Ultrasound fingerprint sensor and ultrasound fingerprint sensing method

Abstract

An ultrasonic fingerprint sensor and ultrasonic fingerprint sensing method, comprising: generating a first ultrasonic wave having a first frequency; receiving a first signal resulting from reflections of the first ultrasonic wave from each of ridges and valleys of a fingerprint; generating a first image based on the first signal; comparing the first image to a registered reference image to produce a match score; and in response to the match score being less than a threshold, generating a second image using a second frequency.

Description

[0001] Cross-references to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2020-0084598, filed on July 9, 2020, with the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. Technical Field

[0003] Aspects of some exemplary embodiments of this disclosure relate to an ultrasonic fingerprint sensor and an ultrasonic fingerprint sensing method using the ultrasonic fingerprint sensor. Background Technology

[0004] Display devices can be used with or incorporated into various electronic devices such as smartphones, tablets, laptops, monitors, and televisions (TVs). With the latest advancements in mobile communication technology, the use of portable electronic devices such as smartphones, tablets, and laptops has increased dramatically. Portable electronic devices contain personal information such as contacts, call logs, messages, photos, notes, user web browsing information, location information, and financial information. To protect the personal information on portable electronic devices, authentication can be performed using fingerprint authentication, which identifies the user's biometric information. In this case, the display device can include a fingerprint sensor for fingerprint authentication.

[0005] Fingerprint sensors can be implemented as optical sensors, ultrasonic sensors, or capacitive sensors, etc.

[0006] In the case of an ultrasonic fingerprint sensor, a fingerprint image can be generated, but the fingerprint image can vary depending on the environment in which the fingerprint is exposed (e.g., temperature and humidity).

[0007] The information disclosed in this background section is only intended to enhance the understanding of the background, and therefore, the information discussed in this background section does not necessarily constitute prior art. Summary of the Invention

[0008] Aspects of some exemplary embodiments of this disclosure may include an ultrasonic fingerprint sensing method capable of improving recognition accuracy in various environments.

[0009] Aspects of some exemplary embodiments of this disclosure may also include an ultrasonic fingerprint sensor with relatively improved recognition accuracy in various environments.

[0010] However, the aspects of embodiments according to this disclosure are not limited to those set forth herein. These and other aspects of the disclosure will become more apparent to those skilled in the art from the following detailed description of the disclosure.

[0011] According to some example embodiments, an ultrasonic fingerprint sensing method includes: generating a first ultrasonic wave having a first frequency; receiving a first signal generated by reflections of the first ultrasonic wave from each of the ridges and valleys of a fingerprint; generating a first image based on the first signal; performing a comparison / determination on the first image and a registered reference image; and generating a second image using a second frequency if a matching score, which is the result of the comparison between the first image and the registered reference image, is determined to be less than a threshold.

[0012] According to some example embodiments, an ultrasonic fingerprint sensing method includes: generating a first ultrasonic wave having a first frequency; receiving a first signal generated by reflections of the first ultrasonic wave from each of the ridges and valleys of a fingerprint; generating a first image based on the first signal; performing a comparison / determination on the first image and a registered reference image; and performing a measurement / determination on the temperature of the fingerprint if a matching score, which is the result of the comparison between the first image and the registered reference image, is determined to be less than a threshold.

[0013] According to some example embodiments, an ultrasonic fingerprint sensor includes: an ultrasonic wave generating unit configured to generate a first ultrasonic wave having a first frequency; a receiving unit configured to receive a first signal generated by reflections of the first ultrasonic wave from each of the ridges and valleys of a fingerprint; an image generating unit configured to generate a first image based on the first signal; and a comparison / determination unit configured to perform a comparison / determination on the first image and a registered reference image; and wherein, if the comparison / determination unit determines that a matching score, as a comparison result between the first image and the registered reference image, is less than a threshold, the image generating unit further generates a second image using a second frequency.

[0014] According to some example embodiments, an ultrasonic fingerprint sensor includes: an ultrasonic wave generating unit configured to generate a first ultrasonic wave having a first frequency; a receiving unit configured to receive a first signal generated by reflections of the first ultrasonic wave from each of the ridges and valleys of a fingerprint; an image generating unit configured to generate a first image based on the first signal; and a comparison / determination unit configured to perform a comparison / determination on the first image and a registered reference image; and wherein the temperature measurement / determination unit is configured to perform a measurement / determination on the temperature of the fingerprint in response to a matching score determined by the comparison / determination unit as a comparison result between the first image and the registered reference image being less than a threshold.

[0015] According to some example embodiments of this disclosure, an ultrasonic fingerprint sensing method and an ultrasonic fingerprint sensor that can improve recognition accuracy in various environments can be provided.

[0016] The features of embodiments according to this disclosure are not limited to those described above, and various other features are included in embodiments according to this disclosure. Attached Figure Description

[0017] The above and other aspects and features of embodiments of the present disclosure will become more apparent from the accompanying drawings, which describe in more detail aspects of some exemplary embodiments of the present disclosure, wherein:

[0018] Figure 1 This is a flowchart illustrating an ultrasonic fingerprint sensing method according to some example embodiments;

[0019] Figure 2 This is a perspective view showing a display device equipped with an ultrasonic fingerprint sensor for ultrasonic fingerprint sensing according to some example embodiments;

[0020] Figure 3 This is a flowchart illustrating the registration of a reference image in an ultrasonic fingerprint sensing method according to some example embodiments, and the operation of comparing the image with the registered reference image to make a determination;

[0021] Figure 4 It is along Figure 2 The cross-sectional view taken by line I-I' also shows a schematic diagram of the propagation path of the first ultrasonic wave and the first signal;

[0022] Figure 5 yes Figure 4 A magnified view of region A;

[0023] Figure 6 Photographs of fingerprint images taken in a first and second environment using a first ultrasonic wave, according to some example embodiments, are shown.

[0024] Figure 7 This is a schematic diagram illustrating the propagation path of a second ultrasonic wave and a second signal according to some example embodiments;

[0025] Figure 8 yes Figure 7 A magnified view of region A;

[0026] Figure 9 This is a diagram illustrating a model for measuring ultrasonic wave reflection characteristics in a first and second environment, according to some example embodiments;

[0027] Figure 10 This illustrates some example embodiments in Figure 9 The curve of the reflection coefficient with respect to the air gap thickness calculated in the model;

[0028] Figure 11 Photographs of fingerprint images taken in a first and second environment using a second ultrasonic wave according to some example embodiments are shown;

[0029] Figure 12 This is a block diagram illustrating an ultrasonic fingerprint sensor according to some example embodiments;

[0030] Figure 13 and Figure 14 This is a flowchart of an ultrasonic fingerprint sensing method according to some example embodiments;

[0031] Figure 15 This is a block diagram of an ultrasonic fingerprint sensor according to some example embodiments;

[0032] Figure 16 This is a flowchart of an ultrasonic fingerprint sensing method according to some example embodiments;

[0033] Figure 17 This is a block diagram of an ultrasonic fingerprint sensor according to some example embodiments;

[0034] Figure 18 This is a flowchart of an ultrasonic fingerprint sensing method according to some example embodiments; and

[0035] Figure 19 This is a block diagram of an ultrasonic fingerprint sensor according to some example embodiments. Detailed Implementation

[0036] The specific structural and functional descriptions of the embodiments of the present invention disclosed herein are for illustrative purposes only. The present invention can be implemented in many different forms without departing from its spirit and essential features. Therefore, the embodiments of the present invention are disclosed for illustrative purposes only and should not be construed as limiting the invention. That is, the present invention is limited only by the scope of the claims and their equivalents.

[0037] It will be understood that when an element is referred to as being associated with another element, such as by being “coupled” or “connected” to another element, the element may be directly coupled or connected to the other element, or there may be an intermediate element between them. Conversely, it should be understood that when an element is referred to as being associated with another element, such as by being “directly coupled” or “directly connected” to another element, there is no intermediate element. Other expressions describing relationships between elements, such as “between,” “directly between,” “proximately to,” or “directly adjacent to,” should be interpreted in the same manner.

[0038] Throughout the specification, the same reference numerals will refer to the same or similar parts.

[0039] It will be understood that although the terms “first,” “second,” “third,” etc., may be used herein to describe various elements, components, areas, layers, and / or parts, these elements, components, areas, layers, and / or parts should not be limited by these terms. These terms are used only to distinguish one element, component, area, layer, or part from another element, component, area, layer, or part. Therefore, without departing from the teachings herein, “first element,” “first component,” “first area,” “first layer,” or “first part” discussed below may be referred to as a second element, second component, second area, second layer, or second part.

[0040] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, unless the context clearly indicates otherwise, “a,” “an,” “the,” and “at least one” do not indicate a limitation on quantity and are intended to include both the singular and the plural. For example, “element” has the same meaning as “at least one element” unless the context clearly indicates otherwise. “At least one” is not construed as limiting “a” or “an.” “Or” means “and / or.” As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. It will be further understood that when the terms “comprising” and / or “including” or “containing” and / or “having” are used in this specification, they specify the presence of the stated features, areas, integrals, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, areas, integrals, steps, operations, elements, components, and / or groups thereof.

[0041] Furthermore, relative terms such as “below” or “bottom” and “above” or “top” may be used herein to describe the relationship between one element and another as shown in the accompanying drawings. It will be understood that, in addition to the orientation depicted in the drawings, the relative terms are intended to cover different orientations of the device. For example, if the device is flipped in a drawing, an element described as being “below” the other element will subsequently be oriented to be “above” the other element. Thus, depending on the specific orientation of the drawing, the exemplary term “below” can cover both “below” and “above” orientations. Similarly, if the device is flipped in a drawing, an element described as being “below” or “under” the other element will subsequently be oriented to be “above” the other element. Thus, the exemplary terms “below” or “under” can cover both “above” and “below” orientations.

[0042] Given the measurements discussed and the errors associated with the measurement of a particular quantity (i.e., the limitations of the measurement system), as used herein, “about” or “approximately” includes the stated value and means within an acceptable range of deviation from the particular value as determined by one of ordinary skill in the art. For example, “about” may mean within one or more standard deviations, or within ±30%, ±20%, ±10%, or ±5% of the stated value.

[0043] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that, unless expressly defined herein, terms such as those defined in a general dictionary should be interpreted as having a meaning consistent with their context in the relevant field and their meaning in this disclosure, and should not be interpreted in an idealized or overly formalized sense.

[0044] This document describes aspects of some exemplary embodiments with reference to cross-sectional views of schematic diagrams as idealized embodiments. Thus, variations in the shape of the diagrams are anticipated due to factors such as manufacturing techniques and / or tolerances. Therefore, the embodiments described herein should not be construed as limited to the specific shapes of the areas shown herein, but rather include deviations in shape, for example, due to manufacturing processes. For instance, an area shown or described as flat may, for example, have rough and / or non-linear characteristics. Furthermore, sharp corners shown may be rounded. Therefore, the areas shown in the drawings are schematic in nature, and their shapes are not intended to show the precise shapes of the areas, nor are they intended to limit the scope of this claim.

[0045] In the following description, aspects of some exemplary embodiments of the invention will be described in more detail with reference to the accompanying drawings.

[0046] Figure 1This is a flowchart illustrating an ultrasonic fingerprint sensing method according to some example embodiments. Although Figure 1 Various operations according to some example embodiments are illustrated; however, the number and order of operations may vary according to some example embodiments. For example, according to some example embodiments, additional or fewer operations may exist, or the order of operations may vary, without departing from the spirit and scope of the embodiments according to this disclosure. Figure 2 This is a perspective view showing a display device equipped with an ultrasonic fingerprint sensor for ultrasonic fingerprint sensing, according to some example embodiments. Figure 3 This is a flowchart illustrating the registration of a reference image in an ultrasonic fingerprint sensing method according to some example embodiments, and the operation of comparing the image with the registered reference image to make a determination. Although Figure 3 Various operations according to some example embodiments are illustrated; however, the number and order of operations may vary according to some example embodiments. For example, according to some example embodiments, additional or fewer operations may exist, or the order of operations may vary, without departing from the spirit and scope of the embodiments according to this disclosure. Figure 4 It is along Figure 2 The cross-sectional view taken by line I-I' also shows a schematic diagram of the propagation path of the first ultrasonic wave and the first signal. Figure 5 yes Figure 4 A magnified view of region A. Figure 7 This is a schematic diagram illustrating the propagation path of a second ultrasonic wave and a second signal according to some example embodiments. Figure 8 yes Figure 7 A magnified view of region A.

[0047] Reference Figures 1 to 7 The ultrasonic fingerprint sensor 400 implements an ultrasonic fingerprint sensing method according to some example embodiments. The ultrasonic fingerprint sensor 400 is used to recognize fingerprints as biometric information for protecting personal information on the display device 10, and to authenticate whether the recognized fingerprint matches a previously captured user's fingerprint (e.g., whether it is the same as a previously captured user's fingerprint). The ultrasonic fingerprint sensor 400 can use ultrasonic waves that can have a driving frequency suitable for penetrating multiple layers to recognize fingerprints.

[0048] First, the configuration of the display device 10 equipped with the ultrasonic fingerprint sensor 400 will be described.

[0049] The display device 10 may be an organic light-emitting display device using organic light-emitting diodes, a quantum dot light-emitting display device including a quantum dot light-emitting layer, an inorganic light-emitting display device including inorganic semiconductors, or a light-emitting display device using micro light-emitting diodes (LEDs).

[0050] The display device 10 includes a display panel 100, a display driving circuit 200, a display circuit board 300, and an ultrasonic fingerprint sensor 400. The display device 10 may also include a cover window CW (see [reference needed]) disposed on the top of the display panel 100. Figure 4 Despite Figure 2 The overlay window CW is not shown, but will be referenced. Figure 4 Describes the stacked structure of the display device 10 on which the cover window CW is positioned.

[0051] In a plan view (e.g., a view orthogonal or perpendicular to the plane of the display surface of the display panel 100), the display panel 100 may be formed as a rectangle having a short side in a first direction DR1 and a long side in a second direction DR2 intersecting the first direction DR1. The corner formed by the intersection of the short side in the first direction DR1 and the long side in the second direction DR2 may be rounded to have curvature (e.g., a set or predetermined curvature). The planar shape of the display panel 100 is not limited to a rectangular shape and may be formed as another polygonal shape, a circular shape, or an elliptical shape. The display panel 100 may be formed as a flat surface, but is not limited to this according to embodiments of the present disclosure. For example, the display panel 100 may include curved portions formed at the left and right ends and having curvature (e.g., a set or predetermined curvature) or varying curvature. Additionally, the display panel 100 may be flexibly formed such that it can be twisted, bent, folded, or rolled.

[0052] Display panel 100 may include a main area MA and a sub-area SBA.

[0053] The main area MA may include a display area DA for displaying images and a non-display area NDA that serves as the outer perimeter of the display area DA. The display area DA may include display pixels for displaying images. The non-display area NDA may be defined as the area from the boundary of the display area DA to the edge of the display panel 100.

[0054] The display area DA may include a fingerprint sensing area FSA. The fingerprint sensing area FSA may correspond to the area where an ultrasonic fingerprint sensor 400 is disposed. The fingerprint sensing area FSA may be as follows: Figure 2 The diagram shows a portion of the display area DA, but embodiments of this disclosure are not limited thereto. According to some example embodiments, the fingerprint sensing area FSA may be substantially the same as the display area DA, covering the entire area of ​​the display area DA.

[0055] The sub-region SBA may protrude from one side of the main region MA in the second direction DR2. The sub-region SBA may be shorter than the main region MA in both the first direction DR1 and the second direction DR2, but the embodiments according to this disclosure are not limited thereto.

[0056] Despite Figure 2 The diagram shows an example where the sub-region SBA is extended, but the sub-region SBA can be bent, and in this case, it is arranged on the bottom surface of the display panel 100. In the case where the sub-region SBA is bent, the sub-region SBA can overlap with the main region MA in the thickness direction of the display panel 100 (e.g., the third direction DR3). The display driving circuitry 200 can be arranged within the sub-region SBA.

[0057] The display driving circuit 200 can generate signals and voltages for driving the display panel 100. The display driving circuit 200 can be formed as an integrated circuit (IC) and can be attached to the display panel 100 by a glass-on-gold (COG) method, a plastic-on-chip (COP) method, or an ultrasonic bonding method, but embodiments according to this disclosure are not limited thereto. For example, the display driving circuit 200 can be adhered to the display circuit board 300 by a thin-film-on-chip (COF) method.

[0058] The display circuit board 300 can be attached to one end of a sub-region SBA of the display panel 100 using a conductive adhesive member such as an anisotropic conductive film. As a result, the display circuit board 300 can be electrically connected to the display panel 100 and the display driving circuit 200. The display panel 100 and the display driving circuit 200 can receive digital video data, timing signals, and driving voltages via the display circuit board 300. The display circuit board 300 can be a flexible film such as a flexible printed circuit board, a printed circuit board, or a thin-film flip-chip.

[0059] The ultrasonic fingerprint sensor 400 can be arranged on the bottom surface of the display panel 100.

[0060] The ultrasonic fingerprint sensing method using the ultrasonic fingerprint sensor 400 is described below. (Refer to later...) Figure 12 The detailed configuration of the ultrasonic fingerprint sensor 400 is described.

[0061] Reference Figure 1 and Figure 4 The ultrasonic fingerprint sensor 400 generates a first ultrasonic wave UW1 with a first frequency (or driving frequency) (operation S10). Figure 4 An example scenario is shown in which a user places their finger F on the overlay window CW of the display device 10 for fingerprint authentication.

[0062] As described above, the first frequency may belong to a frequency band suitable for passing through multiple layers of the display device 10. The display panel 100 and the cover window CW may be positioned on the ultrasonic fingerprint sensor 400 of the display device 10. The cover window CW may be positioned on the display panel 100 to cover the top surface of the display panel 100. The cover window CW may be used to protect the top surface of the display panel 100. The cover window CW may be attached to the top surface of the display panel 100 using a transparent adhesive member. For example, the transparent adhesive member may be a transparent adhesive film such as an optically clear adhesive (OCA) film or a transparent adhesive resin such as an optically clear resin (OCR).

[0063] Cover window CWs can be made of transparent materials such as glass or plastic. For example, if the cover window CW is made of glass, ultra-thin glass (UTG) with a thickness equal to or less than 0.1 mm can be used. If the cover window CW is made of plastic, a transparent polyimide film can be used.

[0064] The ultrasonic fingerprint sensor 400 can be disposed on the bottom surface of the display panel 100. The ultrasonic fingerprint sensor 400 can be adhered to the bottom surface of the display panel 100 using a transparent adhesive component.

[0065] In this configuration, multiple layers may include a display panel 100, a transparent adhesive member, and a cover window (CW). A first frequency may belong to a frequency band optimized for transmission through the display panel 100, the transparent adhesive member, and the cover window (CW).

[0066] Finger F may include a fingerprint facing the overlay window CW. The fingerprint of finger F may include both recessed and raised portions. For example... Figure 4 As shown, the recessed and raised portions of the fingerprint can be arranged repeatedly. In a portion comprising at least one recessed portion and one raised portion taken from the repeated recessed and raised portions, the raised portion can be referred to as a ridge RID, and the recessed portion can be referred to as a valley VAL. The ridge RID of the fingerprint can be closer to the overlay window CW than the valley VAL.

[0067] The first ultrasonic wave UW1 irradiates the ridge RID and valley VAL of the fingerprint and is subsequently reflected by the ridge RID and valley VAL. The first ultrasonic wave UW1 irradiating the ridge RID can penetrate the display panel 100, the transparent adhesive member, and the cover window CW to reach the ridge RID. Figure 4 As shown, because the ridge RID directly contacts the cover window CW, there may be no gap between the ridge RID and the cover window CW, such as an air gap AG.

[0068] Simultaneously, the first ultrasonic wave UW1 irradiating the valley VAL can penetrate the display panel 100, the transparent adhesive member, the cover window CW, and the air gap AG to reach the valley VAL. Although the first ultrasonic wave UW1 irradiating the ridge RID and the first ultrasonic wave UW1 irradiating the valley VAL travel through the same penetration path, namely the display panel 100, the transparent adhesive member, and the cover window CW, the first ultrasonic wave UW1 irradiating the valley VAL can further travel through the air gap AG. Regarding the first ultrasonic wave UW1 emitted by the ultrasonic fingerprint sensor 400, the first ultrasonic wave UW1 irradiated by the ridge RID and reflected by the ridge RID can be converted into a first signal L1. Furthermore, the first ultrasonic wave UW1 irradiated by the valley VAL and reflected by the interface between the air gap AG and the cover window CW can be converted into a first reflected signal L11, and the first ultrasonic wave UW1 irradiated by the valley VAL and reflected by the valley VAL can be converted into a second reflected signal L12. The first reflected signal L11 and the second reflected signal L12 constitute the first signal L1. The magnitude of the first reflected signal L11 can be greater than the magnitude of the second reflected signal L12.

[0069] The ultrasonic fingerprint sensor 400 can identify the ridge RID and valley VAL based on a first time difference between the emission time of the first ultrasonic wave UW1 and the arrival time of the first signal L1 reflected by the ridge RID, and a second time difference between the emission time of the first ultrasonic wave UW1 and the arrival time of the first signal L1 reflected by the valley VAL and the interface between the air gap AG and the cover window CW. However, considering that there is an air gap AG between the valley VAL and the cover window CW and that the ultrasonic wave propagation speed varies with the medium, it may not be easy to distinguish between the ridge RID and the valley VAL.

[0070] To take into account the air gap AG between the valley VAL and the cover window CW for more accurate differentiation between the ridge RID and valley VAL, the ratio of the intensity of the first ultrasonic wave UW1 to the intensity of the first signal L1 can be considered as a method for differentiation between the ridge RID and valley VAL. The ratio of the intensity of the first signal L1 to the intensity of the first ultrasonic wave UW1 is defined as the reflection coefficient R.

[0071] For example, the reflection coefficient R of the first ultrasound wave UW1 irradiating a valley VAL can be greater than the reflection coefficient R of the first ultrasound wave UW1 irradiating a ridge RID. In other words, it can be determined whether it is a ridge RID or a valley VAL based on the reflection coefficient R of the first ultrasound wave UW1.

[0072] Next, refer to Figure 1 and Figure 4 The ultrasonic fingerprint sensor 400 receives the first signal L1 reflected by the ridge RID and valley VAL of the fingerprint (operation S20).

[0073] Next, the ultrasonic fingerprint sensor 400 generates an image based on the first signal L1 (operation S30). In operation S30, the image can be the first image.

[0074] Next, the ultrasonic fingerprint sensor 400 compares the image (or the first image) with the registered reference image to make a determination (operation S40).

[0075] Before comparing the image (or the first image) with the registered reference image to make a determination at operation S40, the reference image (or the first reference image) can be registered (operation S70).

[0076] The reference image can be a fingerprint image of a user registered in an indoor temperature / humidity environment.

[0077] If at operation S40 it is determined that the matching score of the comparison result between the image (or the first image) and the registered reference image is equal to or greater than the threshold, then the user's fingerprint authentication is complete.

[0078] At the same time, such as Figure 5 As shown, the ridge RID of a fingerprint can have a surface profile that varies with the exposure environment. More specifically, when the fingerprint is exposed to low temperature / low humidity (dry) conditions, wrinkles may form on the surface of the ridge RID. Wrinkles on the surface of the ridge RID of the fingerprint may form an undesirable air gap AG with the overlay window CW.

[0079] In other words, even if the reflection coefficient R of the first ultrasonic wave UW1 is used to distinguish between ridge RID and valley VAL, the wrinkles on the surface of the ridge RID that change with the fingerprint exposure environment may make it difficult to distinguish between ridge RID and valley VAL.

[0080] Figure 6 Photographs of fingerprint images captured using a first ultrasonic UW1 sensor are shown in both the first and second environments. Figure 6 In the photograph, a normal finger is shown in a first environment corresponding to indoor temperature / humidity (see image). Figure 4 The photograph of the dried finger shows finger F in a second environment corresponding to a low temperature / low humidity environment. Figure 6 In this context, a frequency optimized for passing through the display panel 100, the transparent adhesive member, and the cover window CW is used as the first frequency. However, the first frequency is not limited to this and can have a frequency equal to or higher than 1 MHz.

[0081] Reference Figure 5 and Figure 6 It was determined that in the second environment, it was not easy to distinguish between ridge RID and valley VAL.

[0082] Reference Figure 6 , Figure 7 and Figure 11 When fingerprints are difficult to identify due to exposure to a second environment, the ultrasonic fingerprint sensing method according to some example embodiments may be able to successfully perform fingerprint recognition by attempting fingerprint recognition using a second ultrasonic wave UW2 at a second frequency that belongs to a frequency band lower than the first frequency, regardless of the environment.

[0083] Return to reference Figure 1 , Figure 7 and Figure 8 If it is difficult to distinguish between ridge RID and valley VAL at operation S40 by comparing the image (or the first image) with the registered reference image and making a determination (or, as a result of the comparison between the first image and the registered reference image, the matching score is less than a threshold), then the ultrasonic fingerprint sensor 400 generates an image (or a second image) by using a second ultrasonic wave UW2 having a second frequency (operation S50). The second frequency may be a frequency belonging to a frequency band lower than the first frequency. For example, the second frequency may have a value equal to or less than approximately 90% of the first frequency, but is not limited thereto.

[0084] Generating an image (or a second image) at operation S50 using a second ultrasonic wave UW2 having a second frequency may include irradiating the second ultrasonic wave UW2 onto the ridge RID and valley VAL, thereby receiving a second signal L2 reflected by the ridge RID and valley VAL, and generating a second image based on the received second signal L2. The second ultrasonic wave UW2 irradiated onto and reflected by the ridge RID can be converted into the second signal L2, and the second ultrasonic wave UW2 irradiated onto the valley VAL and reflected by the interface between the air gap AG and the cover window CW, as well as by the valley VAL, can be converted into a first reflected signal L21 and a second reflected signal L22, respectively. The magnitude of the first reflected signal L21 may be greater than the magnitude of the second reflected signal L22.

[0085] Because the second frequency belongs to a frequency band lower than the first frequency, the reflection coefficient R of the second ultrasonic wave UW2 irradiating the valley valence can be smaller than the reflection coefficient R of the first ultrasonic wave UW1 irradiating the valley valence. (Refer to...) Figure 9 and Figure 10 Describe it.

[0086] Figure 9 This is a diagram illustrating a model for measuring ultrasonic wave reflection characteristics in a first environment and a second environment, according to some example embodiments. Figure 10 This illustrates some example embodiments in Figure 9 A graph showing the reflection coefficient calculated with respect to the air gap thickness in the model. Figure 9In the diagram, (a) shows a first model in which an object (e.g., a finger) is in direct contact with glass, and (b) shows a second model in which an air gap h is formed between the glass and the finger. The first model is a case in which the ridges of the fingerprint are exposed to a first environment and can correspond to a normal finger. The second model is a case in which the ridges of the fingerprint are exposed to a second environment.

[0087] exist Figure 10 In the diagram, the horizontal axis (air gap thickness (nm) corresponds to... Figure 9 The second model uses a gap h, and the vertical axis (reflection coefficient R) corresponds to a simulated value that varies with the gap h in the second model. The second model can correspond to a dry finger. In the second model, the reflection coefficient R is measured at each frequency. For example, the reflection coefficient R is measured using a first ultrasound UW1 at a first frequency, and the reflection coefficient R is measured using a second ultrasound UW2 at a second frequency.

[0088] Reference Figure 4 , Figure 7 , Figure 9 and Figure 10 The reflection coefficient R measured in the first model (or normal finger) is approximately 0.698, and the reflection coefficient R measured in the second model tends to increase with increasing gap h. It is shown that in the second model assuming a constant gap h, the reflection coefficient R measured using a first ultrasound UW1 at a first frequency is greater than the reflection coefficient R measured using a second ultrasound UW2 at a second frequency.

[0089] In other words, a reflection coefficient R is shown to be close to that in a first model (or normal finger) compared to an image (or second image) generated by using a second ultrasound UW2 at a second frequency in a frequency band below the first frequency in a low temperature / low humidity environment, compared to an image (or first image) generated by using a first ultrasound UW1 at the first frequency.

[0090] Figure 11 Photographs of fingerprint images taken in a first and a second environment using a second ultrasonic wave, according to some example embodiments, are shown. Figure 11 In the photograph, a normal finger is shown in a first environment corresponding to indoor temperature / humidity (see image). Figure 4 The photograph of the dried finger shows finger F in a second environment corresponding to a low temperature / low humidity environment. Additionally, a second frequency is applied in... Figure 11 (See also:) Figure 11 As shown above, even in the second environment, ridge RID and valley VAL are well distinguished.

[0091] Return to reference Figure 1 and Figure 7 After generating an image (or a second image) using a second frequency at operation S50, the ultrasonic fingerprint sensor 400 compares the second image with a registered reference image (or a first reference image) to make a determination (operation S40).

[0092] If at operation S40 it is determined that the matching score of the comparison result between the second image and the registered reference image (or the first reference image) is equal to or greater than the threshold, then authentication is complete.

[0093] When fingerprints are difficult to identify due to exposure to a second environment, the ultrasonic fingerprint sensing method according to some example embodiments may be able to successfully perform fingerprint recognition by attempting fingerprint recognition using a second ultrasonic wave UW2 at a second frequency that belongs to a frequency band lower than the first frequency, regardless of the environment.

[0094] In the following description, an ultrasonic fingerprint sensor according to some example embodiments may be described. In the following embodiments, the same components as those in the above embodiments are indicated by the same reference numerals, and some descriptions thereof may be omitted or simplified.

[0095] Figure 12 This is a block diagram illustrating an ultrasonic fingerprint sensor according to some example embodiments.

[0096] Reference Figure 12 According to some example embodiments, the ultrasonic fingerprint sensor 400 includes an ultrasonic wave generating unit 410, an ultrasonic wave receiving unit 420, an image generating unit 430, and a comparison / determination unit 440.

[0097] For reference Figure 1 and Figure 12 As described, the ultrasonic generating unit 410 generates a first ultrasonic wave UW1 having a first frequency (operation S10).

[0098] For reference Figure 1 , Figure 4 and Figure 12 As described, the ultrasonic receiving unit 420 receives the first signal L1 reflected by the ridge RID and valley VAL of the fingerprint (operation S20).

[0099] For reference Figure 1 and Figure 12 As described, the image generation unit 430 generates images (first image and second image) (operations S30 and S50).

[0100] For reference Figure 1 and Figure 12 As described, the comparison / determination unit 440 compares the images (first image and second image) with the registered reference image and makes a determination (operation S40).

[0101] Already referred to Figures 1 to 11 The function of components 410, 420, 430 and 440 of the ultrasonic fingerprint sensor 400 is described in more detail, and therefore their detailed description will be omitted.

[0102] The ultrasonic fingerprint sensor 400 generates a first ultrasonic wave UW1 with a first frequency (operation S10).

[0103] The ultrasonic fingerprint sensing method according to some example embodiments will be described below. In the following embodiments, the same components as those in the above embodiments are indicated by the same reference numerals, and some descriptions therein may be omitted or simplified.

[0104] Figure 13 and Figure 14 This is a flowchart of an ultrasonic fingerprint sensing method according to some example embodiments. Although Figure 13 and Figure 14 Various operations according to some example embodiments have been described; however, the number and order of operations may vary according to some example embodiments. For example, according to some example embodiments, additional or fewer operations may exist, or the order of operations may vary, without departing from the spirit and scope of the embodiments according to this disclosure.

[0105] Reference Figure 13 and Figure 14 The ultrasonic fingerprint sensing method according to some example embodiments differs from the ultrasonic fingerprint sensing method according to the embodiments described above in that, as referred to above... Figure 3 The operation S70 described for registering the reference image can be divided into operation S70_1 for registering the first reference image (or reference image) and operation S70_2 for registering the second reference image.

[0106] More specifically, the ultrasonic fingerprint sensing method according to some example embodiments includes a reference image registration operation, which can be divided into an operation S70_1 for registering a first reference image and an operation S70_2 for registering a second reference image. The first reference image and the reference... Figure 3 The reference image described is the same, and the second reference image is a reference image generated in a second environment, namely a low temperature / low humidity environment.

[0107] With reference Figure 1The ultrasonic fingerprint sensing method described in this embodiment differs from the one described in the following way: a second image is generated using a second frequency (operation S50_1), and then the second image is compared with a registered second reference image to make a determination (operation S80). That is, the determination based on the comparison between the first image and the registered first reference image (operation S40_1) and the determination based on the comparison between the second image and the registered second reference image (operation S80) can be performed independently of each other. Next, if it is determined that the matching score between the second reference image and the second image is equal to or greater than a threshold, authentication is completed.

[0108] Already referred to Figures 1 to 11 Other descriptions have been provided, and therefore, redundant descriptions will be omitted.

[0109] Figure 15 This is a block diagram of an ultrasonic fingerprint sensor according to some example embodiments.

[0110] Reference Figure 15 According to the ultrasonic fingerprint sensor 400_1 in this embodiment and Figure 12 The ultrasonic fingerprint sensor 400 according to some example embodiments differs in that the comparison / determination unit 440_1 is further responsible for, as referred to Figure 13 and Figure 14 The description involves comparing the second image with the registered second reference image and making a determination.

[0111] More specifically, in the ultrasonic fingerprint sensor 400_1 according to some example embodiments, the comparison / determination unit 440_1 may further be responsible for, as referred to Figure 13 and Figure 14 The description involves comparing the second image with the registered second reference image and making a determination.

[0112] Already referred to Figure 12 Other descriptions have been provided, and therefore, redundant descriptions will be omitted.

[0113] Figure 16 This is a flowchart of an ultrasonic fingerprint sensing method according to some example embodiments. Although Figure 16 Various operations according to some example embodiments are illustrated; however, the number and order of operations may vary according to some example embodiments. For example, according to some example embodiments, additional or fewer operations may exist, or the order of operations may vary, without departing from the spirit and scope of the embodiments according to this disclosure.

[0114] Reference Figure 16The ultrasonic fingerprint sensing method according to some example embodiments differs from the ultrasonic fingerprint sensing method according to the above embodiments in that it further includes an operation S90 for measuring temperature and making a determination.

[0115] More specifically, the ultrasonic fingerprint sensing method according to some example embodiments may also include an operation S90 for temperature measurement / determination. The operation S90 for temperature measurement / determination may be performed after an operation S40 for comparing an image (or a first image) with a registered reference image (or a first reference image) and making a determination. The operation S90 for temperature measurement / determination allows the temperature to be determined as the environment in which the fingerprint is exposed. If the operation S90 for temperature measurement / determination determines that the fingerprint is exposed to a low-temperature environment, the ultrasonic fingerprint sensor 400_1 may generate an image (or a second image) using a second frequency belonging to a frequency band specific to the low-temperature environment (operation S50). After generating the image (or second image) at operation S50, the ultrasonic fingerprint sensor 400_1 compares the second image with the registered reference image (or the first reference image), and authentication is completed if the matching score is equal to or greater than a threshold. For example, if it is determined that the temperature measured at the operation S90 for temperature measurement / determination is within or below a first threshold range (e.g., in a low-temperature state below room temperature), the ultrasonic fingerprint sensor 400_1 may use a second frequency belonging to a frequency band below the first frequency.

[0116] Figure 17 This is a block diagram of an ultrasonic fingerprint sensor according to some example embodiments.

[0117] Reference Figure 17 According to some example embodiments, the ultrasonic fingerprint sensor 400_2 may include a temperature measurement / determination unit 450.

[0118] More specifically, the ultrasonic fingerprint sensor 400_2 according to some example embodiments may also include a temperature measurement / determination unit 450.

[0119] Temperature measurement / determination unit 450 is used to perform as referenced Figure 16 The operation of temperature measurement / determination S90 is described above. The operation of temperature measurement / determination S90 and components 410, 420, 430, and 440 have already been described above, and their detailed descriptions will be omitted to avoid redundancy.

[0120] Figure 18 This is a flowchart of an ultrasonic fingerprint sensing method according to some example embodiments. Although Figure 18Various operations according to some example embodiments are illustrated; however, the number and order of operations may vary according to some example embodiments. For example, according to some example embodiments, additional or fewer operations may exist, or the order of operations may vary, without departing from the spirit and scope of the embodiments according to this disclosure.

[0121] Reference Figure 18 The ultrasonic fingerprint sensing method according to some example embodiments and Figure 14 The ultrasonic fingerprint sensing method according to some example embodiments differs in that an operation S90 for temperature measurement / determination is performed between the operation S40_1 for determining based on a comparison between a first image and a registered first reference image and the operation S50_1 for generating a second image by using a second frequency.

[0122] More specifically, the ultrasonic fingerprint sensing method according to some example embodiments may include an operation S90 for temperature measurement / determination, which is performed between an operation S40_1 for comparing a first image with a registered first reference image to make a determination and an operation S50_1 for generating a second image by using a second frequency.

[0123] Already referred to Figure 16 The operation S90 for temperature measurement / determination is described in more detail, and therefore its detailed description is omitted to avoid redundancy.

[0124] Figure 19 This is a block diagram of an ultrasonic fingerprint sensor according to some example embodiments.

[0125] Reference Figure 19 According to some example embodiments, the ultrasonic fingerprint sensor 400_3 may include a temperature measurement / determination unit 450.

[0126] More specifically, the ultrasonic fingerprint sensor 400_3 according to some example embodiments may also include a temperature measurement / determination unit 450.

[0127] Already referred to Figure 17 The temperature measurement / determination unit 450 is described in more detail, and therefore some of its detailed descriptions can be omitted to avoid redundancy.

[0128] Although aspects of some exemplary embodiments of the invention have been described for illustrative purposes, those skilled in the art will understand that various modifications, additions, and substitutions are possible without departing from the scope and spirit of the invention as disclosed in the appended claims and their equivalents.

Claims

1. An ultrasonic fingerprint sensing method, wherein, The ultrasonic fingerprint sensing method includes: Generate a first ultrasonic wave with a first frequency; Receive a first signal generated by the reflection of the first ultrasonic wave from each of the ridges and valleys of the fingerprint; A first image is generated based on the first signal; The first image is compared with the registered reference image to generate a matching score; and In response to the matching score being less than a threshold, a second image is generated using a second frequency, wherein the second frequency belongs to a frequency band lower than the first frequency.

2. The ultrasonic fingerprint sensing method according to claim 1, wherein, The ultrasonic fingerprint sensing method further includes: after generating the second image, comparing the second image with the registered reference image.

3. The ultrasonic fingerprint sensing method according to claim 2, wherein, The generation of the second image using the second frequency includes: Generate a second ultrasonic wave having the second frequency; and Receive a second signal generated by the reflection of the second ultrasonic wave from each of the ridges and valleys of the fingerprint.

4. The ultrasonic fingerprint sensing method according to claim 3, wherein, The ratio of the intensity of the second signal to the intensity of the second ultrasonic wave is less than the ratio of the intensity of the first signal to the intensity of the first ultrasonic wave.

5. The ultrasonic fingerprint sensing method according to claim 3, wherein, Comparing the first image with the registered reference image includes registering the first reference image; Comparing the second image with the registered reference image includes registering the second reference image. The first reference image is generated based on the first signal. The second reference image is generated based on the second signal, and Comparing the second image with the registered reference image includes comparing the second image with the second reference image.

6. The ultrasonic fingerprint sensing method according to any one of claims 1 to 5, wherein, The first ultrasonic wave is configured to penetrate multiple layers to reach the fingerprint, and The multiple layers include a display panel and a cover window.

7. An ultrasonic fingerprint sensing method, wherein, The ultrasonic fingerprint sensing method includes: Generate a first ultrasonic wave with a first frequency; Receive a first signal generated by the reflection of the first ultrasonic wave from each of the ridges and valleys of the fingerprint; A first image is generated based on the first signal; The first image is compared with the registered reference image to generate a matching score; and In response to the matching score being less than a threshold, the temperature of the fingerprint is measured.

8. The ultrasonic fingerprint sensing method according to claim 7, wherein, The ultrasonic fingerprint sensing method further includes: after measuring the temperature of the fingerprint, generating a second image using a second frequency based on the temperature of the fingerprint.

9. The ultrasonic fingerprint sensing method according to claim 8, wherein, The ultrasonic fingerprint sensing method further includes: after generating the second image, comparing the second image with the registered reference image.

10. The ultrasonic fingerprint sensing method according to claim 9, wherein, The generation of the second image using the second frequency includes: Generate a second ultrasonic wave having the second frequency; and Receive a second signal generated by the reflection of the second ultrasonic wave from each of the ridges and valleys of the fingerprint.

11. The ultrasonic fingerprint sensing method according to claim 10, wherein, Comparing the first image with the registered reference image includes registering the first reference image. Comparing the second image with the registered reference image includes registering the second reference image. The first reference image is generated based on the first signal. The second reference image is generated based on the second signal, and Comparing the second image with the registered reference image includes comparing the second image with the second reference image.

12. The ultrasonic fingerprint sensing method according to claim 11, wherein, If the temperature of the fingerprint is within or below a first threshold range, then the second frequency belongs to a frequency band lower than the first frequency.

13. An ultrasonic fingerprint sensor, wherein, The ultrasonic fingerprint sensor includes: An ultrasonic generator, configured to generate a first ultrasonic wave having a first frequency; The receiving unit is configured to receive a first signal generated by the reflection of the first ultrasonic wave from each of the ridges and valleys of the fingerprint; An image generator configured to generate a first image based on the first signal; and The comparison / determination unit is configured to perform a comparison / determination on the first image and the registered reference image; and The image generator is configured to generate a second image using a second frequency in response to a matching score, determined by the comparison / determination unit, between the first image and the registered reference image, being less than a threshold. The second frequency belongs to a frequency band lower than the first frequency.

14. The ultrasonic fingerprint sensor according to claim 13, wherein, The comparison / determination unit is further configured to perform a comparison / determination on the second image and the registered reference image.

15. The ultrasonic fingerprint sensor according to claim 14, wherein, The comparison / determination unit is configured to register a first reference image and a second reference image different from the first reference image, and The first reference image is generated based on the first signal, and the second reference image is generated based on a second signal that is different from the first signal.

16. The ultrasonic fingerprint sensor according to claim 15, wherein, The comparison / determination unit is configured to perform a comparison / determination on the second image and the registered second reference image.

17. An ultrasonic fingerprint sensor, wherein, The ultrasonic fingerprint sensor includes: An ultrasonic generator, configured to generate a first ultrasonic wave having a first frequency; The receiving unit is configured to receive a first signal generated by the reflection of the first ultrasonic wave from each of the ridges and valleys of the fingerprint; An image generator configured to generate a first image based on the first signal; and The comparison / determination unit is configured to perform a comparison / determination on the first image and the registered reference image; A temperature measurement / determination unit is configured to measure / determine the temperature of the fingerprint. The temperature measurement / determination unit is configured to perform a measurement / determination of the temperature of the fingerprint in response to a matching score, which is a comparison result between the first image and the registered reference image, determined by the comparison / determination unit, being less than a threshold.

18. The ultrasonic fingerprint sensor according to claim 17, wherein, The image generator is configured to generate a second image using a second frequency based on the temperature of the fingerprint.

19. The ultrasonic fingerprint sensor according to claim 18, wherein, The comparison / determination unit is further configured to perform a comparison / determination on the second image and the registered reference image.

20. The ultrasonic fingerprint sensor according to claim 19, wherein, The comparison / determination unit is configured to register a first reference image and a second reference image different from the first reference image. The first reference image is generated based on the first signal. The second reference image is generated based on a second signal that is different from the first signal, and The comparison / determination unit is configured to perform a comparison / determination on the second image and the second reference image.

21. The ultrasonic fingerprint sensor according to claim 20, wherein, In response to the temperature of the fingerprint being within or below a first threshold range, the second frequency belongs to a frequency band lower than the first frequency.

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