JP2013084173A - Optical device and imaging method, biometric authentication method, vein sensor, and fingerprint sensor - Google Patents

Abstract

A high-performance optical device is provided.
An optical device includes a light emitting unit and a light receiving unit, irradiates light from the light emitting unit to the object, and receives light reflected from the object by the light receiving unit. . The light emitting unit 10 and the light receiving unit 20 are provided on the same side with respect to the object F, and the light emitting unit 10 is located on the object F side from the light receiving unit 20. The light emitting unit 10 has translucency and includes a light emitting layer 17 between the first electrode 16 and the second electrode 18, and the first electrode 16 includes the first first electrode 112, the second first electrode 122, and the like. Have The first first electrode 112 and the second first electrode 122 are separately connected to a power source to emit light alternately. When one is emitting light, the other receives light and the S / N ratio can be increased. That is, a clear image can be easily captured.
[Selection] Figure 1

Description

  The present invention relates to the technical fields of optical devices, imaging methods, biometric authentication methods, vein sensors, and fingerprint sensors.

  In a biometric authentication device or an image scanner, a light emitting unit and a light receiving unit are arranged on the same side with respect to an object (for example, a part of a living body or a document) placed on a reading area. There is a device that reads an image of an object by irradiating light from a light emitting unit and receiving reflected light by a light receiving unit. For example, in Patent Document 1, light emitted from a light source (near infrared light) is irradiated onto a finger by a plurality of reflecting surfaces formed on the back surface of a light guide plate, and the light reflected from the finger is received by a plurality of pixels. A biometric information acquisition device that captures a vein image of a finger by receiving light with an element is described.

JP 2009-172263 A

  However, the biological information acquisition device described in Patent Document 1 has a problem that it is difficult to capture a clear image. That is, in some cases, outgoing light (noise light) having a larger amount of light than reflected light (signal light) from which information is to be read is introduced into the light receiving element, and the ratio of signal light to noise light (S / N ratio) decreases. Was. This is because the light guide plate that guides the emitted light from the light source having a larger light quantity than the reflected light exists on the optical path of the reflected light incident on each pixel (on the straight line extending in the vertical direction from each pixel). Also, part of the light emitted from the light source passes through the low refractive index layer and the reflective layer (semi-reflective layer) formed on the back side of the light guide plate and leaks to the light receiving element side. As a result, there is a problem that the light receiving element cannot accurately receive the reflected light from the finger.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

Application Example 1 An optical device according to this application example includes a light emitting unit and a light receiving unit, irradiates light from a light emitting unit to an object, and receives reflected light from the object by the light receiving unit. The light emitting unit and the light receiving unit are provided on the same side with respect to the object, the light emitting unit is located on the object side from the light receiving unit, the light emitting unit is translucent, and has the first electrode and the first electrode. The first electrode has a first first electrode and a second first electrode, and the first first electrode and the second first electrode are separately powered. The light receiving unit includes a measurement cell that measures the amount of light.
According to this configuration, light emission by the first first electrode and light emission by the second first electrode can be performed alternately, so that when one region emits light, light can be received by the other region, The ratio of light to noise light (S / N ratio) can be increased. That is, a clear image can be easily captured.

Application Example 2 In the optical device according to the application example described above, it is preferable that the first first electrode and the second first electrode have a comb shape and are arranged so as to mesh with each other.
According to this configuration, the distance between the light emitting area (light emitting area) and the light receiving area (light receiving area) can be optimized without being too close or too far, so that a clear image can be easily captured. it can.

(Application Example 3) An imaging method using the optical device according to Application Example 2, wherein one of the first first electrode and the second first electrode is connected to a power source, and reflected light is received at the light receiving unit. It is characterized in that an image of an object is formed by receiving light.
According to this configuration, since the first electrode portion connected to the power source is a light emitting region and the first electrode portion not connected to the power source is a light receiving region, a clear image can be easily captured. I can do things.

(Application Example 4) A biometric authentication method using the optical device according to Application Example 2, which includes an image forming process and an authentication process. In the image forming process, the first first electrode or the second first electrode The reflected light is received by the light receiving unit while one of them is connected to the power source, and an image of the object is formed. In the authentication step, biometric authentication is performed using the image of the object.
According to this configuration, since biometric authentication is performed using a clear image, the authentication accuracy can be increased.

(Application Example 5) An imaging method using the optical device according to Application Example 2, wherein the first first electrode is connected to a power source, and the reflected light is received by the light receiving unit. An image is formed, and the second first electrode is connected to a power source, and the reflected light is received by the light receiving unit to form a second image of the object, and the first image and the second image are used as a target. It is characterized in that an image of an object is formed.
In the first image, the S / N ratio of the second first electrode portion is high, and in the second image, the S / N ratio of the first first electrode portion is high. Regions having a high S / N ratio in both images are complementary, and a composite image of these can be created. According to this configuration, the S / N ratio can be increased over the entire image.

(Application Example 6) A biometric authentication method using the optical device according to Application Example 2, including an image forming process and an authentication process, in which the first first electrode is connected to a power source The reflected light is received by the light receiving part to form a first image of the object, and the reflected light is received by the light receiving part in a state where the second first electrode is connected to the power source. Is formed, an image of the object is formed using the first image and the second image, and biometric authentication is performed using the image of the object in the authentication step.
According to this configuration, since biometric authentication is performed using a clear image with a high S / N ratio, the authentication accuracy can be increased.

(Application Example 7) An imaging method using the optical device according to Application Example 2, which includes an off-image forming step, an original image forming step, and a difference step. In the off-image forming step, the first first electrode and An off image of the object is formed in a state where the second first electrode is not connected to the power source, and in the original image forming process, one of the first first electrode or the second first electrode is connected to the power source. The reflected light is received by the light receiving unit to form an original image of the object, and in the difference step, the off-image is subtracted from the original image to form an image of the object.
According to this configuration, since background light (background noise light) can be removed, a clearer image can be easily captured.

(Application Example 8) A biometric authentication method using the optical device according to Application Example 2, including an image forming process and an authentication process. In the image forming process, the first first electrode, the second first electrode, The off-image of the object is formed without being connected to the power source, and the first original image of the object is formed by receiving the reflected light at the light receiving portion with the first first electrode connected to the power source. The reflected light is received by the light receiving unit with the second first electrode connected to the power source to form a second original image of the object, and the first image is formed by subtracting the off-image from the first original image. The off-image is subtracted from the second original image to form a second image, and an image of the object is formed using the first image and the second image. It is characterized by authentication.
According to this configuration, since the biometric authentication is performed using a clearer image having a high S / N ratio, the authentication accuracy can be increased.

Application Example 9 A vein sensor comprising the optical device according to Application Example 1 or 2.
According to this configuration, the S / N ratio is high, and a clearer vein image can be obtained.

Application Example 10 A fingerprint sensor comprising the optical device according to Application Example 1 or 2.
According to this configuration, the S / N ratio is high and a clearer fingerprint image can be obtained.

2 is a cross-sectional view of the optical device according to Embodiment 1. FIG. It is the figure explaining the structure of a light emission part and a light-receiving part, (a) is the top view which looked at the light emission part from the front side, (b) expanded the cross section of the optical apparatus corresponded to AA 'of (a). Figure. FIGS. 3A and 3B are diagrams illustrating a configuration of a light emitting unit corresponding to B-B ′ in FIG. 2A, in which FIG. 2A is a plan view and FIG. The figure explaining the circuit structure of the light-receiving part. The figure which showed the state of the light emission part at the time of an off image formation process. The figure which showed the state of the light emission part at the time of a 1st image formation process. The figure which showed the state of the light emission part at the time of a 2nd image formation process. The flowchart figure explaining the procedure which forms the image of a target object in an image formation process. The flowchart figure explaining a biometrics authentication method. Sectional drawing explaining the structure of the light emission part concerning the modification 1. FIG. The top view explaining the structure of the light emission part concerning the modification 2. FIG. The flowchart figure explaining the procedure which forms the image of a target object in the image formation process concerning the modification 3.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the scale of each layer and each member is made different from the actual scale so that each layer and each member can be recognized.

(Embodiment 1)
"Outline of optical device"
First, an outline of the optical device will be described with reference to FIG.
FIG. 1 is a cross-sectional view of an optical device 1 according to the first embodiment. The optical device 1 includes a light emitting unit 10 and a light receiving unit 20, and irradiates an object F such as a finger with irradiation light IL from the light emitting unit 10, and receives the reflected light RL from the object F at the light receiving unit 20. To do. The light emitting unit 10 and the light receiving unit 20 are provided on the same side with respect to the object F, and the light emitting unit 10 is located on the object F side with respect to the light receiving unit 20. That is, the light emitting unit 10 is positioned between the object F such as a finger and the light receiving unit 20. Since the light emitting unit 10 is provided on the front side of the optical device 1 (surface on the side where the object F is installed) with respect to the light receiving unit 20, it is also called a front light. The light emitting unit 10 includes a first light emitting unit 11 and a second light emitting unit 12 and has translucency. The 1st light emission part 11 and the 2nd light emission part 12 are controlled independently, respectively, and can light-emit independently. Of course, the first light emitting unit 11 and the second light emitting unit 12 can emit light simultaneously. In FIG. 1, the first light emitting unit 11 emits the irradiation light IL and the second light emitting unit 12 does not emit light. An inter-part light transmitting part 13 is provided between the first light emitting part 11 and the second light emitting part 12, and the light emitting part 10 and the inter-part light transmitting part 13 transmit the reflected light RL. Therefore, when the first light emitting unit 11 emits light, the reflected light RL is transmitted through the second light emitting unit 12 and the inter-part light transmitting unit 13 to the light receiving unit 20 as shown in FIG. It arrives. Conversely, when the second light emitting unit 12 emits light, the reflected light RL passes through the first light emitting unit 11 and the inter-part light transmitting unit 13 and reaches the light receiving unit 20. The light receiving unit 20 includes a plurality of measurement cells 21 that measure the amount of reflected light RL. Each measurement cell 21 converts the light received by the cell into an electrical signal corresponding to the amount of light.

  The optical apparatus 1 includes a control unit 30, a storage unit 40, and an output unit 50 in addition to the light emitting unit 10 and the light receiving unit 20. The storage unit 40 includes a nonvolatile memory such as a flash memory and a hard disk, and is registered in advance when various programs such as an image forming program and an authentication program, and authentication information (for example, when the optical device 1 is used as a vein sensor). Stored vein image or feature point information thereof) is stored. The storage unit 40 may include a read only memory (ROM) in addition to the nonvolatile memory, and a part or all of the previous information stored in the nonvolatile memory may be stored in the ROM. . The control unit 30 includes a central processing unit (CPU) and a temporary storage device. The temporary storage device is a dynamic random access memory (DRAM), a static random access memory (SRAM), or the like, and temporarily stores an image of the captured object F or the like. Such an apparatus for temporarily storing an image is also called a video random access memory (VRAM). The control unit 30 controls turning on and off of the light emitting unit 10, reads a light reception signal from each measurement cell 21 provided in the light receiving unit 20, and based on the read light reception signal for one frame (for the imaging region) F image is generated. The control unit 30 can also analyze the captured image and collate it with authentication information registered in the storage unit 40 to perform biometric authentication. For example, when the optical device 1 is used as a vein sensor, the control unit 30 includes feature point information (for example, the number of vein branch points) of two vein images to be verified (a captured vein image and a registered vein image). If the similarity is equal to or higher than a predetermined threshold, the finger as the object F is authenticated as a finger registered in the storage unit 40. The output unit 50 is a part that outputs the authentication information and the captured image to the outside. For example, the output unit 50 outputs the authentication information to an external device (ATM or the like) by an electric signal, or displays the image on the display unit. This is a part that produces various forms of output. The VRAM provided in the temporary storage device of the control unit 30 may be provided in a part of the nonvolatile memory.

"Configuration of optical device"
Next, an outline of the optical device will be described with reference to FIG.
FIG. 2 is a diagram illustrating the configuration of the light emitting unit 10 and the light receiving unit 20, (a) is a plan view of the light emitting unit 10 viewed from the front side, and (b) corresponds to AA ′ in (a). It is the figure which expanded the cross section of the optical apparatus 1 to do. As shown in FIG. 2A, the light emitting unit 10 includes a first light emitting unit 11 and a second light emitting unit 12, and the first light emitting unit 11 and the second light emitting unit 12 may overlap in a plane. Instead, they are spaced apart. Moreover, the 1st light emission part 11 and the 2nd light emission part 12 are comb teeth shape, and are formed so that it may mutually mesh | engage. The first electrode 16 includes a first first electrode 112 and a second first electrode 122, the first light emitting unit 11 is connected to the first first electrode 112, and the second light emitting unit 12 is a second first electrode. 122 is connected. Therefore, the first first electrode 112 and the second first electrode 122 do not overlap in a plane but are formed apart from each other. Similarly, the 1st 1st electrode 112 and the 2nd 1st electrode 122 are comb teeth shape, and are formed so that it may mutually mesh. Since the 1st 1st electrode 112 and the 2nd 1st electrode 122 can be separately connected to a power supply, the 1st light emission part 11 and the 2nd light emission part 12 can light-emit separately. A portion between the first light emitting unit 11 and the second light emitting unit 12 (that is, between the first first electrode 112 and the second first electrode 122) is an inter-part translucent unit 13 and has translucency. ing. The light emitting unit 10 emits irradiation light IL having a wavelength suitable for the object F to be imaged. For example, when the object F to be imaged is a finger vein, the irradiation light IL is near infrared light having a wavelength in the range of 750 nm to 3000 nm (more preferably 800 nm to 900 nm). Reduced hemoglobin flowing through veins has the property of absorbing near infrared light. Therefore, when a finger is imaged using near-infrared light, the vein portion under the finger appears darker than the surrounding tissue, and a pattern due to this difference in brightness is captured as a vein image.

  As shown in FIG. 2B, in the optical device 1, the light emitting unit 10 and the light receiving unit 20 are formed by being laminated. The light emitting unit 10 is formed on the first substrate 31, the light receiving unit 20 is formed on the second substrate 32, the surface of the first substrate 31 on which the light emitting element 101 is formed (the surface of the first substrate 31), and the second substrate. Both the substrates are bonded so that the surface on which the 32 measurement cells 21 are formed faces each other. Furthermore, a plurality of microlenses ML are formed on the third substrate 33. The surface of the third substrate 33 on which the microlenses ML are formed (the surface of the third substrate 33) and the back surface of the first substrate 31 (opposite the surface). Surface).

  On the first substrate 31, a plurality of first light emitting elements 111 including the first first electrode 112 are formed on the first light emitting part 11, and a second light emitting element including the second first electrode 122 on the second light emitting part 12. A plurality of 121 are formed. Between the adjacent first light emitting elements 111 and between the adjacent second light emitting elements 121 is an internal light transmitting portion 14, and has a light transmitting property like the inter-part light transmitting portion 13. In short, the first light emitting unit 11 includes a plurality of first light emitting elements 111 and a plurality of internal light transmitting parts 14, and the second light emitting unit 12 includes a plurality of second light emitting elements 121 and a plurality of internal light transmitting parts 14. Have Both the first light-emitting element 111 and the second light-emitting element 121 have low translucency, but the light-emitting unit 10 includes the internal translucent part 14 and thus has translucency.

  A plurality of measurement cells 21 are arranged in a matrix in the light receiving unit 20. In addition, on the normal line of each measurement cell 21, a plurality of microlenses ML are provided in a matrix in the upper part of the light emitting unit 10 (the object F side of the light emitting unit 10). The arrangement pitch of the microlenses ML is the same as the arrangement pitch of the measurement cells 21, and each microlens ML forms an image of the reflected light RL from the object F on the light receiving surface of the measurement cell 21 located directly below. That is, the reflected light RL collected by the microlens ML is transmitted through the internal light transmitting part 14 and the inter-part light transmitting part 13 and reaches the measurement cell 21.

  For the first substrate 31, the third substrate 33, and the microlens ML, a material having high translucency with respect to the irradiation light IL and the reflected light RL is used. For example, transparent glass or transparent plastic is suitable. . A material suitable for forming the measurement cell 21 is used for the second substrate 32. In this embodiment, since the measurement cell 21 is formed using a thin film element, alkali-free glass or quartz glass suitable for forming the thin film element is used. In addition to this, a semiconductor substrate such as a silicon substrate may be used to form the measurement cell 21 with a semiconductor element.

  3A and 3B are diagrams illustrating a configuration of the light emitting unit 10 corresponding to B-B ′ in FIG. 2A, in which FIG. 3A is a plan view and FIG. 3B is a cross-sectional view. Note that the first light emitting unit 11 and the second light emitting unit 12 have the same structure, and when it is not necessary to distinguish between them, the first light emitting unit 11 and the second light emitting element 121 are simply referred to as the light emitting unit 10. And the first first electrode 112 and the second first electrode 122 are collectively referred to as the first electrode 16. As shown in FIG. 3 (a), the light emitting unit 10 includes the light emitting element 101 and the internal light transmitting unit 14 in the horizontal direction (BB ′ direction) and the vertical direction (in the plane of FIG. 3 (a)). The checkerboard pattern (chessboard pattern) is also regularly arranged alternately in the direction orthogonal to the direction. As described above, the measurement cell 21 is formed on the second substrate 32 at a position corresponding to the internal light transmitting portion 14, so that the measurement cell 21 is also arranged on the second substrate 32 in a checkered pattern. Since it is convenient to read out information of the measurement cell 21 every 4 bits or 8 bits, the measurement cell 21 and the corresponding internal light transmitting portion 14 are multiples of 4 or 8 in both the vertical direction and the horizontal direction. Number is made.

  As shown in FIG. 3B, the light emitting element 101 includes a light emitting layer 17 provided between the first electrode 16 and the second electrode 18. The light emitting layer 17 includes a semiconductor material and functions as a light emitting diode. An organic material or an inorganic material is used as the semiconductor material, and an organic semiconductor is used in this embodiment. Therefore, the light emitting element 101 is a so-called organic EL element. The first electrode 16 is an anode (anode) or a cathode (cathode) of the diode, and the second electrode 18 is opposite in polarity to the first electrode 16. That is, if the first electrode 16 is an anode, the second electrode 18 is a cathode, and if the first electrode 16 is a cathode, the second electrode 18 is an anode. In the present embodiment, the first electrode 16 is an anode made of indium tin oxide (ITO), and the second electrode 18 is a cathode made of magnesium silver (MgAg). Magnesium silver is thin and has translucency. The second electrode 18 is formed on almost the entire surface of the first substrate 31, and then the light emitting layer 17, the first electrode 16, and the reflection plate 15 are patterned and laminated. Irradiation light IL generated in the light emitting layer 17 is directly radiated to the first substrate 31 side and radiated to the opposite side of the first substrate 31, reflected by the reflecting plate 15 and radiated to the first substrate 31 side. There are ingredients to be used. The second electrode 18 may also be patterned.

"Receiver circuit"
Next, the circuit configuration of the light receiving unit will be described with reference to FIG.
FIG. 4 is a diagram illustrating the circuit configuration of the light receiving unit 20. The light receiving unit 20 has a measurement region 22, and a plurality of measurement cells 21 are regularly arranged in the measurement region 22. Here, the measurement cells 21 are arranged in a matrix. As described above, the measurement cell 21 is formed at a position where the inter-part light transmitting portion 13 and the internal light transmitting portion 14 are provided on the first substrate 31 on the normal line, and the micro lens ML is provided on the third substrate 33. . These measurement cells 21 individually measure the amount of light so that an image is captured. A selection circuit SC and a parallel / serial conversion circuit PSC are provided outside the measurement region 22. The selection circuit SC includes a first selection circuit SCA and a second selection circuit SCB. The parallel / serial conversion circuit PSC includes a sample hold circuit SHC and a sample hold selection circuit SHS. The measurement area 22, the selection circuit SC, and the parallel / serial conversion circuit PSC are wired to connect to the control unit 30. In FIG. 4, when a plurality of types of wirings are also drawn as a single black line as a symbol (for example, input PSIN to the parallel / serial conversion circuit PSC, input SCIN to the selection circuit SC, and output line DOUT). There is also. In addition, although a plurality of measurement cells 21 are provided in the measurement region 22, one measurement cell 21 and wiring connected thereto are drawn for easy understanding.

  In order to acquire one image with the optical device 1, an initialization process, an exposure process, and an exposure data reading process are required. In the initialization process, the exposure is prepared, the light amount is converted into electrical information in the exposure process, and the obtained electrical information is output to the control unit 30 via the sample hold circuit SHC in the exposure data reading process. The initialization process, the exposure process, and the exposure data reading process are set for each row by the selection circuit SC. In the exposure data reading process, the electrical information of each measurement cell 21 is read individually. Specifically, one row of measurement cells 21 aligned in the row direction is selected by the selection circuit SC. The electrical information acquired by the measurement cells 21 belonging to the selected row is held in the sample hold circuit SHC. The sample hold circuit SHC has a plurality of element circuits in order to hold a plurality of analog data values independently. That is, an element circuit is provided for each column, and one element circuit holds electrical information of analog data output to that column. The sample hold selection circuit SHS selects eight element circuits from the plurality of element circuits, and outputs data of these element circuits to the eight output lines DOUT. Thus, the electrical information parallel in the column direction is output as eight serial data to the eight output lines DOUT.

"Circuit configuration of measurement cell"
Next, the circuit configuration of the measurement cell will be described with reference to FIG. In FIG. 4, the source and drain of the transistor are indicated by s and d, and the anode and cathode of the diode are indicated by A and C. In the measurement region 22, a first selection line GSELA, a readout line Sense, a second selection line GSELB, a reset line GRST, a positive power source Vdd, and a negative power source Vss are wired. Although the measurement cells 21 are arranged in a matrix, the first selection line GSELA defines the row direction, and the readout line Sense defines the column direction. That is, the measurement cell 21 located in the i row and the j column is arranged at the intersection of the first selection line GSELA in the i row and the readout line Sense in the j column. Therefore, when the measurement cells 21 are arranged in a matrix of M rows and N columns, M first selection lines GSELA are provided and N readout lines Sense are provided. M and N are integers of 1 or more. It is preferable that M second selection lines GSELB are provided in one-to-one correspondence with the first selection line GSELA, which is also illustrated in FIG. However, in the present embodiment, the second selection line GSELB is not selected and deselected, and all the measurement cells 21 have the same potential. May be shared. Similarly, the positive power supply Vdd and the negative power supply Vss may share one positive power supply Vdd or one negative power supply Vss in a plurality of rows or columns of measurement cells 21. The first selection line GSELA is electrically connected to the first selection circuit SCA and is selected by the first selection circuit SCA. Similarly, the second selection line GSELB is electrically connected to the second selection circuit SCB and is selected by the second selection circuit SCB. Similarly, the reset line GRST is electrically connected to the third selection circuit SCC and is selected by the third selection circuit SCC. The read line Sense is electrically connected to one element circuit provided for each column. In addition, A and B are electrically connected, in addition to the case where A and B are directly connected by wiring, a switch such as a pass gate is provided between A and B, and the switch is in a conductive state. It also includes the case where A and B become conductive when

  The measurement cell 21 includes a light receiving element PD, a first transistor AMPTFT1, a second transistor AMPTFT2, a selection transistor SELTFT, a reset transistor RSTTFT, and a load element. Here, the load element is the current source transistor CSTFT, but it may be a simple resistor. By providing the load element, the change in the gate potential of the first transistor AMPTFT1 can be converted into the change in the source potential and amplified. As a result, the measurement result of the light amount can be converted into a potential that is easy to measure and highly accurate.

  The light receiving element PD is a photodiode. The first pole of this is the cathode and is electrically connected to the gate of the first transistor AMPTFT1 and the source of the reset transistor RSTTFT. Since the drain of the reset transistor RSTTFT is electrically connected to the positive power source Vdd, the cathode of the photodiode is electrically connected to the positive power source Vdd via the reset transistor RSTTFT. On the other hand, the second pole of the light receiving element PD is an anode, which is electrically connected to a negative power source Vss. Therefore, the light receiving element PD is disposed so as to be in a reverse bias state between the positive power supply Vdd and the negative power supply Vss. The gate of the reset transistor RSTTFT is electrically connected to the reset line GRST, and the reset transistor RSTTFT is controlled by an electric signal supplied to the reset line GRST.

  The drain of the first transistor AMPTFT1 is electrically connected to the positive power supply Vdd, and the source is electrically connected to the gate of the second transistor AMPTFT2 and one terminal of the load element. The other terminal of the load element is electrically connected to the negative power source Vss. As described above, the load element is the current source transistor CSTFT, one terminal corresponds to the drain of the current source transistor CSTFT, and the other terminal corresponds to the source of the current source transistor CSTFT. Therefore, the source of the first transistor AMPTFT1 is electrically connected to the negative power source Vss. The gate of the current source transistor CSTFT is electrically connected to the second selection line GSELB, and the current source transistor CSTLT is controlled by an electric signal supplied to the second selection line GSELB.

  The second transistor AMPTFT2 has a drain electrically connected to the positive power supply Vdd and a source electrically connected to the drain of the selection transistor SELTFT. The source of the selection transistor SELECTFT is electrically connected to the read line Sense. The gate of the selection transistor SELTFT is electrically connected to the first selection line GSELA, and the selection transistor SELTFT is controlled by an electrical signal supplied to the first selection line GSELA.

In this configuration, by narrowing the gate width of the first transistor AMPTFT1, so to reduce the transistor capacitance C _T, it can be a light-receiving portion 20 and the high sensitivity. At the same time, the gate width of the second transistor AMPTFT2 is widened and the on-resistance of the second transistor AMPTFT2 is lowered, so that the time constant determined by the product of the on-resistance and the parasitic capacitance of the readout line can be shortened. Can be output. That is, high sensitivity measurement can be performed quickly.

"Image acquisition method"
Next, a method for acquiring one image using an optical device will be described with reference to FIG. A selection signal or a non-selection signal is supplied to the first selection line GSELA, the second selection line GSELB, and the reset line GRST. The selection signal is a signal for turning on a transistor whose gate is connected to the wiring, and the non-selection signal is a signal for turning off a transistor whose gate is connected to the wiring. In this embodiment, since an N-type transistor is used for the reset transistor RSTTFT, the current source transistor CSTFT, and the selection transistor SELTFT, the selection signal becomes a high potential (a high potential higher than the positive power supply Vdd), and the non-selection signal becomes a low potential ( For example, a negative power source Vss) such as a ground potential.

  In the imaging using the optical device 1, an initialization process, an exposure process, an exposure data reading process, a reset data reading process, and a standby process form one image with one cycle. Hereinafter, this one cycle will be described step by step.

  In the initialization process, a reset selection signal is supplied to the reset line GRST, and the reset transistor RSTFT is turned on. Although a method for forming an object image will be described later, the light emitting unit 10 does not emit light when an off-image is captured during the initialization process. When the first original image is captured, the first light emitting unit 11 emits light and the second light emitting unit 12 does not emit light. When capturing the second original image, the second light emitting unit 12 emits light, and the first light emitting unit 11 does not emit light. The potential of the reset selection signal is higher than the threshold voltage of the reset transistor RSTTFT and is a value that turns on the reset transistor RSTTFT. Preferably, the potential of the reset selection signal is a value equal to or higher than the positive power supply Vdd. As a result, the gate of the first transistor AMPTFT1 is charged to the positive power supply Vdd during the initialization process. A second selection signal is supplied to the second selection line GSELB, and the current source transistor CSTFT is operated as a constant current source. The potential of the second selection signal is about a value (Vth + δ, 0 <δ <0.3V) slightly exceeding the threshold voltage of the current source transistor CSTFT, or slightly smaller than that. If the potential of the second selection signal is about Vth + δ, in most cases, the current source transistor CSTFT performs a saturation operation and becomes a constant current source. On the other hand, if the potential of the second selection signal is smaller than Vth, the current source transistor CSTFT enters the sub-threshold region.

  In the next exposure process, a non-selection signal is supplied to the reset line GRST, and the reset transistor RSTTFT is turned off. When the first image is captured, the first light emitting unit 11 emits light and the second light emitting unit 12 does not emit light during the exposure process. When the second image is captured, the second light emitting unit 12 emits light during the exposure process, and the first light emitting unit 11 does not emit light. When capturing an off-image, neither the first light emitting unit 11 nor the second light emitting unit 12 emits light during the exposure process. In such a state, the light receiving element PD receives the reflected light RL (receives background light during off-image capturing). The light receiving element PD leaks charges according to the amount of light received, and the gate potential of the first transistor AMPTFT1 changes. In accordance with this, the gate potential of the second transistor AMPTFT2 also changes. A second selection signal is supplied to the second selection line GSELB as in the initialization step. A non-selection signal is supplied to the first selection line GSELA.

  When the exposure process is completed, the process proceeds to an exposure data reading process. During this period, a non-selection signal is supplied to the reset line GRST, the reset transistor RSTTFT is turned off, and the gate potential of the first transistor AMPTFT1 is stored. That is, the gate potential of the first transistor AMPTFT1 is fixed to a fixed value corresponding to the exposure amount. The fixed value corresponding to the exposure amount is between zero V and Vdd. A second selection signal is supplied to the second selection line GSELB as in the exposure process. Therefore, during the exposure data read period, the gate potential of the second transistor AMPTFT2 is kept at a fixed value corresponding to the exposure amount. In the measurement cell 21 in which reading is selected, the first selection signal is supplied to the first selection line GSELA. The potential of the first selection signal is a value equal to or higher than the threshold voltage of the selection transistor SELTFT, preferably a value equal to or higher than the positive power supply Vdd. As a result, the selection transistor SELTFT is turned on, and the source potential of the second transistor AMPTFT2 is measured via the read line Sense. On the other hand, in the non-selected measurement cell 21 in which selection of reading is not performed, a non-selection signal is supplied to the first selection line GSELA, and the selection transistor SELTFT is turned off.

  When the exposure data reading process ends, the process proceeds to a reset data reading process. During this period, a reset selection signal is supplied to the reset line GRST, the reset transistor RSTTFT is turned on, and the gate potential of the first transistor AMPTFT1 is set to the positive power supply Vdd. A second selection signal is supplied to the second selection line GSELB as in the exposure process. Therefore, during the reset data read period, the gate potential of the second transistor AMPTFT2 is kept at a fixed value according to the state where the gate potential of the first transistor AMPTFT1 is set to the positive power supply Vdd. In the measurement cell 21 in which reading is selected, the first selection signal is supplied to the first selection line GSELA, and the selection transistor SELTFT is turned on. That is, the source potential of the second transistor AMPTFT2 corresponding to the state where the gate potential of the first transistor AMPTFT1 is set to the positive power supply Vdd is measured via the read line Sense. On the other hand, in the non-selected measurement cell 21 in which selection of reading is not performed, a non-selection signal is supplied to the first selection line GSELA, and the selection transistor SELTFT is turned off.

  In the exposure data reading step, a voltage value (Vphoto + Vth1 + Vth2) corresponding to the sum of the potential (Vphoto) corresponding to the amount of light, the threshold voltage (Vth1) of the first transistor, and the threshold voltage (Vth2) of the second transistor is read. In contrast, in the reset data reading step, a voltage value (Vdd + Vth1 + Vth2) corresponding to the sum of the charged potential (Vdd), the threshold voltage of the first transistor, and the threshold voltage of the second transistor is read. Therefore, by subtracting both of them, the threshold voltage of the first transistor and the threshold voltage of the second transistor can be erased, and the difference between the charged potential and the potential corresponding to the amount of light can be obtained. That is, regardless of variations in the threshold voltage of the first transistor and the threshold voltage of the second transistor between the measurement cells 21, the potential corresponding to the light amount can be measured with the same accuracy in all the measurement cells 21.

  When the reset data reading process ends, the measurement cell 21 enters a standby state. During this period, a selection signal is supplied to the reset line GRST, and the reset transistor RSTTFT is turned on. Further, the first selection line GSELA is supplied with a non-selection signal, and the selection transistor SELTFT is turned off. Thereafter, the standby state is maintained until the next exposure process starts.

"Method of forming object image"
Next, a method for forming an image of an object will be described with reference to FIGS. The image of the object F is formed using the first image, using the second image, or using the first image and the second image. The first image is formed from the first original image or from the first original image and the off image. The second image is formed from the second original image or from the second original image and the off image.

  FIG. 5 is a diagram illustrating a state of the light emitting unit 10 during the off-image forming process. In the off-image forming step, the object F is imaged in accordance with the “image acquisition method” described above, and an off-image is formed. At this time, as shown in FIG. 5, neither the first light emitting unit 11 nor the second light emitting unit 12 emits light during the exposure process. That is, the exposure process is performed in a state where the first first electrode 112 and the second first electrode 122 are not connected to the power source, and an off image of the object F is formed. The off image corresponds to a noise image caused by background light (background light).

  FIG. 6 is a diagram illustrating a state of the light emitting unit 10 during the first image forming process. Also in the first image forming step, the object F is imaged in accordance with the “image acquisition method” described above, and a first original image is first formed. At this time, as shown in FIG. 6, the first light emitting unit 11 emits light and the second light emitting unit 12 does not emit light during the exposure process. That is, the exposure process is performed with the first first electrode 112 connected to the power source and the second first electrode 122 not connected to the power source. The irradiation light IL emitted from the first light emitting unit 11 is reflected by the object F, and the reflected light RL is received by the light receiving unit 20 to form a first original image. In the first original image, the measurement cell 21 located in the region corresponding to the inter-part light transmitting portion 13 and the second light emitting portion 12 mainly receives the reflected light RLIL (signal light), and in this region, the S / N ratio is received. A clear image with high image quality can be obtained. On the other hand, in the first original image, the measurement cell 21 located in the region corresponding to the first light emitting unit 11 receives the reflected light RLIL (signal light) as well as the irregularly reflected or leaked irradiation light IL (noise light). In the region, the S / N ratio may decrease to some extent. The first original image can be used as it is as the first image.

  FIG. 7 is a diagram illustrating a state of the light emitting unit 10 during the second image forming process. Also in the second image forming step, the object F is imaged in accordance with the “image acquisition method” described above, and a second original image is first formed. At this time, as shown in FIG. 7, the second light emitting unit 12 emits light during the exposure process, and the first light emitting unit 11 does not emit light. That is, the exposure process is performed in a state where the second first electrode 122 is connected to the power source and the first first electrode 112 is not connected to the power source. The irradiation light IL radiated from the second light emitting unit 12 is reflected by the object F, and the reflected light RL is received by the light receiving unit 20 to form a second original image. In the second original image, the measurement cell 21 located in the region corresponding to the inter-part light transmitting portion 13 and the first light emitting portion 11 mainly receives the reflected light RLIL (signal light), and in this region, the S / N ratio is received. A clear image with high image quality can be obtained. On the other hand, in the second original image, the measurement cell 21 located in the region corresponding to the second light emitting unit 12 receives the reflected light RLIL (signal light) and the irregularly reflected or leaked irradiation light IL (noise light). In the region, the S / N ratio may decrease to some extent. The second original image can be used as it is as the second image. As described above, in order to capture the original image such as the first original image or the second original image, the object F is in a state where one of the first first electrode 112 or the second first electrode 122 is connected to the power source. Images are captured.

  FIG. 8 is a flowchart illustrating a procedure for forming an image of the object F in the image forming step S1 (see FIG. 9). In order to form an image of the object F, first, an off-image is formed by the above-described method (S11). This is an off-image forming process. Next, the first original image is formed by the above-described method (S12). Further, a second original image is formed by the above-described method (S13). The first original image formation (S12) and the second original image formation (S13) are the original image formation process. Next, the off image is subtracted from the first original image to form a first image (S14). Next, the off image is subtracted from the second original image to form a second image (S15). The first image formation (S14) and the second image formation (S15) are difference steps. The background noise is removed from the first original image and the second original image by the difference step, and a clear first image and second image are obtained. Next, an object F image is formed using the first image and the second image (S16). That is, the object F image is synthesized by combining the region having a high S / N ratio of the first image and the region having a high S / N ratio of the second image. Since the region having a high S / N ratio of the first image and the region having a high S / N ratio of the second image are complementary, the S / N ratio is improved in the entire imaging region (entire image). The object F image formation (S16) is a synthesis process. In this way, an image of the object F is formed.

  The off image formation (S11) to the second original image formation (S13) are preferably performed continuously. That is, when the reset data reading process is completed in the off-image formation (S11), the process immediately proceeds to the initialization process of the first original image formation (S12) without passing through the standby process, and the reset data in the first original image formation (S12). When the reading process is completed, the process immediately proceeds to the initialization process of the second original image formation (S13) without passing through the standby process. The imaging period can be shortened by continuously capturing the off-image, the first original image, the second original image, and the three images. As a result, a change in the external environment and the movement of the object F that occur during the imaging period can be minimized, and a clear image of the object F can be formed. In this embodiment, the order of the first original image formation (S12) and the second original image formation (S13) is taken after the off image formation (S11), but these orders can be arbitrarily set. Specifically, the order with S11-S13-S12, the order with S12-S11-S13, the order with S12-S13-S11, the order with S13-S11-S12, and S13-S12-S11. It may be either of the order.

  Further, when forming a plurality of images of the object F, it is preferable to perform off-image formation (S11) every time one image is formed, but the off-image formation (S11) is used once for a plurality of images. May be.

  In the present embodiment, the image of the object F is formed using the first image and the second image. However, the image of the object F may be formed using only the first image, or the object F may be formed using only the second image. It is good as an image. The first image is created by subtracting the off-image from the first original image, but the first original image may be used as it is as the first image. Similarly, the second image is created by subtracting the off-image from the second original image, but the second original image may be used as it is as the second image.

"Electronics"
The optical device 1 described above can be applied to various biometric authentication sensors such as a vein sensor and a fingerprint sensor. In addition to these, the optical apparatus 1 according to the present embodiment can be applied to electronic devices such as a digital camera, an image sensor, and a scanner. When the optical device 1 is adapted to a vein sensor or a fingerprint sensor, a contact sensor may be provided in the optical device 1 so that the optical device 1 automatically operates when an object touches the optical device 1.

"Biometric authentication method"
The optical device 1 can be applied to various biometric authentication sensors such as a vein sensor and a fingerprint sensor. Here, a biometric authentication method using the optical device 1 will be described with reference to FIG.

  FIG. 9 is a flowchart for explaining the biometric authentication method. The biometric authentication starts from the image formation (S1) of the object F. This is the image forming process as described above. Next, image processing such as emphasizing a vein pattern or fingerprint pattern or extracting feature points is performed using the obtained image (S2), and biometric information is acquired. This is the image processing step. Next, the acquired biometric information (acquired data) is collated with the registered biometric information (registered data) (S3). This is the authentication process. The result of the authentication process is output in the output process (S4). If the acquired data matches the registered data, “permitted” information is output (S4A). On the contrary, if the acquired data and the registered data do not match, the information of “rejection” is output (S4R). Since the biometric information may change little by little every day, when the acquired data matches the registered data, new registered data is created by adding the acquired data to the registered data (S5). This is the update process.

  In the present embodiment, the light emitting unit 10 is divided into the first light emitting unit 11 and the second light emitting unit 12, but the number of divisions may be N (N is an integer of 3 or more). When the number of divisions is N, similarly to the present embodiment, light is emitted sequentially from the first light emitting unit 11 to the Nth light emitting unit 1N, and the Nth original image and the N original images from the first original image are obtained. create. Using these, the Nth image is created from the first image. Further, the Nth image is synthesized from the first image to finally form an image of the object F.

As described above, according to the optical device 1, the imaging method, and the biometric authentication method according to the present embodiment, the following effects can be obtained.
Since the light emission by the first first electrode 112 and the light emission by the second first electrode 122 can be performed alternately, when one region emits light, the other region can receive light. Further, the distance between the light emitting region (light emitting region) and the light receiving region (light receiving region) can be optimized without being too close or too far. As a result, the ratio of signal light to noise light (S / N ratio) can be increased. Further, background light (background noise light) can be removed. Regarding background light removal, dark current correction and temperature correction for each measurement cell, which cannot be performed by subtraction by optical black pixels or by a method of storing off-image data in the storage unit 40 at the time of shipment, can be performed. In addition, the thickness can be reduced as compared with wearing a mechanical shutter, and the influence of external light that cannot be achieved with a mechanical shutter can be eliminated. That is, a clear image can be easily captured. Since biometric authentication is performed using such a clear image, the authentication accuracy can be increased.

  The present invention is not limited to the above-described embodiment, and various changes and improvements can be added to the above-described embodiment. A modification will be described below.

(Modification 1)
"The first electrode and the second electrode are different forms"
FIG. 10 illustrates the configuration of the light emitting unit 10 according to Modification 1, and is an enlarged cross-sectional view taken along line BB ′ of FIG. In addition, about the component same as Embodiment 1, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

  In the present modification (FIG. 10), the first electrode 16 and the second electrode 18 constituting the light emitting element 101 are different from those in the first embodiment (FIG. 3B). Other configurations are almost the same as those of the first embodiment. In the first embodiment, the first electrode 16 is an anode and the second electrode 18 is a cathode. In this modification, the first electrode 16 is a cathode made of aluminum (Al), and the second electrode 18 is an anode made of ITO. is there. The second electrode 18 is formed on almost the entire surface of the first substrate 31, and then the light emitting layer 17 and the first electrode 16 are patterned and laminated. Irradiation light IL generated in the light emitting layer 17 has a component directly emitted to the first substrate 31 side and a component reflected by the first electrode 16 and emitted to the first substrate 31 side. The second electrode 18 may also be patterned.

  As described above, according to the optical device 1 according to this modification, in addition to the effects of the first embodiment, the light emitting element 101 can be formed with a simple configuration.

(Modification 2)
"Forms with different light emitting elements"
FIG. 11 illustrates the configuration of the light emitting unit 10 according to the second modification, and is a plan view in which BB ′ in FIG. 2 is enlarged. In addition, about the component same as Embodiment 1, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

  In the present modification (FIG. 11), the planar shape and size of the light emitting element 101 are different from those of the first embodiment (FIG. 3A). Other configurations are almost the same as those of the first embodiment. In the first embodiment, the light emitting element 101 and the inner light transmitting portion 14 are squares having substantially the same size, but the shape and size of the light emitting element 101 and the inner light transmitting portion 14 are not limited thereto. It is sufficient that the center of the light emitting element 101 and the internal light transmitting portion 14 (where the measurement cell 21 is located) have a checkered pattern that is regularly and alternately arranged in the horizontal direction and the vertical direction. For example, as shown in FIG. 11A, the light-emitting element 101 may be a quadrangle whose one side is shorter than half of the cycle length. The repetition period length is a distance between the center of one light emitting element 101 and the center of the adjacent light emitting element 101. Further, as shown in FIG. 11B, the light emitting element 101 may have a circular shape whose diameter is shorter than half of the repetition period length. On the contrary, one side or the diameter of the light emitting element 101 may be longer than half of the repetitive cycle length as long as the inner light transmitting portion 14 is provided. The planar shape of the light emitting element 101 is not limited to a square or a circle, and may be a rectangle, a rhombus, a polygon, an ellipse, or the like.

  As described above, according to the optical device 1 according to this modification, in addition to the effects of the first embodiment, the planar shape and size of the light emitting element 101 are changed to the light emission amount of the light emitting element 101 and the sensitivity of the detection cell. It can be optimized accordingly.

(Modification 3)
"Forms with different image forming processes"
FIG. 12 is a flowchart illustrating a procedure for forming an image of the object F in the image forming step S1 (see FIG. 9) according to the third modification. In addition, about the component same as Embodiment 1, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

  This modification (FIG. 12) differs from the first embodiment (FIG. 8) in the order of image formation. Other configurations are almost the same as those of the first embodiment. In the first embodiment, after the first original image formation (S12) and the second original image formation (S13) are finished, the first image formation (S14) and the second image formation (S15) are performed. The order may be changed. That is, as shown in FIG. 12, after the off image formation (S11), the first original image formation (S12) is performed. Thereafter, the first image formation (S14), the second original image formation (S13), Two-image formation (S15) or image formation of the object F (S16) may be used.

  DESCRIPTION OF SYMBOLS 1 ... Optical apparatus, 10 ... Light emission part, 11 ... 1st light emission part, 12 ... 2nd light emission part, 13 ... Inter-part light transmission part, 14 ... Internal light transmission part, 15 ... Reflector plate, 16 ... 1st electrode, DESCRIPTION OF SYMBOLS 17 ... Light emitting layer, 18 ... 2nd electrode, 20 ... Light-receiving part, 21 ... Measurement cell, 22 ... Measurement area | region, 30 ... Control part, 31 ... 1st board | substrate, 32 ... 2nd board | substrate, 33 ... 3rd board | substrate, 40 DESCRIPTION OF SYMBOLS ... Memory | storage part, 50 ... Output part, 101 ... Light emitting element, 111 ... 1st light emitting element, 112 ... 1st 1st electrode, 121 ... 2nd light emitting element, 122 ... 2nd 1st electrode.

Claims (10)

An optical device comprising a light emitting part and a light receiving part, irradiating light from the light emitting part to an object, and receiving light reflected from the object by the light receiving part,
The light emitting unit and the light receiving unit are provided on the same side with respect to the object, the light emitting unit is located on the object side from the light receiving unit,
The light emitting part has a light transmitting property and includes a light emitting layer provided between the first electrode and the second electrode,
The first electrode has a first first electrode and a second first electrode, and the first first electrode and the second first electrode are separately connected to a power source,
The optical device, wherein the light receiving unit includes a measurement cell that measures the amount of light.   2. The optical device according to claim 1, wherein the first first electrode and the second first electrode are comb-shaped and are arranged so as to mesh with each other. An imaging method using the optical device according to claim 2,
The reflected light is received by the light receiving unit in a state where one of the first first electrode or the second first electrode is connected to the power source, and an image of the object is formed. Imaging method. A biometric authentication method using the optical device according to claim 2,
Including an image forming process and an authentication process,
In the image forming step, an image of the object is formed by receiving the reflected light at the light receiving unit in a state where one of the first first electrode or the second first electrode is connected to the power source. ,
In the authentication step, biometric authentication is performed using an image of the object. An imaging method using the optical device according to claim 2,
The reflected light is received by the light receiving unit in a state where the first first electrode is connected to the power source, and a first image of the object is formed,
The reflected light is received by the light receiving unit in a state where the second first electrode is connected to the power source, and a second image of the object is formed,
An imaging method, wherein an image of the object is formed using the first image and the second image. A biometric authentication method using the optical device according to claim 2,
Including an image forming process and an authentication process,
In the image forming step, the first image of the object is formed by receiving the reflected light at the light receiving unit in a state where the first first electrode is connected to the power source, and the second first electrode The reflected light is received by the light receiving unit in a state of being connected to the power source to form a second image of the object, and the image of the object is formed using the first image and the second image. Formed,
In the authentication step, biometric authentication is performed using an image of the object. An imaging method using the optical device according to claim 2,
Including an off-image forming step, an original image forming step, and a difference step;
In the off-image forming step, an off-image of the object is formed in a state where the first first electrode and the second first electrode are not connected to the power source,
In the original image forming step, the reflected light is received by the light receiving unit in a state where one of the first first electrode or the second first electrode is connected to the power source, and an original image of the object is obtained. Formed,
In the difference step, an image of the object is formed by subtracting the off-image from the original image. A biometric authentication method using the optical device according to claim 2,
Including an image forming process and an authentication process,
In the image forming step, an off image of the object is formed in a state where the first first electrode and the second first electrode are not connected to the power source, and the first first electrode is connected to the power source. In this state, the reflected light is received by the light receiving unit to form a first original image of the object, and the reflected light is received in the state where the second first electrode is connected to the power source. To receive a second original image of the object, subtract the off-image from the first original image to form a first image, and subtract the off-image from the second original image to form a second image. An image is formed, an image of the object is formed using the first image and the second image,
In the authentication step, biometric authentication is performed using an image of the object.   A vein sensor comprising the optical device according to claim 1.   A fingerprint sensor comprising the optical device according to claim 1.

Images