schematic flowchart of an ultraviolet laser processing method provided in an embodiment of this application.

[0037] Figure 6 This is a schematic diagram of the cross-sectional morphology of a Fresnel membrane groove provided in an embodiment of this application.

[0038] Figure 7 This is a schematic diagram comparing the light-blocking effect of the Fresnel membrane provided in the embodiments of this application.

[0039] Figure 8 This is a schematic diagram of the structure of a Fresnel membrane provided in an embodiment of this application.

[0040] Figure 9 This is a schematic diagram of the structure of a Fresnel membrane provided in an embodiment of this application.

[0041] Figure 10 This is a schematic diagram of the structure of a Fresnel membrane provided in an embodiment of this application.

[0042] Figure 11 This is a schematic diagram of the structure of a Fresnel membrane provided in an embodiment of this application.

[0043] Figure 12 This is a schematic diagram of the structure of a Fresnel membrane provided in an embodiment of this application.

[0044] Figure 13 This is a schematic diagram of the structure of a Fresnel membrane provided in an embodiment of this application.

[0045] Figure 14 This is a schematic diagram of the structure of a PPG module provided in an embodiment of this application. Detailed Implementation

[0046] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0047] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized.

[0048] The terms “including,” “comprising,” “having,” and variations thereof all mean “including but not limited to,” unless otherwise specifically emphasized.

[0049] The development of smart wearable devices has brought new means and channels for health monitoring, enabling people to obtain their own physiological information more conveniently and promptly. Therefore, smart wearable devices are attracting increasing attention, and the demand for and application scenarios for smart wearable products are also growing. Among these, heart rate monitoring modules, as the most important monitoring sensor in wearable devices, are experiencing a dramatic increase in demand, while the requirements for measurement accuracy are becoming increasingly stringent.

[0050] Smart wearable devices may include heart rate monitoring modules for heart rate monitoring, such as photoplethysmogram (PPG) modules. Figure 1 This is a schematic diagram illustrating the working principle of a PPG module provided in an embodiment of this application, as shown below. Figure 1 As shown, the PPG module 110 may include LED 111 and PD 112. LED 111 is used to emit light signals, and PD 112 is used to receive the useful light signals emitted by LED 111 and reflected by the skin 120 to realize the monitoring of heart rate and blood oxygen. Since the heartbeat causes changes in blood volume, the amount of light absorbed by the blood changes accordingly. After receiving the light signals reflected by the human skin 120, PD 112 can sense the change in light intensity and then convert it into information such as heart rate or pulse wave morphology, thereby realizing the monitoring of information such as heart rate and blood sample.

[0051] The PPG module typically includes a Fresnel film for device masking and optical focusing. Figure 2Figures (a) and (b) are the top and front views of the Fresnel membrane structure, respectively. The Fresnel membrane 115 typically includes a flat surface and a serrated surface, which are arranged opposite each other, or in other words, they are arranged opposite each other along the z-axis direction shown in the figures. The serrated surface includes multiple serrations, each of which is positioned around the center of the Fresnel membrane, forming multiple concentric circles. Due to the toothed structure of the Fresnel membrane 115, the light emitted by the LED 111 is continuously reflected within the Fresnel membrane 115, causing multiple light rays to be emitted into the PD 112 without being reflected by the skin 120, resulting in a large amount of light leakage within the Fresnel membrane 115, i.e., optical noise.

[0052] Figure 3 This is a schematic diagram of the optical path of a PPG module. (Example:) Figure 3 As shown, the PPG module includes a printed circuit board (PCB) 114, with LEDs 111 and PDs 112 positioned above the PCB 114. Foam 113 can be used to separate LEDs 111 and PDs 112 to block light. A Fresnel lens 115 is positioned above LEDs 111 and PDs 112, with its serrated surface facing towards LEDs 111 and PDs 112. A lens 116 is positioned above the Fresnel lens 115, which is also the side of the PPG module closest to the skin 120. Due to the sawtooth structure of the Fresnel membrane 115, the light signal emitted by the LED 111 is constantly reflected between the sawtooths within the Fresnel membrane 115. This results in multiple light paths being received by the PD 112 without being reflected by the skin 120, such as light paths 1, 2, and 3 shown in the diagram. However, only the light paths that are reflected by the skin 120, such as light path 4, are useful light signals. These light paths that are not reflected by the skin 120 cannot accurately reflect the human heart rate or blood oxygen level, affecting the accuracy of the measurement results. These light paths that are not reflected by the skin 120 can also be called light noise, or light leakage.

[0053] Therefore, existing technology employs the method of creating a groove in the Fresnel membrane 115 and screen printing ink on the sidewall of the groove to eliminate the optical noise of the Fresnel membrane 115. Specifically, a groove is created in the Fresnel membrane 115 using CO2 infrared laser processing. This groove extends through the Fresnel membrane 115 in the z-axis direction shown in the figure, and the position of the groove can be set in the area of ​​the Fresnel membrane 115 corresponding to the connection portion of LED 111 and PD 112. Ink is screen printed on the sidewall of the groove. For example, the ink color can be black, which can absorb the light emitted by LED 111, thereby preventing the light emitted by LED 111 from passing directly through the Fresnel membrane 115 from the side (in the y-axis direction) and being received by PD 112, thus reducing optical noise.

[0054] CO2 infrared laser processing involves using an infrared laser with CO2 as the medium gas and a wavelength of approximately 1064 nm (mid-infrared band) to irradiate the Fresnel membrane 115 to create a groove. The reaction mechanism of CO2 infrared laser processing is typically photothermal, where the material melts at high temperatures through photothermal action and is then removed through an evaporation process. In other words, the infrared laser-irradiated portion of the Fresnel membrane 115 melts at high temperatures and is then removed through evaporation. After the infrared laser processing is completed, ink is screen-printed on the sidewalls of the groove to achieve a light-shielding effect.

[0055] Therefore, the processing steps for this Fresnel membrane are quite complex, requiring the control of multiple process parameters. Furthermore, due to the large heat-affected zone of infrared laser processing, it is easy for adhesive melts to form in the tank, making waste removal difficult; and screen printing inks can easily cause dirt to accumulate on the Fresnel membrane tank and surface, affecting the product's appearance.

[0056] Therefore, this application provides a method for processing Fresnel membranes that can simultaneously achieve grooving and shielding effects, reduce processing steps, and improve production efficiency.

[0057] Figure 4 This application provides a method for processing a Fresnel membrane. This embodiment uses ultraviolet laser processing to create grooves on the Fresnel membrane 115, specifically by irradiating the Fresnel membrane 115 with an ultraviolet laser in the ultraviolet band. Exemplarily, the ultraviolet laser can be in the near-ultraviolet or mid-ultraviolet band, specifically an ultraviolet laser with a wavelength in the range of approximately 200nm to 400nm. This ultraviolet laser processing can also be N2 ultraviolet laser processing, where N2 is used as the medium gas to generate ultraviolet laser light upon stimulation.

[0058] like Figure 4 As shown, the method may include steps S401 to S402:

[0059] S401, a surface crystallizing agent is applied to the surface of the Fresnel membrane to form a first region.

[0060] This surface crystallizer can also be called a crystallizing agent, and it can be used in inks.

[0061] In some embodiments, the surface crystallizer may include carbon black, which is an amorphous carbon material. This carbon black promotes the absorption of ultraviolet laser energy by the Fresnel film 115 during ultraviolet laser processing, or in other words, promotes the absorption of ultraviolet laser energy by the Fresnel film 115, thereby promoting the decomposition of the Fresnel film 115 and its recrystallization, or promoting the crystallization of products such as carbon black obtained from the decomposition of the Fresnel film 115. After ultraviolet laser processing, the carbon black in the surface crystallizer can remain on the sidewall of the opened tank, improving the light-shielding effect of the Fresnel film 115.

[0062] In some embodiments, the surface crystallizer may further include iron oxide (Fe3O4) to promote the absorption of ultraviolet laser by the Fresnel film 115 and to promote the crystallization of products such as carbon black. After the ultraviolet laser processing is completed, the iron oxide can remain on the side wall of the opened tank to improve the light-shielding effect of the Fresnel film 115.

[0063] The surface crystallizer may also include at least one of the chemical raw materials such as binders, fillers, solvents, and additives.

[0064] In some embodiments, the first region may be a region surrounding the center of the Fresnel membrane 115 and located on the surface of the Fresnel membrane 115, the surface of which may be Figure 2 The image shows the xy plane of the Fresnel membrane 115. This first region can be used to determine the position of the ultraviolet laser irradiation on the Fresnel membrane 115, that is, the position of the first groove. The irradiation path of the ultraviolet laser can coincide with the position of the first region. The shape of the resulting first groove can be the same as the shape of the first region, and the dimension of the first groove in the radial direction of the Fresnel membrane 115 can be the same as or approximately the same as the dimension of the first region in the radial direction. Furthermore, the resulting first groove can surround the center of the Fresnel membrane to better achieve a light-shielding effect in applications such as PPG modules.

[0065] The surface crystallizer can be applied to the upper or lower surface of the Fresnel membrane 115, that is, the flat or serrated surface of the Fresnel membrane 115. Alternatively, the surface crystallizer can be applied to only one side of the Fresnel membrane 115, and the ultraviolet laser can penetrate this first region to form a tank. Applying the surface crystallizer to one side of the Fresnel membrane 115 before ultraviolet laser processing can also reduce processing steps, eliminating the need to print ink on the entire sidewall of the tank after it has been prepared.

[0066] S402, the first region is irradiated with an ultraviolet laser to form the first tank.

[0067] In some embodiments, a surface crystallizing agent can be applied to the surface of the Fresnel membrane 115 before ultraviolet laser processing is performed; that is, step S401 is executed first, followed by step S402. The sidewall of the first tank may include carbon black, which may include carbon black remaining after the surface crystallizing agent is irradiated by ultraviolet laser, or carbon black generated after the long-chain molecules in the Fresnel membrane 115 undergo depolymerization and recrystallization. The position of the first tank may correspond to the position of the first region.

[0068] In other embodiments, instead of applying a surface crystallizing agent to the surface of the Fresnel membrane 115, the area where the groove needs to be formed, i.e., the area corresponding to the first region, can be directly irradiated with an ultraviolet laser. This region can also be pre-marked before ultraviolet laser irradiation. Under the action of the ultraviolet laser, this region can decompose to form the first groove, and generate products such as carbon black that adhere to the sidewall of the first groove, achieving the light-shielding effect of the Fresnel membrane 115. That is, step S402 can be executed directly without executing step S401.

[0069] In some embodiments, the diameter of the ultraviolet laser spot can be the same as or approximately the same as the width of the first region, or its radial dimension. The ultraviolet laser irradiates the Fresnel membrane 115 along the first region, forming a first groove in the Fresnel membrane 115. This eliminates the need for repeated ultraviolet laser irradiation for grooving; that is, after grooving is completed in one irradiation, there is no need to irradiate again along the first groove location defined by the first region. This reduces the processing path, decreases processing steps, improves product yield, and prevents damage to the product from secondary grooving.

[0070] The following is a brief introduction to the principle of the depolymerization reaction of the Fresnel membrane 115 under the action of ultraviolet laser:

[0071] Fresnel membrane 115 can be made of polyethylene terephthalate (PET), with the molecular formula [C 10 H8O4] n The molecular structure is shown in the following formula:

[0072]

[0073] Under ultraviolet laser irradiation, the reaction mechanism of PET molecules can be a photochemical mechanism. That is, the chemical bonds of PET molecules can be broken by the photon energy of ultraviolet laser, resulting in a decomposition reaction, or depolymerization reaction, which decomposes the polymerized long-chain molecules into a variety of short-chain products.

[0074] The decomposition of PET molecules is generally determined by the bond energies of the chemical bonds within the PET molecule. The bond energies of the covalent carbon-oxygen (CO) bond and carbon-carbon (CC) bond in the PET molecule are 326 kJ / mol and 347.9 kJ / mol, respectively. In some embodiments, the wavelength of the ultraviolet laser can be in the mid-ultraviolet or near-ultraviolet band, for example, 280 nm to 400 nm. For example, at a wavelength of 300 nm, the corresponding energy of the ultraviolet light is 399 kJ / mol, and at a wavelength of 350 nm, the corresponding energy of the ultraviolet light is 354 kJ / mol. That is, the photon energy corresponding to the ultraviolet laser at the set wavelength can be greater than the bond energies of the CO and CC bonds, allowing the PET molecules to decompose from the polymerized (C) bonds under the irradiation of the ultraviolet laser. 10 H8O4) n The molecule decomposes into (C 10 Short-chain molecules such as H8O4 (single-chain molecules) and various short-chain products can be further decomposed to form carbon black and other products that remain on the sidewall surface of the first tank. The decomposed short-chain products can also react under photothermal conditions to generate carbon black. The carbon black and other products generated by the reaction adhere to the surface of the first tank and can act as a light-shielding material to achieve the light-shielding effect of the Fresnel membrane 115, eliminating the need for waste removal processes, thus simplifying the processing steps and reducing the technological difficulty.

[0075] In some embodiments, the Fresnel membrane 115 may also be made of polyamide (PA), commonly known as nylon, with the molecular formula [NH-R-CO]. x In this context, R represents the -CH2 group and the number of such groups; for example, the molecular structure of polyamide-6 is [NH(CH2)5CO]. Similar to PET, under the action of ultraviolet laser, PA decomposes from long-chain polymers into short-chain molecules. These short-chain molecules further decompose or undergo photothermal reactions to generate products such as carbon black. The carbon black can remain on the sidewall of the first tank as a light-shielding material. The bond energy of the CN bond is approximately 305 kJ / mol.

[0076] In some embodiments, the Fresnel membrane 115 may also be made of transparent polymer materials such as polycarbonate (PC) or polyethylene (PE), and has a certain absorption of ultraviolet laser, and can undergo depolymerization reaction under the action of ultraviolet laser. This application does not limit the material of the Fresnel membrane 115.

[0077] Furthermore, the following combination Figure 5 This application describes the ultraviolet laser processing technology provided. For example... Figure 5 As shown, the ultraviolet laser method may include steps S501 to S505.

[0078] S501 determines the wavelength and pulse width of the ultraviolet laser.

[0079] As mentioned above, the laser photon energy corresponding to the wavelength of the ultraviolet laser can be greater than the bond energy of each chemical bond in the PET molecule, so that the ultraviolet laser can directly break the long chain molecules of PET polymerization and form short chain molecules, thereby causing the Fresnel film 115 to be broken down to form a tank, and causing the short chain molecules to further decompose to form carbon black that adheres to the side wall of the first tank to form a light-shielding layer.

[0080] In some embodiments, the wavelength of the ultraviolet laser can be 280nm to 400nm, and can be in the mid-ultraviolet or near-ultraviolet band. For example, the wavelength of the ultraviolet laser can be 355nm.

[0081] Pulse width, also known as pulse length, refers to the duration of the ultraviolet laser at a high level, or the duration of its action. The heat-affected zone (HAZ) in pulsed laser processing is typically small, especially when the pulse width is short. This results in a smaller molten layer within the Fresnel film 115, reducing melting phenomena.

[0082] In some embodiments, the pulse width of the ultraviolet laser can be determined based on the thickness of the Fresnel film 115 and the absorption rate of the Fresnel film 115 to the ultraviolet laser.

[0083] In some embodiments, the pulse width of the ultraviolet laser can be on the picosecond (ps) level. For example, the pulse width of the ultraviolet laser can be 10ps, 50ps, or 100ps, etc.

[0084] After determining the wavelength and pulse width of the ultraviolet laser, an ultraviolet laser can be selected. Furthermore, the laser processing parameters of the ultraviolet laser can be adjusted.

[0085] S502, determine the processing power, processing frequency and processing speed of the ultraviolet laser.

[0086] In some embodiments, the processing power, processing frequency, and processing speed of the ultraviolet laser can be determined based on at least one of the following: the pulse width of the ultraviolet laser, the total heat consumed by the ultraviolet laser processing, the path length of the ultraviolet laser processing, and the thickness of the Fresnel film 115. The total heat is determined based on the absorptivity of the ultraviolet laser by the Fresnel film 115. The path length of the ultraviolet laser processing is also the perimeter of the first tank.

[0087] For example, the processing power of the ultraviolet laser can be calculated based on the total heat consumed by the ultraviolet laser processing, the length of the processing path, and the processing speed.

[0088] The same material responds differently to the energy field at different frequencies. The mechanism of forming the first groove on the Fresnel film 115 can be different at different processing frequencies. By determining a suitable processing frequency, the mechanism of forming the first groove on the Fresnel film 115 can be mainly based on photochemical corrosion.

[0089] In some embodiments, the method further includes determining the spot diameter of the ultraviolet laser, or in other words, determining the wire diameter for ultraviolet laser processing. The spot diameter of the ultraviolet laser can be 0.01 mm to 0.1 mm. A smaller spot diameter results in stronger laser energy focusing, which can improve the accuracy of the first groove. Correspondingly, the width of the resulting first groove, that is, the radial dimension of the first groove, is 0.01 mm to 0.1 mm. For example, the radial dimension of the first groove can be 0.01 mm, 0.02 mm, 0.03 mm, 0.04 mm, 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, or 0.1 mm, etc.

[0090] S503, ultraviolet laser processing.

[0091] This step can be found in [link / reference]. Figure 4 In step S402, after adjusting the processing parameters, the ultraviolet laser is irradiated on the first region of the Fresnel film 115 to form the first groove. To avoid repetition, this will not be described again here.

[0092] S504, determine the quality of the sidewall of the first tank.

[0093] In some embodiments, the morphology of the cut end face of the Fresnel membrane 115, i.e., the sidewall morphology of the first groove, can be directly observed, or the sidewall morphology of the first groove can be observed using a scanning electron microscope (SEM) or a high-power optical microscope to determine the quality of the sidewall of the first groove. Since the ultraviolet laser processing method can leave a light-shielding material, i.e., carbon black, on the sidewall of the first groove to form a light-shielding layer, the sidewall of the first groove can be a rough surface, and micropores can exist on the sidewall.

[0094] In some embodiments, samples can be taken from the cut end face, and the specific gravity of elements such as C, O, and Fe on the surface of the first tank can be measured using gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FT-IR), or energy dispersive spectroscopy (EDS). Because the Fresnel membrane 115 undergoes a depolymerization reaction under ultraviolet laser irradiation to generate carbon black, the C content on the surface of the first tank is high, while the contents of elements such as O, H, and Fe are low.

[0095] In some embodiments, a slice can be taken from the cut end face of the Fresnel membrane 115, for example, from the xy plane shown in the figure, to determine the quality of the sidewall of the first groove. This slice can be found in [reference needed]. Figure 6 The black area 135 is the sidewall surface of the first tank. This area is close to the ultraviolet laser irradiation area, and the reaction mechanism is mainly photochemical corrosion. The Fresnel film 115 undergoes depolymerization, and the carbon black generated in the reaction, as well as the carbon black and iron oxide and other light-shielding substances in the surface crystallizer, can be directly retained on the sidewall surface, thus forming the black area 135. The gray area, or area 136, is adjacent to the black area 135. Due to the photothermal effect, the Fresnel film 115 can have a certain heat-affected zone in the area close to the ultraviolet laser irradiation. The intermolecular forces are relatively large, and the carbon black generated by the depolymerization of the Fresnel film 115, as well as the carbon black and iron oxide in the surface crystallizer, can bond with the molten PET to form the gray area 136. The white area 137 is the body of the Fresnel film 115. This area is far away from the ultraviolet laser irradiation area and will not experience thermal melting or decomposition.

[0096] In some embodiments, the light-blocking effect of the processed Fresnel membrane 115 can be detected by light leakage testing to determine the quality of the sidewall of the first tank. Figure 7 This comparison shows the light-blocking effect of Fresnel membrane 115 from different manufacturers after grooving with UV laser processing, compared to the effect before grooving. The thickness of the Fresnel membrane 115 is 100μm. Figure 7As shown, the horizontal axis represents Fresnel membranes 115 from different manufacturers, and the vertical axis represents the light leakage value of the Fresnel membrane 115, in nanoamperes (nA). The higher the light leakage value, the more severe the light leakage phenomenon, or the worse the light-blocking effect. Specifically, Fn-1, Fn-2, and Fn-3 represent the light leakage of the ungrooved Fresnel membrane 115; Fn-4, Fn-5, and Fn-6 represent the light leakage of the Fresnel membrane 115 after grooving using infrared laser processing; and Fn-7, Fn-8, and Fn-9 represent the light leakage of the Fresnel membrane 115 after grooving using the processing method provided in this application embodiment. The light source irradiated by Fn-1, Fn-4, and Fn-7 is green light; the light source irradiated by Fn-2, Fn-5, and Fn-8 is infrared light; and the light source irradiated by Fn-3, Fn-6, and Fn-9 is red light.

[0097] from Figure 7 As can be seen, the light-blocking effect of Fresnel membranes 115 from different manufacturers is significantly improved after grooving using the ultraviolet laser processing method provided in this application embodiment, compared to the Fresnel membranes 115 without grooving and those grooved using the infrared laser processing method. Specifically, the Fresnel membrane grooved using the ultraviolet laser processing method has its green light leakage reduced to approximately 1 / 20 of that without grooving, and its infrared and red light leakage reduced to approximately 1 / 10 of that without grooving; while the Fresnel membrane grooved using the infrared laser processing method has its green light leakage reduced to approximately 1 / 4 of that without grooving, its infrared light leakage reduced to approximately 1 / 3 of that without grooving, and its red light leakage reduced to approximately 2 / 5 of that without grooving.

[0098] S505 includes S505a and S505b, where S505a locks the machining parameters.

[0099] In some embodiments, if the light-shielding effect of the processed Fresnel membrane 115 meets the expected requirements, such as the cut port morphology or slice morphology meeting the expected requirements, or the light-shielding effect meeting the expected requirements, then the above-mentioned scheme is highly feasible, and the processing parameters involved can be locked. Otherwise, the processing parameters are adjusted until the processed Fresnel membrane 115 meets the expected requirements.

[0100] S505b, adjust machining parameters.

[0101] In some embodiments, if the light-blocking effect or the morphology of the cut port of the processed Fresnel film 115 does not meet the expected requirements, the processing parameters can be adjusted to improve the product yield and promote stable mass production.

[0102] The method provided in this application for grooving Fresnel membranes can simultaneously achieve grooving and light-shielding effects through ultraviolet laser processing. After grooving, there is no need to screen print ink on the sidewall of the first tank, thereby reducing processing steps and improving product yield. In addition, the main reaction mechanism of ultraviolet laser processing is photo-corrosion, resulting in a small heat-affected zone and less likely to leave sticky molten material on the sidewall of the first tank. Furthermore, light-shielding materials such as carbon black can be directly left on the sidewall of the first tank without the need for waste removal. The reduction in screen printing ink steps also makes the product appearance cleaner.

[0103] The above combination Figures 4 to 7 This application introduces a method for laser processing of a Fresnel film 115 according to embodiments. The following is a detailed explanation. Figures 8 to 13 The structure of the Fresnel membrane 115 obtained by the above processing method is described in the embodiments of this application.

[0104] Figure 8 This is a schematic diagram of the structure of a Fresnel membrane 115 provided in an embodiment of this application, as shown below. Figure 8 As shown, the Fresnel membrane 115 includes a first tank 130, the position of which corresponds to the position of the first region, or in other words, the position of the first tank 130 can be the position of the first region. The first tank 130 is formed by irradiating the first region with ultraviolet laser. The sidewalls of the first tank 130 may include carbon black, which may include carbon black generated by depolymerization and recrystallization of the Fresnel membrane 115 under ultraviolet laser irradiation. When the surface crystallizer includes carbon black, the sidewalls of the first tank 130 may also include carbon black from the surface crystallizer.

[0105] In some embodiments, when the surface crystallizer contains iron oxide, the sidewall of the first tank 130 may also contain iron oxide, which may remain on the sidewall of the first tank 130 after ultraviolet laser processing.

[0106] In some embodiments, the first groove 130 may include a first curved groove 131 and a second curved groove 132, the first curved groove 131 and the second curved groove 132 being spaced apart around the center of the Fresnel membrane 115, and the projections of the ends of the first curved groove 131 and the ends of the second curved groove 132 in the radial direction of the Fresnel membrane 115 at least partially overlap.

[0107] As an example, such as Figure 8 and Figure 9As shown, the first groove 131 may include a groove, and the second groove 132 may include a groove. The first groove 131 and the second groove 132 may be arc-shaped and spaced apart around the center of the Fresnel membrane 115. Alternatively, the first groove 131 and the second groove 132 may be arranged opposite to each other, and the radial projections of the ends of the first groove 131 and the second groove 132 at least partially overlap.

[0108] For example, when the first groove 131 and the second groove 132 each include a groove, the central angles of the first groove 131 and the second groove 132 can be the same, for example... Figure 8 or Figure 9 As shown, the central angles of the first groove 131 and the second groove 132 can be 181° to 360°, for example, 182° as shown in the figure. The central angles of the first groove 131 and the second groove 132 can also be different. For example, the central angle of the first groove 131 can be 0° to 90°, and correspondingly, the central angle of the second groove 132 can be 270° to 360°; or, the central angle of the first groove 131 can be 90° to 180°, and correspondingly, the central angle of the second groove 132 can be 180° to 270°; or, the central angle of the first groove 131 can be 180° to 270°, and correspondingly, the central angle of the second groove 132 can be 0° to 90°, so that the first groove 130 completely surrounds the center of the Fresnel membrane 115. The central angle of the overlapping portion of the first curved groove 131 and the second curved groove 132 in the radial direction can be greater than 1°, for example, it can be 2°, 5°, 10°, 20°, etc., and this application does not limit it.

[0109] As another example, such as Figure 10 and Figure 11 As shown, the first curved groove 131 may also include two curved grooves, namely curved groove 131-1 and curved groove 131-2, and the second curved groove 132 may also include two curved grooves, namely curved groove 132-1 and curved groove 132-2. The first groove 131 and the second groove 132 are spaced apart around the center of the Fresnel membrane 115. That is, the grooves 131-1, 131-2, 132-1 and 132-2 surround the center of the Fresnel membrane 115, and the groove 132-1 is located between the grooves 131-1 and 131-2. One end of the groove 132-1 and the projection of one end of the groove 131-1 in the radial direction at least partially overlap, and the other end of the groove 132-1 and the projection of one end of the groove 132-2 in the radial direction at least partially overlap. Similarly, the groove 132-2 is located between the grooves 131-1 and 131-2 and is located opposite to the groove 132-1.

[0110] For example, when the first groove 131 and the second groove 132 each include two grooves, the central angles of the first groove 131 and the second groove 132 can be the same, such as... Figure 10 As shown in Figure 11, for example, the central angles of the first curved groove 131 and the second curved groove 132 can both be 92°. The central angles of the first curved groove 131 and the second curved groove 132 can also be different. For example, the central angles of the first curved groove 131, namely curved groove 131-1 and curved groove 131-2, can be 0° to 90°, and correspondingly, the central angles of the second curved groove 132, namely curved groove 132-1 and curved groove 132-2, can be 90° to 180°; or, the central angles of the first curved groove 131, namely curved groove 131-1 and curved groove 131-2, can be 90° to 180°, and correspondingly, the central angles of the second curved groove 132, namely curved groove 132-1 and curved groove 132-2, can be 0° to 90°. The central angles of the first curved groove 131 and the curved groove 131-1 and the curved groove 131-2 can be the same or different; the central angles of the second curved groove 132-1 and the curved groove 132-2 can also be the same or different.

[0111] The central angle of the overlapping portion of the radial projections of the first groove 131 and the second groove 132 can be greater than 1°, for example, it can be 2°, 5°, 10°, 20°, etc., and this application does not limit it.

[0112] In some embodiments, the first groove 130 may further include a third curved groove 133 and a fourth curved groove 134, which are located radially around the first curved groove 131 and the second curved groove 132. That is, the first curved groove 131 and the second curved groove 132 are located near the center of the Fresnel membrane 115, while the third curved groove 133 and the fourth curved groove 134 are located away from the center of the Fresnel membrane 115. The third curved groove 133 and the fourth curved groove 134 are spaced apart around the center of the Fresnel membrane 115, and the projections of the ends of the third curved groove 133 and the fourth curved groove 134 in the radial direction at least partially overlap.

[0113] As an example, see further. Figure 8 and Figure 9The third groove 133 may include a single bend, and the fourth groove 134 may include a single bend. The third and fourth grooves 133 and 134 may be arc-shaped and arranged around the center of the Fresnel membrane 115. Alternatively, the first and second grooves 131 and 132 may be arranged opposite each other, and the radial projections of the ends of the first and second grooves 131 and 132 may at least partially overlap. Similar to the first and second grooves 131 and 132, when the third and fourth grooves 133 and 134 each include a single bend, their central angles may be the same and may range from 181° to 360°, for example, 182°. The central angles of the third groove 133 and the fourth groove 134 can also be different. For example, the central angle of the third groove 133 can be 0° to 90°, and correspondingly, the central angle of the fourth groove 134 can be 270° to 360°; or, the central angle of the third groove 133 can be 90° to 180°, and correspondingly, the central angle of the fourth groove 134 can be 180° to 270°; or, the central angle of the third groove 133 can be 180° to 270°, and correspondingly, the central angle of the fourth groove 134 can be 0° to 90°, so that the first groove 130 completely surrounds the center of the Fresnel membrane 115. The central angle of the overlapping portion of the radial projections of the third groove 133 and the fourth groove 134 can be greater than 1°, for example, 2°, 5°, 10°, 20°, etc., which is not limited in this application.

[0114] When the central angles of the first bend 131 and the third bend 133 are the same, the opening directions of the third bend 133 and the first bend 131 can be the same; when the central angles of the second bend 132 and the fourth bend 134 are the same, the opening directions of the fourth bend 134 and the second bend 132 can be the same, such as... Figure 8 As shown; the opening directions of the third curved groove 133 and the first curved groove 131 can also be different, and the opening directions of the fourth curved groove 134 and the second curved groove 132 can also be different, such as Figure 9 As shown.

[0115] As another example, such as Figure 10 and Figure 11As shown, the third bend 133 may include two bends, namely bend 133-1 and bend 133-2, and the fourth bend 134 may also include two bends, namely bend 134-1 and bend 134-2. The third groove 133 and the fourth groove 134 are arranged at intervals around the center of the Fresnel membrane 115. That is, the grooves 133-1, 133-2, 134-1 and 134-2 surround the center of the Fresnel membrane 115, and the groove 134-1 is located between the grooves 133-1 and 133-2. One end of the groove 134-1 and the projection of one end of the groove 133-1 in the radial direction at least partially overlap, and the other end of the groove 134-1 and the projection of one end of the groove 133-2 in the radial direction at least partially overlap. Similarly, the groove 134-2 is located between the grooves 133-1 and 133-2, and is arranged opposite to the groove 134-1.

[0116] Similar to the first and second curved grooves 131 and 132, when the third curved groove 133 and the fourth curved groove 134 each include two curved grooves, the central angles of the third curved groove 133 and the fourth curved groove 134 can be the same, such as... Figure 10 As shown in Figure 11, for example, the central angles of the third bend 133 and the fourth bend 134 can both be 92°. The central angles of the third bend 133 and the fourth bend 134 can also be different. For example, the central angles of the third bend 133, which is also bend 133-1 and bend 133-2, can be 0° to 90°, and correspondingly, the central angles of the fourth bend 134, which is also bend 134-1 and bend 134-2, can be 90° to 180°; or, the central angles of the third bend 133, which is also bend 133-1 and bend 133-2, can be 90° to 180°, and correspondingly, the central angles of the fourth bend 134, which is also bend 134-1 and bend 134-2, can be 0° to 90°. The central angles of the third curved groove 133-1 and the curved groove 133-2 can be the same or different; the central angles of the fourth curved groove 134-1 and the curved groove 134-2 can also be the same or different.

[0117] When the central angles of the third bend 133 and the first bend 131 are the same, such as Figure 10 As shown, the opening directions of the third bend 133 and the first bend 131 can be the same, that is, the opening directions of bend 133-1 and bend 131-1 can be the same, and the opening directions of bend 133-2 and bend 131-2 can be the same; the opening directions of the fourth bend 134 and the second bend 132 can be the same, that is, the opening directions of bend 134-1 and bend 132-1 can be the same, and the opening directions of bend 134-2 and bend 133-2 can be the same; as Figure 11As shown, the opening directions of the third bend 133 and the first bend 131 can also be different, that is, the opening directions of bend 133-1 and bend 131-1 can be different, and the opening directions of bend 133-2 and bend 131-2 can be different; the opening directions of the fourth bend 134 and the second bend 132 can also be different, that is, the opening directions of bend 134-1 and bend 132-1 can be different, and the opening directions of bend 134-2 and bend 133-2 can be different.

[0118] The width of the first groove 130, or its radial dimension d, can be 0.01 mm to 0.1 mm. The first curved groove 131, the second curved groove 132, the third curved groove 133, and the fourth curved groove 134 can have the same radial dimension, as described above. Figures 8 to 11 The first tank 130 is described above. Figures 8 to 11 The width of the first groove 130 described is a uniform width, with Figure 8 Taking the first curved groove 131 as an example, the first curved groove 131 can be a uniform arc shape, that is, any part of the first curved groove 131 has the same size in the radial direction. The second curved groove 132, the third curved groove 133 and the fourth curved groove 134 are similar. The dimensions of each curved groove in the first groove body 130 in the radial direction can also be different.

[0119] As an example, such as Figure 12 As shown, the radial dimensions of the two ends of the first curved groove 131 can be smaller than the radial dimensions of the middle portion of the first curved groove 131, for example, forming... Figure 2 The first groove 131 has a radial dimension that gradually decreases from the middle to both ends. The radial dimensions of the second groove 132, the third groove 133, and the fourth groove 134 are similar to those of the first groove 131, and will not be described further here.

[0120] As another example, such as Figure 13 As shown, the radial dimensions of the two ends of the first curved groove 131 can be larger than the radial dimensions of the middle portion of the first curved groove 131. The radial dimensions of the first curved groove 131 can gradually increase from the middle portion to the two ends. The radial dimensions of the second curved groove 132, the third curved groove 133, and the fourth curved groove 134 can be similar to those of the first curved groove 131, and will not be described in detail here.

[0121] It should be understood that the above Figures 8 to 13The structure of the first groove 130 is only illustrated by example. This application does not limit the number, shape, corresponding central angle, or groove width of the first curved groove 131, the second curved groove 132, the third curved groove 133, and the fourth curved groove 134. For example, the first groove 131 and the second groove 132 may also include three or more grooves. Similarly, the third groove 133 and the fourth groove 134 may also include three or more grooves. The shape of the first groove 130 may also be other than the arc shape shown in the figure. For example, each groove may be composed of two rectangles at a certain angle, or it may be other irregular shapes. The shapes of the first groove 131, the second groove 132, the third groove 133 and the fourth groove 134 may be the same or different, as long as the first groove 130 surrounds the center of the Fresnel membrane 115, so that when the Fresnel membrane 115 is used for the PPG module, the light emitted by the LED in the area surrounded by the first groove 130 will not pass through the first groove 130 and be received by the PD located outside the surrounding area.

[0122] The above Figures 8 to 13 The described Fresnel membrane can be applied in PPG modules to detect information such as heart rate and blood oxygenation in the human body. This application also provides a PPG module comprising the above-described components. Figures 8 to 13 Any Fresnel membrane described herein, such as the PPG module Figure 14 As shown.

[0123] The PPG module may include a PCB114 for providing electrical connections to devices such as LEDs and PDs. LEDs111 and PDs112 may be disposed on and electrically connected to the PCB114. The PPG module may include two PDs112 or one PD112. When the PPG module includes two PDs112, the two PDs112 and LEDs111 may be spaced apart.

[0124] Foam 113 may be included between PD112 and LED111 to prevent the light signal emitted by LED111 from directly passing through the PPG module and being absorbed by PD112. Foam 113 can also be used for shock absorption of the PPG module. Foam 113 and PCB114 can be fixedly connected by silicone pad 117.

[0125] A Fresnel membrane 115 is disposed on the other side of LEDs 111 and PDs 112, spaced apart from PCB 114. The serrated surface of the Fresnel membrane 115 faces LEDs 111 and PDs 112. The Fresnel membrane 115 is connected to foam 113 via a silicone pad 117. The first groove 130 of the Fresnel membrane 115 is located at a position on the Fresnel membrane 115 corresponding to the connection area of ​​LEDs 111 and PDs 112. For example, as... Figures 8 to 13As shown, the first groove 130 can be located within the area formed by the two concentric circles shown by the dashed lines, that is, within the area enclosed by circles 1151 and 1152. Circle 1151 can be the area where the LED 111 is installed; for example, the LED 111 can be located at the center of the Fresnel membrane 115. The outer perimeter of circle 1152 to the edge of the Fresnel membrane 115 can be the area where the PD 112 is installed. Furthermore, the sidewall of the first groove 130 includes a light-shielding material such as carbon black, which is area 135 shown in the figure. The light emitted by the LED 111 can be absorbed or reflected by the first groove 130, preventing the light emitted by the LED 111 from being received by the PD 112 without skin reflection, thus preventing light noise.

[0126] The PPG module may also include a lens 116, which serves as the outer shell of the PPG module to protect the components inside. The lens 116 can be made of a transparent material such as glass, allowing light emitted by the LED 111 to pass through the lens 116 and reach the user's skin, then be reflected by the skin and received by the PD 112. The lens 116 can be positioned on the side of the Fresnel membrane 115 away from the LED 111 and PD 112, and is fixedly connected to the Fresnel membrane 115 by an adhesive 118 and a silicone pad 117. The adhesive 118 is bonded to the plane of the Fresnel membrane 115, and the silicone pad 117 is bonded to the side of the adhesive 118 away from the Fresnel membrane 115, thus being fixedly connected to the lens 116.

[0127] This application also provides an electronic device, which includes the above-mentioned components. Figure 14 The described PPG module, wherein the Fresnel membrane 115 can be configured into different shapes according to the shape of the electronic device, for example, it can also be a detached form. Figures 8 to 13 Other shapes besides the circle shown include ellipses, rectangles, squares, etc. This electronic device can be a smart wearable device, such as a smartwatch. When the user wears the electronic device, the lens 116 of the PPG module is located closer to the user's skin, while the PCB 114 is farther away. The light emitted by the LED 111 passes through the Fresnel membrane 115 and the lens 116 to illuminate the user's skin. After being reflected by the skin, it passes through the lens 116 and the Fresnel membrane 115 and is received by the PD, thereby achieving heart rate and blood oxygen monitoring.

[0128] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for processing a Fresnel membrane, characterized in that, The processing method includes: A surface crystallizer is applied to the surface of the Fresnel film to form a first region, the surface crystallizer being used to promote the absorption of ultraviolet laser by the Fresnel film; The first region is irradiated with the ultraviolet laser to form a first tank. The sidewall of the first tank includes carbon black, which includes carbon black generated by the reaction of the Fresnel membrane under the ultraviolet laser irradiation. The position of the first tank corresponds to the position of the first region.

2. The processing method according to claim 1, characterized in that, The surface crystallizer is also used to promote the recrystallization of the Fresnel film.

3. The processing method according to claim 1 or 2, characterized in that, The carbon black also includes the carbon black in the surface crystallizing agent.

4. The processing method according to claim 1 or 2, characterized in that, The sidewall of the first tank also includes iron(III) oxide, which is contained in the surface crystallizing agent.

5. The processing method according to claim 1 or 2, characterized in that, The first region is the region surrounding the center of the Fresnel membrane and located on the surface of the Fresnel membrane.

6. The processing method according to claim 1 or 2, characterized in that, The photon energy of the ultraviolet laser is greater than the bond energy of the CO and C bonds in the Fresnel film.

7. The processing method according to claim 6, characterized in that, The wavelength of the ultraviolet laser is 280nm to 400nm.

8. The processing method according to claim 1 or 2, characterized in that, The processing method further includes: The pulse width of the ultraviolet laser is determined based on the thickness of the Fresnel film and the absorption rate of the Fresnel film for the ultraviolet laser.

9. The processing method according to claim 8, characterized in that, The processing method further includes: The processing power, processing frequency, and processing speed of the ultraviolet laser are determined based on at least one of the following parameters: The pulse width, the total heat consumed by the ultraviolet laser processing, the path length of the ultraviolet laser processing, and the thickness of the Fresnel film are mentioned. The total heat is determined based on the absorption rate of the Fresnel membrane for the ultraviolet laser.

10. The processing method according to claim 1 or 2, characterized in that, The diameter of the ultraviolet laser spot is 0.01 mm to 0.1 mm.

11. A Fresnel membrane, characterized in that, The Fresnel membrane is formed by the processing method as described in any one of claims 1 to 10.

12. The Fresnel membrane according to claim 11, characterized in that, The first groove includes a first curved groove and a second curved groove, the first curved groove and the second curved groove are spaced apart around the center of the Fresnel membrane, and the projections of the ends of the first curved groove and the ends of the second curved groove in the radial direction of the Fresnel membrane at least partially overlap.

13. The Fresnel membrane according to claim 12, characterized in that, The first groove also includes a third bend and a fourth bend, which are located around the first bend and the second bend in the radial direction and are spaced apart around the center of the Fresnel membrane. The projections of the ends of the third bend and the fourth bend in the radial direction at least partially overlap.

14. The Fresnel membrane according to claim 12 or 13, characterized in that, The first groove has a dimension of 0.01 mm to 0.1 mm in the radial direction.

15. A photoplethysmography (PPG) module, characterized in that, Includes the Fresnel membrane according to any one of claims 11 to 14; The PPG module also includes a light-emitting diode (LED) and a photodetector (PD). The LED and the PD are located on the toothed surface of the Fresnel membrane. The LED is used to emit light signals, and the PD is used to receive the light signals emitted by the LED and reflected by the skin to achieve heart rate monitoring. The first groove is located at the position of the Fresnel membrane corresponding to the connection area between the PD and the LED.

16. An electronic device, characterized in that, Includes the PPG module as described in claim 15.

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