Fingerprint sensor

This application claims the priority benefits of U.S. provisional application Ser. No. 62/848,587, filed on May 16, 2019, and China application serial no. 202010040545.0, filed on Jan. 15, 2020. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification.

The disclosure relates to a sensor, and in particular to, a fingerprint sensor.

In a conventional large-area fingerprint sensor, in each fingerprint sensing operation, the conventional fingerprint sensor needs to drive all sensing units on the sensing array to perform sensing, so the conventional fingerprint sensor needs to spend more time to perform fingerprint sensing. Besides, in each fingerprint sensing operation, the conventional fingerprint sensor also needs to read out sensing results of a plurality of sensing units through a multiplexer (MUX) in a time-sharing manner, so the conventional fingerprint sensor also has the problem of poor image acquisition efficiency. In view of this, solutions of several embodiments will be provided below.

The invention is directed to a fingerprint sensor that can provide a fast and energy-saving large-area fingerprint sensing effect.

According to embodiments of the invention, the fingerprint sensor of the invention includes a sensing array. The sensing array includes a plurality of sensing units to form a plurality of sensing regions arranged in an array. Each of the plurality of sensing regions includes at least one column of sensing units. A first part of the plurality of sensing regions receives a power signal to perform fingerprint sensing. A second part of the plurality of sensing regions does not receive a power signal.

Based on the above, the fingerprint sensor of the invention can perform fingerprint sensing by providing the power signal to a part of the plurality of sensing regions of the sensing array corresponding to the sensing units in the current fingerprint sensing region, and other parts of the plurality of sensing regions of the sensing array that do not perform fingerprint sensing do not receive a fingerprint signal. Therefore, the fingerprint sensor of the invention can provide a fast and energy-saving large-area fingerprint sensing effect.

To make the features and advantages of the invention clear and easy to understand, the following gives a detailed description of embodiments with reference to accompanying drawings.

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 accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification.

FIG. 1 shows a schematic diagram of a fingerprint sensor according to an embodiment of the invention.

FIG. 2 shows a driving schematic diagram of a sensing array according to a first embodiment of the invention.

FIG. 3 shows a driving schematic diagram of a sensing array according to a second embodiment of the invention.

FIG. 4 shows a driving schematic diagram of a sensing array according to a third embodiment of the invention.

FIG. 5 shows a circuit schematic diagram of a sensing array according to an embodiment of the invention.

Exemplary embodiments of the invention are described in detail, and examples of the exemplary embodiments are shown in the accompanying drawings. Whenever possible, the same component symbols are used in the drawings and descriptions to indicate the same or similar parts.

FIG. 1 shows a schematic diagram of a fingerprint sensor according to an embodiment of the invention. With reference to FIG. 1 , a fingerprint sensor 100 is an optical sensor capable of providing a large-area sensing range, and may be used for in-screen fingerprint recognition, for example, but the invention is not limited thereto. The fingerprint sensor 100 includes a sensing array 110 and a readout circuit 120 . The sensing array 110 includes a plurality of sensing regions 110 _ 1 - 110 _M arranged in an array formed by a plurality of sensing units, and each of the sensing regions 110 _ 1 - 110 _M includes at least one column of sensing units. M is a positive integer greater than 1. The fingerprint sensor 100 may illuminate a finger through a self-luminous display panel or an additional illuminating component, and sense reflected light with fingerprint information reflected by the finger through the sensing array 110 . In the present embodiment, the size of a sensing area that is provided by the sensing array 110 is much larger than the size of a corresponding single fingerprint area when a single finger of a user is pressed on the fingerprint sensor 100 .

In the present embodiment, when the finger of the user is, for example, pressed and covered on sensing regions 110 _ a and 110 _ b , the sensing regions 110 _ a and 110 _ b will receive a power signal to perform fingerprint sensing, where a and b are integers between 1 and M. In such cases, the other sensing regions will not receive a power signal. It is worth noting that the fingerprint sensor 100 may, for example, determine a sensing region object to receive the power signal to perform fingerprint sensing according to the touch point reporting from a touch panel, but the invention is not limited thereto. In other words, when the fingerprint sensor 100 performs fingerprint sensing, the readout circuit 120 only needs to read out sensing signals of the sensing regions 110 _ a and 110 _ b to a back-end arithmetic unit. In this regard, since the fingerprint sensor 100 of the present embodiment does not need to drive the overall sensing array 110 and does not need to read out the sensing signal of each sensing region, the fingerprint sensor 100 of the present embodiment can effectively shorten the fingerprint sensing time and can increase the speed of acquiring a fingerprint image.

In addition, the fingerprint sensor 100 of the present embodiment may further include other necessary circuit components, for example, a digital signal processor (DSP), an analog-to-digital converter (ADC), or an analog front end (AFE) circuit, but the invention is not limited thereto.

FIG. 2 shows a driving schematic diagram of a sensing array according to a first embodiment of the invention. With reference to FIG. 2 , a fingerprint sensor 200 includes a sensing array 210 and a plurality of switch circuits 230 _ 1 - 230 _P. P is a positive integer greater than 1. The sensing array 210 includes a plurality of sensing regions 210 _ 1 - 210 _M arranged in an array formed by a plurality of sensing units, and each column of the sensing regions are coupled to a readout circuit (not shown) via signal readout lines R_ 1 -R_N. In the present embodiment, the switch circuits 230 _ 1 - 230 _P are respectively coupled between the corresponding sensing regions and a power input terminal 240 , and respectively receive corresponding control signals C_ 1 -C_P. Each of the switch circuits 230 _ 1 - 230 _P includes switch components S_ 1 -S_N. N is a positive integer equal to or greater than 1. In the present embodiment, the switch components S_ 1 -S_N of each of the switch circuits 230 _ 1 - 230 _P are coupled in a one-to-one manner between the at least one column of corresponding sensing units in the corresponding sensing region and the power input terminal 240 via corresponding power lines L_ 1 -L_N, and a plurality of switch components of a same switch circuit receive a same signal.

In other words, the fingerprint sensor 200 may selectively turn on the corresponding switch components S_ 1 -S_N of the switch circuits 230 _ 1 - 230 _P through the control signals C_ 1 -C_P according to the sensing regions where the finger is located, thereby providing a power signal to the sensing regions where the finger is located (for example, a part of the sensing regions 210 _ 1 - 210 _M) to perform fingerprint sensing. Therefore, the fingerprint sensor 200 of the present embodiment can selectively drive only the plurality of sensing units in partial and necessary sensing regions to perform fingerprint sensing, and therefore, can effectively shorten the fingerprint sensing time and can increase the speed of acquiring a fingerprint image.

FIG. 3 shows a driving schematic diagram of a sensing array according to a second embodiment of the invention. With reference to FIG. 3 , a fingerprint sensor 300 includes a sensing array 310 and a plurality of switch circuits 330 _ 1 - 330 _P. Each of the switch circuit 330 _ 1 - 330 _P is a switch component. The sensing array 310 includes a plurality of sensing regions 310 _ 1 - 310 _M arranged in an array formed by a plurality of sensing units, and each column of the sensing regions are coupled to a readout circuit (not shown) via signal readout lines R_ 1 -R_N. In the present embodiment, the switch circuits 330 _ 1 - 330 _P are respectively coupled between the corresponding sensing regions and a power input terminal 240 , and respectively receive corresponding control signals C_ 1 -C_P. In the present embodiment, the switch component of each of the switch circuits 330 _ 1 - 330 _P is coupled in a one-to-many manner between the plurality of columns of corresponding sensing units in the corresponding sensing region and a power input terminal 340 via corresponding power lines L_ 1 -L_N.

In other words, the fingerprint sensor 300 may selectively turn on the corresponding switch components of the switch circuits 330 _ 1 - 330 _P through the control signals C_ 1 -C_P according to the sensing regions where the finger is located, thereby providing a power signal to the sensing regions where the finger is located (for example, a part of the sensing regions 310 _ 1 - 310 _M) to perform fingerprint sensing. Therefore, the fingerprint sensor 300 of the present embodiment can selectively drive only the plurality of sensing units in partial and necessary sensing regions to perform fingerprint sensing, and therefore, can effectively shorten the fingerprint sensing time and can increase the speed of acquiring a fingerprint image.

FIG. 4 shows a driving schematic diagram of a sensing array according to a third embodiment of the invention. With reference to FIG. 4 , a fingerprint sensor 400 includes a sensing array 410 and a power supply 450 . The sensing array 410 includes a plurality of sensing regions 410 _ 1 - 410 _M arranged in an array formed by a plurality of sensing units, and each column of the sensing regions are coupled to a readout circuit (not shown) via signal readout lines R_ 1 -R_N. In the present embodiment, the plurality of sensing regions 410 _ 1 - 410 _M of the sensing array 410 are directly coupled to the power supply 450 . In the present embodiment, the power supply 450 directly provides a power signal to the corresponding sensing regions (for example, a part of the sensing regions 410 _ 1 - 410 _M) through power lines L_ 1 -L_N corresponding to the sensing regions where the finger is located to perform fingerprint sensing. Therefore, the fingerprint sensor 400 of the present embodiment can selectively provide the power signal to drive only the plurality of sensing units in partial and necessary sensing regions to perform fingerprint sensing, and therefore, can effectively shorten the fingerprint sensing time and can increase the speed of acquiring a fingerprint image.

FIG. 5 shows a circuit schematic diagram of a sensing array according to an embodiment of the invention. With reference to FIG. 5 , the present embodiment takes a sensing array 500 of two adjacent sensing regions 500 _ 1 and 500 _ 2 as an example, and is applicable to each sensing region and sensing unit in the embodiments of FIG. 2 to FIG. 4 described above. In the present embodiment, the sensing region 500 _ 1 includes, for example, 2×2 sensing units 510 - 540 , and the sensing region 500 _ 2 includes, for example, 2×2 sensing units 550 - 580 . The sensing unit 510 includes a photodiode 511 and transistors 512 - 514 . A first terminal of the transistor 512 is coupled to a power input terminal, and a control terminal of the transistor 512 receives a reset signal RS 1 . A first terminal of the photodiode 511 is connected to ground, and a second terminal of the photodiode 511 is coupled to a second terminal of the transistor 512 and a control terminal of the transistor 513 . A first terminal of the transistor 513 is coupled to a power line S_ 1 , and a second terminal of the transistor 513 is coupled to a first terminal of the transistor 514 . A control terminal of the transistor 514 receives a selection signal SW 1 , and a second terminal of the transistor 514 is coupled to a signal readout line R_ 1 . By analogy, photodiodes 521 , 531 , 541 , 551 , 561 , 571 and 581 and the transistors 522 - 524 , 532 - 534 , 542 - 544 , 552 - 554 , 562 - 564 , 572 - 574 and 582 - 584 of the sensing units 520 - 580 have the same circuit coupling relationship.

In the present embodiment, control terminals of the transistors 512 , 522 , 532 and 542 of the sensing units 510 - 540 of the sensing region 500 _ 1 receive the same reset signal RS 1 to perform the reset synchronously. Control terminals of the transistors 552 , 562 , 572 and 582 of the sensing units 550 - 580 of the sensing region 500 _ 2 receive a same reset signal RS 2 to perform the reset synchronously. Control terminals of the transistors 514 , 534 , 554 and 574 of the sensing units 510 , 530 , 550 and 570 receive the same selection signal SW 1 . Control terminals of the transistors 524 , 544 , 564 and 584 of the sensing units 520 , 540 , 560 and 580 receive a same selection signal SW 2 . The transistors 513 and 523 of the sensing units 510 and 520 of the sensing region 500 _ 1 are coupled to the same power line S_ 1 , and the transistors 533 and 543 of the sensing units 530 and 540 of the sensing region 500 _ 1 are coupled to a same power line S_ 2 . The transistors 553 and 563 of the sensing units 550 and 560 of the sensing region 500 _ 2 are coupled to a same power line S_ 1 ′, and the transistors 573 and 583 of the sensing units 570 and 580 of the sensing region 500 _ 2 are coupled to a same power line S_ 2 ′.

For example, when fingerprints of the user cover the sensing region 500 _ 1 and do not cover the sensing region 500 _ 2 , the power lines S_ 1 and S_ 2 of the sensing region 500 _ 1 are provided with the power signal, and the photodiodes 511 , 521 , 531 and 541 of the sensing units 510 - 540 perform sensing after resetting via the transistors 512 , 522 , 532 and 542 . Next, the transistors 514 , 524 , 534 and 544 are turned on via the selection signals SW 1 and SW 2 , so that a readout circuit 600 reads out sensing results of the photodiodes 511 , 521 , 531 and 541 of the sensing units 510 - 540 through the signal readout lines R_ 1 and R_ 2 . In contrast, since the power lines S_ 1 ′ and S_ 2 ′ of the sensing region 500 _ 2 are not provided with the power signal, no signal is output from the signal readout lines R_ 1 ′ and R_ 2 ′. In other words, the readout circuit 600 of the present embodiment can obtain the fingerprint sensing results only by spending the time to read out the sensing signals transmitted by the signal readout lines R_ 1 and R_ 2 , and does not need to spend additional time on the signal readout lines R_ 1 ′, R_ 2 ′ of the sensing region 500 _ 2 .

In addition, the 1 st column of the sensing units 510 and 520 in the sensing region 500 _ 1 and the 1 st column of the sensing units 550 and 560 in the sensing region 500 _ 2 are coupled to each other via a same row signal line RL 1 , and the 2 nd column of the sensing units 530 and 540 in the sensing region 500 _ 1 and the 2 nd column of the sensing units 570 and 580 in the sensing region 500 _ 2 are coupled to each other via a same row signal line RL 2 . Therefore, the readout circuit 600 does not need to read the sensing units of different regions through an additional multiplexer (MUX) circuit. Besides, since traces of the row signal lines RL 1 and RL 2 may be disposed in the sensing array 500 , the fingerprint sensor to which the sensing array 500 of the present embodiment is applied can also effectively reduce the trace area of signal lines between the sensing array 500 and the readout circuit 600 .

In summary, the fingerprint sensor of the invention provides a fast large-area fingerprint sensing effect by the design of selectively providing the power signal to a part of the plurality of sensing regions of the sensing array, and the fingerprint sensor of the invention further provides a function of effectively reducing the trace area of the signal lines by matching a coupling manner of the row signal lines of each corresponding column between different sensing regions.

Finally, it should be noted that the foregoing embodiments are merely used for describing the technical solutions of the invention, but are not intended to limit the invention. Although the invention is described in detail with reference to the foregoing embodiments, a person of ordinary skill in the art should understand that, modifications may still be made to the technical solutions in the foregoing embodiments, or equivalent replacements may be made to some or all of the technical features; and such modifications or replacements will not cause the essence of corresponding technical solutions to depart from the scope of the technical solutions in the embodiments of the invention.