Patent Application
20200394380
The invention relates to a fingerprint sensing device and more particularly, to an optical fingerprint sensing device and an operation method thereof.
In recent years, demands for fingerprint sensing have been gradually increased. In order to reduce a volume of an electronic device, a fingerprint sensing region may be disposed in a display region of a display panel. For example, an under-display fingerprint recognition technique is to dispose/attach a fingerprint sensor beneath (on a back surface of) the display panel. When a finger touches the display panel, a fingerprint sensor may sense/capture a fingerprint image of the finger through the display panel. Due to the restriction in a transmittance capability of a capacitive sensor, the under-display fingerprint recognition technique adopts an optical imaging or optical sensing technique.
Based on a design requirement for further reducing a thickness of the display device, an in-display fingerprint recognition technique has been accordingly developed. Different from the under-display fingerprint recognition technique, the in-display fingerprint recognition technique is to embed a fingerprint sensor array in the display panel. Namely, the display panel with the in-display fingerprint recognition function has a pixel circuit array and an in-display fingerprint sensor array.
However, a conventional optical fingerprint recognition sensor commonly captures the fingerprint image according to specific (fixed) operation parameters, instead of adaptively adjusting the operation parameters in accordance with various actual use environments, which results in non-optimal quality of the fingerprint image, reduction in a success rate of the fingerprint recognition and unpleasant experience to users. For example, in a situation with intensive environment light, the fingerprint image captured by the conventional optical fingerprint recognition sensor may likely have an issue of overexposure. In addition, not only the environment issue, a light source (e.g., an organic light-emitting diode (OLED) display panel) used to capture the image may encounter an issue of brightness decay. In different actual use environments, if the conventional optical fingerprint recognition sensor captures the fingerprint image by using the specific (fixed) operation parameters, the quality of the captured fingerprint image may be likely unbearable to be used.
It should be noted that the contents of the section of “Description of Related Art” is used for facilitating the understanding of the invention. A part of the contents (or all of the contents) disclosed in the section of “Description of Related Art” may not pertain to the conventional technology known to the persons with ordinary skilled in the art. The contents disclosed in the section of “Description of Related Art” do not represent that the contents have been known to the persons with ordinary skilled in the art prior to the filing of this invention application.
The invention provides an optical fingerprint sensing device and an operation method thereof capable of being adapted to an environment to dynamically adjust operation parameters of an optical fingerprint sensing circuit.
According to an embodiment of the invention, an optical fingerprint sensing device is provided. The optical fingerprint sensing device includes an optical fingerprint sensing circuit and a control circuit. The optical fingerprint sensing circuit is configured to capture a fingerprint image of the fingerprint. The control circuit is coupled to the optical fingerprint sensing circuit. The control circuit is configured to dynamically adjust at least one operation parameter of the optical fingerprint sensing circuit in accordance with environment information. The optical fingerprint sensing circuit captures the fingerprint image according to the at least one operation parameter.
According to an embodiment of the invention, an operation method of an optical fingerprint sensing device is provided. The operation method includes: dynamically adjusting at least one operation parameter of the optical fingerprint sensing circuit according to environment information; and capturing a fingerprint image according to the at least one operation parameter by the optical fingerprint sensing circuit.
To sum up, the optical fingerprint sensing device and the operation method thereof provided by the embodiments of the invention can obtain the environment information associated with the optical fingerprint sensing circuit and/or sensors. According to the environment information, the control circuit can dynamically adjust the at least one operation parameter of the optical fingerprint sensing circuit. Therefore, the optical fingerprint sensing device can be adapted to the environment to dynamically adjust the operation parameters of the optical fingerprint sensing circuit, so as to optimize the quality of the captured fingerprint image.
To make the above features and advantages of the invention more comprehensible, embodiments accompanied with drawings are described in detail below.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
The term “couple (or connect)” throughout the specification (including the claims) of this application are used broadly and encompass direct and indirect connection or coupling means. For example, if the disclosure describes a first device being coupled (or connected) to a second device, then it should be interpreted that the first device can be directly connected to the second device, or the first device can be indirectly connected to the second device through other devices or by a certain coupling means. In addition, terms such as “first” and “second” mentioned throughout the specification (including the claims) of this application are only for naming the names of the elements or distinguishing different embodiments or scopes and are not intended to limit the upper limit or the lower limit of the number of the elements not intended to limit sequences of the elements. Moreover, elements/components/steps with same reference numerals represent same or similar parts in the drawings and embodiments. Elements/components/notations with the same reference numerals in different embodiments may be referenced to the related description.
For example, in the embodiment illustrated in
According to the operation parameter dynamically set by the control circuit 120, the pre-processing circuit 112 may perform image pre-processing (e.g., image correction) on the original fingerprint image provided by the fingerprint sensor 111 and output an pre-processed image (i.e., the fingerprint image of the finger 10) to the control circuit 120. The implementation manner of the pre-processing circuit 112 is not limited in the present embodiment. Based on a design requirement, the pre-processing circuit 112 may be a conventional image preprocessing circuit or any other fingerprint image preprocessing circuit. According to the environment information INF associated with the optical fingerprint sensing circuit 110, the control circuit 120 may dynamically adjust at least one operation parameter of the pre-processing circuit 112. By adaptively adjusting the operation parameter, the quality of fingerprint image captured by the optical fingerprint sensing circuit 110 may be optimized by the control circuit 120.
After obtaining the fingerprint image, the control circuit 120 may perform post processing (e.g., fingerprint feature capturing), fingerprint registration and/or fingerprint recognition (e.g., fingerprint matching) on the fingerprint image. For example, a storage module 130 may store a registered fingerprint, and the control circuit 120 may compare the fingerprint image with the registered fingerprint.
The implementation aspect of the environment information INF may be determined based on a design requirement. For example, in some embodiments, the environment information INF includes an environment light brightness of the optical fingerprint sensing circuit 110. When the finger 10 does not press on the panel 140, the control circuit 120 may sense the environment light brightness through the optical fingerprint sensing circuit 110 and serve the environment light brightness as the environment information INF. The control circuit 120 may dynamically adjust the operation parameter of the optical fingerprint sensing circuit 110 according to the environment light brightness. Based on a design requirement, the operation parameter may include at least one of a photosensitivity, a sensitivity and a denoise degree of the optical fingerprint sensing circuit 110.
When the environment light brightness is low (e.g., the environment light brightness is lower than a standard brightness), the fingerprint image captured by the optical fingerprint sensing circuit 110 may usually tend to be dark, and thus, the control circuit 120 may increase the photosensitivity of the optical fingerprint sensing circuit 110. For example, in some embodiments, the control circuit 120 may dynamically adjust the photosensitivity of the optical fingerprint sensing circuit 110 by adjusting an exposure time of the optical fingerprint sensing circuit 110. For example, the control circuit 120 may dynamically increase the photosensitivity by increasing the exposure time of the optical fingerprint sensing circuit 110. When the environment light brightness is high (e.g., the environment light brightness is higher than the standard brightness), the fingerprint image captured by the optical fingerprint sensing circuit 110 may usually be overexposed, and thus, the control circuit 120 may dynamically decrease the photosensitivity of the optical fingerprint sensing circuit 110 by reducing the exposure time of the optical fingerprint sensing circuit 110.
In some embodiments, the control circuit 120 may dynamically adjust the sensitivity of the optical fingerprint sensing circuit 110 by adjusting an analog gain of the optical fingerprint sensing circuit 110. For example, the control circuit 120 may dynamically increase the sensitivity by increasing the analog gain of the pre-processing circuit 112.
In some embodiments, the pre-processing circuit 112 of the optical fingerprint sensing circuit 110 may repeatedly capture n images of the fingerprint through the fingerprint sensor 111 (wherein n may be any integer determined based on a design requirement) and perform image superposition on the n images (or perform averaging on co-located pixels of the n images) to remove noise. The control circuit 120 may dynamically adjusts the denoise degree of the optical fingerprint sensing circuit 110 by adjusting the number of n of the n images. For example, the control circuit 120 may dynamically increase the denoise degree according to the number of n.
In some other embodiments, the environment information INF may include a signal-to-noise ratio (SNR) of the fingerprint image captured by the optical fingerprint sensing circuit 110. After obtaining the fingerprint image captured by the optical fingerprint sensing circuit 110, the control circuit 120 may calculate the SNR of the captured fingerprint image. The calculation details related to the SNR are not limited in the present embodiment. For example, based on a design requirement, the method that the control circuit 120 calculates the SNR may be a conventional SNR calculation method or other calculation methods. The control circuit 120 may obtain the SNR of the optical fingerprint sensing circuit 110 according to the fingerprint image captured by the optical fingerprint sensing circuit 110. According to the SNR, the control circuit 120 may dynamically adjust the operation parameter of the optical fingerprint sensing circuit 110. Based on a design requirement, the operation parameter may include at least one of a photosensitivity, a sensitivity and a denoise degree of the optical fingerprint sensing circuit 110. Regarding the photosensitivity, the sensitivity and the denoise degree of the example described in this paragraph, they may be inferred with reference to the description related to the previous example and will no longer be repeated.
Based on a design requirement, in some embodiments, the panel 140 may be a self-luminous display panel, for example, an organic light emitting diode (OLED) display panel. The self-luminous display panel may display an image. In addition, the self-luminous display panel may serve as a light source for the optical fingerprint sensing circuit 110 to capture the fingerprint image of the finger 10. In some embodiments, the environment information INF includes a light source brightness of the optical fingerprint sensing circuit 110. The control circuit 120 may sense the light source brightness of the light source (i.e., the panel 140) through the optical fingerprint sensing circuit 110. The control circuit 120 may dynamically adjust the operation parameter of the optical fingerprint sensing circuit 110 according to the light source brightness. Based on a design requirement, the operation parameter may include at least one of a photosensitivity, a sensitivity and a denoise degree of the optical fingerprint sensing circuit 110. Regarding the photosensitivity, the sensitivity and the denoise degree of the example described in this paragraph, they may be inferred with reference to the description related to the previous example and will no longer be repeated. Thus, when the brightness of the light source (i.e., the panel 140) decays, the control circuit 120 may dynamically adjust the operation parameter of the optical fingerprint sensing circuit 110, so as to optimize the quality of the captured fingerprint image.
Based on a design requirement, in some embodiments, the panel 140 may include a touch sensing panel. When a touch event occurs to the touch sensing panel (e.g., the finger presses the panel 140), the touch sensing panel may sense a touch position and a touch area of the touch event. In some embodiments, the environment information INF may include a press area ratio of the finger 10 to the optical fingerprint sensing circuit 110. The control circuit 120 may determine the press area ratio of the finger 10 to the optical fingerprint sensing circuit 110 according to the touch position and the touch area. The control circuit 120 may dynamically adjust the operation parameter of the optical fingerprint sensing circuit 110 according to the press area ratio. Based on a design requirement, the operation parameter may include the photosensitivity of the optical fingerprint sensing circuit 110. Regarding the photosensitivity of the example described in this paragraph, it may be inferred with reference to the description related to the previous example and will no longer be repeated.
Based on a design requirement, the sensor 150 may include one or more sensors. For example, in some embodiments, the sensor 150 may include a light sensor. The light sensor may sense an environment light brightness. In some embodiments, the environment information INF may include the environment light brightness of the optical fingerprint sensing circuit 110. The control circuit 120 may dynamically adjust the operation parameter of the optical fingerprint sensing circuit 110 according to the environment light brightness. Based on a design requirement, the operation parameter may include the photosensitivity and/or the sensitivity of the optical fingerprint sensing circuit 110. Regarding the photosensitivity and the sensitivity of the example described in this paragraph, they may be inferred with reference to the description related to the previous example and will no longer be repeated.
In some other embodiments, the sensor 150 may include a camera. The camera may capture an image. The control circuit 120 may determine the environment light brightness of the optical fingerprint sensing circuit 150 according to the image captured by the camera (the sensor 150), or determine the environment light brightness of the optical fingerprint sensing circuit 110 according to exposure corresponding to the camera. In some embodiments, the environment information INF includes the environment light brightness of the optical fingerprint sensing circuit 110. The control circuit 120 may dynamically adjust the operation parameter of the optical fingerprint sensing circuit 110 according to the environment light brightness. Based on a design requirement, the operation parameter may include the photosensitivity and/or the sensitivity of the optical fingerprint sensing circuit 110. Regarding the photosensitivity and the sensitivity of the example described in this paragraph, they may be inferred with reference to the description related to the previous example and will no longer be repeated.
In some other embodiments, the sensor 150 may include a temperature sensor. The temperature sensor may sense an environment temperature. In some embodiments, the environment information INF includes the environment temperature of the optical fingerprint sensing circuit 110. The control circuit 120 may dynamically adjust the operation parameter of the optical fingerprint sensing circuit 110 according to the environment temperature. Based on a design requirement, the operation parameter may include the photosensitivity and/or the denoise degree of the optical fingerprint sensing circuit 110. Regarding the photosensitivity and the denoise degree of the example described in this paragraph, they may be inferred with reference to the description related to the previous example and will no longer be repeated.
In yet other embodiments, the sensor 150 may include a humidity sensor. The humidity sensor may sense an environment humidity. In some embodiments, the environment information INF includes the environment humidity of the optical fingerprint sensing circuit 110. The control circuit 120 may dynamically adjust the operation parameter of the optical fingerprint sensing circuit 110 according to the environment humidity of the optical fingerprint sensing circuit 110. Based on a design requirement, the operation parameter may include at least one of the photosensitivity, the sensitivity and the denoise degree of the optical fingerprint sensing circuit 110. Regarding the photosensitivity, the sensitivity and the denoise degree of the example described in this paragraph, they may be inferred with reference to the description related to the previous example and will no longer be repeated.
According to the press area ratio of step S420, the control circuit 120 may, in step S430, determine whether the press area ratio is greater than a threshold. When the press area ratio is greater than the threshold (i.e., the determination result of step S430 is “Yes”), the control circuit 120 may dynamically adjust the operation parameter of the optical fingerprint sensing circuit 110 according to the environment temperature and the environment humidity obtained in step S410 (step S440). Based on a design requirement, the operation parameter may include the photosensitivity or other parameters of the optical fingerprint sensing circuit 110. In some embodiments, the control circuit 120 may dynamically adjust the photosensitivity of the optical fingerprint sensing circuit 110 by adjusting the exposure time of the optical fingerprint sensing circuit 110. The control circuit 120 may control the pre-processing circuit 112 according to the environment temperature and the environment humidity of the optical fingerprint sensing circuit 110, so as to dynamically adjust the exposure time of the fingerprint sensor 111. For example, the control circuit 120 may, in step S440, determine the exposure time of the fingerprint sensor 111 according to Table 1 below.
When the press area ratio is not greater than a threshold (i.e., the determination result of step S430 is “No”), the control circuit 120 may dynamically adjust the operation parameter of the optical fingerprint sensing circuit 110 according to the environment temperature, the environment humidity and the environment light brightness obtained in step S410 and the press area ratio obtained in step S420 (step S450). Based on a design requirement, the operation parameter may include the photosensitivity or other parameters of the optical fingerprint sensing circuit 110. In some embodiments, the control circuit 120 may dynamically adjust the photosensitivity of the optical fingerprint sensing circuit 110 by adjusting the exposure time of the optical fingerprint sensing circuit 110. The control circuit 120 may control the pre-processing circuit 112 according to the environment temperature, the environment humidity, the environment light brightness and the press area ratio of the optical fingerprint sensing circuit 110, so as to dynamically adjust the exposure time of the fingerprint sensor 111. For example, the control circuit 120 may, in step S450, determine the exposure time of the fingerprint sensor 111 according to Table 2, Table 3 and Table 4 below.
In other embodiments, the control circuit 120 may dynamically adjust the operation parameter of the optical fingerprint sensing circuit 110 according to the press area ratio and the environment light brightness. Based on a design requirement, the operation parameter may include the photosensitivity or other parameters of the optical fingerprint sensing circuit 110. In some embodiments, the control circuit 120 may dynamically adjust the photosensitivity of the optical fingerprint sensing circuit 110 by adjusting the exposure time of the optical fingerprint sensing circuit 110. The control circuit 120 may control the pre-processing circuit 112 according to the press area ratio and the environment light brightness, so as to dynamically adjust the exposure time of the fingerprint sensor 111. For example, the control circuit 120 may determine the exposure time of the fingerprint sensor 111 according to Table 5 below.
In other embodiments, the control circuit 120 may dynamically adjust the operation parameter of the optical fingerprint sensing circuit 110 according to the press area ratio, the environment light brightness and the environment temperature. Based on a design requirement, the operation parameter may include the photosensitivity and the denoise degree of the optical fingerprint sensing circuit 110. In some embodiments, the control circuit 120 may dynamically adjust the photosensitivity of the optical fingerprint sensing circuit 110 by adjusting the exposure time of the optical fingerprint sensing circuit 110. The pre-processing circuit 112 may repeatedly capture n images of the fingerprint through the fingerprint sensor 111 and perform the image superposition on the n images to remove noise. The control circuit 120 may dynamically adjust the denoise degree of the optical fingerprint sensing circuit 110 by adjusting the number of n of the n images. The control circuit 120 may control the pre-processing circuit 112 according to the press area ratio, the environment light brightness and the environment temperature, so as to dynamically adjust the exposure time and the number of n of the images of the fingerprint sensor 111. For example, the control circuit 120 may determine the exposure time and the number of n (it is assumed herein that n is a standard number) of the images of the fingerprint sensor 111 according to Table 6, Table 7 and Table 8 below.
According to the environment temperature of step S505, the control circuit 120 may, in step 510, determine whether the environment temperature is low (e.g., determine whether the environment temperature is lower than a standard temperature). When the environment temperature is low (i.e., the determination result of step S510 is “Yes”), the control circuit 120 may perform step S515, so as to determine whether the finger 10 fully presses (fully covers) the fingerprint sensing region of the optical fingerprint sensing circuit 110. According to the press area ratio obtained in step S505, when the finger 10 fully presses (fully covers) the fingerprint sensing region of the optical fingerprint sensing circuit 110 (i.e., the determination result of step S515 is “Yes”), the control circuit 120 may dynamically increase the denoise degree of the optical fingerprint sensing circuit 110 (step S520). When the finger 10 does not fully press (fully cover) the fingerprint sensing region of the optical fingerprint sensing circuit 110 (i.e., the determination result of step S515 is “No”), the control circuit 120 may dynamically increase the photosensitivity and the denoise degree of the optical fingerprint sensing circuit 110 (step S525).
When the environment temperature is high (i.e., the determination result of step S510 is “No”, for example, the environment temperature is higher than a standard temperature), the control circuit 120 may perform step S530 to determine whether the finger 10 fully presses (fully covers) the fingerprint sensing region of the optical fingerprint sensing circuit 110. According to the press area ratio obtained in step S505, when the finger 10 fully presses (fully covers) the fingerprint sensing region of the optical fingerprint sensing circuit 110 (i.e., the determination result of step S530 is “Yes”), the control circuit 120 may perform step S535 to determine whether the light source brightness of step S505 is high (e.g., determine whether the light source brightness is higher than the standard brightness). When the light source brightness is high (i.e., the determination result of step S535 is “Yes”), the control circuit 120 may dynamically decrease the photosensitivity or the sensitivity of the optical fingerprint sensing circuit 110 (step S540).
When the light source brightness is dark (i.e., the determination result of step S535 is “No”, and the light source brightness is lower than the standard brightness). The control circuit 120 may perform step S545, so as to determine whether the SNR of the optical fingerprint sensing circuit 110 is low (e.g., determine whether the SNR is lower than a standard value). When the SNR is low (i.e., the determination result of step S545 is “Yes”), the control circuit 120 may dynamically increase the denoise degree of the optical fingerprint sensing circuit 110 (step S550). When the SNR is high (i.e., the determination result of step S545 is “No”), the control circuit 120 may not adjust the operation parameter of the optical fingerprint sensing circuit 110 (step S555).
According to the press area ratio obtained in step S505, when the finger 10 does not fully press (fully cover) the fingerprint sensing region of the optical fingerprint sensing circuit 110 (i.e., the determination result of step S530 is “No”), the control circuit 120 may perform step S560 to determine the environment light brightness of step S505 is high (e.g., whether the environment light brightness is higher than the standard brightness). When the environment light brightness is high (i.e., the determination result of step S560 is “Yes”), the control circuit 120 may dynamically decrease the photosensitivity or the sensitivity of the optical fingerprint sensing circuit 110 (step S565). When the environment light brightness is low (i.e., the determination result of step S560 is “No”), the control circuit 120 may not change the operation parameter of the optical fingerprint sensing circuit 110 (step S555).
Based on different design demands, the block of the control circuit 120 may be implemented in a form of hardware, firmware, software (i.e., programs) or in a combination of many of the aforementioned three forms. In terms of the hardware form, the control circuit 120 may be implemented in a logic circuit on an integrated circuit. Related functions of the control circuit 120 may be implemented in a form of hardware by utilizing hardware description languages (e.g., Verilog HDL or VHDL) or other suitable programming languages. For example, the related functions of the control circuit 120 may be implemented by one or more controllers, a micro-controller, a microprocessor, an application-specific integrated circuit (ASIC), a digital signal processor (DSP), a field programmable gate array (FPGA) and/or various logic blocks, modules and circuits in other processing units.
In terms of the software form and/or the firmware form, the related functions of the control circuit 120 may be implemented as programming codes. For example, the control circuit 120 may be implemented by using general programming languages (e.g., C or C++) or other suitable programming languages. The programming codes may be recorded/stored in recording media. The aforementioned recording media include, for example, a read only memory (ROM), a storage device and/or a random access memory (RAM). Additionally, the programming codes may be accessed from the recording medium and executed by a computer, a central processing unit (CPU), a controller, a micro-controller or a microprocessor to accomplish the related functions. As for the recording medium, a non-transitory computer readable medium, such as a tape, a disk, a card, a semiconductor memory or a programming logic circuit, may be used. In addition, the programs may be provided to the computer (or the CPU) through any transmission medium (e.g., a communication network or radio waves). The communication network is, for example, the Internet, wired communication, wireless communication or other communication media.
In light of the foregoing, the optical fingerprint sensing device and the operation method thereof provided by the embodiments of the invention can obtain the environment information associated with the optical fingerprint sensing circuit and/or other sensors. The implementation aspect of the environment information INF may be determined based on a design requirement. For example, in some embodiments, the environment information can include the environment light brightness, the environment temperature, the environment humidity, the SNR, the light source brightness and the press area ratio of the optical fingerprint sensing circuit. The control circuit can dynamically adjust the at least one operation parameter of the optical fingerprint sensing circuit according to the environment information. Based on a design requirement, the operation parameter can include at least one of the photosensitivity, the sensitivity and the denoise degree of the optical fingerprint sensing circuit. Therefore, the optical fingerprint sensing device can be adapted to the environment to dynamically adjust the operation parameters of the optical fingerprint sensing circuit, so as to optimize the quality of the captured fingerprint image.
It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.
