Detection device

A detection device comprising: an insulating substrate; a plurality of gate lines that are provided on the insulating substrate, and extend in a first direction; a plurality of signal lines that are provided on the insulating substrate, and extend in a second direction intersecting the first direction; a switching element coupled to each of the gate lines and each of the signal lines; a first photoelectric conversion element that comprises a first semiconductor layer containing amorphous silicon, and is coupled to the switching element; and a second photoelectric conversion element that comprises a second semiconductor layer containing polysilicon, and is coupled to the switching element.

BACKGROUND

1. Technical Field

The present disclosure relates to a detection device.

2. Description of the Related Art

In these years, optical biosensors are known as biosensors used, for example, for personal authentication. Fingerprint sensors (refer, for example, to United States Patent Application Publication No. 2018/0012069 (US-A-2018/0012069)) and vein sensors are known as the biosensors. In such a fingerprint sensor described in US-A-2018/0012069, a plurality of photoelectric conversion elements, such as photodiodes, are arranged on a semiconductor substrate. Signals output from the photoelectric conversion elements change with an amount of irradiating light.

Such a biosensor using an optical sensor is required to detect not only a shape of a fingerprint of an object to be detected such as a finger or a palm, but also various types of biological information on the object to be detected. For example, the wavelength of light and the detection sensitivity differ between fingerprint detection and vein detection. For example, in US-A-2018/0012069, a sensitive wavelength range is determined by characteristics of the photoelectric conversion elements. Therefore, a plurality of different types of biological information, such as the fingerprint and the veins, may be difficult to be well detected using the same detection device.

SUMMARY

A detection device according to an embodiment of the present disclosure comprising: an insulating substrate; a plurality of gate lines that are provided on the insulating substrate, and extend in a first direction; a plurality of signal lines that are provided on the insulating substrate, and extend in a second direction intersecting the first direction; a switching element coupled to each of the gate lines and each of the signal lines; a first photoelectric conversion element that comprises a first semiconductor layer containing amorphous silicon, and is coupled to the switching element; and a second photoelectric conversion element that comprises a second semiconductor layer containing polysilicon, and is coupled to the switching element.

DETAILED DESCRIPTION

The following describes embodiments for carrying out the present disclosure in detail with reference to the drawings. The present disclosure is not limited to the description of the embodiments given below. Components to be described below include those easily conceivable by those skilled in the art or those substantially identical thereto. Moreover, the components to be described below can be appropriately combined. What is disclosed herein is merely an example, and the present disclosure naturally encompasses appropriate modifications easily conceivable by those skilled in the art while maintaining the gist of the disclosure. To further clarify the description, the drawings schematically illustrate, for example, widths, thicknesses, and shapes of various parts as compared with actual aspects thereof, in some cases. However, they are merely examples, and interpretation of the present disclosure is not limited thereto. The same element as that illustrated in a drawing that has already been discussed is denoted by the same reference numeral through the description and the drawings, and detailed description thereof will not be repeated in some cases where appropriate.

First Embodiment

FIG.1is a sectional view illustrating a schematic sectional configuration of a detection apparatus having a lighting device including a detection device according to a first embodiment of the present disclosure. As illustrated inFIG.1, a detection apparatus120having a lighting device includes a detection device1, a lighting device121, and a cover glass122. The lighting device121, the detection device1, and the cover glass122are stacked in this order in a direction orthogonal to a surface of the detection device1.

The lighting device121has a light-emitting surface121afor emitting light, and emits light L1from the light-emitting surface121atoward the detection device1. The lighting device121is backlight. The lighting device121may be what is called a side light-type backlight that includes a light guide plate provided in a position corresponding to a detection area AA and a plurality of light sources arranged at one end or both ends of the light guide plate. For example, light-emitting diodes (LEDs) for emitting light in a predetermined color are used as the light sources. The lighting device121may be what is called a directly below-type backlight that includes light sources (such as LEDs) provided directly below the detection area AA. The lighting device121is not limited to the backlight. The lighting device121may be provided on a lateral side or an upper side of the detection device1, and may emit the light L1from the lateral side or the upper side of a finger Fg.

The detection device1is provided so as to face the light-emitting surface121aof the lighting device121. In other words, the detection device1is provided between the lighting device121and the cover glass122. The light L1emitted from the lighting device121passes through the detection device1and the cover glass122. The detection device1is, for example, a light reflective fingerprint sensor, and can detect asperities (such as a fingerprint) on a surface of the finger Fg by detecting light L2reflected on an interface between the cover glass122and air. Alternatively, the detection device1may detect biological information by detecting the light L2reflected in the finger Fg, in addition to detecting the fingerprint. The biological information is, for example, a blood vessel image of veins or the like, pulsation, and a pulse wave. The color of the light L1from the lighting device121may be changed depending on the detection target. For example, in the case of the fingerprint detection, the lighting device121can emit the blue or green light L1, and in the case of the vein detection, the lighting device121can emit the infrared light L1.

The cover glass122is a member for protecting the detection device1and the lighting device121, and covers the detection device1and the lighting device121. The cover glass122is, for example, a glass substrate. The cover glass122is not limited to the glass substrate, and may be, for example, a resin substrate. The cover glass122need not be provided. In this case, a protection layer is provided on the surface of the detection device1, and the finger Fg makes contact with the protection layer of the detection device1.

The detection apparatus120having a lighting device may be provided with a display panel instead of the lighting device121. The display panel may be, for example, an organic electroluminescent (EL) (organic light-emitting diode (OLED)) display panel or an inorganic EL (μ-LED or mini-LED) display. Alternatively, the display panel may be a liquid crystal display (LCD) panel that uses liquid crystal elements as display elements, or an electrophoretic display (EPD) panel that uses electrophoretic elements as the display elements. Even in this case, display light emitted from the display panel passes through the detection device1, and the fingerprint of the finger Fg and the biological information can be detected based on the light L2reflected by the finger Fg.

FIG.2is a plan view illustrating the detection device according to the first embodiment.FIG.3is a block diagram illustrating a configuration example of the detection device according to the first embodiment. As illustrated inFIG.2, the detection device1includes an insulating substrate21, a sensor10, a gate line drive circuit15, a signal line selection circuit16, an analog front-end circuit (hereinafter, called “AFE”)48, a control circuit102, and a power supply circuit103.

As illustrated inFIG.2, a control board101is electrically coupled to the insulating substrate21through a flexible printed circuit board110. The flexible printed circuit board110is provided with the AFE48. The control board101is provided with the control circuit102and the power supply circuit103. The control circuit102is, for example, a field programmable gate array (FPGA). The control circuit102supplies control signals to the sensor10, the gate line drive circuit15, and the signal line selection circuit16to control a detection operation of the sensor10. The power supply circuit103supplies voltage signals including, for example, a power supply signal SVS (refer toFIG.6) to the sensor10and the gate line drive circuit15.

The insulating substrate21has a detection area AA and a peripheral area GA. The detection area AA is an area overlapping a plurality of first photodiodes PD1and a plurality of second photodiodes PD2(refer toFIG.5) included in the sensor10. The peripheral area GA is an area outside the detection area AA, and is an area overlapping neither the first photodiodes PD1nor the second photodiodes PD2. That is, the peripheral area GA is an area between the outer circumference of the detection area AA and the ends of the insulating substrate21. The gate line drive circuit15and the signal line selection circuit16are provided in the peripheral area GA.

As illustrated inFIG.3, the detection device1further includes a detection controller11and a detector40. The control circuit102includes some or all functions of the detection controller11. The control circuit102also includes some or all functions of the detector40except that of the AFE48.

The sensor10is an optical sensor including the first and the second photodiodes PD1and PD2that serve as photoelectric conversion elements. Each of the first and the second photodiodes PD1and PD2included in the sensor10outputs an electrical signal corresponding to light emitted thereto as a detection signal Vdet to the signal line selection circuit16. The sensor10performs the detection in response to a gate drive signal VGCL supplied from the gate line drive circuit15.

The detection controller11is a circuit that supplies respective control signals to the gate line drive circuit15, the signal line selection circuit16, and the detector40to control operations thereof. The detection controller11supplies various control signals including, for example, a start signal STV, a clock signal CK, and a reset signal RST1to the gate line drive circuit15. The detection controller11also supplies various control signals including, for example, a selection signal SEL to the signal line selection circuit16.

The gate line drive circuit15is a circuit that drives a plurality of gate lines GCL (refer toFIG.4) based on the various control signals. The gate line drive circuit15sequentially or simultaneously selects the gate lines GCL, and supplies the gate drive signals VGCL to the selected gate lines GCL. Through this operation, the gate line drive circuit15selects the first and the second photodiodes PD1and PD2coupled to the gate lines GCL.

The signal line selection circuit16is a switch circuit that sequentially or simultaneously selects a plurality of signal lines SGL (refer toFIG.4). The signal line selection circuit16couples the selected signal lines SGL to the AFE48serving as a detection circuit based on the selection signal SEL supplied from the detection controller11. Through this operation, the signal line selection circuit16outputs the detection signal Vdet of each of the first and the second photodiodes PD1and PD2to the detector40. The signal line selection circuit16is, for example, a multiplexer.

The detector40includes the AFE48, a signal processor44, a coordinate extractor45, a storage46, and a detection timing controller47. The detection timing controller47controls, based on a control signal supplied from the detection controller11, the AFE48, the signal processor44, and the coordinate extractor45so as to operate in synchronization with one another.

The AFE48is a signal processing circuit having functions of at least a detection signal amplifier42and an analog-to-digital (A/D) converter43. The detection signal amplifier42amplifies the detection signal Vdet. The A/D converter43converts an analog signal output from the detection signal amplifier42into a digital signal.

The signal processor44is a logic circuit that detects a predetermined physical quantity received by the sensor10based on an output signal of the AFE48. When the finger Fg is in contact with or in proximity to a detection surface, the signal processor44can detect the asperities of the surface of the finger Fg or the palm based on the signal from the AFE48.

The storage46temporarily stores therein a signal calculated by the signal processor44. The storage46may be, for example, a random-access memory (RAM) or a register circuit.

The coordinate extractor45is a logic circuit that obtains detected coordinates of the asperities of the surface of, for example, the finger Fg when the contact or the proximity of the finger Fg is detected by the signal processor44. The coordinate extractor45combines the detection signals Vdet output from the first and the second photodiodes PD1and PD2of the sensor10to generate two-dimensional information representing a shape of the asperities of the surface of, for example, the finger Fg. The coordinate extractor45may output the detection signals Vdet as sensor outputs Vo, without calculating the detected coordinates.

The following describes a circuit configuration example and an operation example of the detection device1.FIG.4is a circuit diagram illustrating the detection device.FIG.5is a circuit diagram illustrating a partial detection area.FIG.6is a timing waveform diagram illustrating the operation example of the detection device.

As illustrated inFIG.4, the sensor10has a plurality of partial detection areas PAA arranged in a matrix having a row-column configuration. As illustrated inFIG.5, each of the partial detection areas PAA includes the first and the second photodiodes PD1and PD2, a capacitive element Ca, and a first switching element Tr. The first switching element Tr is provided correspondingly to the first and the second photodiodes PD1and PD2. The first switching element Tr is constituted by a thin-film transistor, and in this example, constituted by an re-channel metal oxide semiconductor (MOS) thin-film transistor (TFT).

The gates of the first switching element Tr are coupled to each of the gate lines GCL. The source of the first switching element Tr is coupled to each of the signal lines SGL. The drain of the first switching element Tr is coupled to a cathode electrode34of a corresponding one of the first photodiodes PD1, a cathode electrode54of a corresponding one of the second photodiodes PD2, and one end of the capacitive element Ca. An anode electrode35of the first photodiode PD1, an anode electrode55of the second photodiode PD2, and the other end of the capacitive element Ca are coupled to a reference potential, for example, a ground potential. In this way, the first and the second photodiodes PD1and PD2are coupled in parallel in the same direction to the first switching element Tr.

A third switching element TrS and a fourth switching element TrR are coupled to the signal line SGL. The third switching element TrS and the fourth switching element TrR are elements included in a drive circuit that drives the first switching element Tr. In the present embodiment, the drive circuit includes, for example, the gate line drive circuit15, the signal line selection circuit16, and a reset circuit17that are provided in the peripheral area GA. The third switching element TrS is constituted by, for example, a complementary metal-oxide semiconductor (CMOS) transistor obtained by combining a p-channel transistor p-TrS with an n-channel transistor n-TrS. In the same manner, the fourth switching element TrR is constituted by a CMOS transistor.

When the fourth switching element TrR of the reset circuit17is turned on, the capacitive element Ca is supplied with a reference signal VR1serving as an initial potential of the capacitive element Ca from the power supply circuit103. This operation resets the capacitive element Ca. When the partial detection area PAA is irradiated with light, a current corresponding to an amount of the light flows through each of the first and the second photodiodes PD1and PD2. As a result, an electrical charge is stored in the capacitive element Ca. After the first switching element Tr is turned on, a current corresponding to the electrical charge stored in the capacitive element Ca flows through the signal line SGL. The signal line SGL is coupled to the AFE48through the third switching element TrS of the signal line selection circuit16. Thus, the detection device1can detect a signal corresponding to the amount of the light emitted to the first and the second photodiodes PD1and PD2for each of the partial detection areas PAA.

As illustrated inFIG.4, the gate lines GCL extend in a first direction Dx, and are coupled to the partial detection areas PAA arranged in the first direction Dx. A plurality of gate lines GCL1, GCL2, . . . , GCL8are arranged in a second direction Dy, and are each coupled to the gate line drive circuit15. In the following description, the gate lines GCL1, GCL2, . . . , GCL8will each be simply referred to as the gate line GCL when need not be distinguished from one another. Although the number of the gate lines GCL is eight, this is merely an example. Eight or more, such as 256, of the gate lines GCL may be arranged.

The first direction Dx is a direction in a plane parallel to the insulating substrate21, and is, for example, a direction parallel to the gate lines GCL. The second direction Dy is a direction in a plane parallel to the insulating substrate21, and is, for example, a direction orthogonal to the first direction Dx. The second direction Dy may intersect the first direction Dx without being orthogonal thereto. A third direction Dz is a direction orthogonal to the first direction Dx and the second direction Dy, and is a direction orthogonal to the insulating substrate21.

The signal lines SGL extend in the second direction Dy, and are coupled to the partial detection areas PAA arranged in the second direction Dy. A plurality of signal lines SGL1, SGL2, . . . , SGL12are arranged in the first direction Dx, and are each coupled to the signal line selection circuit16and the reset circuit17. Although the number of the signal lines SGL is 12, this is merely an example. Twelve or more, such as 252, of the signal lines SGL may be arranged. InFIG.4, the sensor10is provided between the signal line selection circuit16and the reset circuit17. The present disclosure is not limited thereto. The signal line selection circuit16and the reset circuit17may be coupled to the same ends of the signal lines SGL.

The gate line drive circuit15receives the various control signals such as the start signal STV, the clock signal CK, and the reset signal RST1through a level shifter151. The gate line drive circuit15includes a plurality of second switching elements TrG (not illustrated). The gate line drive circuit15sequentially selects the gate lines GCL1, GCL2, . . . , GCL8in a time-division manner through operations of the second switching elements TrG. The gate line drive circuit15supplies the gate drive signal VGCL through a selected one of the gate lines GCL to corresponding ones of the first switching elements Tr. This operation selects the partial detection areas PAA arranged in the first direction Dx as the detection targets.

The signal line selection circuit16includes a plurality of selection signal lines Lsel, a plurality of output signal lines Lout, and the third switching elements TrS. The third switching elements TrS are provided correspondingly to the respective signal lines SGL. Six of the signal lines SGL1, SGL2, . . . , SGL6are coupled to a common output signal line Lout1. Six of the signal lines SGL7, SGL8, . . . , SGL12are coupled to a common output signal line Lout2. The output signal lines Lout1and Lout2are each coupled to the AFE48.

The signal lines SGL1, SGL2, . . . , SGL6are grouped into a first signal line block, and the signal lines SGL7, SGL8, . . . , SGL12are grouped into a second signal line block. The selection signal lines Lsel are coupled to the gates of the respective third switching elements TrS included in one of the signal line blocks. One of the selection signal lines Lsel is coupled to the gates of the third switching elements TrS in the signal line blocks. Specifically, selection signal lines Lsel1, Lsel2, . . . , Lsel6are coupled to the third switching elements TrS corresponding to the signal lines SGL1, SGL2, . . . , SGL6. The selection signal line Lsel1is coupled to one of the third switching elements TrS corresponding to the signal line SGL1and one of the third switching elements TrS corresponding to the signal line SGL7. The selection signal line Lsel2is coupled to one of the third switching elements TrS corresponding to the signal line SGL2and one of the third switching elements TrS corresponding to the signal line SGL8.

The control circuit102(refer toFIG.2) sequentially supplies the selection signals SEL to the selection signal lines Lsel through level shifters161. This operation causes the signal line selection circuit16to operate the third switching elements TrS to sequentially select the signal lines SGL in one of the signal line blocks in a time-division manner. The signal line selection circuit16simultaneously selects one of the signal lines SGL in each of the signal line blocks. With the above-described configuration, the detection device1can reduce the number of integrated circuits (ICs) including the AFE48or the number of terminals of the ICs.

As illustrated inFIG.4, the reset circuit17includes a reference signal line Lvr, a reset signal line Lrst, and the fourth switching elements TrR. The fourth switching elements TrR are provided correspondingly to the signal lines SGL. The reference signal line Lvr is coupled to either the sources or the drains of the fourth switching elements TrR. The reset signal line Lrst is coupled to the gates of the fourth switching elements TrR.

The control circuit102supplies a reset signal RST2to the reset signal line Lrst through a level shifter171. This operation turns on the fourth switching elements TrR to electrically couple the signal lines SGL to the reference signal line Lvr. The power supply circuit103supplies the reference signal VR1to the reference signal line Lvr. This operation supplies the reference signal VR1to the capacitive elements Ca included in the partial detection areas PAA.

As illustrated inFIG.6, the detection device1includes a reset period Prst, an exposure period Pex, and a reading period Pdet. The power supply circuit103supplies the power supply signal SVS to the first and the second photodiodes PD1and PD2through the reset period Prst, the exposure period Pex, and the reading period Pdet. The control circuit102supplies the reference signal VR1and the reset signal RST2serving as high-level voltage signals to the reset circuit17from a time before the reset period Prst starts. The control circuit102supplies the start signal STV to the gate line drive circuit15, and the reset period Prst starts.

During the reset period Prst, the gate line drive circuit15sequentially selects the gate line GCL based on the start signal STV, the clock signal CK, and the reset signal RST1. The gate line drive circuit15sequentially supplies the gate drive signal VGCL to the gate line GCL. The gate drive signal VGCL has a pulsed waveform having a high-level voltage VGH and a low-level voltage VGL. InFIG.6, 256 of the gate lines GCL are provided, and gate drive signals VGCL1, . . . , VGCL256are sequentially supplied to the gate lines GCL.

Thus, during the reset period Prst, the capacitive elements Ca of all the partial detection areas PAA are sequentially electrically coupled to the signal lines SGL, and are supplied with the reference signal VR1. As a result, capacities of the capacitive elements Ca are reset.

After the gate drive signal VGCL256is supplied to the gate line GCL, the exposure period Pex starts. The start timing and end timing of actual exposure periods Pex1, . . . , Pex256in the partial detection areas PAA corresponding to the respective gate lines GCL differ from one another. Each of the exposure periods Pex1, . . . , Pex256starts at a time when the gate drive signal VGCL changes from the high-level voltage VGH to the low-level voltage VGL during the reset period Prst. Each of the exposure periods Pex1, . . . , Pex256ends at a time when the gate drive signal VGCL changes from the low-level voltage VGL to the high-level voltage VGH during the reading period Pdet. The lengths of exposure time of the exposure periods Pex1, . . . , Pex256are equal.

During the exposure period Pex, the current corresponding to the light emitted to the first and the second photodiodes PD1and PD2flows in each of the partial detection areas PAA. As a result, the electrical charge is stored in each of the capacitive elements Ca.

At a time before the reading period Pdet starts, the control circuit102sets the reset signal RST2to a low-level voltage. This operation stops the reset circuit17operating. During the reading period Pdet, the gate line drive circuit15sequentially supplies the gate drive signals VGCL1, . . . , VGCL256to the gate lines GCL in the same manner as during the reset period Prst.

For example, during a period in which the gate drive signal VGCL1is at the high-level voltage VGH, the control circuit102sequentially supplies selection signals SEL1, . . . , SEL6to the signal line selection circuit16. This operation sequentially or simultaneously couples the signal lines SGL for the partial detection areas PAA selected by the gate drive signal VGCL1to the AFE48. As a result, the detection signal Vdet is supplied to the AFE48. In the same manner, the signal line selection circuit16sequentially selects the signal line SGL in each period in which a corresponding one of the gate drive signals VGCL is set to the high-level voltage VGH. Thus, the detection device1can output the detection signals Vdet of all the partial detection areas PAA to the AFE48during the reading period Pdet.

The detection device1may perform the detection by repeatedly performing the processing during the reset period Prst, the exposure period Pex, and the reading period Pdet. Alternatively, the detection device1may start the detection operation when having detected that the finger Fg, for example, is in contact with or in proximity to the detection surface.

The following describes a detailed configuration of the detection device1.FIG.7is a plan view schematically illustrating the partial detection area of the detection device according to the first embodiment.FIG.8is a VIII-VIII′ sectional view ofFIG.7. For ease of viewing,FIG.7illustrates the cathode electrode34and the anode electrode35with long dashed double-short dashed lines.

In the following description, in a direction orthogonal to a surface of the insulating substrate21, a direction from the insulating substrate21toward the first photodiode PD1will be referred to as the “upper side” or simply as “above”, and a direction from the first photodiode PD1toward the insulating substrate21will be referred to as the “lower side” or simply as “below”. The term “plan view” refers to a case of viewing from the direction orthogonal to the surface of the insulating substrate21.

As illustrated inFIG.7, the partial detection area PAA is an area surrounded by the gate lines GCL and the signal lines SGL. The first photodiode PD1, the second photodiode PD2, and the first switching element Tr are provided in the partial detection area PAA, that is, in the area surrounded by the gate lines GCL and the signal lines SGL. Each of the first and the second photodiodes PD1and PD2is, for example, a positive-intrinsic-negative (PIN) photodiode.

The first photodiode PD1includes a first semiconductor layer31, the cathode electrode34and the anode electrode35. The first semiconductor layer31includes a first partial semiconductor layer31aand a second partial semiconductor layer31b. The first and the second partial semiconductor layers31aand31bof the first photodiode PD1are of amorphous silicon (a-Si). The first and the second partial semiconductor layers31aand31bare provided adjacent to each other with a space SP provided therebetween in the first direction Dx. The cathode electrode34and the anode electrode35are continuously provided over an area overlapping the first partial semiconductor layer31a, the second partial semiconductor layer31b, and the space SP. In the following description, the first and the second partial semiconductor layers31aand31bmay each be simply referred to as the first semiconductor layer31when need not be distinguished from one another.

The first photodiode PD1is provided so as to overlap the second photodiode PD2. Specifically, the first partial semiconductor layer31aof the first photodiode PD1overlaps the second photodiode PD2. The second photodiode PD2includes a second semiconductor layer51, the cathode electrode54, and the anode electrode55. The second semiconductor layer51is of polysilicon. The second semiconductor layer51is more preferably of low-temperature polysilicon (hereinafter, referred to as low-temperature polycrystalline silicon (LIPS)).

The second semiconductor layer51has an i region52a, a p region52b, and an n region52c. The i region52ais disposed between the p region52band the n region52cin plan view. Specifically, the p region52b, the i region52a, and the n region52care arranged in this order in the first direction Dx. The polysilicon of the n region52cis doped with impurities to form an n+ region. The polysilicon of the p region52bis doped with impurities to form a p+ region. The i region52ais, for example, a non-doped intrinsic semiconductor, and has lower conductivity than those of the p region52band the n region52c.

The second semiconductor layer51is coupled to the first partial semiconductor layer31aof the first photodiode PD1through a first relay electrode56and a second relay electrode57. In the present embodiment, a portion of the first relay electrode56overlapping the second semiconductor layer51serves as the cathode electrode54, and a portion of the second relay electrode57overlapping the second semiconductor layer51serves as the anode electrode55. A detailed coupling configuration between the second semiconductor layer51and the first photodiode PD1will be described later.

The first switching element Tr is provided in an area overlapping the second partial semiconductor layer31bof the first photodiode PD1. The first switching element Tr includes a third semiconductor layer61, a source electrode62, a drain electrode63, and gate electrodes64. The third semiconductor layer61is of polysilicon in the same manner as the second semiconductor layer51. The third semiconductor layer61is more preferably of LTPS.

In the present embodiment, a portion of the first relay electrode56overlapping the third semiconductor layer61serves as the source electrode62, and a portion of the signal line SGL overlapping the third semiconductor layer61serves as the drain electrode63. The gate electrodes64branch in the second direction Dy from the gate line GCL, and overlap the third semiconductor layer61. In the present embodiment, the two gate electrodes64are provided so as to overlap the third semiconductor layer61to form what is called a double-gate structure.

The first switching element Tr is coupled to the cathode electrode34of the first photodiode PD1and the cathode electrode54of the second photodiode PD2through the first relay electrode56. The first switching element Tr is also coupled to the signal line SGL.

More specifically, the first switching element Tr is provided on the insulating substrate21as illustrated inFIG.8. The insulating substrate21is, for example, a light-transmitting glass substrate. The insulating substrate21may alternatively be a resin substrate or a resin film formed of a light-transmitting resin such as polyimide. In the detection device1, the first photodiode PD1, the second photodiode PD2, and the first switching element Tr are formed above the insulating substrate21. This configuration allows the detection device1to have an area of the detection area AA larger than that in a case of using a semiconductor substrate such as a silicon substrate.

Light-blocking layers67and68are provided above the insulating substrate21. An undercoat film22is provided above the insulating substrate21so as to cover the light-blocking layers67and68. The undercoat film22, a gate insulating film23, and a first interlayer insulating film24are inorganic insulating films, and are formed using, for example, a silicon oxide (SiO) film, a silicon nitride (SiN) film, or a silicon oxynitride (SiON) film. Each of the inorganic insulating films is not limited to a single layer, but may be a laminated film.

The second semiconductor layer51and the third semiconductor layer61are provided above the undercoat film22. That is, the second semiconductor layer51of the second photodiode PD2and the third semiconductor layer61of the first switching element Tr are provided in the same layer. The light-blocking layer67is provided between the second semiconductor layer51and the insulating substrate21in the third direction Dz. This configuration can restrain the light L1from the lighting device121(refer toFIG.1) from directly irradiating the second photodiode PD2. The light-blocking layer68is provided between the third semiconductor layer61and the insulating substrate21in the third direction Dz. This configuration can reduce a light leakage current of the first switching element Tr.

The third semiconductor layer61includes i regions61a, lightly doped drain (LDD) regions61b, and n regions61c. The i regions61aare formed in areas overlapping the respective gate electrodes64. The n regions61care high-concentration impurity regions that are formed in areas coupled to the source electrode62and the drain electrode63. The LDD regions61bare low-concentration impurity regions that are formed between the n regions61cand the i regions61aand between the two i regions61a.

The gate insulating film23is provided above the undercoat film22so as to cover the second semiconductor layer51and the third semiconductor layer61. The gate electrodes64are provided above the gate insulating film23. That is, the first switching element Tr has what is called a top-gate structure in which the gate electrodes64are provided on the upper side of the third semiconductor layer61. However, the first switching element Tr may have what is called a dual-gate structure in which the gate electrodes64are provided on both the upper side and the lower side of the third semiconductor layer61, or may have a bottom-gate structure in which the gate electrodes64are provided on the lower side of the third semiconductor layer61.

The first interlayer insulating film24is provided above the gate insulating film23so as to cover the gate electrodes64. The first interlayer insulating film24is also provided on the upper side of the second semiconductor layer51. The first relay electrode56, the second relay electrode57, and the signal line SGL are provided above the first interlayer insulating film24. In the first switching element Tr, the source electrode62(first relay electrode56) is coupled to the third semiconductor layer61through a contact hole H8, and the drain electrode63(signal line SGL) is coupled to the third semiconductor layer61through a contact hole H7.

In the second photodiode PD2, the cathode electrode54(first relay electrode56) is coupled to the n region52cof the second semiconductor layer51through a contact hole H6. This configuration couples the cathode electrode54of the second photodiode PD2to the first switching element Tr. The anode electrode55(second relay electrode57) is coupled to the p region52bof the second semiconductor layer51through a contact hole H5.

A second interlayer insulating film25is provided above the first interlayer insulating film24so as to cover the second photodiode PD2and the first switching element Tr. The second interlayer insulating film25is an organic film, and is a planarizing film that planarizes asperities formed by various conductive layers. The second interlayer insulating film25may be formed of one of the above-mentioned inorganic materials.

The anode electrode35of the first photodiode PD1is provided above the second interlayer insulating film25of a backplane2. The anode electrode35, the first and the second partial semiconductor layers31aand31b, and the cathode electrode34are stacked in this order to form the first photodiode PD1. The backplane2is a drive circuit board that drives the sensor on a per predetermined detection area basis. The backplane2includes the insulating substrate21, and the first switching elements Tr, the second switching elements TrG, various types of wiring, and so forth provided on the insulating substrate21.

The first partial semiconductor layer31aincludes an i-type semiconductor layer32a, a p-type semiconductor layer32b, and an n-type semiconductor layer32c. The second partial semiconductor layer31bincludes an i-type semiconductor layer33a, a p-type semiconductor layer33b, and an n-type semiconductor layer33c. The i-type semiconductor layers32a,33a, the p-type semiconductor layers32b,33b, and the n-type semiconductor layers32c,33care specific examples of the photoelectric conversion elements. InFIG.8, the i-type semiconductor layers32a,33aare provided between the p-type semiconductor layers32b,33band the n-type semiconductor layers32c,33cin the direction (third direction Dz) orthogonal to the surface of the insulating substrate21. In the present embodiment, the p-type semiconductor layers32b,33b, the i-type semiconductor layers32a,33a, and the n-type semiconductor layers32c,33care stacked in this order above the anode electrode35.

In the n-type semiconductor layers32c,33c, a-Si is doped with impurities to form the n+ regions. In the p-type semiconductor layers32b,33b, a-Si is doped with impurities to form the p+ regions. The i-type semiconductor layers32a,33aare, for example, non-doped intrinsic semiconductors, and have lower conductivity than those of the n-type semiconductor layers32c,33cand the p-type semiconductor layers32b,33b.

The cathode electrode34and the anode electrode35are of a light-transmitting conductive material such as indium tin oxide (ITO). The cathode electrode34is an electrode for supplying the power supply signal SVS to the photoelectric conversion layer. The anode electrode35is an electrode for reading the detection signal Vdet.

The anode electrode35is provided above the second interlayer insulating film25. The anode electrode35is continuously provided across the first and the second partial semiconductor layers31aand31b. The anode electrode35is coupled to the second relay electrode57through a contact hole H4provided in the second interlayer insulating film25.

A third interlayer insulating film26is provided so as to cover the first and the second partial semiconductor layers31aand31b. The third interlayer insulating film26is an organic film, and is a planarizing film that planarizes asperities formed by the first and the second partial semiconductor layers31aand31b. The cathode electrode34is provided above the third interlayer insulating film26. The cathode electrode34is continuously provided above the first and the second partial semiconductor layers31aand31b. The cathode electrode34is coupled to the first and the second partial semiconductor layers31aand31bthrough contact holes H2and H1provided in the third interlayer insulating film26. With this configuration, the first and the second partial semiconductor layers31aand31bare coupled in parallel between the anode electrode35and the cathode electrode34, and serve as one photoelectric conversion element.

The cathode electrode34is coupled to the first relay electrode56through a contact hole H3in the space SP between the first and the second partial semiconductor layers31aand31b. The contact hole H3is a through-hole passing through the second interlayer insulating film25and the third interlayer insulating film26in the third direction Dz. An opening35ais provided at a portion of the anode electrode35overlapping the contact hole H3, and the contact hole H3is formed through the opening35a. With the above-described configuration, the cathode electrode34of the first photodiode PD1and the cathode electrode54of the second photodiode PD2are coupled to the first switching element Tr through the first relay electrode56. In addition, the anode electrode35of the first photodiode PD1is couple to the anode electrode55of the second photodiode PD2through the second relay electrode57.

The capacity of the capacitive element Ca illustrated inFIG.5is provided in the space SP located between the anode electrode35and the cathode electrode34facing each other with the third interlayer insulating film26interposed therebetween, or is provided in a space SPa at the periphery of the first photodiode PD1located between the anode electrode35and the cathode electrode34facing each other with the third interlayer insulating film26interposed therebetween. The capacitive element Ca stores therein a positive electrical charge during the exposure period Pex.

FIG.9is a graph schematically illustrating a relation between a wavelength and an optical absorption coefficient of each of the first photodiode and the second photodiode. InFIG.9, the horizontal axis represents the wavelength, and the vertical axis represents the optical absorption coefficient. The optical absorption coefficient is an optical constant that represents a degree of absorption of light traveling through a substance.

As illustrated inFIG.9, the first photodiode PD1containing a-Si exhibits a good optical absorption coefficient in the visible light range, for example, in a wavelength range from 300 nm to 800 nm. In contrast, the second photodiode PD2containing polysilicon exhibits a good optical absorption coefficient in a range of, for example, from 500 nm to 1100 nm, including visible to infrared ranges. In other words, the first photodiode PD1has high sensitivity in the visible light range, and the second photodiode PD2has high sensitivity in a range from the red wavelength range to the infrared range that differs from the range of the first photodiode PD1.

In the detection device1of the present embodiment, the first and the second photodiodes PD1and PD2having different sensitive wavelength ranges are stacked. With this configuration, the wavelength range having high sensitivity can be wider than in a configuration including only either of the photodiodes.

The light L1(refer toFIG.1) penetrates the detection device1through the space SP and the space SPa. The light L2reflected by the finger Fg (refer toFIG.1) enters the first photodiode PD1. Of the light L2, light in a wavelength range not absorbed by the first photodiode PD1passes through the first photodiode PD1, and enters the second photodiode PD2. For example, in the fingerprint detection, the first photodiode PD1can well detect the blue or green light L2. In the vein detection, the infrared light L2is not absorbed by the first photodiode PD1, and enters the second photodiode PD2. Thus, the second photodiode PD2can well detect the infrared light L2. As a result, the detection device1can detect the various types of biological information using the same device (detection device1).

Even if the i region52aof the second photodiode PD2has changed to the n-type under the influence of electrical charges or impurities of the insulating films including, for example, the first interlayer insulating film24, the i region52ais neutralized by the cathode electrode34of the first photodiode PD1. As a result, the detection device1can be increased in optical sensitivity.

The first and the second photodiodes PD1and PD2are provided in the partial detection area PAA, that is, in the area surrounded by the gate lines GCL and the signal lines SGL. With this configuration, the number of switching elements and the number of wires can be smaller than in a case where each of the first and the second photodiodes PD1and PD2is provided with the first switching element Tr, the gate line GCL, and the signal line SGL. Accordingly, the detection device1can improve the resolution of the detection.

The detection device1is not limited to the case of being used as the fingerprint sensor for detecting the fingerprint of the finger Fg and the sensor for detecting the veins. The detection device1can also be used as a biosensor for detecting various types of biological information such as the blood vessel image of the finger Fg or the palm, the pulse wave, the pulsation, and a blood oxygen concentration.

FIG.10is a sectional view illustrating a schematic sectional configuration of the switching element included in the drive circuit.FIG.10explains the third switching element TrS included as a drive circuit switching element in the signal line selection circuit16. However, the explanation ofFIG.10can also be applied to switching elements included in other drive circuits. That is, the same configuration as that ofFIG.10can be applied to the second switching elements TrG included in the gate line drive circuit15and the fourth switching element TrR included in the reset circuit17.

As illustrated inFIG.10, the n-channel transistor n-TrS of the third switching element TrS includes a fourth semiconductor layer71, a source electrode72, a drain electrode73, and a gate electrode74. The p-channel transistor p-TrS includes a fifth semiconductor layer81, a source electrode82, a drain electrode83, and a gate electrode84. A light-blocking layer75is provided between the fourth semiconductor layer71and the insulating substrate21. A light-blocking layer85is provided between the fifth semiconductor layer81and the insulating substrate21.

Both the fourth semiconductor layer71and the fifth semiconductor layer81are of polysilicon. The fourth semiconductor layer71and the fifth semiconductor layer81are more preferably of LTPS. The fourth semiconductor layer71includes an i region71a, LDD regions71b, and the n regions71c. The fifth semiconductor layer81includes an i region81aandpregions81b.

The n-channel transistor n-TrS and the p-channel transistor p-TrS have the same layer configuration as that of the first switching element Tr illustrated inFIG.8. That is, the fourth semiconductor layer71and the fifth semiconductor layer81are provided in the same layer as those of the second semiconductor layer51and the third semiconductor layer61illustrated inFIG.8; the gate electrode74and the gate electrode84are provided in the same layer as those of the gate electrodes64illustrated inFIG.8; and the source electrode72, the drain electrode73, the source electrode82, and the drain electrode83are provided in the same layer as those of the source electrode62(first relay electrode56) and the drain electrode63(signal line SGL) illustrated inFIG.8.

As described above, the second photodiode PD2and the first switching element Tr provided in the detection area AA use the same material and are provided in the same layer as the switching elements are, such as the third switching element TrS provided in the peripheral area GA. This configuration can simplify the manufacturing process and reduce the manufacturing cost of the detection device1. The drive circuit provided in the peripheral area GA is not limited to being constituted by the CMOS transistor, and may be constituted by either the n-channel transistor n-TrS or the p-channel transistor p-TrS.

First Modification of First Embodiment

FIG.11is a plan view schematically illustrating the partial detection area of the detection device according to a first modification of the first embodiment. The same components as those described in the above-described first embodiment are denoted by the same reference numerals, and the description of the same components will not be repeated. As illustrated inFIG.11, the first modification differs from the above-described first embodiment in configuration in which the first photodiode PD1is provided adjacent to the second photodiode PD2in plan view.

As illustrated inFIG.11, the first photodiode PD1is disposed away from the gate line GCL in the second direction Dy. Specifically, one side35sof the anode electrode35of the first photodiode PD1is disposed away from the gate line GCL in the second direction Dy in plan view, and a space SPb is provided between the one side35sof the anode electrode35and the gate line GCL. The one side35sis a side closer to the second photodiode PD2among sides of the anode electrode35along the first direction Dx.

The second photodiode PD2and the first switching element Tr are provided between the first photodiode PD1and the gate line GCL that are adjacent in the second direction Dy. Each of the first relay electrode56and the second relay electrode57has a portion overlapping the anode electrode35of the first photodiode PD1and a portion not overlapping the anode electrode35of the first photodiode PD1. The first photodiode PD1, the second photodiode PD2, and the first switching element Tr are coupled to one another through the first relay electrode56and the second relay electrode57in the same manner as in the first embodiment.

As illustrated inFIG.12, the second photodiode PD2is provided in an area not overlapping the first photodiode PD1. That is, the second interlayer insulating film25and the third interlayer insulating film26are stacked above the anode electrode55of the second photodiode PD2, and the second semiconductor layer51is not provided between the insulating substrate21and the first photodiode PD1in the third direction Dz.

With such a configuration, in the first modification, the light L2reflected by the finger Fg enters the second photodiode PD2without passing through the first photodiode PD1. As a result, the intensity of the light L2incident on the second photodiode PD2is higher than that in the first embodiment, thus increasing the light usage efficiency of the second photodiode PD2.

Second Embodiment

FIG.13is a circuit diagram illustrating the partial detection area according to a second embodiment of the present disclosure.FIG.14is a sectional view illustrating a schematic sectional configuration of the detection device according to the second embodiment. As illustrated inFIG.13, the anode electrode35of the first photodiode PD1and the anode electrode55of the second photodiode PD2are coupled to the first switching element Tr. The cathode electrode34of the first photodiode PD1and the cathode electrode54of the second photodiode PD2are coupled to the reference potential, for example, the ground potential. That is, in the second embodiment, the first and the second photodiodes PD1and PD2are coupled in parallel to the first switching element Tr in a direction opposite to that in the first embodiment.

As illustrated inFIG.14, the cathode electrode34of the first photodiode PD1is provided above the second interlayer insulating film25. The cathode electrode34, the first and the second partial semiconductor layers31aand31b, and the anode electrode35are stacked in this order to form the first photodiode PD1. The n-type semiconductor layers32c,33c, the i-type semiconductor layers32a,33a, and the p-type semiconductor layers32b,33bare stacked in this order in the third direction Dz to form the first and the second partial semiconductor layers31aand31babove the cathode electrode34.

The anode electrode35is provided above the first and the second partial semiconductor layers31aand31b. The anode electrode35is coupled to the first relay electrode56through the contact hole H3in the space SP between the first and the second partial semiconductor layers31aand31b. In this case, an opening34ais formed in an area of the cathode electrode34overlapping the contact hole H3. The cathode electrode34is coupled to the second relay electrode57through the contact hole H4.

In the second semiconductor layer51of the second photodiode PD2, the n region52c, the i region52a, and the p region52bare arranged in this order in the first direction Dx. A portion of the first relay electrode56overlapping the second semiconductor layer51serves as the anode electrode55. A portion of the second relay electrode57overlapping the second semiconductor layer51serves as the cathode electrode54. The anode electrode55(first relay electrode56) is coupled to the p region52bof the second semiconductor layer51through the contact hole H6. The cathode electrode54(second relay electrode57) is coupled to the n region52cof the second semiconductor layer51through the contact hole H5.

With the above-described configuration, the cathode electrode34of the first photodiode PD1is coupled to the cathode electrode54of the second photodiode PD2through the second relay electrode57. In addition, the anode electrode35of the first photodiode PD1and the anode electrode55of the second photodiode PD2are coupled to the first switching element Tr through the first relay electrode56.

In the present embodiment, the capacitive element Ca stores therein a negative electrical charge during the exposure period Pex. Also in the second embodiment, the detection device1can widen the wavelength range having high sensitivity in the same manner as in the first embodiment. The planar configuration of the second embodiment is similar to that ofFIG.7, and therefore, is not illustrated. Specifically, the planar configuration of the second embodiment is obtained by interchanging the cathode electrode34of the first photodiode PD1with the anode electrode35, and interchanging the cathode electrode54and the n region52cof the second photodiode PD2with the anode electrode55and the p region52b, inFIG.7. The configuration of the first modification can also be applied to the second embodiment.

Third Embodiment

FIG.15is a plan view schematically illustrating the partial detection area of the detection device according to a third embodiment of the present disclosure.FIG.16is a XVI-XVI′ sectional view ofFIG.15. As illustrated inFIG.15, the first photodiode PD1includes the single first semiconductor layer31. The anode electrode35has a portion projecting outside the outer circumference of the cathode electrode34near a portion of the anode electrode35overlapping the second photodiode PD2. Specifically, one side34sof the cathode electrode34is disposed away from the gate line GCL in the second direction Dy. The one side35sof the anode electrode35is disposed in a position overlapping the gate line GCL. The anode electrode35is coupled to the second relay electrode57in an area overlapping the gate line GCL, that is, in an area between the one side34sof the cathode electrode34and the one side35sof the anode electrode35.

The second photodiode PD2and the first switching element Tr are provided in areas overlapping the first photodiode PD1. The configuration in plan view of the second photodiode PD2and the first switching element Tr is the same as that in the first embodiment.

As illustrated inFIG.16, the cathode electrode34, the first semiconductor layer31, and the anode electrode35are stacked in this order to form the first photodiode PD1above the second interlayer insulating film25. The first semiconductor layer31includes an i-type semiconductor layer36a, a p-type semiconductor layer36b, and an n-type semiconductor layer36c. The n-type semiconductor layer36c, the i-type semiconductor layer36a, and the p-type semiconductor layer36bare stacked in this order in the third direction Dz above the cathode electrode34.

The cathode electrode34is coupled to the first relay electrode56through the contact hole H3. The contact hole H3is formed so as to penetrate the second interlayer insulating film25in the third direction Dz. The second relay electrode57extends from an area overlapping the second semiconductor layer51to an area overlapping the gate line GCL. In other words, the second relay electrode57includes a portion overlapping the second semiconductor layer51and a portion overlapping the gate line GCL. The anode electrode35is coupled to a portion of the second relay electrode57overlapping the gate line GCL through the contact hole H4. The contact hole H4is formed so as to penetrate the second interlayer insulating film25and the third interlayer insulating film26in the third direction Dz. The second photodiode PD2has the same stacking configuration as that of the first embodiment illustrated inFIG.8.

With the above-described configuration, the cathode electrode34of the first photodiode PD1and the cathode electrode54of the second photodiode PD2are coupled to the first switching element Tr through the first relay electrode56. In addition, the anode electrode35of the first photodiode PD1is coupled to the anode electrode55of the second photodiode PD2through the second relay electrode57. That is, the circuit configuration of the third embodiment is the same as that ofFIG.5for the first embodiment.

In the third embodiment, the first photodiode PD1is constituted by the single first semiconductor layer31, and does not have the space SP illustrated inFIG.8. This configuration can increase an area of the first photodiode PD1that can receive the light L2, and therefore, increases the light usage efficiency of the first photodiode PD1. The capacity of the capacitive element Ca is provided between the cathode electrode34and the anode electrode35facing each other, for example, in the space SPa between the outer circumference of the first semiconductor layer31and the signal line SGL illustrated inFIG.7.

Second Modification of Third Embodiment

FIG.17is a plan view schematically illustrating the partial detection area of the detection device according to a second modification of the third embodiment. As illustrated inFIG.17, in the second modification, the second photodiode PD2and the first switching element Tr are provided between the first photodiode PD1and the gate line GCL that are adjacent in the second direction Dy. More specifically, the second photodiode PD2and the first switching element Tr are provided between the one side35sof the anode electrode35and the gate line GCL.

The anode electrode35has a coupling portion35tprojecting from the one side35stoward the gate line GCL. The second relay electrode57extends along the gate line GCL. One end side of the second relay electrode57is coupled to the coupling portion35tof the anode electrode35through the contact hole H4. The other end side (anode electrode55) of the second relay electrode57is coupled to the second semiconductor layer51of the second photodiode PD2through the contact hole H5.

In the second modification, the intensity of the light L2incident on the second photodiode PD2is higher than that in the third embodiment, thus increasing the light usage efficiency of the second photodiode PD2.

Fourth Embodiment

FIG.18is a sectional view illustrating a schematic sectional configuration of the detection device according to a fourth embodiment of the present disclosure. The circuit configuration of the fourth embodiment is the same as the circuit configuration illustrated inFIG.13for the second embodiment, in which the anode electrode35of the first photodiode PD1and the anode electrode55of the second photodiode PD2are coupled to the first switching element Tr. The cathode electrode34of the first photodiode PD1and the cathode electrode54of the second photodiode PD2are coupled to the reference potential, for example, the ground potential. That is, in the fourth embodiment, the first and the second photodiodes PD1and PD2are coupled in parallel to the first switching element Tr in a direction opposite to that in the third embodiment.

As illustrated inFIG.18, the anode electrode35, the first semiconductor layer31, and the cathode electrode34are stacked in this order to form the first photodiode PD1above the second interlayer insulating film25. The p-type semiconductor layer36b, the i-type semiconductor layer36a, and the n-type semiconductor layer36care stacked in this order in the third direction Dz to form the first semiconductor layer31above the anode electrode35.

The anode electrode35is coupled to the first relay electrode56through the contact hole H3. The cathode electrode34projects outside the anode electrode35. An end on the one side34sof the cathode electrode34is provided in a position not overlapping the anode electrode35, and is coupled to the second relay electrode57through the contact hole H4.

In the second semiconductor layer51of the second photodiode PD2, the n region52c, the i region52a, and the p region52bare arranged in this order in the first direction Dx. A portion of the first relay electrode56overlapping the second semiconductor layer51serves as the anode electrode55. A portion of the second relay electrode57overlapping the second semiconductor layer51serves as the cathode electrode54.

With the above-described configuration, the cathode electrode34of the first photodiode PD1is coupled to the cathode electrode54of the second photodiode PD2. In addition, the anode electrode35of the first photodiode PD1and the anode electrode55of the second photodiode PD2are coupled to the first switching element Tr.

In the present embodiment, the capacitive element Ca stores therein a negative electrical charge during the exposure period Pex. The planar configuration of the fourth embodiment is similar to that ofFIG.15for the third embodiment, and therefore, is not illustrated. Specifically, the planar configuration of the fourth embodiment is obtained by interchanging the cathode electrode34of the first photodiode PD1with the anode electrode35, and interchanging the cathode electrode54and the n region52cof the second photodiode PD2with the anode electrode55and the p region52b, inFIG.15. The configuration of the second modification can also be applied to the fourth embodiment.

Fifth Embodiment

FIG.19is a circuit diagram illustrating the partial detection area of the detection device according to a fifth embodiment of the present disclosure.FIG.20is a timing waveform diagram illustrating an operation example of the detection device according to the fifth embodiment. As illustrated inFIG.19, in the fifth embodiment, the partial detection area PAA does not include the capacitive element Ca. That is, the source of the first switching element Tr is coupled to the signal line SGL, and the drain of the first switching element Tr is coupled to the cathode electrode34of the first photodiode PD1and the cathode electrode54of the second photodiode PD2. The coupling direction of the first and the second photodiodes PD1and PD2may be the same as that in the second embodiment.

When the partial detection area PAA is irradiated with light while the first switching element Tr is on, currents corresponding to an amount of the light flow through the first and the second photodiodes PD1and PD2. The currents flow from the first and the second photodiodes PD1and PD2through the signal line SGL to the AFE48. That is, in the fifth embodiment, the time to store the electrical charge in the capacitive element Ca can be saved.

As illustrated inFIG.20, after the gate drive signal VGCL256is supplied to the gate line GCL256in the reset period Prst, the exposure period Pex is skipped, and the reading period Pdet starts. During the reading period Pdet, when the gate drive signal VGCL is sequentially supplied to each of the gate lines GCL, the first switching element Tr is turned on to couple the first and the second photodiodes PD1and PD2to the signal line SGL. While the first switching element Tr is on, the currents flow from the first and the second photodiodes PD1and PD2to the AFE48. In other words, in the reading period Pdet, a period while the gate drive signal VGCL serving as a high-level voltage signal is supplied serves as the exposure period Pex.

In the fifth embodiment, since the capacitive element Ca is not included, the circuit configuration of the partial detection area PAA can be simplified. In addition, since the detection in the entire area of the detection area AA can be quickly performed, a change in the blood vessel image with time, such as the pulse wave, can be well detected.

While the preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above. The content disclosed in the embodiments is merely an example, and can be variously modified within the scope not departing from the gist of the present disclosure. Modifications appropriately made within the scope not departing from the gist of the present disclosure naturally belong to the technical scope of the present disclosure.