Optical fingerprint sensor with enhanced anti-counterfeiting features

Abstract

The present disclosure relates to optical fingerprint sensors with enhanced anti-counterfeiting features. An image sensing device is disclosed. The image sensing device includes a pixel array and a microlens disposed above the pixel array. The pixel array includes a sensing pixel configured to capture a minutia of a fingerprint and a positioning pixel configured to provide a positioning code.

Description

Technical Field

[0001] This disclosure relates to an optical fingerprint sensor with enhanced anti-counterfeiting features. Background Technology

[0002] The semiconductor integrated circuit (IC) industry has experienced exponential growth. Technological advancements in IC materials and design have yielded several generations of ICs, each featuring smaller and more complex circuitry than the previous generation. In the evolution of ICs, functional density (i.e., the number of interconnect devices per chip area) typically increases, while geometry (i.e., the smallest component (or line) that can be created using manufacturing processes) decreases. For example, there is considerable interest in providing fingerprint sensing applications (e.g., optical sensors for fingerprint recognition) within a limited device enclosure for consumer and / or portable electronic devices (e.g., smartphones, tablets, wearables, etc.) without compromising the level of security provided by the fingerprint sensing application.

[0003] In some fingerprint sensing applications, the grayscale image of a fingerprint is sensed by pixels of an optical fingerprint sensor that can only sense grayscale images (i.e., not color images). Furthermore, this grayscale image does not include any specific locator or pattern. This type of fingerprint sensing application is susceptible to forgery. Therefore, traditional optical fingerprint sensors are not satisfactory in all aspects. Summary of the Invention

[0004] According to one embodiment of the present disclosure, an image sensing device is provided, comprising: a pixel array, the pixel array including: a plurality of sensing pixels configured to acquire minute details of a fingerprint; a plurality of positioning pixels configured to provide a positioning code; and a plurality of microlenses disposed on the pixel array.

[0005] According to another embodiment of this disclosure, an optical fingerprint sensor is provided, comprising: a filter array arranged in columns and rows; a light receiving element array below the filter array, the light receiving element array being configured to convert incident light reflected from a fingerprint into a fingerprint image; and a plurality of opaque films disposed above a portion of the light receiving elements, the portion of the light receiving elements being configured to add dark pixels to the fingerprint image.

[0006] According to another embodiment of this disclosure, a fingerprint verification method is provided, comprising: acquiring a fingerprint image using an image sensing device, the image sensing device including a pixel array of a combination of sensing pixels and positioning pixels, the sensing pixels being configured to acquire minutiae in the fingerprint image, and the positioning pixels being configured to provide a positioning code; calculating a vector of the minutiae with reference to the positioning code; and comparing the vector with a reference vector generated from a reference fingerprint image to determine a match between the fingerprint image and the reference fingerprint image. Attached Figure Description

[0007] This disclosure can be best understood from the following detailed description when read in conjunction with the accompanying drawings. It should be emphasized that, according to industry standard practice, the features are not drawn to scale but are for illustrative purposes only. In fact, for clarity of discussion, the dimensions of the features can be arbitrarily increased or decreased.

[0008] Figure 1 An electronic device having a fingerprint sensing area in surface space according to aspects of the present disclosure is shown.

[0009] Figure 2 This is a cross-sectional view of an electronic device with an optical fingerprint sensor integrated below a display panel, according to various aspects of this disclosure.

[0010] Figure 3 Based on the various aspects of this disclosure, such as Figure 2 A cross-sectional view of an embodiment of the optical fingerprint sensor shown.

[0011] Figure 4A , Figure 4B and Figure 4C This is a top view of a pixel array according to various aspects of the present disclosure, the pixel array having positioning pixels that overlay the fingerprint image at different stages of fingerprint recognition.

[0012] Figure 5 , Figure 6 and Figure 7 An embodiment of the distribution of positioning pixels in a pixel array according to various aspects of this disclosure is shown.

[0013] Figure 8A , Figure 8B , Figure 8C , Figure 8D , Figure 8E , Figure 8F and Figure 8G An embodiment of the distribution of positioning pixels and color pixels in a pixel array according to various aspects of this disclosure is shown.

[0014] Figure 9A flowchart of a method for fingerprint recognition according to various aspects of this disclosure is shown. Detailed Implementation

[0015] The following disclosure provides numerous different embodiments or examples for implementing various features of this disclosure. Specific examples of components and arrangements are described below to simplify this disclosure. Of course, these are merely examples and are not intended to be limiting. For example, in the following description, forming a first feature on or over a second feature may include embodiments where the first and second features are formed in direct contact, and may also include embodiments where an additional feature may be formed between the first and second features such that the first and second features may not be in direct contact. Furthermore, reference numerals and / or letters may be repeated in various examples of this disclosure. This repetition is for the purpose of brevity and clarity and does not, in itself, indicate a relationship between various embodiments and / or configurations beyond the scope described.

[0016] Furthermore, in this disclosure, the formation of a feature on, connected to, and / or coupled to another feature may include embodiments in which the features are formed in direct contact, and may also include embodiments in which additional features are formed in an intercalation manner such that the features are not in direct contact. Additionally, for ease of describing the relationship of one feature relative to another, spatially related terms such as “lower,” “higher,” “horizontal,” “vertical,” “above,” “above,” “below,” “under,” “upper,” “bottom,” etc., and their derivatives (e.g., “horizontally,” “downward,” “upward,” etc.) are used. Spatially related terms are intended to cover different orientations of devices including these features.

[0017] This disclosure generally relates to designs and methods for fingerprint sensing (e.g., in anti-counterfeiting applications using optical fingerprint sensors (OFPS)). More specifically, some embodiments relate to specific patterns that integrate positioning pixels (also called positioning codes) and / or additional color pixels to add skin color codes to the OFPS to enhance its anti-counterfeiting capabilities.

[0018] OFPS (Optical Frequency Perception) is a method of biometric sensing that has generated considerable interest in providing security features to electronic devices (more specifically, consumer and / or portable electronic devices such as smartphones, tablets, wearables, etc.). OFPS-based fingerprint recognition (or fingerprint sensing) systems are based on the user's unique characteristics and can operate independently of the user's memory or use of other input devices, such as passwords. For the same reason, OFPS-based fingerprint recognition systems also offer the advantage of being difficult to hack.

[0019] Among various biometric sensing technologies, fingerprint recognition is a reliable and widely used technique for personal identification or authentication. A fingerprint recognition system generally includes fingerprint sensing and matching functions, such as collecting fingerprint images and comparing these images with known fingerprint information. Specifically, one method of fingerprint recognition involves scanning a reference fingerprint and storing the acquired reference image. The characteristics of a new fingerprint can be scanned and compared with reference images already stored in a database to determine the correct identification of an individual (e.g., for authentication purposes). Fingerprint recognition systems can be particularly advantageous for authentication in consumer and / or portable electronic devices. For example, the optical sensor used to acquire fingerprint images can be housed within the casing of the electronic device.

[0020] The effectiveness of biometric security systems can be affected by the accuracy with which specific biometric data can be detected. In the case of fingerprint recognition systems, this means improving accuracy when comparing an acquired fingerprint image with a reference fingerprint image stored in a database. The reference fingerprint image stored in the database is typically a set of minutia points representing the ridges and valleys of the fingerprint. This set of minutia points is also known as a minutia map. If the minutia map is hacked or leaked, the fingerprint image can be reconstructed through reverse engineering. Therefore, the security provided by the fingerprint recognition system is compromised. In some embodiments of this disclosure, location pixels are added to the pixel array of the OFPS to add an additional code to the minutia map. This code is called a fingerprint location code or position reference code. The fingerprint location code converts the direct record of the minutia points where the ridges and valleys are located into a vector representing the relative position of the minutia points with respect to the location pixels. Therefore, even if the minutia map is hacked or leaked, the fingerprint image still cannot be reconstructed from the minutia map without knowing the distribution of the location pixels and how the location pixels are referenced. Thus, adding a location code enhances the anti-counterfeiting capability of the OFPS.

[0021] Furthermore, in some fingerprint sensing applications, the fingerprint grayscale image is sensed by image sensing pixels (abbreviated as pixels) that can only sense grayscale images (i.e., cannot sense color images). Such pixels are called grayscale pixels or "W" pixels. For example, a monochrome image sensor is typically adapted to produce grayscale images for fingerprint recognition applications. In some embodiments of this disclosure, one or more color image sensors are added to the pixel array as color pixels (RGB), thereby adding a fingerprint color code representing skin color to a reference fingerprint image and the acquired fingerprint image. The fingerprint color code further enhances the anti-counterfeiting capability of the OFPS. In various embodiments, the positioning pixels that generate the fingerprint positioning code and the color pixels that generate the fingerprint color code can be applied independently or jointly to the pixel array of the OFPS. For example, the OFPS may include a pixel array where some grayscale pixels are replaced by positioning pixels, a pixel array where some grayscale pixels are replaced by color pixels, a pixel array where some grayscale pixels are replaced by positioning pixels and some grayscale pixels are replaced by color pixels, or even a pixel array with no grayscale pixels but a combination of color pixels and positioning pixels.

[0022] Figure 1 An electronic device 100 having a fingerprint sensing area in surface space according to some embodiments of the present disclosure is shown. For example... Figure 1 As illustrated, illustratively, electronic device 100 is a mobile wireless communication device (e.g., a smartphone). In other embodiments, electronic device 100 may be any other suitable electronic device, such as a laptop computer, tablet computer, portable gaming device, navigation device, or wearable device. Electronic device 100 includes a housing 102 and other components within the housing 102, such as one or more processors and memory. Display panel 104 is carried by housing 102. In the illustrated embodiment, display panel 104 is an organic light-emitting diode (OLED) display panel. In various embodiments, display panel 104 may be any other suitable type of display panel as understood by those skilled in the art, such as a liquid crystal display (LCD) panel, a light-emitting diode (LED) display panel, or an active-matrix organic light-emitting diode (AMOLED) display panel.

[0023] In the illustrated embodiment, the display panel 104 extends substantially across the entire surface space of the electronic device 100. Some space between the edges of the display panel 104 and the housing 102 may be reserved for the bezel panel 106. The display panel 104 is stacked on top of an image sensing feature or other suitable biometric sensing feature for fingerprint detection. The image sensing feature will be described in further detail later. The display panel 104 acts as both a display and an input device through which the image sensing feature acquires a fingerprint image. Thus, the display panel 104 performs multiple device functions in response to user input. For example, when the electronic device 100 is locked, the display panel 104 may first display a prompt on the screen (e.g., a finger icon or instruction text). The display panel 104 may also highlight a sensing area 108. When a user's finger 110 is placed within the sensing area 108 (in the near field or in direct contact with the display panel 104), the image sensing feature is activated and acquires a fingerprint image from the user's finger 110. This acquired fingerprint image (biometric data) is sent to one or more processors for matching and / or spoofing detection. If the acquired fingerprint image matches a reference fingerprint image stored in memory, the electronic device 100 can then switch to an unlocked state, and the display panel 104 begins displaying desktop icons or responding to various other user inputs. The display panel 104 can also be integrated with a touch sensor array. In this case, the display panel 104 is also a touch display panel.

[0024] Figure 2 This is a cross-sectional view of a portion of an electronic device 100. This portion of the electronic device 100 carries fingerprint recognition functionality and can be considered as a fingerprint recognition system 200. The fingerprint recognition system 200 is configured in a stacked manner, including a top display panel 202, a middle light modulation layer 204, and a bottom OFPS 206. The display panel 202 illuminates an upper sensing area 108. When light emitted from the display panel 202 is reflected from a user's finger 110, the reflected light passes downward through the display panel 202 and the light modulation layer 204 and eventually reaches the OFPS 206. In one embodiment, the image OFPS 206 includes an array of optical sensing elements 207, such as a complementary metal oxide semiconductor (CMOS) image sensor and / or a charge-coupled device (CCD) sensor. The optical sensing elements 207 are capable of detecting the intensity of incident light. Therefore, the OFPS 206 converts the incident light into a pixel image that includes the biometric characteristics of the user's finger 110. Each pixel of the pixel image can correspond to the intensity of the incident light recorded at the corresponding position on the optical sensing element 207.

[0025] In some embodiments, the display panel 202 includes a cover glass 214 (or cover lens) that protects internal components of the electronic device 100. A sensing area 108 is defined over the cover glass 214. The top surface 216 of the cover glass 214 forms a sensing surface that provides a contact area for a user's finger 110 or other suitable object. Within the sensing area 108, during near-field sensing, the user's finger 110 can directly touch the top surface 216 or maintain a small distance from the top surface 216. The cover glass 214 may be made of glass, a transparent polymer material, or other suitable materials.

[0026] Display panel 202 includes an illumination layer or display layer 220 beneath cover glass 214. Display layer 220 includes an array of light-emitting pixels 222. Different light-emitting pixels 222 can be configured to emit different colors, for example, pixels emitting red light, pixels emitting green light, or pixels emitting blue light. Due to their geometric relationship with sensing region 108, the light-emitting pixels 222 can be classified into two groups, one group directly below sensing region 108 and the other group outside sensing region 108. The light-emitting pixels 222 outside sensing region 108 perform conventional display functions, while the light-emitting pixels 222 directly below sensing region 108 perform both conventional display functions and illumination functions during biometric sensing, depending on the application. In various embodiments, the pixel distance D1 between adjacent light-emitting pixels 222 ranges from about 5 micrometers to about 30 micrometers, with other values ​​and intervals within this range being within the scope of this disclosure. In a specific example, the pixel distance D1 can range from about 10 micrometers to about 20 micrometers.

[0027] In some embodiments, the display panel 202 further includes a barrier layer 224. The barrier layer 224 is a translucent or opaque layer that may be disposed below the display layer 220. Outside the sensing region 108, the barrier layer 224 is continuous and blocks the components below the display layer 220 to prevent light emitted from the light-emitting pixels 222 and ambient light from entering. Directly below the sensing region 108, the barrier layer 224 has a plurality of openings 226. Each opening 226 is located between two adjacent light-emitting pixels 222. The openings 226 allow light reflected from the sensing region 108 to pass through. In the illustrated embodiment, there is one opening 226 between two adjacent light-emitting pixels 222. The opening 226 may have a width (or diameter) D2, the ratio of D2 to the pixel distance D1 being from about 40% to about 90%, with other values ​​and intervals within this range being within the scope of this disclosure. In some other embodiments, there are two or more openings 226 between two adjacent light-emitting pixels 222. Therefore, the opening 226 can have a width (or diameter) D2, and the ratio of D2 to the pixel distance D1 is from about 20% to about 40%.

[0028] In various embodiments, display layer 220 can be an LCD display (using a backlight with color filters to form RGB pixels), an LED display (e.g., microLED, in which the pixel material can be an inorganic material used in LEDs), an OLED display, or any other suitable display. In the illustrated embodiment, the light-emitting pixel 222 is an organic light-emitting diode (OLED), and display layer 220 is an OLED display. Examples of OLED displays can include active-matrix OLED (AMOLED), passive-matrix OLED (PMOLED), white OLED (WOLED), and RBG-OLED, and / or other suitable types of OLEDs. OLED displays are generally thinner, lighter, and more flexible than other types of displays (e.g., LCD or LED displays). OLED displays do not require backlighting because light can be generated from the organic light-emitting material in the OLED, which allows pixels to be completely turned off. The organic light-emitting material can be an organic polymer, such as polyphenylenevinylene and polyfluorene. Because the organic light-emitting material generates its own light, OLED displays can also have a wider viewing angle. This can be compared to an LCD display, which works by blocking light that might obstruct certain viewing angles.

[0029] OLED diodes emit light using a process called electroluminescence, which is the phenomenon where organic light-emitting materials emit light in response to a passing current. In some examples, an OLED diode may include a hole injection layer, a hole transport layer, an electron injection layer, an emission layer, and an electron transport layer. The color of the light emitted by an OLED diode depends on the type of organic light-emitting material used in the emission layer. Different colors can be obtained using various chemical structures of organic light-emitting materials. The intensity of the light can depend on the number of photons emitted or the voltage applied to the OLED diode. In some embodiments, each emitting pixel is formed from the same organic light-emitting material that produces white light, but each emitting pixel also includes a red, green, or blue color filter to filter out colors other than the target color, respectively. The color filters can be formed using cholesteric filter materials, such as multilayer dielectric stacks comprising materials with different refractive indices configured to form optical filters.

[0030] like Figure 2As shown, below the sensing region 108, a light modulation layer 204 is stacked below the display panel 202. The light modulation layer 204 includes a semiconductor layer 240 and an optical filter film 242. In one embodiment, the semiconductor layer 240 includes a silicon microelectromechanical system (MEMS) structure. For example, the semiconductor layer 240 includes a collimator 245, which includes an array of apertures 246. Each aperture 246 is located directly above one or more optical sensing elements 207 in the OFPS 206. The array of apertures 246 can be formed by any suitable technique (e.g., plasma etching, laser drilling, etc.). The array of apertures 246 modulates the incident light reflected from the sensing region 108. By stacking OFPS 206 at the bottom, the display panel 202 (especially the relatively thick cover glass 214) increases the additional vertical distance between the user's finger 110 and the OFPS 206. This allows stray light from the vicinity of the user's finger 110 to reach the optical sensing element 207 along with light from a small spot directly above. The stray light causes image blurring. The array of apertures 246 helps filter out stray light and essentially allows only light from the small spot directly above to be detected, resulting in a sharper image.

[0031] The dimension of collimator 245 is the aspect ratio of aperture 246, defined as the height (a) of aperture 246 divided by the diameter (e) of aperture 246. The aspect ratio of aperture 246 is large enough to allow light incident perpendicularly or nearly perpendicularly to collimator 245 to pass through and reach optical sensing element 207. Examples of suitable aspect ratios for aperture 246 are in the range of about 5:1 to about 50:1, and sometimes from about 10:1 to about 15:1. Other values ​​and ranges are within the scope of this disclosure. In embodiments, the height (a) of aperture 246 is in the range of about 30 micrometers to 300 micrometers, for example, about 150 micrometers. In various embodiments, collimator 245 may be an opaque layer having an array of apertures. In some embodiments, collimator 245 is a monolithic semiconductor layer, such as a silicon layer. Other examples of collimator 245 may include plastics, such as polycarbonate, PET, polyimide, carbon black, inorganic insulating or metallized materials, or SU-8.

[0032] like Figure 2As shown, the light conditioning layer 204 also includes an optical filter 242 on top of the semiconductor layer 240. The optical filter 242 selectively absorbs or reflects certain spectra of incident light, especially components from ambient light 250, such as infrared light and / or other portions of visible light (e.g., red light). The optical filter 242 helps reduce the sensitivity of the optical sensing element 207 to ambient light 250 and increases its sensitivity to light emitted from the light-emitting pixel 222. The optical filter 242 may extend continuously directly above the collimator 245 and has an opening 260 on the exterior of the collimator 245.

[0033] In one example, the optical filter 242 may include a thin metal layer or metal oxide layer that absorbs or reflects light in certain spectra. In another example, the optical filter 242 may include one or more dyes and / or one or more pigments that absorb or reflect certain components of light. Alternatively, the optical filter 242 may include several sublayers or nanoscale features designed to cause interference at certain wavelengths of incident light. In one embodiment, the optical filter 242 may include one or more materials, such as silicon oxide, titanium oxide, or another metal oxide.

[0034] An optical filter film 242 can be deposited on a dielectric layer 241, which can be a buried oxide layer on a semiconductor layer 240. In one embodiment, the buried oxide layer 241 can include one or more materials, such as thermal oxide, plasma-enhanced oxide (PEOX), high-density-plasma (HDP) oxide, etc. Furthermore, the light conditioning layer 204 also includes a passive oxide layer 255 beneath the semiconductor layer 240. In one embodiment, the passive oxide layer 255 can include one or more materials, such as PEOX, HDP oxide, etc.

[0035] In this example, OFPS 206 includes a substrate 268, a plurality of optical sensing elements 207 within the substrate 268, and bonding pads 264 within the substrate 268. Each bonding pad may be a metal pad comprising a conductive material. Figure 2As shown, the stack of passive oxide layer 255, semiconductor layer 240, buried oxide layer 241, and optical filter film 242 may also have several openings 260. The openings 260 allow conductive features (e.g., bonding lines 262) to interconnect at least one bonding pad among the bonding pads 264 on the top surface of the image sensing layer 206 to external circuitry (e.g., a processor of electronic device 100). The bonding pads 264 are routed to control signal lines and power / ground lines embedded in the image sensing layer 206. The image sensing layer 206 may also include alignment marks for alignment control during manufacturing and assembly. In other embodiments, the alignment marks are located in the passive oxide layer 255 or the metal pad / bonding pad layer of the image sensing layer 206 for alignment control during manufacturing and assembly.

[0036] In one embodiment, semiconductor layer 240 has a thickness of about 50 micrometers to 200 micrometers (a). In one embodiment, passive oxide layer 255 has a thickness of about 400 nanometers to 2000 nanometers (b). In one embodiment, buried oxide layer 241 has a thickness of about 1000 nanometers to 2000 nanometers (c). In one embodiment, optical filter film 242 has a thickness of about 1 micrometer to 5 micrometers (d). In one embodiment, each aperture 246 of collimator 245 has a diameter of about 5 micrometers to 30 micrometers. According to various embodiments, the openings 260 of passive oxide layer 255, semiconductor layer 240, and buried oxide layer 241 have different diameters. For example, the opening of buried oxide layer 241 has a diameter of about 100 micrometers to 140 micrometers (f); the opening of semiconductor layer 240 has a diameter of about 80 micrometers to 120 micrometers (g); and the opening of passive oxide layer 255 has a diameter of about 60 micrometers to 100 micrometers (h).

[0037] In one embodiment, a method for acquiring a fingerprint image from a user's finger illuminated by a display panel integrated with a light modulation layer is described below. The screen of the electronic device 100 may initially be in a locked state. A prompt is displayed, which may be an icon (e.g., a fingerprint icon or command text) highlighting a sensing area 108 on the screen. This prompt is indicated by light-emitting pixels 222 below the sensing area 108. The light-emitting pixels 222 may be OLED diodes. Light-emitting pixels 222 outside the sensing area 108 may be turned off in the locked state or when displaying a preset screensaver image. Then, when the user's finger 110 remains stable within the sensing area 108 for a predetermined time, for example, the user holds their finger stable for approximately 100 milliseconds, a biometric detection mode is initiated. Otherwise, the method returns to waiting for new user input.

[0038] In biometric detection mode, the on-screen prompts are turned off, and the luminescent pixels 222 below the sensing area 108 begin to illuminate the user's finger 110. Light 270 emitted from the luminescent pixels 222 can pass through the cover glass 214 and reach the user's finger 110. The user's finger 110 may include ridges 272 and valleys 274. Because the distance to the top surface 216 is closer than the valleys 274, the ridges 272 of the finger can reflect more light, while the valleys 274 can reflect less light. The light 270 is then reflected back to the light modulation layer 204.

[0039] Then, the optical filter 242 filters light of certain spectra. In some embodiments, the optical filter 242 is an infrared light cutoff filter that filters (or reduces) the infrared light component from the incident light, for example, by absorption or reflection. Ambient light 250 (e.g., sunlight) is the primary source of infrared light. Infrared light can easily penetrate a user's finger 110. Therefore, infrared light does not carry useful information about the biostatistical characteristics of the finger and can be considered part of the noise. Mixing the infrared light component from ambient light with reflected light from the emitting pixels reduces the sensitivity of the optical sensing element 207. By filtering infrared light before sensing, the signal-to-noise ratio (SNR) of the incident light will increase. In some other embodiments, the optical filter 242 may target light in certain spectra other than infrared light, such as red light or ultraviolet light in the visible spectrum. The filtering profile of the optical filter 242 can be formulated to give a specific appearance of color, texture, or reflective quality, thereby allowing optimized filtering performance. In some embodiments, the optical filter membrane 242 is an infrared light cutoff filter and has separate membranes stacked below or above for filtering red light to reduce ghosting.

[0040] Then, collimator 245 filters stray light components from light 270. Because of the high aspect ratio of aperture 246, collimator 245 only allows light reflected from sensing area 108 that is incident perpendicularly or nearly perpendicularly onto collimator 245 to pass through and eventually reach OFPS 206. Optical sensing element 207 can be used to measure the intensity of light and convert the measured intensity into a pixel image of an input object, such as a user's finger 110. On the other hand, stray light at a large angle to the normal strikes collimator 245 on its top surface or on a surface within aperture 246 (e.g., aperture sidewalls) and is blocked and prevented from reaching the underlying image sensing layer 206. The aspect ratio of aperture 246 is sufficiently large (e.g., from about 5:1 to about 50:1) to prevent stray light from passing through collimator 245.

[0041] Then, OFPS 206 acquires a fingerprint image. Optical sensing elements 207 within the image sensing layer 206 can convert incident light into electrical output. The output of each optical sensing element 207 can correspond to a pixel in the fingerprint image. Optical sensing elements 207 may include monochrome image sensors (grayscale pixels) and / or color image sensors (color pixels). In some embodiments, each optical sensing element in the optical sensing elements 207 can be configured to correspond to a specific light wavelength, for example, a sensor element directly below the red light emitting pixel 222 for sensing red light wavelengths, a sensor element directly below the green light emitting pixel 222 for sensing green light wavelengths, and a sensor element directly below the blue light emitting pixel 222 for sensing blue light wavelengths.

[0042] The acquired fingerprint image is compared with a real reference image previously stored in memory (or a database). If the fingerprint images match, the screen is unlocked. The luminescent pixels 222 below the sensing area 108 stop illuminating and combine with other luminescent pixels 222 outside the sensing area 108 to begin displaying the regular desktop icons in the unlocked state. If the fingerprint images do not match, the method returns to wait for new biometric detection.

[0043] refer to Figure 3 Cross-sectional views of some embodiments of the semiconductor structure of OFPS 300 are provided. OFPS 300 can be substantially the same as reference numerals. Figure 2 Similar to the OFPS 206 described above, OFPS 300 includes a pixel array 336 of image sensing pixels (abbreviated as pixels) 302 arranged in rows and columns. For example, the pixel array may include approximately three million pixels 302 arranged in 1536 rows and 2048 columns. The semiconductor structure includes a semiconductor substrate 304 in which photodiodes 306 corresponding to the pixels 302 are disposed. The photodiodes 306 are arranged in rows and / or columns within the semiconductor substrate 304 and are configured to accumulate charge (e.g., electrons) from photons incident on the photodiodes 306. The semiconductor substrate 304 may be, for example, a bulk semiconductor substrate, such as a bulk silicon substrate or a silicon-on-insulator (SOI) substrate.

[0044] DTI region 308 defines a substrate isolation grid consisting of grid segments (e.g., individual rectangles or squares adjacent to each other). Further, DTI region 308 extends from approximately flush with the upper surface of substrate 304 into the semiconductor substrate 304. DTI region 308 is laterally arranged around and between photodiodes 306 to advantageously provide optical isolation between adjacent photodiodes 306. DTI region 308 may be, for example, a metal, such as tungsten, copper, or aluminum copper. Alternatively, DTI region 308 may be, for example, a low-n material. The low-n material has a refractive index less than that of filter 310, which is overlaid on the corresponding pixel 302. Filter 310 may be a color filter for color pixels, a transparent color filter for monochrome pixels (grayscale pixels), or a combination of a color filter and a transparent color filter. In some embodiments, DTI region 308 has a refractive index less than about 1.6. Furthermore, in some embodiments, the DTI region 308 is a dielectric such as an oxide (e.g., SiO2) or hafnium oxide (e.g., HfO2), or a material with a refractive index less than silicon.

[0045] An antireflective coating (ARC) 316 and / or a first dielectric layer 318 of the semiconductor structure are disposed on the semiconductor substrate 304 along the upper surface of the semiconductor substrate 304. In embodiments where ARC 316 and the first dielectric layer 318 are present, the first dielectric layer 318 is typically disposed on top of ARC 316. ARC 316 and / or the first dielectric layer 318 separate the semiconductor substrate 304 from the composite gate 320 of the semiconductor structure overlying the substrate 304. The first dielectric layer 318 may be, for example, an oxide, such as silicon dioxide.

[0046] A composite grid 320 is laterally arranged around and between photodiodes 306 to define openings in which filters 310 are disposed. The openings correspond to pixels 302 and are aligned with the center of the photodiode 306 of the corresponding pixel 302. The composite grid 120 includes one or more of a metal grid 324, a low-n grid 326, and a hard mask grid 328, which are stacked in this order on a semiconductor substrate 304. Each grid 324, 326, and 328 is composed of grid segments (e.g., adjacent to each other to collectively form a grid 324, 326, or 328 and a separate rectangle or square surrounding the corresponding photodiode 306). Each grid 324, 326, and 328 also includes openings between and overlying the photodiode 306. The metal grid 324 blocks light from passing between adjacent pixels 302 to help reduce crosstalk. The metal grid 324 may be, for example, tungsten, copper, or aluminum copper. The low-n grid 326 is a transparent material with a refractive index less than that of the filter 310. Because of its low refractive index, the low-n grid 326 acts as a light guide to direct light to the filter 310 and effectively increases the size of the filter 310. Furthermore, because of its low refractive index, the low-n grid 326 is used to provide optical isolation between adjacent pixels 302. Because of its refractive index, light striking the boundary of the low-n grid 326 within the filter 310 typically undergoes total internal reflection. In some embodiments, the low-n grid 326 is a dielectric such as an oxide (e.g., SiO2) or hafnium oxide (e.g., HfO2), or a material with a refractive index less than that of silicon. The hard mask grid 328 may be, for example, silicon nitride or silicon oxynitride.

[0047] Filter 310 is disposed over ARC 316 and / or the first dielectric layer 318. Further, filter 310 is disposed over the photodiode 306 of the corresponding pixel 302 within the opening of the composite grid 320. Filter 310 has an upper surface approximately flush with the upper surface of the composite grid 320. Further, for the color filter in filter 310, filter 310 is assigned light of a corresponding color or wavelength and is configured to filter out all colors or wavelengths of light other than the assigned color or wavelength. Typically, the color filter assignment alternates between red, green, and blue light, such that the color filter includes a red filter, a green filter, and a blue filter. In some embodiments, the color filter assignment alternates between red, green, and blue light according to a Bayer color filter mosaic. Pixel 302 corresponding to the red filter is designated as a red (“R”) pixel; pixel 302 corresponding to the blue filter is designated as a blue (“B”) pixel; pixel 302 corresponding to the green filter is designated as a green (“G”) pixel; and pixel 302 corresponding to the transparent filter is designated as a grayscale (“W”) pixel. These pixels are configured for light sensing and are also designated as sensing pixels 302S. In addition to the sensing pixels 302S used for light sensing, there are also specific pixels distributed in the pixel array that are not used for light sensing but for providing positioning codes, designated as positioning pixels 302P. The bottom surface of the opening of the composite grid 320 corresponding to the positioning pixels 302P is covered by an opaque film 330. In some embodiments, the opaque film 330 has the same material composition as the metal grid 324, forming a continuous metal layer that blocks incident light. In some embodiments, the opaque film 330 is formed of a semiconductor or dielectric material. Because of the opaque film 330, the photodiode 306 of the corresponding positioning pixel 302P cannot sense light, and the output from the positioning pixel 302P is approximately zero (i.e., dark pixels in the fingerprint image).

[0048] A second dielectric layer 130, lining the composite grid 320, separates the filter 310 from the composite grid 320, and a microlens 332 corresponding to the pixel 302 covers the filter 310. The second dielectric layer 130 may be, for example, an oxide such as silicon dioxide, and may be the same material as or a different material from the low-n grid 326. The microlens 332 is centered on the photodiode 306 of the corresponding pixel 302 and is generally symmetrical about a vertical axis centered on the photodiode 306. Furthermore, the microlens 132 is generally suspended above the composite grid 320 around the opening, so that adjacent edges of the microlens 332 are adjacent. The depicted embodiment shows that the microlens 332 is also above the photodiode 306 of the positioning pixel 302P. However, in some embodiments, the microlens 332 may not be present above the photodiode 306 of the positioning pixel 302P.

[0049] Integrated circuit 338 includes a semiconductor substrate 304 and a device region (partially shown). The device region is disposed along the lower surface of the semiconductor substrate 304 and extends into the semiconductor substrate 304. The device region includes a photodiode 306 corresponding to pixel 302 and logic devices, such as transistors, for reading out the photodiode 306. The photodiodes 306 are arranged in rows and columns within the semiconductor substrate 304 and configured to accumulate charge from photons incident on the photodiodes 306. Furthermore, the photodiodes 306 are optically isolated from each other by a DTI region 308 in the semiconductor substrate 304, thereby reducing crosstalk.

[0050] The back-end-of-line (BEOL) metallization stack 340 of integrated circuit 338 is located beneath semiconductor substrate 304 and includes multiple metallization layers 342 and 344 stacked within an interlayer dielectric (ILD) layer 346. One or more contacts 348 of the BEOL metallization stack 340 extend from the metallization layer 344 to the device region. Further, one or more first vias 350 of the BEOL metallization stack 340 extend between the metallization layers 342 and 344 to interconnect the metallization layers 342 and 344. The ILD layer 346 may be, for example, a low-k dielectric (i.e., a dielectric with a dielectric constant less than about 3.9) or an oxide. The metallization layers 342 and 344, the contacts 348, and the first vias 350 may be, for example, metals such as copper or aluminum.

[0051] A carrier substrate 352 lies beneath the integrated circuit 338 and between the integrated circuit 338 and the ball grid array (BGA) 354. The BGA 354 includes a redistribution layer (RDL) 356 disposed along the lower surface of the carrier substrate 352 and electrically coupled to metallization layers 342 and 344 of the BEOL metallization stack 340 via one or more second silicon vias 358 extending through the carrier substrate 352. The RDL 356 is covered by a BGA dielectric layer 360, and an under-bump metallization (UBM) layer 362 extends through the BGA dielectric layer 360 to electrically couple solder balls 364 under the UBM layer 362 to the RDL 356. The BGA dielectric layer 360 may be, for example, epoxy resin. RDL 356, UBM layer 362, second via 358, and solder ball 364 can be metals such as copper, aluminum, and tungsten. Bonding pads (e.g., see reference) Figure 2The aforementioned bonding pad 264 can also be provided on the upper surface of OFPS 300.

[0052] To illustrate the function of locating pixels in a pixel array Figures 4A-4C A top view of a pixel array 400 at different stages of fingerprint recognition is shown. The pixel array 400 can be substantially the same as a reference. Figure 3 Similar to the pixel array 336 described above. Pixel array 400 includes pixels 402 arranged in rows and columns. Pixel 402 includes sensing pixels 402S and positioning pixels 402P. Sensing pixels 402S can all be grayscale pixels, color pixels, or a combination of grayscale and color pixels. Four positioning pixels 402P are shown, including a first positioning pixel 402P-a and a second positioning pixel 402P-b. However, any number of positioning pixels can exist in pixel array 400. The fingerprint image acquired by pixel array 400 is superimposed. Sensing pixels 402S acquire light intensity changes caused by the ridges and valleys of the fingerprint and generate a fingerprint image. In the illustrated embodiment, sensing pixels 402S are all grayscale pixels, and the fingerprint image is a grayscale image. Because the photodiodes of positioning pixels 402P are shielded by an opaque film, no light intensity is sensed at the location of positioning pixels 402P. On the fingerprint image, black dots (dark pixels) appear at the location of positioning pixels 402P.

[0053] refer to Figure 4A An initial fingerprint image is acquired as a reference fingerprint image and stored in memory (or a database). Fingerprint features (mino points) are located using reference vectors to locate pixels. Figure 4A A first vector Va and a second vector Vb are shown. The first vector Va marks a first minutiae at a first location located on a ridge of a reference first positioning pixel 402P-a, and the second vector Vb marks a second minutiae at a second location located on another ridge of a reference second positioning pixel 402P-b. A reference fingerprint image with vectors from the reference positioning pixels is recorded.

[0054] refer to Figure 4B When a user's identity needs to be verified, a new fingerprint image is acquired. The user's finger may not fall in the exact same position as before, and the acquired fingerprint image may be shifted relative to the reference fingerprint image. The localized pixels in the form of reference vectors representing the characteristics (minutions) of the acquired fingerprint are then repositioned. Figure 4B The diagram shows a third vector Va' and a fourth vector Vb', where the third vector Va' is labeled with... Figure 4A The same first detail point, but shifted relative to the first positioning pixel 402P-a, the fourth vector Vb' marks the same... Figure 4AThe same second detail point, but shifted relative to the second positioning pixel 402P-b.

[0055] refer to Figure 4C The acquired fingerprint image is compared with a reference fingerprint image stored in memory. Instead of directional comparisons of the fingerprint's feature set (detail image) (which is easier to forge), vectors are compared. For example, the third vector Va' is compared with the first vector Va, and a shift ΔVa in vector form is calculated. The fourth vector Vb' and the second vector Vb are compared, and a shift ΔVb in vector form is calculated. Then, the shift ΔVa and shift ΔVb are compared. The shift ΔVa should be equal to the shift ΔVb (and many other vectors not repeated herein) to arrive at a match.

[0056] Figures 5-7 Various embodiments of the distribution of positioned pixels 402P in pixel array 400 are shown. (Refer to...) Figure 5 The pixel array 400 can be constructed by repeating unit tiles (or tiles) 400a in columns and rows. Each tile 400a includes sensing pixels 402S and positioning pixels 402P located at the center of the tile 400a. Therefore, the positioning pixels 402P are repeatedly arranged in the pixel array 400. That is, the positioning pixels 402P have a regular pattern.

[0057] refer to Figure 6 The pixel array 400 can be constructed by repeating unit tiles 400b in columns and rows. Tile 400b includes sensing pixels 402S and a plurality of positioning pixels 402P. Based on the arrangement of adjacent positioning pixels 402P, the positioning pixels 402P can be classified into different types of patterns. In the illustrated embodiment, a type I pattern includes two adjacent positioning pixels 402P arranged diagonally, a type II pattern includes isolated positioning pixels 402P, and a type III pattern includes three adjacent positioning pixels 402P forming a triangle. Because of the repetition of tiles 400b, the different types of patterns of positioning pixels 402P are also repeatedly arranged in the pixel array 400. That is, the positioning pixels 402P have regular patterns. The different types of patterns of positioning pixels 402P provide further enhanced anti-counterfeiting features. For example, vector comparison can be performed individually in type I, type II, and type III patterns, and shifting should pass a test within each of the type I, type II, and type III patterns. Then, the shifts from each of the Type I, Type II, and Type III patterns are compared, and these shifts should be identical to arrive at a match. That is, the vector comparison can derive the same shift ΔV based on the Type I pattern for the location pixel 402P. typeI The same shift ΔV is derived based on the Type II pattern of the positioning pixel 402P. typeIIAnd the same shift ΔV is derived from the Type III pattern based on the positioning pixel 402P. typeIII Furthermore, shift ΔV typeI , shift ΔV typeII and shift ΔV typeIII They should also be equal to arrive at a match.

[0058] refer to Figure 7 The positioning pixels 402P can be randomly distributed within the pixel array 400. That is, the positioning pixels 402P can have random patterns. Furthermore, adjacent positioning pixels 402P can form various types of patterns, or even be randomly distributed as a whole within the pixel array 400. For example, in addition to other isolated positioning pixels 402P, Figure 7 The dashed circle in the image highlights two adjacent positioning pixels 402P that form the linear pattern. This combination increases the difficulty of forgery. In various embodiments, for example, in Figures 5-7 In this process, the percentage of the positioning pixel 402P in the total number of pixels in the pixel array 400 can range from about 1% to about 10%. This range is not negligible. If the percentage of the positioning pixel is less than 1%, the anti-counterfeiting feature may not be sufficiently enhanced; if the percentage of the positioning pixel is greater than 10%, the area of ​​the pixel array may not be fully utilized for fingerprint image acquisition. In other words, the fingerprint image acquired by the pixel array implementing the positioning pixel may have dark pixels in an area percentage of 1% to about 10% of the total area of ​​the fingerprint image.

[0059] In addition to the positioning pixels, color pixels can be added to the grayscale pixel array to add skin tone information to the fingerprint. Besides comparing the details of the fingerprint, skin tone information adds another layer of security. Figures 8A-8G Various embodiments are illustrated, showing the addition of multiple colored pixels to an array of all grayscale pixels (denoted as "W"). Positioning pixels also aid in identifying the location of colored pixels by positioning them next to the positioning pixels. This helps software algorithms quickly identify the location of colored pixels from a fingerprint image. Colored pixels can also form patterns of the same type as the positioning pixels. Reference Figure 8A The three positioning pixels form a triangle shape, and the three color pixels for red, green, and blue (RGB) are arranged in the same shape and located next to the positioning pixels. (Reference) Figure 8B Two positioning pixels form a diagonal shape, and two color pixels (e.g., RB, GG, or other suitable combinations) are arranged in the same shape and located next to the positioning pixels. (See reference...) Figure 8C Two positioning pixels form a horizontal line shape, and two color pixels (e.g., RG, GB, or other suitable combinations) are arranged in the same shape and located next to the positioning pixels. (Reference) Figure 8DTwo positioning pixels form a vertical line, and two color pixels (e.g., GB, RG, or other suitable combinations) are arranged in the same shape and located next to the positioning pixels, with a column of grayscale pixels between the positioning pixels and the color pixels. (Reference) Figure 8E The above reference Figure 6 The tile 400b under discussion is reproduced using added color pixels. Color pixels are added next to positioning pixels having the same type of pattern. In the illustrated embodiment, type I patterns include two diagonally arranged adjacent positioning pixels and two diagonally arranged adjacent color pixels; type II patterns include isolated positioning pixels and adjacent isolated color pixels; and type III patterns include three adjacent positioning pixels forming a triangle and three adjacent color pixels forming a triangle. (Reference) Figure 8F The number of color pixels can even exceed the number of grayscale pixels, and the number of grayscale pixels exceeds the number of positioning pixels. In the illustrated embodiment, grayscale pixels appear only in every other row and every other column, while color pixels fill the remaining pixels not occupied by positioning pixels, and positioning pixels are randomly or repeatedly distributed. (See reference...) Figure 8G All sensing pixels in the pixel array can be color pixels, and the positioning pixels are randomly or repeatedly distributed. As those skilled in the art will understand, in addition to Figures 8A-8G Besides those shown, any other suitable combination and arrangement of positioning pixels and color pixels is possible.

[0060] Figure 9 A flowchart illustrating a method 900 for acquiring and identifying a fingerprint image from a user's finger illuminated by a display panel integrated with OFPS, according to an example of this disclosure, is shown below. Reference will be made below. Figure 2 The method 900 is described using an exemplary electronic device 100 shown.

[0061] At frame 902, method 900 begins by displaying a prompt on the screen. The screen of the electronic device 100 may be locked. The prompt may be an icon, such as a fingerprint image or command text. The prompt highlights the sensing area 108 on the screen. The prompt is indicated by light-emitting pixels 222 below the sensing area 108. The light-emitting pixels 222 may be OLED diodes. The light-emitting pixels 222 outside the sensing area 108 may be turned off when the device is locked or when a preset screensaver image is displayed.

[0062] At box 904, method 900 detects an input object, such as a user's finger 110, shown in sensing area 108. This detection can be achieved by sensing changes in incident light at optical sensing element 207. Alternatively, display panel 202 may be a touchscreen and include one or more touch sensors, and detection can be achieved by those touch sensors. In some applications, the user's finger 110 does not need to physically touch the top surface 216 of display panel 202. Instead, near-field imaging can be used to sense touches detected through the user's gloves or other barriers (e.g., oil, gel, and moisture). When the user's finger 110 remains stable for more than a predetermined time, for example, the user keeps their finger stable for about 100 milliseconds, method 900 enters biometric detection mode. Otherwise, method 900 returns to box 902, waiting for new user input.

[0063] At frame 906, the prompt displayed on the screen is turned off, and the luminescent pixel 222 below the sensing area 108 begins to illuminate the user's finger 110. Light 270 emitted from the luminescent pixel 222 passes through the cover glass 214 and reaches the user's finger 110. The user's finger 110 may include ridges 272 and valleys 274. Because the distance to the top surface 216 is closer than the valleys 274, the ridges 272 of the finger can reflect more light, while the valleys 274 can reflect less light. The light 270 is then reflected back to the light-adjusting layer 204.

[0064] At frame 908, method 400 filters stray light components in light 270 at collimator 240. Because of the high aspect ratio of aperture 246, collimator 240 only allows light reflected from sensing area 108 that is incident perpendicularly or nearly perpendicularly onto collimator 240 to pass through and eventually reach image sensing layer 206. Optical sensing element 207 can be used to measure light intensity and convert the measured intensity into a pixel image of user finger 110. On the other hand, stray light at a large angle to the normal strikes collimator 245 on the top surface of collimator 240 or on a surface within aperture 246 (e.g., aperture sidewalls) and is blocked and prevented from reaching the underlying image sensing layer 206. The aspect ratio of aperture 246 is sufficiently large (from about 5:1 to about 50:1) to prevent stray light from passing through collimator 240. As an example, without collimator 240, light reflected from valley 274 can propagate at a large angle relative to the normal direction and reach a sensor element directly below ridge 272. Therefore, the image generated by this sensor element becomes blurred due to the mixing of light from the regions of ridge 272 and valley 274. This light is referred to as stray light. The large aspect ratio of aperture 246 restricts the light receiving cone to a smaller angle, thereby improving the optical resolution of the system. In some embodiments, aperture 246 is cylindrical or conical. The sidewalls of aperture 246 may also include grooves or other structures to prevent stray light from reflecting off the walls and reaching the OFPS 206 below.

[0065] At box 910, method 900 acquires a fingerprint image at OFPS 206. Sensing pixels 207 in the pixel array of image sensing layer 206 convert incident light into electrical output. The pixel array may include sensing pixels that are monochrome (grayscale) pixels, color pixels, or a combination of monochrome and color pixels. Color pixels add skin color information to the fingerprint image. The pixel array also includes positioning pixels that are uniformly or randomly distributed in the pixel array. The output of each sensing pixel 207 may correspond to a pixel in the fingerprint image that has a grayscale level (or RGB color if a color pixel is presented). The output of each positioning pixel may correspond to a dark pixel in the fingerprint image. In some embodiments, each sensing pixel may be configured to correspond to a specific light wavelength, for example, a sensing pixel below a red light emitting pixel (222R) for sensing a red light wavelength, a sensing pixel below a green light emitting pixel (222G) for sensing a green light wavelength, and a sensing pixel below a blue light emitting pixel (222B) for sensing a blue light wavelength.

[0066] At box 912, method 900 obtains a vector representing the characteristics (minarea) of the fingerprint representing the location of the referenced localization pixel. Based on the pattern type of the localization pixel, the vector can also be classified into different groups, for example, a first group of vectors for localization pixels referencing a first type of pattern and a second group of vectors for localization pixels referencing a second type of pattern.

[0067] At box 914, method 900 compares the acquired fingerprint image with a real reference image previously stored in memory (or a database). The comparison involves comparing the vectors of the two images. Vector comparison can be added to the comparison of the detail map at box 914, simply adding another layer of security to the detail map. Alternatively, only the vectors can be compared at box 914. The vectors may differ because fingerprints can shift relative to positioning pixels, but the vector shifts should be identical to arrive at a match. Further, if the vectors are classified into different groups (pattern types), two levels of comparison can be performed. The lower level compares vectors and vector shifts within the same group, which should be identical. The higher level compares vectors and shifts between different groups, which should also be identical to arrive at a match. Skin color information can optionally be another comparison criterion to arrive at a match. If the fingerprint images match, method 900 proceeds to box 916 to unlock the screen. The luminescent pixel 222 below the sensing area 108 will stop illuminating and combine with other luminescent pixels 222 outside the sensing area 108 to begin displaying the regular desktop icons in the unlocked state. If the fingerprint image does not match, method 900 returns to box 902 to wait for new biometric detection.

[0068] While not intended to be limiting, one or more embodiments of this disclosure provide numerous benefits for fingerprint recognition systems (e.g., in consumer (or portable) electronic devices). For example, some sensing pixels in a pixel array are replaced with positioning pixels distributed in a certain pattern. Positioning pixels provide reference points to identify characteristics of the acquired fingerprint and optionally indicate the positions of adjacent color pixels used to provide skin color information. The anti-counterfeiting capability of the fingerprint recognition system is further enhanced.

[0069] In one exemplary aspect, this disclosure relates to a sensing device. In an embodiment, the sensing device includes: a pixel array comprising: a plurality of sensing pixels configured to acquire minute details of a fingerprint; a plurality of positioning pixels configured to provide a positioning code; and a plurality of microlenses disposed on the pixel array.

[0070] In another exemplary aspect, this disclosure relates to a device. In an embodiment, the device includes: an array of filters arranged in columns and rows; an array of light-receiving elements below the filter array, the light-receiving element array being configured to convert incident light reflected from a fingerprint into a fingerprint image; and a plurality of opaque films disposed above a portion of the light-receiving elements, the portion of the light-receiving elements being configured to add dark pixels to the fingerprint image.

[0071] In another exemplary aspect, this disclosure relates to a method. In an embodiment, the method includes: acquiring a fingerprint image using an image sensing device, the image sensing device including a pixel array of a combination of sensing pixels and positioning pixels, the sensing pixels being configured to acquire minutiae in the fingerprint image, and the positioning pixels being configured to provide a positioning code; calculating a vector of the minutiae with reference to the positioning code; and comparing the vector with a reference vector generated from a reference fingerprint image to determine a match between the fingerprint image and the reference fingerprint image.

[0072] The foregoing summary outlines features of several embodiments, enabling those skilled in the art to better understand various aspects of this disclosure. Those skilled in the art should appreciate that they can readily use this disclosure as a basis for designing or modifying other processes and structures for performing the same purposes and / or achieving the same advantages of the embodiments described herein. Those skilled in the art should also recognize that these equivalent constructions do not depart from the spirit and scope of this disclosure, and that various changes, substitutions, and modifications can be made without departing from the spirit and scope of this disclosure.

[0073] Example 1 is an image sensing device comprising: a pixel array including: a plurality of sensing pixels configured to acquire minute details of a fingerprint; a plurality of positioning pixels configured to provide a positioning code; and a plurality of microlenses disposed on the pixel array.

[0074] Example 2 is the image sensing device described in Example 1, wherein all of the sensing pixels are grayscale pixels.

[0075] Example 3 is the image sensing device described in Example 1, wherein all of the sensing pixels are color pixels.

[0076] Example 4 is the image sensing device described in Example 1, wherein the sensing pixel includes a plurality of grayscale pixels and a plurality of color pixels.

[0077] Example 5 is the image sensing device described in Example 4, wherein the color pixel is positioned adjacent to the positioned pixel.

[0078] Example 6 is the image sensing device described in Example 5, wherein the color pixels are arranged in the same pattern as the pattern formed by adjacent positioning pixels.

[0079] Example 7 is the image sensing device described in Example 1, wherein the positioning pixels are arranged in a repeating pattern in the pixel array.

[0080] Example 8 is the image sensing device described in Example 1, wherein the positioning pixels are randomly distributed in the pixel array.

[0081] Example 9 is the image sensing device described in Example 1, further comprising: a collimator on the microlens; and an illumination layer on the collimator.

[0082] Example 10 is the image sensing device described in Example 1, wherein the microlens is positioned directly above the sensing pixel, but not above the positioning pixel.

[0083] Example 11 is an optical fingerprint sensor comprising: an array of filters arranged in columns and rows; an array of light receiving elements below the array of filters, the array of light receiving elements being configured to convert incident light reflected from a fingerprint into a fingerprint image; and a plurality of opaque films disposed above a portion of the light receiving elements, the portion of the light receiving elements being configured to add dark pixels to the fingerprint image.

[0084] Example 12 is the optical fingerprint sensor described in Example 11, wherein the opaque film is made of metal.

[0085] Example 13 is the optical fingerprint sensor described in Example 11, wherein the opaque film is disposed between the filter array and the light receiving element array.

[0086] Example 14 is the optical fingerprint sensor described in Example 11, wherein the positions of the light-receiving elements in this part form a regular pattern.

[0087] Example 15 is the optical fingerprint sensor described in Example 14, wherein, within the regular pattern, the portion of the light-receiving element forms at least two distinct sub-patterns.

[0088] Example 16 is the optical fingerprint sensor described in Example 11, wherein the positions of the light receiving elements described in this part are randomly distributed.

[0089] Example 17 is the optical fingerprint sensor described in Example 11, wherein the filter array includes a combination of color filters and transparent filters.

[0090] Example 18 is a fingerprint verification method comprising: acquiring a fingerprint image via an image sensing device, the image sensing device including a pixel array of a combination of sensing pixels and positioning pixels, the sensing pixels being configured to acquire minutiae in the fingerprint image and the positioning pixels being configured to provide a positioning code; calculating a vector of the minutiae with reference to the positioning code; and comparing the vector with a reference vector generated from a reference fingerprint image to determine a match between the fingerprint image and the reference fingerprint image.

[0091] Example 19 is the method described in Example 18, wherein the vector includes a first set of vectors referencing the positioning code of a first type and a second set of vectors referencing the positioning code of a second type.

[0092] Example 20 is the method of Example 18, further comprising: determining a shift between the vector and the reference vector; and determining whether the shifts are substantially equal to determine the match.

Claims

1. An image sensing device, comprising: Pixel array, the pixel array comprising: Multiple sensing pixels are configured to capture minute details of the fingerprint; and Multiple positioning pixels are configured to provide a positioning code; and Multiple microlenses are disposed on the pixel array. The positioning code is used to convert the direct record of the minutiae into a vector representing the relative position of the minutiae with respect to the positioning pixel, so as to perform anti-counterfeiting identification.

2. The image sensing device according to claim 1, wherein, All of the aforementioned sensing pixels are grayscale pixels.

3. The image sensing device according to claim 1, wherein, All of the aforementioned sensing pixels are color pixels.

4. The image sensing device according to claim 1, wherein, The sensing pixels include multiple grayscale pixels and multiple color pixels.

5. The image sensing device according to claim 4, wherein, The colored pixel is positioned adjacent to the positioned pixel.

6. The image sensing device according to claim 5, wherein, The colored pixels are arranged in the same pattern as the pattern formed by adjacent positioned pixels.

7. The image sensing device according to claim 1, wherein, The positioning pixels are arranged in a repeating pattern in the pixel array.

8. The image sensing device according to claim 1, wherein, The positioning pixels are randomly distributed in the pixel array.

9. The image sensing device according to claim 1, further comprising: A collimator is located above the microlens; as well as An illumination layer is placed above the collimator.

10. The image sensing device according to claim 1, wherein, The microlens is positioned directly above the sensing pixel, but not above the positioning pixel.

11. An optical fingerprint sensor, comprising: The filter array is arranged in columns and rows; Below the filter array, the light receiving element array is configured to convert incident light reflected from a fingerprint into a fingerprint image; as well as Multiple opaque films are disposed on a portion of the light-receiving elements, which are configured to add dark pixels to the fingerprint image. The portion of the light-receiving elements is also configured to provide a positioning code for converting a direct record of a minutiae in the fingerprint image into a vector representing the relative position of the minutiae with respect to the dark pixels, for anti-counterfeiting identification.

12. The optical fingerprint sensor according to claim 11, wherein, The opaque film is made of metal.

13. The optical fingerprint sensor according to claim 11, wherein, The opaque film is disposed between the filter array and the light receiving element array.

14. The optical fingerprint sensor according to claim 11, wherein, The positions of the light-receiving elements described in this section form a regular pattern.

15. The optical fingerprint sensor according to claim 14, wherein, Within the regular pattern, this portion of the light-receiving element forms at least two different sub-patterns.

16. The optical fingerprint sensor according to claim 11, wherein, The positions of the optical receiving elements described in this section are randomly distributed.

17. The optical fingerprint sensor according to claim 11, wherein, The filter array includes a combination of color filters and transparent filters.

18. A fingerprint verification method, comprising: A fingerprint image is acquired by an image sensing device, the image sensing device comprising a pixel array of a combination of sensing pixels and positioning pixels, the sensing pixels being configured to acquire minutiae in the fingerprint image, and the positioning pixels being configured to provide a positioning code, wherein the positioning code is used to convert the direct record of the minutiae into a vector representing the relative position of the minutiae with respect to the positioning pixel for anti-counterfeiting identification. The vector of the minutiae is calculated by referring to the location code; and The vector is compared with a reference vector generated from a reference fingerprint image to determine a match between the fingerprint image and the reference fingerprint image.

19. The method according to claim 18, wherein, The vectors include a first set of vectors referencing the positioning code of the first type and a second set of vectors referencing the positioning code of the second type.

20. The method of claim 18, further comprising: Determine the shift between the vector and the reference vector; as well as Determine whether the shifts are equal to determine the match.

Images