A biometric detection structure and a manufacturing method thereof

Abstract

The present application discloses a biometric detection structure and a manufacturing method thereof. The biometric detection structure includes a light-transmitting layer, a light source and a photosensitive element are arranged on one side of the light-transmitting layer, and a high-refractive-index layer is arranged on the other side of the light-transmitting layer. By utilizing the original light source of the display screen and the light-transmitting layer, the light source necessary for optical detection is combined with the light source of the display screen itself, and a high-refractive-index layer is arranged on the original glass layer. Under the premise of not affecting the screen display performance, fingerprint detection is innovatively realized, and the detection effect is enhanced by arranging a dielectric layer between the light-transmitting layer and the high-refractive-index layer, realizing the compatibility between the display screen of the electronic device and the fingerprint recognition detection system. The manufacturing method provided by the present application is simple and easy to implement, and can be realized by continuously coating on the basis of the original structure of the display screen of the electronic device.

Description

Technical Field

[0001] The present invention relates to the field of optical detection, and particularly to a biometric detection structure and a manufacturing method thereof. Background Art

[0002] With the development of social economy, science and technology, and the continuous deepening of the modernization process, various electronic devices emerge in an endless stream. Common electronic devices include mobile phones, desktop computers, laptop computers, tablet computers, etc. Generally speaking, these electronic devices all have a display screen. For some electronic devices, in addition to providing a display function, the display screen is also used to implement other human-computer interaction functions, such as touch detection and other functions. For example, the display screen of a smart phone is often also used to make the smart phone respond to the contact of a finger.

[0003] To meet the above human-computer interaction functions, the display screens of electronic devices have numerous technical requirements and technical processing methods. For example, in order to save power consumption and reduce the screen thickness, etc., LCD screens and OLED screens have been developed.

[0004] With the development of fingerprint recognition technology, the application of fingerprint recognition technology in electronic devices has become more and more popular, such as fingerprint unlocking and other functions in smart phones. Usually, the fingerprint recognition structure is set on the components outside the display screen of the electronic device. For example, on a smart phone, a dedicated area is usually opened on the back of the phone to set the fingerprint recognition setting, and the fingerprint detection / recognition function cannot be realized on the display screen. This is because there are many practical difficulties in realizing the fingerprint detection / recognition function on the display screen. Currently, fingerprint detection technology is mainly based on the following three technologies. One is the capacitive detection method, the second is the ultrasonic detection method, and the third is the optical detection method. However, it is very difficult to apply the first two detections to the display screen. Specifically:

[0005] The capacitive detection material used in the capacitive detection method is usually an opaque material. Setting an opaque capacitive material on the display screen will greatly reduce the effective display area of the display screen, which is contrary to the demand for a large display screen; for the ultrasonic fingerprint detection method, since the detection end can only be placed under the display screen, the resolution is low and the fingerprint cannot be recognized.

[0006] The fingerprint detection / recognition structure using the optical detection method needs to set optical devices such as prisms, which will greatly increase the thickness of the electronic device, which is contrary to the requirement for the electronic device to be lighter and thinner. Moreover, the detection structure with optical devices such as prisms causes the display screen to be unable to display normally and cannot be integrated with the existing display screen.

[0007] Since the physical and chemical parameters of the display screens used on electronic devices by electronic device manufacturers, such as transmittance, intensity, toughness, etc., have been strictly screened and set, and the current display screens have been selected based on comprehensive indicators, therefore, how to clearly detect fingerprints and palm prints with minor modifications to the existing screen and achieve the compatibility of the display screen with fingerprint detection devices is an urgent problem to be solved. Summary of the Invention

[0008] This application provides a biometric detection structure. The detection structure directly uses the display screen glass and the display screen light source of the electronic device as the light-transmitting layer and the light source. By setting a high refractive index layer on the light-transmitting layer, the detection structure can obtain clear fingerprint images. The detection structure can be compatible with electronic devices such as smart phones and can realize the functions of collecting and identifying fingerprints and / or palm prints, etc. on the display screen of the electronic device without affecting the display effect of the electronic device.

[0009] The detection structure includes a light-transmitting layer 1. A photosensitive element 2 is arranged on one side of the light-transmitting layer 1, and a high refractive index layer 3 is arranged on the other side of the light-transmitting layer 1. Moreover, the refractive index of the high refractive index layer 3 is greater than that of the light-transmitting layer 1. The biometric feature is fingerprint and / or palm print. During detection, the biometric feature is in contact with the high refractive index layer.

[0010] In an implementable manner, the detection structure further includes a light source 4. The light source 4 and the photosensitive element 2 are arranged on the same side of the light-transmitting layer 1.

[0011] Further, the light source 4 is a display screen light source, and the light-transmitting layer 1 is a display screen glass.

[0012] Optionally, the high refractive index layer 3 is attached to the light-transmitting layer 1.

[0013] In addition, the inventor of the present application has found through both theoretical calculations and experiments that if the refractive index of the high refractive index layer 3 is further increased, more reflections will occur when light enters the high refractive index layer 3 from the light-transmitting layer 1, thereby reducing the intensity of the light entering and reaching the upper surface of the high refractive index layer 3, thus reducing the intensity of the reflected light on the upper surface of the high refractive index layer 3, and further reducing the clarity of the collected fingerprint image.

[0014] To eliminate the reduction in the clarity of the texture image caused by the excessive refractive index of the high refractive index layer 3, one or more dielectric layers 5 are provided between the high refractive index layer 3 and the light-transmitting layer 1 in the fingerprint detection structure. The dielectric layer 5 has a preset refractive index and / or thickness, and the dielectric layer 5 is used to increase the clarity of the biometric feature image obtained by the photosensitive element compared to not providing the dielectric layer 5.

[0015] In an implementable manner, a dielectric layer 5 is disposed between the high refractive index layer 3 and the light-transmitting layer 1, and the refractive index of the dielectric layer 5 is less than that of the high refractive index layer 3 and greater than that of the light-transmitting layer 1.

[0016] In an implementable manner, multiple dielectric layers 5 are disposed between the high refractive index layer 3 and the light-transmitting layer 1. The refractive index of each dielectric layer 5 is less than that of the high refractive index layer 3 and greater than that of the light-transmitting layer 1. From the side close to the light-transmitting layer 1 to the side close to the high refractive index layer 3, the refractive indices of the dielectric layers 5 increase in sequence.

[0017] Interference addition can occur between the reflected lights on the upper and lower surfaces of the high refractive index layer 3, so that under the condition of the same incident light intensity, the reflected light intensity from the fingerprint valley area is greater, thereby obtaining a clearer fingerprint image.

[0018] In an implementable manner, the thickness of the high refractive index layer is 1 / 4 of the wavelength of light in the high refractive index layer.

[0019] However, the above-mentioned high refractive index layer will cause color shift of the display screen. Moreover, if the incident light wavelength is not fixed, for example, in the case of natural light, which is broadband light, the high refractive index layer 3 with a gradually changing refractive index only has a good effect on the incident light within a certain wavelength range, while the other wavelength components in the incident light have a poor effect. If the high refractive index layer 3 includes multiple refractive film sub-layers with different refractive indices and different thicknesses, the effect of enhancing the reflected light can be achieved for broadband incident light.

[0020] Therefore, multiple first dielectric layers 6 and multiple second dielectric layers 7 are disposed between the high refractive index layer 3 and the light-transmitting layer 1 of the fingerprint detection structure. The refractive index of the first dielectric layer 6 is different from that of the second dielectric layer 7, and the first dielectric layer 6 and the second dielectric layer 7 are alternately arranged, so that the first dielectric layer 6 and the second dielectric layer 7 can increase the intensity of the light transmitted to the high refractive index layer for multiple monochromatic lights in a beam containing multiple wavelengths.

[0021] Optionally, the thicknesses of the multiple first dielectric layers 6 are different.

[0022] Optionally, in order to prevent water stains, oil stains and other stains from remaining on the surface of the display screen after being touched by a finger, an AF layer (Anti-Fingerprint layer) for waterproofing and oil-proofing is provided on the surface of the high refractive index layer far from the light-transmitting layer, and the AF layer is attached to the high refractive index layer.

[0023] The biometric detection structure provided by this application includes a light-transmitting layer. A light source and a photosensitive element are arranged on one side of the light-transmitting layer, and a high-refractive-index layer is arranged on the other side of the light-transmitting layer. By using the original light source of the display screen and the light-transmitting layer, the light source necessary for optical detection is combined with the light source of the display screen itself, and a high-refractive-index layer is arranged on the original glass layer. Without affecting the screen display performance, fingerprint detection is innovatively realized, and the detection effect is enhanced by arranging a dielectric layer between the light-transmitting layer and the high-refractive-index layer, realizing the compatibility between the display screen of the electronic device and the fingerprint recognition detection system.

[0024] This application also provides a manufacturing method for an optical structure for biometric detection. The method includes:

[0025] Prepare a light-transmitting layer 1, and arrange a light source 4 and a photosensitive element 2 on one side of the light-transmitting layer 1;

[0026] Prepare a high-refractive-index layer 3 on the surface of the other side of the light-transmitting layer 1. The refractive index of the high-refractive-index layer 3 is greater than that of the light-transmitting layer 1. During detection, the biometric feature is in contact with the high-refractive-index layer.

[0027] Optionally, the optical structure is used for a display screen. The light-transmitting layer 1 is the display screen glass, and the light source 4 is the display screen light source.

[0028] Optionally, the thickness of the high-refractive-index layer 3 is 1 / 4 of the wavelength of the light source light in the high-refractive-index layer.

[0029] Optionally, before preparing the high-refractive-index layer 3, a dielectric layer 5 can also be prepared on the surface of the light-transmitting layer 1 on the same side as the high-refractive-index layer 3. The refractive index of the dielectric layer 5 is greater than that of the light-transmitting layer 1 and less than that of the high-refractive-index layer 3.

[0030] Optionally, the adjacent two layers among the light-transmitting layer 1, the dielectric layer 5, and the high-refractive-index layer 3 are bonded to each other.

[0031] For each layer of the dielectric layer, the refractive index increases sequentially from the side close to the light-transmitting layer 1 to the side close to the high-refractive-index layer 3.

[0032] Alternatively, before preparing the high-refractive-index layer 3, a plurality of first dielectric layers 6 and a plurality of second dielectric layers 7 can also be prepared on the surface of the light-transmitting layer 1 on the same side as the high-refractive-index layer 3. The refractive index of the first dielectric layer 6 is different from that of the second dielectric layer 7, and the first dielectric layer 6 and the second dielectric layer 7 are arranged alternately, so that the first dielectric layer 6 and the second dielectric layer 7 can increase the intensity of the light transmitted to the high-refractive-index layer for a variety of monochromatic lights in a light beam containing a variety of wavelengths.

[0033] Optionally, two adjacent layers among the light-transmitting layer 1, the first dielectric layer 6, the second dielectric layer 7, and the high-refractive-index layer 3 are bonded to each other.

[0034] Optionally, the thicknesses of multiple first dielectric layers 6 are different.

[0035] In this application, the method for preparing the high-refractive-index layer 3, the dielectric layer 5, the first dielectric layer 6, or the second dielectric layer 7 on the surface of the light-transmitting layer 1 can be any method for coating a film on the surface of glass in the prior art, such as vacuum coating, magnetron sputtering coating, etc.

[0036] In this application, the optical structure for biometric detection is the aforementioned biometric detection structure.

[0037] The manufacturing method provided in this application is simple and easy to implement, and can be achieved by continuing to coat a film on the basis of the original structure of the display screen of the electronic device. Description of the Drawings

[0038] Figure 1 It is a schematic structural diagram of a display screen in the prior art;

[0039] Figure 2 Shows Figure 1 A schematic diagram of realizing fingerprint detection on the shown display screen;

[0040] Figure 3 It is a schematic structural diagram of Embodiment 1 of this application;

[0041] Figure 4 It is a fingerprint image detected by directly contacting a finger with the display screen for a display screen based on the prior art;

[0042] Figure 5 It is a fingerprint image detected when a finger contacts the display screen through the high-refractive-index layer by applying the technical solution proposed in this application;

[0043] Figure 6 It is a schematic structural diagram of Embodiment 2 of this application;

[0044] Figure 7 It is a schematic detection structure diagram of Embodiment 3 of this application.

[0045] Description of the Reference Numerals

[0046] 1 - Light-transmitting layer, 2 - Photosensitive element, 3 - High-refractive-index layer, 4 - Light source, 5 - Dielectric, 6 - First dielectric layer, 7 - Second dielectric layer, 8 - Anti-fingerprint film layer, 91 - Fingerprint ridge, 92 - Fingerprint valley, 93 - Air layer. Detailed Embodiments

[0047] Before specifically introducing the technical solution of the present application, the basic formulas of light reflection and transmission are first introduced. If the incident light is incident from a first medium with a refractive index of n1 to a second medium with a refractive index of n2, part of the light passes through the second medium, which is called the transmitted light, and the other part of the light is reflected at the interface between the first medium and the second medium, which is called the reflected light. R It can be calculated according to the following formula (1):

[0048] I R =(n1-n2) 2 / (n1+n2) 2 Formula (1)

[0049] Without considering the absorption of the medium, the transmittance of the incident light is I T It can be calculated according to the following formula (2):

[0050] I T =1-I R Formula (2)

[0051] Obviously, it can be seen from the above formula (1) and formula (2) that the closer the values ​​of n1 and n2 are, the higher the transmittance and the lower the reflectance of the incident light when it is emitted from the first medium to the second medium.

[0052] The following describes the technical solution of the present invention by taking fingerprint detection as an example.

[0053] Figure 1 The schematic diagram of the structure of a display screen in the prior art includes a light source 4 and a light-transmitting layer 1, wherein the light-transmitting layer can be a glass layer. The principle of displaying content on this display screen is that the light L emitted by the light source passes through the glass layer, and part of the light L 1 It is transmitted through the glass layer into the human eye, so that people can see the display content on the screen. It is worth noting that since this light source is the display screen itself, rather than natural light sources such as sunlight, it is also called display screen light source.

[0054] It is worth noting that the above introduction to display technology is preliminary and principle-based. In reality, display technology may also include various changes, such as OLED (Organic Light-Emitting Diode) light-emitting layer, touch layer, etc.

[0055] The display screen light source described in the present application can be any display screen light source in the prior art, such as a light-emitting layer, a pixel, etc.

[0056] Figure 2 Shown in Figure 1Schematic diagram of implementing fingerprint detection on the display screen shown. As Figure 2 shown, since there are fingerprint ridges 91 and fingerprint valleys 92 with different heights on the finger, when the finger touches the surface of the glass layer, the fingerprint ridges 91 can fit with the glass layer, while there is an air layer 93 between the fingerprint valleys 92 and the glass layer. Generally, the refractive index of the fingerprint ridge is between 1.4 and 1.45, while the refractive index of air is 1.0. Due to the different refractive indices of the fingerprint ridge and air, according to the above formulas (1) and (2), it can be known that the intensity of the reflected light formed at the interface between the glass layer and the fingerprint ridge or air layer by the light emitted from the light source will also be different. As Figure 2 shown, the side of the glass layer in contact with the finger is denoted as the upper surface of the glass layer, and the reflected light from the fingerprint ridge is L 2 , and the reflected light from the air (which is also the position where the fingerprint valley is located) is denoted as L 3 . The photosensitive element (sensor) arranged on the side of the light source receives the reflected light L 2 and L 3 . After that, the fingerprint ridges and the air layer can be identified according to the different intensities of L 2 and L 3 , that is, the positions where the fingerprint ridges and fingerprint valleys are located are identified, and thus the fingerprint is identified.

[0057] Obviously, the greater the intensity difference between L 2 and L 3 , the clearer the identified fingerprint. At the same time, due to the existence of ambient light, this ambient light has an interference effect on fingerprint identification. Therefore, the greater the intensity of the reflected light at the positions where the fingerprint ridges and fingerprint valleys are located, the stronger the anti-interference ability, and thus the clearer the obtained fingerprint image. In the display, the ambient light may include the scattered light of the display screen light source, the diffuse reflection or total reflection light at certain interfaces, and even include some external light, such as sunlight in the natural environment, etc.

[0058] The clarity D is used to measure the clarity of the fingerprint image, and the clarity D can be calculated according to the following formula (3):

[0059] D = I Rvallry - I Rridgr (Formula (3))

[0060] Among them, I Rvalley is the light intensity of the reflected light from the fingerprint valley under the unit light source, that is, the normalized L 2 , and I Rridge is the light intensity of the reflected light from the fingerprint ridge under the unit light source, that is, the normalized L 3 .

[0061] The greater the clarity D, the clearer the fingerprint image is considered.

[0062] To obtain a clearer fingerprint image, a direct idea is to increase the intensity of the light source. However, for a display screen, there is an upper limit to the light source intensity. Moreover, the inventors of the present application found that a stronger light source means stronger scattered light interference, that is, stronger ambient light, which will also cause stronger interference to the fingerprint image, resulting in no obvious improvement in the clarity of the obtained fingerprint image. Therefore, using the difference between L under the unitized light source and L 2 and L 3 can better reflect the clarity.

[0063] In the prior art, the refractive index of the display screen glass layer is usually between 1.4 and 1.7. Let's assume the refractive index of the glass layer is 1.5, which is the most common refractive index of the glass layer. If the finger directly contacts the display screen in the prior art, that is Figure 2 the situation shown, taking the refractive index of the finger as 1.45, according to the above formula (1), it can be calculated that:

[0064] I Rvalley1 =(n glass -n air ) 2 / (n glass +n air ) 2 =(1.5 - 1) 2 / (1.5 + 1) 2 = 0.040

[0065] I Rridge1 =(n glass -n skin ) 2 / (n glass +n skin ) 2 =(1.5 - 1.45) 2 / (1.5 + 1.45) 2 = 0.00028

[0066] Among them, n glass is the glass refractive index, and n air is the air refractive index.

[0067] Thus, according to formula (3), it can be calculated that:

[0068] D 1 = I Rvalley1 - I Rridge1 = 0.040 - 0.00028 = 0.03972

[0069] It can be seen that this value is relatively small, that is to say, in the prior art, it is impossible to obtain a clear fingerprint image completely using the display screen in the prior art without affecting the display performance of the display screen.

[0070] To improve clarity D, the present application proposes an optical detection structure, which can be used for biometric detection, and the biometrics include fingerprints and / or palm prints. Figure 3 As shown in the schematic structural diagram of Embodiment 1 of the present application, the detection structure includes a light-transmitting layer 1, a light source 4 (source) and a photosensitive element 2 (sensor) disposed on one side of the light-transmitting layer 1, and a high-refractive-index layer 3 disposed on the other side of the light-transmitting layer 1. In this embodiment, the light-transmitting layer is attached to the high-refractive-index layer. The high-refractive-index layer can be disposed on the light-transmitting layer by means of coating.

[0071] Denote the surface of the high-refractive-index layer away from the light-transmitting layer as the upper surface of the high-refractive-index layer. When performing fingerprint detection, the finger touches the upper surface of the high-refractive-index layer. The light emitted by the light source 4 passes through the light-transmitting layer 1 and the high-refractive-index layer 3, and is reflected and transmitted on the upper surface of the high-refractive-index layer. Similar to the situation when the finger touches the upper surface of the glass layer in the above text, since there are fingerprint ridges and valleys of different heights on the finger, the fingerprint ridges will contact the high-refractive-index layer, while there is an air layer between the fingerprint valleys and the high-refractive-index layer. Since the refractive index of the fingerprint ridges is different from that of the air layer, the intensity of the light reflected from the upper surface of the high-refractive-index layer will also be different, that is Figure 3 L in 2 and L 3 have different intensities. The photosensitive element (sensor) disposed on one side of the light source receives the reflected light L 2 and L 3 After that, the fingerprint ridges and the air layer can be identified according to the different intensities of L 2 and L 3 , that is, the positions where the fingerprint ridges and the fingerprint valleys are located are identified, and thus the fingerprint is identified.

[0072] In this embodiment, the light source can be a display screen light source, the light-transmitting layer can be a display screen glass layer (glass), and the high-refractive-index layer can be plated on the glass layer by means of coating. Thus, this embodiment can be well compatible with the existing display technology without significant modification to the existing display screen.

[0073] Without loss of generality, zirconia is selected as the material of the high-refractive-index layer in this embodiment. Zirconia has the advantages of high light transmittance, high refractive index, high hardness and high stability during the coating process, and is suitable as the material of the high-refractive-index layer described in the present application.

[0074] The refractive index of zirconia is 1.9. Substituting this refractive index into formulas (1) and (2) and considering the transmission of light from the glass layer into the high-refractive-index layer, it can be calculated that:

[0075] I Rvalley2

[0076] =(1-(n coating -n glass )) 2 / (n glass +n coating )) 2 )×(n coating -n air ) 2 / (n coating +n air )) 2

[0077] =(1-(1.9 - 1.5) 2 / (1.5 + 1.9) 2 )×(1.9 - 1) 2 / (1.9 + 1) 2 =0.095

[0078] I Rridge2

[0079] =(1-(n coating -n glass )) 2 / (n glass +n coating )) 2 )×(n coating -n skin )) 2 / (n coating +n skin )) 2

[0080] =(1-(1.9 - 1.5) 2 / (1.5 + 1.9) 2 )×(1.9 - 1.45) 2 / (1.9 + 1.45) 2 =0.0178

[0081] where n coating is the refractive index of the high refractive index layer, and n skin is the refractive index of the biometric feature to be detected.

[0082] According to formula (3), it can be calculated that:

[0083] D 2 =I Rvalley2 -I Rridge2 =0.095 - 0.0178 = 0.0772

[0084] The value of D 2 (0.0772) is greater than the D 1The value (0.0392) shows that the high refractive index layer with a refractive index higher than that of the light-transmitting layer can improve the clarity of the fingerprint image.

[0085] Figure 4 is a display screen based on the prior art, and the fingerprint image is detected by directly contacting the finger with the display screen. Figure 5 employs the technical solution proposed in this application. The finger contacts the display screen through the high refractive index layer, and the detected fingerprint image. Obviously, compared with Figure 4 compared Figure 5 has higher clarity, and the experimental results illustrate the superiority of the technical solution of this application.

[0086] The applicant found that compared with the fingerprint image directly obtained by using the display screen in the prior art, if the refractive index of the high refractive index layer 3 is greater than 1.5 and less than 2.6, the obtained fingerprint image has better clarity and has a lower impact on the performance of the display screen. If the refractive index of the high refractive index layer 3 is less than 1.5, the clarity of the obtained fingerprint image is not much different from that of the fingerprint image directly obtained by using the display screen in the prior art; and if the refractive index of the high refractive index layer 3 is greater than 2.6, when no fingerprint is detected, more light will be reflected by the upper surface of the high refractive index layer, thereby reducing the light transmitted through the upper surface of the high refractive index layer and entering the human eye, and further making the display screen darker and reducing the performance of the display screen. Moreover, materials with a refractive index greater than 2.6 are also difficult to manufacture industrially or difficult to stably adhere to the display screen glass.

[0087] In addition to zirconia, metal oxides such as titanium oxide, aluminum oxide, thallium oxide, or mixtures mainly composed of metal oxides are also suitable for manufacturing the high refractive index layer. The high refractive index layer is often prepared by a vapor deposition process, and its thickness is usually between 45 nm and 300 nm.

[0088] The applicant further found that when light enters the high refractive index layer from the glass layer, more reflections will occur, thereby reducing the intensity of the light entering the high refractive index layer and reaching the upper surface of the high refractive index layer, and further reducing the intensity of the reflected light on the upper surface of the high refractive index layer, resulting in a decrease in the clarity of the fingerprint image. To solve this problem, the technical solution of Embodiment 2 of this application is further proposed.

[0089] Figure 6 is a schematic structural diagram of Embodiment 2 of this application, and the optical path diagram is also shown in Figure 6 below. In combination with Figure 6Introduce Embodiment 2 of the present application. The biggest difference between this embodiment and Embodiment 1 is that in this embodiment, one or more dielectric layers 5 are further included between the high refractive index layer 3 and the light transmissive layer 1. For example, it includes N dielectric layers, where the bottom dielectric layer is in contact with the light transmissive layer, and its refractive index is greater than that of the light transmissive layer; the top dielectric layer is located below the high refractive index layer, in contact with the high refractive index layer, and its refractive index is less than that of the high refractive index layer; the high refractive index layer is located above the top dielectric layer, and the finger contacts the high refractive index layer 3 when detecting a fingerprint. From the side close to the light transmissive layer 1 to the side close to the high refractive index layer 3, the refractive indices of the dielectric layers 5 increase in sequence.

[0090] For the convenience of description, as Figure 6 shown, let's assume N = 2 for example, that is, there are also a bottom dielectric layer 5 and a top dielectric layer 5 between the high refractive index layer and the light transmissive layer, and assume that the refractive index of the light transmissive layer 1 is 1.5 and the refractive index of the high refractive index layer is 1.9.

[0091] Then, through material selection, it is made that:

[0092] The refractive index of the bottom dielectric layer = 1.7,

[0093] The refractive index of the top dielectric layer is 1.8,

[0094] Without considering volatility, but considering light transmission between adjacent layers:

[0095] Calculate the reflections of adjacent layers from the glass layer to the high refractive index layer in sequence:

[0096] I 1 =(1.7 - 1.5) 2 / (1.7 + 1.5) 2 =0.0039

[0097] I 2 =(1 - 0.0039)(1.8 - 1.7) 2 / (1.7 + 1.8) 2 =0.00081

[0098] I 3 =(1 - 0.0039 - 0.00081)(1.9 - 1.8) 2 / (1.8 + 1.9) 2 =0.00073

[0099] I Rvalley ′=(1 - 0.0039 - 0.00081 - 0.00073)(1 - 1.9) 2 / (1 + 1.9) 2 =0.0958

[0100] I Rridge ′ = (1 - 0.0039 - 0.00081 - 0.00073)(1.45 - 1.9) 2 / (1.45 + 1.9) 2 = 0.0179

[0101] Among them, I 1 represents the reflection between the light-transmitting layer and the first dielectric layer; I 2 represents the reflection between the first dielectric layer and the second dielectric layer; I 3 represents the reflection between the second dielectric layer and the high-refractive-index layer; I Rvalley ′ represents the reflection between the high-refractive-index layer and the fingerprint valley; I Rridge ′ represents the reflection between the high-refractive-index layer and the fingerprint ridge.

[0102] According to formula (3), it can be obtained that:

[0103] D′ = I′ Rvalley - I′ Rridge = 0.0778 > D 2

[0104] Thus, it can be seen that when the refractive indices of the light-transmitting layer and the high-refractive-index layer remain unchanged (the refractive index of the light-transmitting layer in both Example 1 and Example 2 is 1.5, and the refractive index of the high-refractive-index layer is 1.9), setting a multi-layer dielectric layer with a gradually increasing refractive index does improve the clarity of the fingerprint image. By setting a dielectric layer between the high-refractive-index layer and the light-transmitting layer, when the light emitted by the light source arranged on one side of the light-transmitting layer travels from the light-transmitting layer to the high-refractive-index layer, the light reflected on the upper surface of the light-transmitting layer decreases, and the transmitted light increases. As a result, more light reaches the upper surface of the high-refractive-index layer, increasing the intensity of the reflected light formed on the upper surface of the high-refractive-index layer, thereby improving the clarity of the fingerprint image.

[0105] If only one dielectric layer is provided between the high-refractive-index layer 3 and the light-transmitting layer 1, as long as the refractive index of this dielectric layer is less than the refractive index of the high-refractive-index layer and greater than the refractive index of the light-transmitting layer, it can also achieve the effect of increasing the image clarity. The specific proof process can refer to the foregoing case where multiple dielectric layers 5 are provided between the high-refractive-index layer 3 and the light-transmitting layer 1, which will not be elaborated here.

[0106] Similar to Example 1, in this embodiment, the light source can also be the display screen light source, the light-transmitting layer can also be the display screen glass layer (glass), and the dielectric layer and the high-refractive-index layer can be sequentially deposited on the glass layer by means of coating. Thus, this embodiment can be well compatible with the existing display technology without significant modification to the existing display screen.

[0107] Furthermore, the present inventors have found that the intensity of the reflected light can be enhanced by utilizing the wave nature of light and making the light interfere coherently.

[0108] Specifically, for a detection structure that only has a single high-refractive-index layer and does not include a dielectric layer, the thickness of the high-refractive-index layer can be set to 1 / 4 of the wavelength of the light source light in the high-refractive-index layer, so that the reflected light formed on the upper surface of the high-refractive-index layer and the reflected light formed on the upper surface of the glass layer interfere and add up, thereby increasing the reflected light from the fingerprint.

[0109] The present inventors have found that using the above-mentioned high-refractive-index layer will cause color shift in the display screen. Moreover, if the wavelength of the incident light is not fixed, such as broadband light like natural light, the above method will only have a good effect on a part of the incident light, and the other wavelength components in the incident light will have a poor effect.

[0110] To solve the above problems, the present application further proposes to provide multiple dielectric layers with different thicknesses and refractive indices between the high-refractive-index layer and the glass layer. In one feasible way, as Figure 7 shown, multiple first dielectric layers 6 and multiple second dielectric layers 7 are provided between the high-refractive-index layer 3 and the light-transmitting layer 1. The refractive index of the first dielectric layer 6 is different from that of the second dielectric layer 7, and the first dielectric layer 6 and the second dielectric layer 7 are arranged alternately, so that both the first dielectric layer 6 and the second dielectric layer 7 can increase the intensity of the light transmitted to the high-refractive-index layer for multiple monochromatic lights in a light beam containing multiple wavelengths. For example, if the refractive index of the light-transmitting layer is 1.5, the refractive index of the first dielectric layer is 1.6, the refractive index of the second dielectric layer is 1.8, and the refractive index of the high-refractive-index layer is 1.9, then multiple first dielectric layers and second dielectric layers can be alternately arranged between the light-transmitting layer and the high-refractive-index layer, such as alternately arranging two first dielectric layers and two second dielectric layers. Specifically, if two first dielectric layers and two second dielectric layers are alternately arranged, the refractive indices of each layer from the light-transmitting layer to the high-refractive-index layer can be set to 1.5, 1.6, 1.8, 1.6, 1.8, 1.9 in sequence; if three first dielectric layers and three second dielectric layers are alternately arranged, the refractive indices of each layer from the light-transmitting layer to the high-refractive-index layer can be set to 1.5, 1.8, 1.6, 1.8, 1.6, 1.8, 1.6, 1.9 in sequence. By setting the thickness of each first dielectric layer and second dielectric layer, the intensity of the light transmitted to the upper surface of the high-refractive-index layer can be enhanced in a broad spectral range, thereby enhancing the intensity of the reflected light of the fingerprint.

[0111] The thickness and refractive index of each layer can be specifically set based on the principle of wave optics, and the principle of wave optics can refer to the design and calculation of optical antireflection and antireflection multilayer films [J], Materials Science, 2017, 7(1): 78-87.

[0112] Optionally, for the solutions in either Embodiment 1 or Embodiment 2, an AF (Anti-Fingerprint) film, i.e., an anti-fingerprint film, can be coated on the upper surface of the high refractive index layer to enable the display screen to have functions such as water and oil resistance. The thickness of this AF film is selected to be very thin, between 1 nm and 20 nm. This thickness is much smaller than the visible light wavelength, so it will not have an obvious impact on the optical properties of the entire implementation scheme. When detecting fingerprints, the finger is placed on the high refractive index layer. Although the finger is in contact with the AF film at this time, from the perspective of optical properties, it can still be considered that the finger is in contact with the high refractive index layer.

[0113] In the prior art, there is no technical solution that can detect fingerprints by touching the screen with a finger while not affecting the display performance of the finger-touching area. By combining the light source necessary for optical detection with the display screen's own light source and setting a high refractive index layer on the original glass layer, the present application innovatively realizes fingerprint detection without affecting the screen display performance, solves the long-standing problem in this field, and has great innovation significance and economic value. Moreover, this detection structure can be used not only on display screens but also on other optical fingerprint detection instruments. By coating a high refractive index medium on the finger-contact interface, the clarity of the reflected light from the fingerprint can be increased.

[0114] The present application also provides a manufacturing method for an optical structure for biometric detection, and the method includes:

[0115] Prepare a light-transmitting layer 1, and set a light source 4 and a photosensitive element 2 on one side of the light-transmitting layer 1;

[0116] Prepare a high refractive index layer 3 on the surface of the other side of the light-transmitting layer 1. The refractive index of the high refractive index layer 3 is greater than that of the light-transmitting layer 1. During detection, the biometric feature is in contact with the high refractive index layer.

[0117] Optionally, the optical structure is used for a display screen, the light-transmitting layer 1 is a display screen glass, and the light source 4 is a display screen light source.

[0118] Optionally, the thickness of the high refractive index layer 3 is 1 / 4 of the wavelength of the light source light in the high refractive index layer.

[0119] Optionally, before preparing the high refractive index layer 3, a dielectric layer 5 can also be prepared on the surface of the light-transmitting layer 1 on the same side as the high refractive index layer 3 to be prepared. The refractive index of the dielectric layer 5 is greater than that of the light-transmitting layer and less than that of the high refractive index layer 3.

[0120] Optionally, the adjacent two layers among the light-transmitting layer 1, the dielectric layer 5, and the high refractive index layer 3 are adhered to each other.

[0121] The refractive index of each of the dielectric layers increases successively from the side close to the light-transmitting layer 1 to the side close to the high-refractive-index layer 3.

[0122] Alternatively, before preparing the high-refractive-index layer 3, a plurality of first dielectric layers 6 and a plurality of second dielectric layers 7 may also be prepared on the surface of the light-transmitting layer 1 on the same side as the high-refractive-index layer 3. The refractive index of the first dielectric layer 6 is different from that of the second dielectric layer 7, and the first dielectric layer 6 and the second dielectric layer 7 are alternately arranged, so that the first dielectric layer 6 and the second dielectric layer 7 can increase the intensity of light transmitted to the high-refractive-index layer for a variety of monochromatic lights in a light beam containing a variety of wavelengths.

[0123] Optionally, two adjacent layers among the light-transmitting layer 1, the first dielectric layer 6, the second dielectric layer 7, and the high-refractive-index layer 3 are bonded to each other.

[0124] Optionally, the thicknesses of the plurality of first dielectric layers 6 are different.

[0125] In the present application, the method for preparing the high-refractive-index layer 3, the dielectric layer 5, the first dielectric layer 6, or the second dielectric layer 7 on the surface of the other side of the light-transmitting layer 1 may be any method in the prior art for coating a film on the surface of glass, such as vacuum coating, magnetron sputtering coating, etc.

[0126] The present application has been described in detail above in combination with specific embodiments and exemplary examples, but these descriptions should not be construed as limiting the present application. Those skilled in the art understand that without departing from the spirit and scope of the present application, various equivalent substitutions, modifications, or improvements can be made to the technical solutions and their implementation manners of the present application, and these all fall within the scope of the present application. The protection scope of the present application is subject to the appended claims.

Claims

1. A biometric detection structure, characterized in that, the detection structure includes a light-transmitting layer (1), a photosensitive element (2) is arranged on one side of the light-transmitting layer (1), a high-refractive-index layer (3) is arranged on the other side of the light-transmitting layer (1), and the refractive index of the high-refractive-index layer (3) is greater than that of the light-transmitting layer (1). During detection, the biometric feature is in contact with the high-refractive-index layer; one or more dielectric layers (5) are arranged between the high-refractive-index layer (3) and the light-transmitting layer (1), and the dielectric layer (5) has a preset refractive index and / or thickness, so that the clarity of the biometric image obtained by the photosensitive element is increased compared with the case where the dielectric layer (5) is not provided; a dielectric layer (5) is arranged between the high-refractive-index layer (3) and the light-transmitting layer (1), and the refractive index of the dielectric layer (5) is less than that of the high-refractive-index layer (3) and greater than that of the light-transmitting layer (1); multiple dielectric layers (5) are arranged between the high-refractive-index layer (3) and the light-transmitting layer (1), and the refractive index of each dielectric layer (5) is less than that of the high-refractive-index layer (3) and greater than that of the light-transmitting layer (1). From the side close to the light-transmitting layer (1) to the side close to the high-refractive-index layer (3), the refractive indices of the dielectric layers (5) increase in sequence; multiple first dielectric layers (6) and multiple second dielectric layers (7) are arranged between the high-refractive-index layer (3) and the light-transmitting layer (1), the refractive indices of the first dielectric layer (6) and the second dielectric layer (7) are different, and the first dielectric layer (6) and the second dielectric layer (7) are arranged alternately, so that the first dielectric layer (6) and the second dielectric layer (7) can increase the intensity of the light transmitted to the high-refractive-index layer for multiple monochromatic lights in a light beam containing multiple wavelengths.

2. The detection structure according to claim 1, characterized in that, the detection structure further includes a light source (4), and the light source (4) and the photosensitive element (2) are arranged on the same side of the light-transmitting layer (1).

3. The detection structure according to claim 2, characterized in that, the light source (4) is a display screen light source, and the light-transmitting layer (1) is a display screen glass.

4. The detection structure according to claim 1, characterized in that, the high-refractive-index layer (3) is attached to the light-transmitting layer (1).

5. The detection structure according to claim 1, characterized in that, an anti-fingerprint film layer (8) is plated on the surface of the high-refractive-index layer (3) away from the light-transmitting layer (1).

6. A manufacturing method for a biometric detection structure, which is applied to the biometric detection structure according to any one of claims 1-5, characterized in that, the method includes: preparing a light-transmitting layer (1), and arranging a light source (4) and a photosensitive element (2) on one side of the light-transmitting layer (1); preparing a high-refractive-index layer (3) on the surface of the other side of the light-transmitting layer (1), and the refractive index of the high-refractive-index layer (3) is greater than that of the light-transmitting layer (1). During detection, the biometric feature is in contact with the high-refractive-index layer.

7. The method according to claim 6, wherein, the biometric detection structure is for a display screen, the light-transmitting layer (1) is display screen glass, and the light source (4) is a display screen light source.

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