Patent Application
20140205160
1. Field of the Invention
The disclosed embodiments of the present invention relate to image sensing, and more particularly, to an image sensing apparatus which identifies/recognizes fingerprints by detecting reflected light.
2. Description of the Prior Art
Due to the advent of personal mobile devices (e.g. a smart phone), many users use their mobile devices to access services requiring user information (e.g. electronic transaction and membership control). In order to ensure the security of transaction, the service provider will confirm the user information (e.g. user name and password) provided by the client before providing related services. However, this kind of authentication may not identify a fraudulent use.
Thus, an authentication mechanism of high security is needed to protect user's rights.
It is therefore one objective of the present invention to provide an image sensing apparatus for fingerprint recognition/identification/authentication to ensure the security of electronic transaction and protect user's rights.
It is therefore another objective of the present invention to provide a decoder circuit of an image sensing apparatus to reduce the number of traces required by the image sensing apparatus.
According to an embodiment of the present invention, an exemplary image sensing apparatus is disclosed. The exemplary image sensing apparatus comprises a substrate, a light guide plate, a plurality of photosensors and a light source. The substrate has a first side. The light guide plate has a light exit surface and a light entry surface, wherein the light exit surface faces the first side of the substrate. The photosensors are disposed on the first side of the substrate. The light source is disposed near the light entry surface of the light guide plate, wherein light generated from the light source enters the light guide plate through the light entry surface.
According to an embodiment of the present invention, an exemplary decoder circuit of an image sensing apparatus is disclosed. The image sensing apparatus comprises a photosensor array and a processing circuit. The photosensor array has a plurality of rows, a plurality of row control lines, a plurality of columns and a plurality of column data lines. The processing circuit has at least one input terminal and is arranged for processing a plurality of sensing signals of the column data lines. The exemplary decoder circuit comprises a control circuit and a column decoder circuit. The control circuit is arranged for generating at least one set of column selection signals, wherein each set of column selection signals comprises a plurality of column selection signals. The column decoder circuit is coupled to the control circuit, the processing circuit and the photosensor array, wherein the column decoder circuit couples the column data lines to the at least one input terminal according to the at least one set of column selection signals, and comprises at least one switch stage. The at least one switch stage is controlled by the at least one set of column selection signals, respectively, wherein the at least one switch stage has a plurality of input nodes and at least one output node, and couples the input nodes to the at least one output node according to the at least one set of column selection signals.
According to an embodiment of the present invention, an exemplary decoder circuit of an image sensing apparatus is disclosed. The image sensing apparatus comprises a photosensor array. The photosensor array has a plurality of rows, a plurality of row control lines, a plurality of columns and a plurality of column data lines. The exemplary decoder circuit comprises a control circuit and a row decoder circuit. The control circuit is arranged for generating a plurality of row control signals and at least one set of row selection signals, wherein the row control lines comprises a plurality of groups of row control lines; the row control signals are coupled to the groups of row control lines, respectively, and each set of row selection signals comprises a plurality of row selection signals. The row decoder circuit is coupled to the control circuit and the photosensor array, and comprises a plurality of switch circuits. The switch circuits are disposed in correspondence with the columns, respectively, wherein each switch circuit couples a plurality of photosensors of a column corresponding to the switch circuit to a column data line corresponding to the column according to the at least one set of row selection signals, and comprises at least one switch stage. The at least one switch stage is controlled by the at least one set of row selection signals, respectively, wherein the at least one switch stage has a plurality of input nodes and at least one output node, and couples the input nodes to the at least one output node according to the at least one set of row selection signals.
The proposed image sensing apparatus may sense an image of an object according to reflected light reflected from the object, and have different image sensing region based on different light paths. The proposed image sensing apparatus may be fabricated easily and have advantages of low cost and light weight. Additionally, the proposed decoder circuit of an image sensing apparatus may greatly reduce the number of traces required by the image sensing apparatus, thus not only saving cost but also reducing signal interferences to improve sensing quality. Further, the proposed image sensing apparatus may be employed in a mobile device capable of fingerprint identification to ensure the safety of electronic transaction and protect user's rights.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
When light meets a surface of an object, different light rays may reflect off the surface due to surface roughness. The proposed image sensing apparatus may identify an object image based on this principle. For example, as a fingerprint may have ridges and grooves, the proposed image sensing apparatus may be employed in fingerprint recognition/identification and/or fingerprint authentication. For the sake of brevity, an implementation of an exemplary fingerprint image sensing apparatus is described below. However, a person skilled in the art should understand that this is not meant to be a limitation of the present invention.
Please refer to
Depending on designs of light paths, the image sensing apparatus 100 may define the light guide plate 120 or the substrate 132 as a fingerprint identification region. In other words, one of the light guide plate 120 and the substrate 132 may have a contact surface, wherein when a finger touches the contact surface to generate reflected light, the reflected light may pass though the contact surface and falls on the photosensors PS(1, 1)-PS(M, N), and the photosensor array 130 may identify a fingerprint image accordingly. For example, in a case where a side of the substrate 132 which faces away from the light guide plate 120 (i.e. the side opposite to another side of the substrate 132 which faces the light guide plate 120) is defined as the fingerprint identification region (i.e. the contact surface), the light entering the light guide plate 120 may be guided to the photosensor array 130 (e.g. by crosstalk between the light guide plate 120 and the photosensor array 130). Hence, when the finger touches the side of the of the substrate 132 facing away from the light guide plate 120, the photosensor array 130 may identify the fingerprint image according to the reflected light reflected from the finger. Additionally, in a case a side of the light guide plate 120 which faces away from the substrate 132 (i.e. the side opposite to another side of the light guide plate 120 which faces the substrate 132) is defined as the fingerprint identification region (i.e. the contact surface), the light entering the light guide plate 120 may be substantially confined within the light guide plate 120 (e.g. the light travels by total internal reflection). When the finger touches the side of the light guide plate 120 facing away from the substrate 132, the confinement fails (e.g. frustrated total internal reflection (FTIR)) and the photosensor array 130 may identify the fingerprint image according to the reflected light reflected from the finger. First, an implementation of an exemplary image sensing apparatus which defines a side of a substrate as a fingerprint identification region is described below.
Please refer to
The light guide plate 220 may have a first surface LS1, a second surface LS2 opposite to the first surface LS1, and a lateral side LSE. The light source S is disposed near the lateral side LSE of the light guide plate 220 (e.g. disposed in correspondence with the lateral side LSE) so that light generated from the light source S may enter the light guide plate 220 through the lateral side LSE. In other words, the lateral side LSE is a light entry surface of the light guide plate 220. For example, the light source S may be implemented by an infrared (IR) light emitter and disposed on the lateral side LSE. As shown in
The substrate 232 may have transparency so that the light from the light guide plate 220 may travel therein. When an object (e.g. a user's finger F) touches the second side SS2 of the substrate 232 (e.g. a contact surface for fingerprint identification) and reflect light in the substrate 232 (e.g. light L2), the photosensors PS1-PS10 may receive reflected light reflected from the finger F (e.g. light L2′) to detect an image of the finger F (e.g. identifying ridges of the finger F). In practice, the substrate 232 may be a glass substrate or other substrate having transparency, and the photosensor array corresponding to the photosensors PS1-PS10 may be an amorphous, single-crystalline or polysilicon photosensor array. As the glass substrate has advantages of thin thickness and low cost, the proposed image sensing apparatus is very suitable for use in person mobile apparatuses when the glass substrate is used as the substrate 232.
In order to ensure the light received by the photosensors PS1-PS10 is from the light reflected from the finger F rather than the light traveling in the light guide plate 220, the image sensing apparatus 200 may further include a plurality of light shielding devices SH1-SH10, which are disposed respectively in correspondence with the photosensors (i.e. each shielding device is disposed at a side of a corresponding photosensor facing the first surface LS1) in order to prevent the light generated from the light source S from falling on the photosensors PS1-PS10 directly (e.g. light L3 and light L3′). Hence, the light entering the light guide plate 220 is ensured to travel toward the substrate 232 through a region where the first surface LS1 abuts against the first side SS1 (i.e. the region where no light shielding device is disposed).
It should be noted that, as the light generated from the light source S enters the light guide plate 220 from the lateral side LSE, the light in the light guide plate 220 may fall on the second surface LS2 at a larger angle. When a refractive index of a medium inside the light guide plate 220 is higher than a refractive index of a medium outside the light guide plate 220, the light in the light guide plate 220 may travel by total internal reflection (e.g. light L4 falling on the second surface LS2 and reflected light L4′ thereof). Hence, after entering the light guide plate 220, the light generated from the light source S may distribute uniformly in the light guide plate 220 rather than pass out of the second surface LS2, thus reducing power dissipation.
In alternative design, a microstructure may be disposed in the light guide plate to ensure that the light travels in light guide plate instead of dissipating from the light guide plate. Please refer to
Please refer to
An implementation of an exemplary image sensing apparatus which defines a side of a light guide plate a fingerprint identification region is described below. Please refer to
In one implementation, frustrated total internal reflection may be utilized to ensure the light received by the photosensors PS1′-PS10′ is from the light reflected from the finger F. Specifically, as the light generated from the light source S enters the light guide plate 520 from the lateral side LSE, the light in the light guide plate 520 may fall on the first surface LS1 and/or the second surface LS2 at a larger angle. When a refractive index of a medium inside the light guide plate 520 is higher than a refractive index of a medium outside the light guide plate 520, the light in the light guide plate 520 may travel by total internal reflection (e.g. light L2 falling on the second surface LS2 and reflected light L2′ thereof, and light L2″ reflected from the first surface LS1).
When a ridge of the finger F touches the second surface LS2 of the light guide plate 520, total internal reflection is destroyed in a touched area. The light in the light guide plate 520 may be reflected by the finger F (e.g. the light L1 and the light L1′), and the reflected light may pass through the first surface LS1 toward a photosensor (e.g. light L1″). The photosensor (e.g. the photosensor PS2′) may detect the image of the finger F accordingly. Regarding untouched area (s) on the second surface LS2, the light may still travel in the light guide plate 520 by total internal reflection (e.g. light L3 and light L3′). Hence, photosensor(s) corresponding to groove(s) of the finger F (e.g. the photosensor PS5′) may not receive reflected signal(s).
In this implementation, the medium outside the light guide plate 520 may be air (i.e. the substrate 532 and the first surface LS1 are separated by air). Hence, the refractive index of the medium outside the light guide plate 520 is less than the refractive index of the medium inside the light guide plate 520, allowing the light generated from the light source S to travel in the light guide plate 520 by total internal reflection. In alternative design, the medium between the substrate 532 and the first surface LS1 may be another medium other than air. As long as the refractive index of the medium located between the substrate 532 and the first surface LS1 is higher than the refractive index of the light guide plate 520, the light generated from the light source S may travel in the light guide plate 520 by total internal reflection, thus allowing the use of frustrated total internal reflection to identify fingerprints.
Please note that the substrate 532 may be a glass substrate, and a photosensor array corresponding to the photosensors PS1′-PS10′ may be an amorphous, single-crystalline or polysilicon photosensor array. Hence, the requirements of thin thickness and low cost can be met.
In the implementations shown in
In one implementation, the peripheral circuit 260 shown in
The control circuit 722, the processing circuit 724, the column decoder circuit 726, the row decoder circuit 728 may be used to implement at least a portion of the peripheral circuit 260 shown in
The row decoder circuit 728 is coupled to the control circuit 722 and the photosensor array 730, and may include a plurality of switch circuits 728—1-728_N. The switch circuits 728—1-728_N are disposed in correspondence with the columns of the photosensor array 730 (i.e. the column data lines D1-DN), respectively, wherein each switch circuit may couple photosensors coupled to the switch circuit to a column data line corresponding to the switch circuit according to the row selection signals S1-SZ, thereby transmitting sensing signals of the photosensors to the column data line. By way of example, but not limitation, the row control lines W1-WM may be divided into a plurality of groups of row control lines (corresponding to row control signals R1-RY, respectively), wherein each group of row control lines may have a plurality of row control lines. Regarding a switch circuit, photosensors coupled to each group of row control lines may be coupled to a column data line corresponding to the switch circuit according to the row selection signals S1-SZ. Additionally, the processing circuit 724 may process sensing signals of the column data lines D1-DN to obtain an image of an object to be detected (e.g. a fingerprint image).
As shown in
Please refer to
The control circuit 822 may further generate a set of column selection signals C1-C4 for column decoding operations. The column decoder circuit 826 may include a plurality of sets of switches SW1-SWP, wherein the sets of switches SW1-SWP are coupled in parallel between the processing circuit 824 and the photosensor array 830. Each set of switches may include a plurality of input nodes and an output node, and couple one of the input nodes to the output node according to a corresponding set of column selection signals. For example, the set of switches SW1 may couple one of input nodes I1-I4 to an output node O1 according to the set of column selection signals C1-C4, and the set of switches SWP may couple one of input nodes IN-3-IN to an output node OP according to the set of column selection signals C1-C4.
In this embodiment, each set of switches may include a plurality of switches, wherein each switch may be implemented by a transistor M′. switches of each set of switches may couple one of input nodes of the set of switches to an output node of the set of switches according to the set of column selection signals C1-C4, respectively, thereby outputting sensing signals of corresponding column data lines to the processing circuit 822. For example, when the control circuit 822 enables the row control line W1 and the column selection signal C1 is at a specific level (e.g. a high level), sensing signals of column data lines, which correspond to (i.e. enabled by) the column selection signal C1, of rows corresponding to (i.e. enabled by) the row control line W1 may be outputted to the processing circuit 824.
As the input nodes I1-IN are coupled to the column data lines D1-DN, respectively, and the output nodes O1-OP are coupled to the input terminals T1-TP of the processing circuit 824, respectively, the number of traces connected to the processing circuit 824 may be decreased from N to P. For example, if the photosensor array 830 has 240 column data lines (i.e. N equals 240), using the column decoder circuit 826 may reduce the number of traces from 240 to 64, wherein 60 traces are signal traces connected to the processing circuit 824, and 4 traces are signal traces of the set of column selection signals C1-C4.
The processing circuit 824 may include at least one analog-to-digital converter (not shown in
Please note that the number of column selection signals and/or the number of sets of switches shown in
Please refer to
As shown in
In this embodiment, the switch stages G1-G3 may include a plurality sets of switches SA1-SAX, SB1-SBY and SC1-SCZ, wherein each set of switches may have a plurality of input nodes and an output node, and couple one of the input nodes to the output node according to a set of column selection signals of a corresponding switch stage, thereby outputting a sensing signal of a corresponding column data line to a next stage. In practice, each set of switches may include a plurality of switches (e.g. the transistor M′), and the switches may couple one of input nodes of the set of switches to an output node of the set of switches according to a set of column selection signals of a corresponding switch stage.
For example, the set of switches SA1 may couple one of input nodes I1-I2 to an output node P1 according to the set of column selection signals CA1-CA2, the set of switches SB1 may couple one of input nodes Q1-Q2 to an output node R1 according to the set of column selection signals CB1 CB2, and the set of switches SC1 may couple one of the nodes U1-U2 to an output node Q1 according to the set of column selection signals CC1-CC2. Hence, when the control circuit 822 enables the row control line W1 and each of the column selection signals CA1, CB1 and CC1 is at a specific level (e.g. a high level), the sensing signal of the column data line D1 may be outputted to the processing circuit 824.
Please note that the column decoder circuit 826 shown in
Please note that the number of column selection signals and/or the number of sets of switches shown in
The row decoder circuit may be utilized to reduce the number of traces required by the image sensing apparatus. Please refer to
The control circuit 1022 may generate a plurality of row control signals R1-RQ and a set of row selection signals S1-S4, wherein a plurality of row control lines W1-WM may be regarded as a plurality of groups of row control lines, and the groups of row control lines W1-WM are coupled to the row control signals R1-RQ, respectively (e.g. the row control lines W1-W4 may be regarded as a set of row control lines coupled to the row control signal R1). The row decoder circuit 1028 may include a plurality of switch circuits 1028—1-1028_N, which are disposed in correspondence with a plurality of columns of the photosensor array 1030, respectively. Each switch circuit may couple photosensors of a column corresponding to the switch circuit to a column data line corresponding to the column according to the set of row selection signals S1-S4.
In this embodiment, each switch circuit may include a plurality of sets of switches SW′1-SW′Q, wherein the sets of switches SW′1-SW′Q are coupled in parallel between a column corresponding to the switch circuit and a column data line corresponding to the column. Each set of switches may include a plurality of input nodes and an output node, and couple one of the input nodes to the output node according a corresponding set of row selection signals. For example, the set of switches SW′1 may couple one of input nodes I1-I4 to an output node O1 according the set of row selection signals S1-S4. Additionally, all of input nodes I1-IM of the sets of switches SW′1-SW′Q are coupled to photosensors of a corresponding column, respectively, and all of output nodes O1-OQ are coupled to a column data line corresponding to the column.
Each set of switches may include a plurality of switches, wherein each switch may be implemented by the transistor M′. The switches of each set of switches may couple one of input nodes of the set of switches to an output node of the set of switches according to the row selection signals S1-S4, respectively, thereby outputting sensing signals to a corresponding column data line. For example, when each of the row control signal R1 and the row selection signal S1 is at a specific level (e.g. a high level), sensing signals of photosensors, which correspond to (i.e. enabled by) the row selection signal S1, of the row control lines W1-W4 may be outputted to the column data lines D1-DN.
As the row control lines W1-WM are coupled to the row control signals R1-RQ, respectively, the number of traces connected to the control circuit 1022 may be decreased from M to Q. For example, if the photosensor array 1030 has 240 row control lines (i.e. M equals 240), using the row decoder circuit 1028 may reduce the number of traces from 240 to 64, wherein 60 traces are signal traces connected to the control circuit 1022, and 4 traces are signal traces of the set of row selection signals S1-S4.
Please note that the number of row selection signals and/or the number of sets of switches shown in
Please refer to
The control circuit 1122 may generate a plurality of row control signals R1-RQ and a set of row selection signals SA1-SA2, SB1-SB2 and SC1-SC2, wherein a plurality of row control lines W1-WM may be regarded as a plurality of groups of row control lines, and the groups of row control lines W1-WM are coupled to the row control signals R1-RQ, respectively. The row decoder circuit 1128 may include a plurality of switch circuits 1128—1-1128_N, which are disposed in correspondence with a plurality of columns of the photosensor array 1130, respectively. In this embodiment, each switch circuit may have an identical topology (e.g. the topology of the switch circuit 1128—1). However, this is for illustrative purposes only, and is not meant to be a limitation of the present invention.
As show in
As the switch stage the switch stage G′1 is adjacent to respective photosensors corresponding to switch circuits 1128—1-1128_N, input nodes of the switch stage G′1 may be coupled to the photosensors corresponding to each switch circuit, respectively; as the switch stage G′3 is adjacent to respective column data lines corresponding to switch circuits 1128—1-1128_N, output nodes of the switch stage G′3 may be coupled to a column data line corresponding to each switch circuit. Further, as the switch stage G′2 is coupled in series between the switch stage G′1 and the switch stage G′3, input nodes of the switch stage G′2 may be coupled to output nodes of the switch stage G′1, respectively, and output nodes of the switch stage G′2 may be coupled to input nodes of the switch stage G′3, respectively.
In this embodiment, the switch stages G1-G3 may include a plurality of sets of switches SA′1-SA′X, SB′1-SB′Y and SC′1-SC′Z, wherein each set of switches may have a plurality of input nodes and an output node, and couple one of the input nodes to the output node according a set of row selection signal of a corresponding switch stage, thereby outputting a sensing signal of a corresponding photosensor to a next stage. In practice, each set of switches may include a plurality of switches (e.g. the transistor M′), and the switches may couple one of input nodes of the set of switches to an output node of the set of switches according to a set of row selection signals of a corresponding switch stage.
For example, the set of switches SA′1 may couple one of input nodes I1-I2 to an output node P1 according to the set of row selection signals SA1-SA2, the set of switches SB′1 may couple one of input nodes Q1-Q2 to an output node R1 according to the set of row selection signals SB1-SB2, and the set of switches SC′1 may couple one of input nodes U1-U2 to an output node O1 according to the set of row selection signals SC1-Sc2. Hence, when each of the row control signal R1 and the row selection signals SA1, SB1 and SC1 is at a specific level (e.g. a high level), sensing signals of photosensors corresponding to (i.e. enabled by) the row control line W1 may be outputted to the column data lines D1-DN.
Please note that each switch circuit shown in
Please note that the number of column selection signals and/or the number of sets of switches shown in
Although only one of a column decoder circuit and a row decoder circuit is shown in each of the embodiments shown in
In view of above, when the proposed column decoder circuits and/or row decoder circuits are disposed on a substrate of an image sensing apparatus, the number of traces disposed on the substrate may be greatly decreased. For example, if a column decoder circuit (the column decoder circuit 826 shown in
Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102137393 | Oct 2013 | TW | national |
This application claims the benefit of U.S. provisional application No. 61/754,654, filed on Jan. 21, 2013, the contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61754654 | Jan 2013 | US |
