Under-display optical fingerprint sensor arrangement for mitigating moiré effect

Abstract

The present invention relates to an optical fingerprint sensor arrangement structure under a display for mitigating the moire effect, and in particular discloses a system and method for an electronic device for imaging a biometric feature object having a structural feature of interest. The electronic device comprises: a display, the display comprising rows of pixel elements, the rows of pixel elements being parallel to a first main direction along a first axis; and an optical sensor, the optical sensor being mounted below the display, the optical sensor being parallel to a second main direction along a second axis. The second axis is rotated at an angle relative to the first axis to adjust the moire pattern to be outside the frequency range of the structural feature of interest.

Description

Technical Field

[0001] The present disclosure relates generally to optical sensors, and more particularly to an under-display optical fingerprint sensor arrangement that mitigates moire effects. Background Art

[0002] Object imaging is used in a variety of applications. For example, a biometric recognition system images a biometric object for identification and / or verification of a user of a device that includes the recognition system. Biometric imaging provides a reliable, non-invasive way to verify an individual's identity for identification purposes. Various types of sensors can be used for biometric imaging.

[0003] Fingerprints, like other biometric features, are based on unique personal characteristics and therefore provide a reliable mechanism for identifying individuals. Therefore, fingerprint sensors have many potential applications. For example, fingerprint sensors can be used to provide access control in stationary applications (such as security checkpoints). Fingerprint sensors can also be used to provide access control in mobile devices, such as mobile phones, wearable smart devices (such as smart watches and activity trackers), tablets, personal data assistants (PDAs), navigation devices, and portable gaming devices. Therefore, some applications, especially those related to mobile devices, require identification systems that are both small in size and very reliable.

[0004] The fingerprint sensor in most mobile devices is a capacitive sensor having a sensing array configured to sense the ridge and valley features of a fingerprint. Typically, these fingerprint sensors detect either absolute capacitance (sometimes referred to as "self capacitance") or transfer capacitance (sometimes referred to as "mutual capacitance"). In either case, the capacitance at each sensing element in the array varies depending on whether a ridge or valley is present, and these variations are electrically detected to form an image of the fingerprint.

[0005] While capacitive fingerprint sensors offer certain advantages, most commercially available capacitive fingerprint sensors have difficulty sensing fine ridge and valley features over large distances, requiring the fingerprint to contact the sensing surface close to the sensing array. It remains a significant challenge for capacitive sensors to detect fingerprints through thick layers, such as the thick cover glass (sometimes referred to as a "cover lens") that protects the displays of many smartphones and other mobile devices.

[0006] Optical fingerprint sensors offer an alternative to capacitive fingerprint sensors. Recently, attempts have been made to implement optical fingerprint sensors in the active area of ​​a display, such as under the display of a mobile device. Display components such as pixels and sub-pixels will typically have a periodicity due to the repetitive nature of the display components. Similarly, individual optical sensor elements on an optical sensor that may be mounted under a display will have their own periodicity. The combined periodicity of the optical sensor elements and display components can result in a moire effect, resulting in some parts of the fingerprint image having light and dark areas, which in turn can interfere with analyzing fingerprint features such as ridges and valleys. Summary of the invention

[0007] One embodiment provides an electronic device for imaging a biometric feature object having a structural feature of interest. The electronic device includes: a display having rows of pixel elements parallel to a first principal direction along a first axis; and an optical sensor disposed below the display, the optical sensor parallel to a second principal direction along a second axis. The second axis has an angle relative to the first axis, and wherein the angle adjusts a moiré pattern frequency to be outside a frequency range corresponding to the structural feature of interest.

[0008] Another embodiment provides an electronic device. The electronic device includes: a display having rows of pixel elements, the rows of pixel elements parallel to a first principal axis; and an optical sensor having rows of sensing elements, the rows of sensing elements parallel to a second principal axis, the optical sensor configured to image a fingerprint. The optical sensor is disposed below the display and oriented such that the second principal axis is rotated relative to the first principal axis at an angle Ɵ sufficient to reduce a moire effect on the image when imaging the fingerprint.

[0009] Yet another embodiment provides a method for determining an angle at which to mount an optical sensor relative to a display to mitigate moiré patterns. The method includes: determining a frequency of a component of the display; determining a frequency of a component of the optical sensor; determining a frequency of a moiré pattern; and determining the angle based on the frequency of the component of the display and the frequency of the component of the sensor, wherein the angle adjusts the frequency of the moiré pattern. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 is a block diagram of an exemplary input device.

[0011] Figure 2 is a block diagram of an electronic device with an optical sensor integrated within an active display area.

[0012] Figure 3 is a block diagram illustrating a side view of an example of an electronic device having an optical sensor integrated within an active display area.

[0013] Figures 4A-4C An example of a top view of an optical sensor array and an optical element arrangement is shown.

[0014] Figure 5A-5B Examples of display pixel and sub-pixel arrangements are shown.

[0015] Figure 6 is a block diagram of an electronic device with an optical sensor integrated within an active display area with angle adjustment to mitigate moire effects.

[0016] Figure 7 Images from an optical sensor integrated within an active display with and without sensor adjustment are shown.

[0017] Figure 8 Images from an optical sensor integrated within an active display with and without sensor adjustment are shown.

[0018] Fig. 9 An alternative embodiment of a sensing element formed at an angle on a die is shown.

[0019] Fig.10 A method of fabricating an optical sensor integrated under a display that mitigates the moire effect is shown. DETAILED DESCRIPTION

[0020] The following specific embodiments are merely exemplary in nature and are not intended to limit the invention or the application and use of the invention. In addition, it is not intended to be bound by any express or implied theory presented in the aforementioned technical field, background technology, invention content, accompanying drawings, or the following specific embodiments.

[0021] An optical fingerprint sensor for use under a display is described. The display has a periodic structure corresponding to the pitch of individual display pixels and sub-pixels. The optical fingerprint sensor also has a periodic structure corresponding to the pitch of individual sensor pixels or elements. One solution is to design the optical fingerprint sensor so that all sensor elements fall directly under an opening in the display, such as under an area of ​​the display not occupied by display pixels. However, it is difficult to design the sensor to exactly match the opening in the display. The problem becomes even more complicated when trying to design an optical sensor that can be used for a variety of displays with different geometric configurations and structural features. When the fingerprint sensor does not exactly match the opening in the display, a moiré pattern will appear in any resulting fingerprint image. The problem of the amount of degradation of the fingerprint image is particularly acute when the frequency of the moiré pattern is of the same order of magnitude as the frequency of features of interest, such as fingerprint ridges and valleys.

[0022] The optical fingerprint sensor described herein is designed to mitigate the moire effect by adjusting the angle or rotation of the sensor element relative to the display pixel so that the spatial frequency of the moire pattern does not interfere with the fingerprint image. By adjusting the rotation angle, the disclosed fingerprint sensor reduces the magnitude of the moire effect and / or causes the moire frequency to be outside the range of interest. The specific rotation angle can vary and depends on the periodicity of the display structure (e.g., pixels, sub-pixels, electrodes, etc.) and the optical sensor structure (e.g., sensor elements and optical elements such as collimators).

[0023] See the attached picture, Figure 1 1 is a block diagram of an exemplary electronic device 102 having a sensor 100. The sensor 100 may be configured to provide input to an electronic system (also referred to as an "electronic device"). It will be appreciated that the sensor 100 is described as an optical biometric feature sensor (e.g., a fingerprint sensor) mounted under a display. The display may include other sensors, such as a touch sensor, which may use any suitable sensing technology, including but not limited to capacitive or optical sensing technology.

[0024] Some non-limiting examples of electronic systems include personal computers of all sizes and shapes, such as desktop computers, laptops, netbooks, tablet computers, e-book readers, personal digital assistants (PDAs), and wearable computers such as smart watches and activity tracker devices. In fact, the present disclosure contemplates any electronic device or system having an optical sensor under a display. As appropriate, the sensor 100 can communicate with some portion of the electronic system using any one or more of the following: a bus, a network, and other wired or wireless interconnection methods. Examples include I 2 C, SPI, PS / 2, Universal Serial Bus (USB), Bluetooth, RF, and IRDA.

[0025] The sensor 100 is configured to sense input provided by one or more input objects 140 in the sensing area 120. In one embodiment, the input object 140 is a finger, and the sensor 100 is implemented as a fingerprint sensor (also referred to as a "fingerprint scanner"), which is configured to detect fingerprint features of the input object 140. In other embodiments, the sensor 100 may be implemented as a blood vessel sensor (e.g., for finger vein recognition), a hand geometry feature sensor, or a proximity sensor (e.g., a touch pad, a touch screen, and or other touch sensor devices). Therefore, the sensor 100 is more broadly understood as a biometric feature sensor.

[0026] The sensing region 120 includes any space above, around, in, and / or near the sensor 100 in which the sensor 100 is able to detect input (e.g., user input provided by one or more input objects 140). The size, shape, and location of a specific sensing region may vary widely for different embodiments. In some embodiments, the sensing region 120 extends from the surface of the sensor 100 into space in one or more directions. In various embodiments, the input surface may be provided by the surface of a housing in which the sensor element is located, by a panel applied to the sensor element or any housing, etc. In some embodiments, the sensing region 120 has a rectangular shape when projected onto the input surface of the input device. The sensing region 120 may include the entire area of ​​the display or only a portion of the display.

[0027] The sensor 100 includes one or more optical detector elements (or "sensing elements") for detecting user input and imaging input objects. Some embodiments utilize arrays or other regular or irregular patterns of sensing elements to detect and image input objects 140. One or more detector elements detect light from a sensing area. In various embodiments, the detected light may be reflected from an input object in the sensing area, emitted by an input object in the sensing area, or some combination thereof. Example optical detector elements include photodiodes, CMOS arrays, CCD arrays, photodiodes, and other types of light sensors configured to detect light in the visible or invisible spectrum (such as infrared or ultraviolet light). The light sensor may also be a thin film transistor (TFT) or a thin film diode (TFD).

[0028] Some optical embodiments provide illumination of the sensing region. Light reflected or scattered from the sensing region in (one or more) illumination wavelengths is detected to determine input information corresponding to the input object. Illumination of the sensing region may be provided by display pixels (e.g., OLED), backlighting, or a separate light source.

[0029] Some optical embodiments rely on the principle of direct illumination of an input object, which may or may not be in contact with the input surface of the sensing region, depending on the configuration. One or more light sources and / or light directing structures may be used to direct light to the sensing region. When an input object is present, the light is reflected from the surface of the input object, which reflection may be detected by the optical sensing element and used to determine information about the input object.

[0030] Some optical implementations rely on the principle of internal reflection to detect an input object in contact with the input surface of the sensing region. One or more light sources may be used to direct light in the transmission medium at an angle that is internally reflected at the input surface of the sensing region at the angle due to the different refractive indices at opposite sides of the boundary defined by the sensing surface. The refractive index is varied across the boundary caused by the input object contacting the input surface, which changes the internal reflection characteristics at the input surface. If the frustrated total internal reflection (FTIR) principle is used to detect the input object, a higher contrast signal can generally be achieved. In such an embodiment, light can be directed to the input surface at an incident angle that is completely internally reflected at the incident angle, except where the input object contacts the input surface and causes the light to be partially transmitted across this interface. An example of this situation is the presence of a finger directed to the input surface defined by the glass-to-air interface. Compared to air, the higher refractive index of human skin causes light incident at the input surface at the critical angle of the interface to air to be partially transmitted through the finger, otherwise the light would be completely internally reflected at the glass-to-air interface in this case. This optical response can be detected by the system and used to determine spatial information. In some embodiments, this can be used to image small-scale fingerprint features where the internal reflection of incident light differs depending on whether a ridge or valley is in contact with that portion of the input surface.

[0031] Some embodiments are configured to provide images spanning one, two, three, or higher dimensional spaces. The input device may have a sensor resolution that varies between embodiments depending on factors such as the specific sensing technology involved and / or the scale of the information of interest. The sensor 100 is implemented as a fingerprint sensor having a sensor resolution high enough to capture fingerprint features. In some embodiments, the fingerprint sensor has a resolution sufficient to capture detail locations (including ridge ends and bifurcations), directional fields (sometimes referred to as "ridge flows"), and / or ridge architectures. These are sometimes referred to as level 1 features and level 2 features, and in exemplary embodiments, a resolution of 0.1 mm or less is capable of reliably capturing these features. In some embodiments, the fingerprint sensor has a resolution sufficient to capture higher level features, such as sweat pores or edge contours (i.e., the shape of the edges of individual ridges). These are sometimes referred to as level 3 features, and in exemplary embodiments, a resolution of at least 0.05 mm or less is capable of reliably capturing these features.

[0032] In some embodiments, the fingerprint sensor is implemented as a placement sensor (also known as an "area" sensor or a "static" sensor) or a swipe sensor (also known as a "sliding" sensor or a "sweeping" sensor). In a placement sensor embodiment, the sensor is configured to capture fingerprint input when the user's finger remains stationary over the sensing area. Typically, a placement sensor includes sensing elements that form a two-dimensional array capable of capturing the desired area of ​​a fingerprint in a single image frame. In a swipe sensor embodiment, the sensor is configured to capture fingerprint input based on the relative motion between the user's finger and the sensing area. Typically, a swipe sensor includes sensing elements that form a linear array or a narrow two-dimensional array, which is configured to capture multiple image frames when the user's finger is swiped over the sensing area. The multiple image frames can then be reconstructed to form an image of the fingerprint corresponding to the fingerprint input. In some embodiments, the sensor is configured to capture both placement and swipe inputs.

[0033] In some embodiments, the fingerprint sensor is configured to capture a smaller area than the entire area of ​​the user's fingerprint in a single user input (referred to herein as a "partial" fingerprint sensor). Typically, the resulting partial area of ​​a fingerprint captured by a partial fingerprint sensor is sufficient for the system to perform a fingerprint match from a single user input of the fingerprint (e.g., a single finger placement or a single finger swipe). Some example imaging areas for partial placement sensors include 100 mm 2 In another exemplary embodiment, the partially placed sensor has an imaging area of ​​20–50 mm. 2In some embodiments, a portion of the fingerprint sensor has an input surface that is the same size as the imaging area.

[0034] Although generally Figure 1 The input device is described in the context of a fingerprint sensor in , but embodiments of the present disclosure include other biometric sensor devices. In various embodiments, the biometric sensor device can be configured to capture physiological biometric features of a user. Some exemplary physiological biometric features include fingerprint patterns, blood vessel patterns (sometimes referred to as "vein patterns"), palm prints, and hand geometry. In addition, the described embodiments apply to any optical sensor that can be set below the display, such as using an optical sensor mounted or set under the display to sense an area on the top of the display.

[0035] exist Figure 1 , a processing system 110 is shown in communication with the sensor 100. The processing system 110 includes part or all of one or more integrated circuits (ICs) and / or other circuit system components. In some embodiments, the processing system can be configured to operate the hardware of the input device to capture input data, and / or perform a biometric feature determination process or other process based on the input data captured by the sensor 100.

[0036] In some embodiments, the processing system 110 is configured to operate the sensor hardware of the sensor 100 to detect an input in the sensing region 120. In some embodiments, the processing system includes a driver circuit system configured to drive a signal with the sensing hardware of the input device and / or a receiver circuit system configured to receive a signal with the sensing hardware. For example, a processing system for an optical sensor device may include a driver circuit system configured to drive an illumination signal to one or more LEDs, LCD backlights, or other light sources, and / or a receiver circuit system configured to receive a signal with an optical sensing element.

[0037] In some embodiments, the processing system 110 includes electronically readable instructions, such as firmware code, software code, and / or the like. In some embodiments, the processing system 110 includes a memory for storing electronically readable instructions and / or other data (e.g., reference templates for biometric feature recognition). The processing system 110 may be implemented as a physical part of the sensor 100, or may be physically separate from the sensor 100. The processing system 110 may communicate with some parts of the sensor 100 using a bus, a network, and / or other wired or wireless interconnection. In some embodiments, the components that make up the processing system 110 are placed together, such as near the (one or more) sensing elements of the sensor 100. In other embodiments, the components of the processing system 110 are physically separated from one or more components near the (one or more) sensing elements of the sensor 100 and one or more components elsewhere. For example, the sensor 100 may be a peripheral device connected to a computing device, and the processing system 110 may include software configured to run on a central processing unit of the computing device and one or more ICs (perhaps with associated firmware) separate from the central processing unit.

[0038] As another example, the sensor 100 may be physically integrated into a mobile device, and the processing system 110 may include circuitry and / or firmware that is part of a central processing unit or other main processor of the mobile device. In some embodiments, the processing system 110 is dedicated to implementing the sensor 100. In other embodiments, the processing system 110 performs functions associated with the sensor and also performs other functions, such as operating a display screen, driving a haptic actuator, running an operating system (OS) for an electronic system, and the like.

[0039] The processing system 110 may be implemented as a set of modules that operate different functions of the processing system 110. Each module may include a circuit system, firmware, software, or a combination thereof that is part of the processing system 110. In various embodiments, different combinations of modules may be used. Example modules include hardware operation modules for operating hardware (e.g., sensing elements, electrodes, and display screens), data processing modules for processing data (e.g., sensor signals and position information), and reporting modules for reporting information. Other example modules include sensor operation modules configured to operate (one or more) sensing elements to detect input and / or image input objects, recognition modules configured to recognize action representations (e.g., mode change action representations (gestures)), and mode change modules for changing operating modes. In one or more embodiments, the first and second modules may be included in separate integrated circuits. For example, the first module may be at least partially included in a first integrated circuit, and the separate module may be at least partially included in a second integrated circuit. In addition, some parts of a single module may span multiple integrated circuits.

[0040] In some embodiments, the processing system 110 responds to user input (or lack of user input) in the sensing region 120 directly by taking one or more actions. Example actions include unlocking the device or otherwise changing the operating mode, as well as GUI actions, such as cursor movement, selection, menu navigation, and other functions. In some embodiments, the processing system 110 provides information about the input (or lack of input) to some portion of the electronic system (e.g., to a central processing system of the electronic system that is separate from the processing system 110, if such a separate central processing system exists). In some embodiments, some portion of the electronic system processes the information received from the processing system 110 to act on the user input, e.g., to facilitate a full range of actions, including mode change actions and GUI actions.

[0041] In some embodiments, the processing system 110 operates the sensing element(s) of the sensor 100 to generate an electrical signal indicating an input (or lack of input) in the sensing region 120. The processing system 110 may perform any appropriate amount of processing on the electrical signal when generating information provided to the electronic system. For example, the processing system 110 may digitize an analog electrical signal obtained from the sensor element. As another example, the processing system 110 may perform filtering or other signal conditioning. As yet another example, the processing system 110 may subtract or otherwise take into account a baseline so that the information reflects the difference between the electrical signal and the baseline. As yet another example, the processing system 110 may determine location information, identify input as a command, authenticate a user, and the like.

[0042] As mentioned, the sensing area 120 of the sensor 100 overlaps at least a portion of the active area of ​​the display screen. The display screen can be any type of dynamic display capable of displaying a visual interface to a user, such as an organic LED (OLED) display. Of course, it will be understood that the disclosed embodiments can be used with other types of displays that are transparent or translucent. The display screen can also be flexible or rigid, and can be flat, curved, or have other geometric configurations. In some embodiments, the display screen includes a glass or plastic substrate for TFT circuit systems and / or other circuit systems, which can be used to provide visibility and / or provide other functions. In some embodiments, the display device includes a cover glass (sometimes referred to as a "glass cover") disposed above the display circuit system, which can be optically transparent and also provides an input surface for the input device. Example cover glass materials include amorphous glass (which can be chemically hardened), sapphire, and plastic.

[0043] Figure 22 is a block diagram illustrating an exemplary electronic device 200 (e.g., a mobile device such as a smartphone or tablet) having both a display 204 and an optical biometric (e.g., fingerprint) image sensor 202. The display 204 includes various pixels and sub-pixels (e.g., red, green, blue) 208, which are schematically illustrated but not to scale. The pixels and sub-pixels are generally arranged in rows and columns along an X-axis and a Y-axis, respectively. The biometric sensor 202 includes an array of sensing elements and is integrated with the display 204, such as being mounted or otherwise disposed under the display pixels such that the biometric sensor 202 overlays the display 204. Although the fingerprint sensor 202 is illustrated as occupying only a portion of the area of ​​the display 204, it will be appreciated that the biometric sensor 202 may cover an area substantially equivalent to the area of ​​the display 204. As described in more detail herein, the biometric sensor 202 is adjusted (e.g., rotated) to be at an angle Ɵ relative to the display in order to reduce moire effects.

[0044] Figure 3 An example of a stacked structure of a biometric optical image sensor device 300 used to acquire an image of a biometric object 301, such as a fingerprint, is shown. The image sensor device 300 includes an optical sensor 302. The optical sensor 302 includes a sensing element array 304 and an optional optical element or light conditioning layer 306 disposed above the sensing element array 304. The optical sensor 302 is mounted or otherwise disposed below a display 308. It will be understood that the stacked structure is shown in a simplified manner and may include other layers and / or components. As just a few examples, a stacked layer (e.g., a glass cover or cover glass) may be disposed above the display, and various fibers, adhesives, etc. may be inserted between the layers. In addition, the exact layers will vary depending on the display technology used (e.g., OLED, LCD, etc.).

[0045] The sensing area of ​​the input object 301 is shown above the display 308. The top surface 310 may form a sensing surface that provides a contact area for the input object 301 (e.g., a fingerprint). The display 308 includes an array of pixels 312, which are used to generate graphics, text, etc. visible to the user. Each pixel 312 can be further decomposed into sub-pixels 314, such as red, green, and blue sub-pixels, which can be arranged in various patterns, such as straight lines, rectangles, triangles, stripes, diagonal lines, PenTile patterns.

[0046] Although generally described in the context of a fingerprint (or other biometric feature) for illustrative purposes, the input object 301 can be any object to be imaged. Generally speaking, the object 301 will have various features. For example, the object 301 has ridges and valleys. Due to their convex nature, the ridges contact the sensing surface 310. In contrast, the valleys do not contact the sensing surface 310, but instead form an air gap between the input object 301 and the sensing surface 310. In the case of a fingerprint, for example, the frequency of the ridges is in the range of about 2 to 3 / mm, which feature can be detected and optically imaged using the sensing element array 304. Other features such as pores, minutiae, etc. can be imaged and similarly have corresponding spatial frequency ranges.

[0047] The sensing element array 304 detects light from the input object 301. A non-limiting example of a suitable sensor array is a complementary metal oxide semiconductor (CMOS) sensor array, although the systems and methods contemplate any suitable sensor array. The sensing element array 304 includes a plurality of individual optical sensing elements capable of detecting the intensity of incident light. The sensing elements form the sensing element array 304, which may be a regular pattern (e.g., a rectangular array) or an irregular pattern. An example of a sensor pitch would be approximately 1 μm to 200 μm, with a corresponding spatial frequency of 1000 / mm to 5 / mm.

[0048] In order to achieve optical sensing of fingerprints and fingerprint size characteristics, the light reflected from the fingerprint can be conditioned by an optical element 306, which can be, for example, a collimator, a color filter, a polarizer, or other light conditioning element, so that the light reaching each sensing element in the sensing element array 304 comes only from a small spot on the input object 301 that is directly above the sensor element (e.g., orthogonal or nearly orthogonal to the plane defined by the sensing element array 304). In general, the optical element 306 can be provided with an array of apertures or collimator holes 320, each aperture being located directly above one or more optical sensing elements on the sensing element array 304. The spacing of the apertures can be, for example, about 50 μm, which corresponds to a spatial frequency of about 20 / mm.

[0049] As further described below, the primary direction or orientation of the optical sensor 302 (e.g., the axis of the rows or columns of sensing elements) is rotated relative to the primary direction of the display 308 (e.g., the axis of the rows or columns of pixel elements) in order to reduce moire effects. Such rotation may include rotating the sensing element array 304 relative to the display 308, rotating the optical element 306 (if provided) relative to the display 308, or rotating both the sensing element array 304 and the optical element 306. The degree of rotation of the optical element 306 and / or the sensing element array 304 depends on their respective periodicities compared to the periodicity of the display component, the resulting moire frequencies, and the degree to which the resulting moire frequencies interfere with the imaged structural features of interest (e.g., fingerprint ridges, pores, minutiae, etc.).

[0050] Figure 4A -4C shows various sensors 302 ( Figure 3 ) is a plan view of the component. As described below, the sensor 302 has a periodicity. Figure 3 As mentioned, the optical sensor 302 may include an optical element and an array of sensing elements. The periodicity of the sensing elements may be the same as or different from that of the optical elements.

[0051] Figure 4A 4 shows a sensing element array 400 comprising rows and columns of individual sensing elements 402. In the example, the rows are parallel to X Axis and columns parallel to Y axis. Although the sensing element array 400 is shown as a regular pattern of rows and columns (e.g., a rectangle), the sensing array 400 can be implemented in an irregular pattern. Also, although the individual sensing elements 402 are shown as being more or less adjacent to each other, the sensing elements 402 can be spaced apart from each other. In addition, although the sensing elements 402 are shown as having a rectangular cross-section, the cross-section can be of any geometric configuration. However, in general, the individual sensing elements 402 are spaced apart from each other by a distance of P ,distance P represents the pitch or spatial period of the sensing array. Therefore, the spatial frequency of the sensing element ( f )yes P The reciprocal of or 1 / P .Although Figure 4A The sensing elements in are shown as forming a rectangular array, but other regular or irregular patterns may be used, such as straight lines, triangles, PenTile patterns.

[0052] Figure 4B-4C Examples of optional optical elements are shown, for example, in combination with Figure 3 As described in 306. As described, optical elements can be used to provide light conditioning to reduce image blur. Figure 4B-4CIn the particular embodiment shown in , the optical element is a collimator, although other light modifiers such as color filters or polarizing films may be used. Figure 4B In , the collimator includes a rectangular array of apertures 412 formed by sidewalls 414. The sidewalls 414 may be formed of a light absorbing material or a light blocking material. The apertures 412 may be air gaps or filled with a transparent or translucent material. Figure 4C In the embodiment, the collimator has an array of apertures 422 having a circular cross-section formed by openings in a light blocking or blocking material 424. As in the case of the sensing element ( Figure 4A ), Figure 4B-4C The array of pores shown in the figure may be formed in a regular or irregular pattern and generally follows the X Lines and along the axis Y As further shown, each individual optical element (e.g., collimator opening) has a spatial periodicity or pitch ( P′ ) and the corresponding spatial frequency ( f′ ). Although Figure 4B-4C The apertures in are shown as forming a rectangular array, but other regular or irregular patterns may be used.

[0053] Figure 5A-5B Various examples of arrangement structures of display pixels and sub-pixels of a display are shown. Figure 5A As shown, the pixels extend generally in a straight line forming a row, wherein each pixel 502 has, for example, red, green and blue sub-pixels 504. Of course, the display will typically have multiple rows of pixels. The first periodicity ( P1 ) and frequency (1 / P1 ) is defined by the distance between adjacent sub-pixels 504. The second periodicity ( P2 ) and frequency (1 / P2 ) is defined by the distance between adjacent sub-pixels 502. Each of these periods is relevant to analyzing the moiré effect and therefore to the rotation to be applied to the sensor relative to the display.

[0054] For example, assuming that the distance between each pixel is 60 μm and the distance between sub-pixels is 20 μm, the two periods 60 μm and 20 μm (and corresponding frequencies of approximately 16-17 pixels / mm and 50 sub-pixels / mm) are relevant for the purpose of analyzing potential moiré effects.

[0055] Figure 5B Another example of a display pixel pattern is shown. In this example, the distance between adjacent display sub-pixels (e.g., the distance between the red sub-pixel 512 and the green sub-pixel 514) is P′ 1, and the distance between adjacent display pixels (e.g., 510 and 510′) is P′2. Each of P'1 and P'2 forms a periodicity to be accounted for with respect to the moiré effect. However, in the example, each adjacent pixel (e.g., 510 and 510') is not identical to the immediately adjacent pixel, but rather includes sub-pixels that are mirror images of each other. For example, the red sub-pixel 512 of pixel 510 is a mirror image of sub-pixel 512' of pixel 510'. Thus, there is an additional periodicity P'3, which is the distance before a given sub-pixel color repeats in a non-mirror form.

[0056] It will be understood that the illustrated display pixels are shown in simplified form. The display pixels may include other structures, such as electrodes that may further increase the periodicity of the display. In addition, the specific arrangement structures shown are for example purposes. Any layout of pixels and sub-pixels may be used (e.g., straight lines, rectangles, triangles, PenTile, etc.), and each layout includes a periodicity that is taken into account when determining the appropriate rotation angle. The specific layout of pixels and sub-pixels and optical sensor elements is not critical, as long as the periodicity of the structure is taken into account when mitigating the moire effect due to positioning and adjusting (e.g., rotating) the sensor relative to the display.

[0057] Figure 6 An electronic device 600 (eg, a mobile phone) is shown having a display 602 and an optical sensor 604 mounted below the display. As shown, the electronic device 600 and the display 602 include an optical sensor 604 disposed along an axis. X The axis (or direction) and along Y Axis of axis. X The axis generally represents the direction of the display pixel rows (for example, the pixel rows are parallel to the X axis), and Y The axis lines generally represent columns of display pixels. For ease of reference, X The axis (the direction of the rows of display pixels) will be referred to as the principal direction of the display. The optical sensor 604 is mounted along the axis (or direction) X', meaning that the rows of sensing elements on the optical sensor 604 are parallel to the X' axis. For ease of reference, the X' axis (the direction of the rows of sensing elements) is referred to as the principal direction of the sensor. As shown, there is an angle between the X axis and the X' axis. Ɵ This angle is chosen to mitigate moire effects.

[0058] Selected Angle ƟWill depend on the periodicity of the optical sensor and the display. With respect to the sensor, the periodicity of both any optical elements (e.g., collimators) and the sensor elements are considered. In addition, the periodicity of the display may include consideration of multiple periodicities, such as the periodicity of each sub-pixel, pixel, and any other repeating structural features (e.g., electrodes). The main consideration is to avoid the appearance of Moire patterns at spatial frequencies near the spatial frequency corresponding to the feature of interest. For example, in the case of fingerprint ridges, Moire patterns in the range of 2-5 / mm will be avoided. Moire frequency magnitudes above or below the frequency of interest may exist without substantially affecting the quality of the fingerprint image.

[0059] As a simple example, consider a single frequency f 1 (e.g., pixels / mm) and displays with a single frequency f 2 (e.g., sensing elements / mm). In addition, assume that what is desired is to optically acquire a fingerprint image with a ridge pitch spatial frequency of approximately 2-3 lines / mm. The moiré frequencies due to the arbitrarily non-rotating sensing element and display pixel array will result in f 1 ± f 2 If the moiré frequency is on the order of the frequency corresponding to the feature of interest (2-3 / mm), significant interference with fingerprint imaging will occur. Therefore, according to the methods and systems described herein, the optical sensor (e.g., an array of sensing elements and / or optical elements) is arranged at an angle Ɵ Rotation, where Ɵ is selected so that the moiré frequencies are significantly mitigated, e.g., the moiré frequencies are substantially increased or decreased above or below the frequencies corresponding to the structural features of interest. For example, in the case of a fingerprint with a frequency of about 2-3 / mm, a moiré frequency of less than 1 / mm or greater than 10-20 / mm may be sufficient.

[0060] Combination Figure 7-8 Specific examples are shown. For example, Figure 7Results obtained for an optical sensor mounted under a display are shown with the optical sensor not rotated relative to the display (left) and rotated (right). A specific example includes a display with a pixel pitch of 44 μm and an optical sensor with a pitch of 50.8 μm. With the sensor not rotated relative to the display, the moiré pattern has a frequency of approximately 3 / mm, as shown by the dashed box labeled 704. The example on the right shows the results when the primary direction of the sensor is rotated at an angle of approximately 26 degrees relative to the primary direction of the display (e.g., approximately 26 degrees from horizontal in the orientation shown). Note that the example on the right still has a moiré pattern; however, the pattern is approximately 10 / mm and is therefore primarily outside the range of the spatial frequency of the fingerprint ridges.

[0061] Figure 8 A display with a pixel pitch of 48 μm and an optical sensor with a pitch of 50.8 μm are shown. In the left example, the sensor is not rotated relative to the display, resulting in a moiré pattern of approximately 1 / mm depicted by dashed box 804, which is also close to the fingerprint frequency of interest. In the right example, the sensor is also rotated approximately 26 degrees relative to the display. In the rotated design shown on the right, the moiré pattern has a high frequency pattern (approximately 10 / mm), which provides sufficient mitigation of the moiré pattern.

[0062] It will be appreciated that specific examples of display and sensor spacings and rotation angles have been provided to illustrate the methods and systems described herein. The systems and methods can be used with any display and sensor spacing, and any rotation angle can be used, as long as the angle gives an appropriate level of mitigation of the moire effect. The appropriate level will vary depending on the specific application; however, it will generally be sufficient to accurately image and analyze features of interest of the input object (e.g., ridges and valleys in the case of fingerprints). Examples of rotation angles are 26-27 degrees, 20-30 degrees, 10-40 degrees, and 1 to 90 degrees.

[0063] and Figure 6 compared to, Fig. 9 An alternative optical sensor arrangement is shown. Fig. 9 In an embodiment of the present invention, an electronic device having a display 900 includes an optical sensor 902. The optical sensor 902 includes an optical sensor die 904 and a sensing element array 906. It will be noted that the display 900 and the sensor die 904 are not rotated relative to the X axis, for example, the major axes of the display 900 and the sensor die 904 are the same and parallel to the X axis. However, the sensing element array 906 is formed in the sensor die so that the sensing element array is parallel to the X' axis, and the X' axis has an angle relative to the X axis. Ɵ, thereby creating a desired rotation between the sensing element array 906 and the display 900 to mitigate moiré patterns.

[0064] It will also be noted that the sheet (e.g., silicon sheet) includes an area 908 that is not occupied by the sensor element array 906, and that the unoccupied area 908 is a major portion of the sensor sheet 904, as generally shown. Such unoccupied area can be used to implement sensor circuitry for controlling the sensing elements, e.g., turning the elements on and off, processing data, etc.

[0065] Fig.10 A method of manufacturing an optical sensor for mounting under a display is shown, which includes rotating an angle to mitigate moire effects. In step 1002, the periodicity or frequency of a feature of interest is determined. For example, in the case of a fingerprint sensor, the frequency of the spatial information of the fingerprint is determined. Such spatial information may correspond to features such as ridges and valleys, minutiae, pores, etc.

[0066] In step 1004, the periodicity or frequency of display components is determined. Such components may include pixels, sub-pixels, subsets or supersets thereof, and other components (e.g., electrodes, liquid crystal elements, and / or color filters, to name a few).

[0067] In step 1006, the periodicity or frequency of the sensor components is determined. These components will typically include the spacing and frequency of the individual sensing elements of the sensor array. If optical elements are used, such as collimators, the periodicity or frequency of the individual optical elements may also be considered (e.g., the distance between the apertures).

[0068] In step 1008, the appropriate rotation angle is determined. The rotation angle will depend on the frequency of the sensor and display and the analysis of the resulting moiré pattern. If the moiré pattern has a frequency of the same order of magnitude as the feature of interest, the sensor is rotated by a selected angle sufficient to mitigate the moiré effect (e.g., so that the moiré pattern has a frequency that is greater or less than the order of magnitude of the feature of interest).

[0069] All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference in its entirety and were set forth in its entirety herein.

[0070] The use of "a", "an", "said", "at least one" and similar terms in the context of describing the present invention (especially in the context of the appended claims) is to be interpreted as covering both the singular and plural meanings, unless otherwise indicated herein or clearly contradicted by the context. The use of the term "at least one" followed by a list of one or more items (e.g., "at least one of A and B") will be interpreted as meaning one item (A or B) selected from the listed items or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by the context. The terms "include", "have", "include" and "contain" should be interpreted as open terms (i.e., meaning "including but not limited to") unless otherwise noted. The description of the numerical range herein is intended to be used only as a shorthand method of expression, which individually indicates that each individual value falls within the range, unless otherwise indicated herein, and each individual value is included in the specification as if it were individually described herein.

[0071] All methods described herein may be performed in any suitable order, unless otherwise indicated herein or clearly contradictory to the text. The use of any or all examples or exemplary terms (e.g., "such as") provided herein is intended only to better illustrate the present invention and does not limit the scope of the present invention unless otherwise required. The language in the specification should not be interpreted as indicating any element that is necessary but not required to practice the present invention.

[0072] Example embodiments of the present invention are described herein. Those of ordinary skill in the art will understand variations of these exemplary embodiments upon reading the foregoing description. The inventors expect those of ordinary skill in the art to use these variations as appropriate, and the inventors intend to practice the present invention in a manner different from that specifically described herein. Therefore, to the extent permitted by applicable law, the present invention includes all modifications and equivalents of the subject matter recited in the appended claims. In addition, the present invention includes any combination of the elements described above in all possible variations thereof, unless otherwise noted herein or clearly contradictory to the content herein.

Claims

1. An electronic device for imaging a biometric object having a structural feature of interest, comprising: A display comprising rows of pixel elements parallel to a first main direction along a first axis; wherein the display is an organic LED display; and an optical sensor disposed below the display, the optical sensor being parallel to a second principal direction along a second axis, Wherein the second axis has an angle relative to the first axis, and wherein the angle adjusts the frequency of the moiré pattern to be outside of a frequency range corresponding to the structural feature of interest.

2. The electronic device according to claim 1, wherein: The biometric feature object is a fingerprint and the frequency range of the structural feature of interest corresponds to the frequency of ridges and valleys.

3. The electronic device according to claim 1, wherein: The angle is between 20 and 30 degrees.

4. The electronic device according to claim 1, wherein: The angle is between 26 and 27 degrees.

5. The electronic device according to claim 1, wherein: The optical sensor comprises an optical element having rows of apertures and a sensor array having rows of sensing elements, the rows of apertures and the rows of sensing elements being parallel to the second axis.

6. The electronic device according to claim 1, wherein: The optical sensor includes an optical element having rows of apertures parallel to the first axis and a sensor array having rows of sensing elements parallel to the second axis.

7. The electronic device according to claim 1, wherein: The optical sensor includes an optical element having rows of apertures parallel to the second axis and a sensor array having rows of sensing elements parallel to the first axis.

8. The electronic device according to claim 1, wherein: The optical sensor comprises an array of sensing elements mounted on a sheet having a principal axis parallel to the first axis and the array of sensing elements having a principal axis parallel to the second axis.

9. An electronic device comprising: A display having rows of pixel elements, the rows of pixel elements being parallel to a first principal axis; wherein the display is an organic LED display; and an optical sensor having a row of sensing elements parallel to the second principal axis, the optical sensor being configured to image a fingerprint, Wherein the optical sensor is disposed below the display and oriented such that the second principal axis is rotated relative to the first principal axis by an angle θ sufficient to reduce a moire effect on the image when imaging the fingerprint.

10. The electronic device according to claim 9, wherein: The angle θ is sufficient to reduce the pattern of the moiré effect by an order of magnitude compared to an unrotated optical sensor.

11. The electronic device according to claim 9, wherein: The row of sensing elements is disposed on a sheet having a third principal axis parallel to the first principal axis and the row of sensing elements is parallel to the second principal axis.

12. The electronic device according to claim 9, wherein: The angle θ is between 20 and 30 degrees.

13. The electronic device according to claim 9, wherein: The angle θ is 27 degrees.

14. The electronic device according to claim 9, wherein: The optical sensor also includes a collimator.

15. A method for determining an angle at which an optical sensor is mounted relative to a display to mitigate moiré patterns, the method being applied to an electronic device as claimed in any one of claims 1 to 14, the method comprising: determining a frequency of a component of the display; determining a frequency of a component of the optical sensor; Determine the frequency of the moiré pattern; as well as The angle is determined based on a frequency of a component of the display and a frequency of a component of the sensor, wherein the angle adjusts the frequency of the moiré pattern.

16. The method according to claim 15, further comprising: determining a frequency of a feature of interest; the feature of interest corresponding to a structural feature of an input object; Wherein the step of determining the angle comprises selecting the angle to adjust the frequency of the moiré pattern to be higher or lower than the frequency of the feature of interest.

17. The method according to claim 16, wherein: The step of determining the angle includes selecting the angle so that the frequency of the moiré pattern is an order of magnitude higher or lower than the frequency of the feature of interest.

18. The method according to claim 15, wherein: The angle is between 25 and 30 degrees.

19. The method according to claim 15, wherein: The step of determining the frequencies of components of the display may further comprise determining the frequencies of pixels and sub-pixels.

20. The method according to claim 19, wherein: The step of determining the frequency of a component of the display may further comprise determining the frequency of an electrode.

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