Detection device

Abstract

A detection device is provided with: a light sensor; a light source that irradiates light to the light sensor; a detection signal amplification circuit that performs voltage conversion on fluctuations in the current supplied from the optical sensor; and an A / D conversion circuit that converts the voltage-converted output voltage signal to a digital detection value (Raw). When the light source is turned off, the A / D conversion circuit limits the detection value (Raw) to the maximum gradation (Rawmax) or the minimum gradation (Rawmin) of the digital value.

Description

Technical Field

[0001] The invention relates to a detection device. Background Art

[0002] There is known a detection device that obtains the oxygen saturation in the blood (hereinafter referred to as blood oxygen saturation (SpO2) based on transcutaneous data obtained by irradiating light from the skin into the body and detecting light that passes through or is reflected from the artery. 2 )). Blood oxygen saturation (SpO 2 ) refers to the ratio of the amount of oxygen actually bound to hemoglobin to the total amount of oxygen assuming that oxygen is bound to all hemoglobin in the blood. 2 ), for example, a pulse wave acquired using red light and a pulse wave acquired using infrared light are used (for example, Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-180861 Summary of the invention

[0006] Technical problem to be solved by the invention

[0007] In a structure that uses an optical sensor such as an organic photodiode (OPD) to obtain a pulse wave, the change in current supplied from the optical sensor is converted into a change in voltage and amplified, and the output voltage signal after the voltage conversion is converted into a digital value to obtain the pulse wave. In such a structure, the pulse wave fluctuation component is small relative to the full scale range of the digital value, and sometimes sufficient accuracy cannot be obtained.

[0008] An object of the present disclosure is to provide a detection device capable of improving the detection accuracy of a pulse wave waveform.

[0009] Solutions for solving technical problems

[0010] A detection device involved in one form of the present disclosure includes: a light sensor; a light source that irradiates light to the light sensor; a detection signal amplification circuit that performs voltage conversion on changes in current supplied from the light sensor; and an A / D conversion circuit that converts an output voltage signal after the voltage conversion into a detection value of a digital value, and the A / D conversion circuit limits the detection value to a maximum grayscale or a minimum grayscale of a digital value when the light source is off.

[0011] A detection device involved in one form of the present disclosure includes: a light sensor; a light source that irradiates light to the light sensor; a detection signal amplification circuit that converts the change in current supplied from the light sensor into a voltage; and an output circuit that converts the output voltage signal after the voltage conversion into a detection value, and the output circuit limits the detection value to a maximum detection value or a minimum detection value when the light source is off. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a plan view showing the detection device according to the first embodiment.

[0013] Figure 2 This is a block diagram showing a configuration example of a detection device according to Embodiment 1.

[0014] Figure 3 1 is a circuit diagram showing a detection device according to the first embodiment.

[0015] Figure 4 : is a circuit diagram showing a configuration example of an AFE circuit according to the first embodiment.

[0016] Figure 5 This is a schematic partial cross-sectional view of the optical sensor according to Embodiment 1.

[0017] Figure 6 It is a timing waveform chart showing an operation example of the detection device according to the comparative example of the first embodiment.

[0018] Figure 7 yes Figure 6 The timing waveform diagram shown is an enlarged view of the readout period of each photosensor.

[0019] Figure 8 This is a diagram showing the correspondence between the detection value of the AFE circuit and the light receiving intensity of the photosensor in the operation example of the detection device according to the comparative example of the first embodiment.

[0020] Fig. 9 This is a timing waveform diagram showing an operation example of the detection device according to the first embodiment.

[0021] Fig.10 yes Fig. 9 The timing waveform diagram shown is an enlarged view of the readout period of each photosensor.

[0022] Fig.11 This is a first diagram showing the correspondence between the detection value of the AFE circuit and the light receiving intensity of the photosensor in the first operation example of the detection device according to the first embodiment.

[0023] Fig.12This is a second diagram showing the correspondence between the detection value of the AFE circuit and the light receiving intensity of the photosensor in the first operation example of the detection device according to the first embodiment.

[0024] Fig.13 This is a first diagram showing the correspondence between the detection value of the AFE circuit and the light receiving intensity of the photosensor in the second operation example of the detection device according to the first embodiment.

[0025] Fig.14 This is a second diagram showing the correspondence between the detection value of the AFE circuit and the light receiving intensity of the photosensor in the second operation example of the detection device according to the first embodiment.

[0026] Fig.15 : is a circuit diagram showing a configuration example of an AFE circuit according to a modification of the first embodiment.

[0027] Fig.16 This is a timing waveform chart showing an operation example of the detection device according to the modification of the first embodiment.

[0028] Fig.17 yes Fig.16 The timing waveform diagram shown is an enlarged view of the readout period of each photosensor.

[0029] Fig.18 This is a diagram showing the correspondence between the detection value of the AFE circuit and the light receiving intensity of the photosensor in the operation example of the detection device according to the modification of the first embodiment.

[0030] Fig.19 1 is a circuit diagram showing a detection device according to the second embodiment.

[0031] Fig. 20 : is a circuit diagram showing a configuration example of an AFE circuit according to the second embodiment.

[0032] Fig.21 This is a diagram showing the correspondence between the detection value of the AFE circuit and the light receiving intensity of the photosensor in the operation example of the detection device according to the comparative example of the second embodiment.

[0033] Fig. 22 This is a timing waveform diagram showing an operation example of the detection device involved in the second embodiment.

[0034] Fig.23 yes Fig. 22 The timing waveform diagram shown is an enlarged view of the readout period of each photosensor.

[0035] Fig.24 This is a first diagram showing the correspondence between the detection value of the AFE circuit and the light receiving intensity of the photosensor in the operation example of the detection device according to the second embodiment.

[0036] Fig.25 This is a second diagram showing the correspondence between the detection value of the AFE circuit and the light receiving intensity of the photosensor in the operation example of the detection device according to the second embodiment.

[0037] Fig.26 : is a circuit diagram showing a configuration example of an AFE circuit according to a modification of the second embodiment.

[0038] Fig. 27 It is a timing waveform diagram showing an operation example of the detection device involved in the modification example of the second embodiment.

[0039] Fig.28 yes Fig. 27 The timing waveform diagram shown is an enlarged view of the readout period of each photosensor.

[0040] Fig.29 This is a diagram showing the correspondence between the detection value of the AFE circuit and the light receiving intensity of the photosensor in the operation example of the detection device according to the modification of the second embodiment. DETAILED DESCRIPTION

[0041] The mode (implementation method) for implementing the present invention is described in detail with reference to the accompanying drawings. In addition, the present invention is not limited to the contents described in the following implementation methods. In addition, the constituent elements described below include elements that can be easily thought of by a person skilled in the art, and substantially the same elements. Furthermore, the constituent elements described below can be appropriately combined. In addition, the disclosure is only an example, and appropriate changes that can be easily thought of by a person skilled in the art to maintain the gist of the invention are of course included in the scope of the present disclosure. In addition, in order to make the description clearer, the accompanying drawings sometimes schematically indicate the width, thickness, shape, etc. of each part compared to the actual form, but this is only an example and does not limit the interpretation of the present disclosure. In addition, in this specification and each figure, the same figure mark is sometimes used for the same element as the element described previously with respect to the figure that has already appeared, and the detailed description is appropriately omitted.

[0042] (Implementation Method 1)

[0043] Figure 1 FIG. 2 is a top view showing the detection device involved in Embodiment 1. Figure 1 As shown, the detection device 1 has a sensor substrate 21, a sensor area 10, a gate line driving circuit 15, a signal line selection circuit 16, an AFE (Analog Front End) circuit 48, a control circuit 122, a power supply circuit 123, a first light source 61 and a second light source 62. Figure 1In the example shown, a plurality of first light sources 61 are provided on the first light source substrate 51, and a plurality of second light sources 62 are provided on the second light source substrate 52. Figure 1 The configuration of the first light source 61 and the second light source 62 shown is only an example and can be changed appropriately. For example, a plurality of first light sources 61 and a plurality of second light sources 62 may be respectively configured on the first light source substrate 51 and the second light source substrate 52. In this case, a group including a plurality of first light sources 61 and a group including a plurality of second light sources 62 may be arranged side by side in the second direction Dy, and the first light source 61 and the second light source 62 may also be alternately arranged in the second direction Dy. In addition, the light source substrate provided with the first light source 61 and the second light source 62 may also be one or more than three.

[0044] The detection device 1 is electrically connected to a host computer 200. The host computer 200 is, for example, a host control device of a device (not shown) to which the detection device 1 is applied. The host computer 200 performs a predetermined biological information acquisition process based on data output from the detection device 1.

[0045] The control substrate 121 is electrically connected to the sensor base 21 via the flexible printed substrate 71. The AFE circuit 48 is provided on the flexible printed substrate 71. The control substrate 121 is provided with a control circuit 122, a power supply circuit 123, and an output circuit 126.

[0046] The control circuit 122 is, for example, a control IC (Control Integrated Circuit) that outputs a logic control signal. The control circuit 122 may be, for example, a PLD (Programmable Logic Device) such as an FPGA (Field Programmable Gate Array).

[0047] The control circuit 122 supplies control signals to the sensor region 10, the gate line driving circuit 15, and the signal line selection circuit 16 to control the detection operation of the sensor region 10. In addition, the control circuit 122 supplies control signals to the first light source 61 and the second light source 62 to control whether the first light source 61 and the second light source 62 emit light or not.

[0048] The power circuit 123 supplies voltage signals such as the sensor power potential Vorg to the sensor region 10 , the gate line driving circuit 15 , the signal line selection circuit 16 , and the AFE circuit 48 . The power circuit 123 also supplies power supply voltage to the first light source 61 and the second light source 62 .

[0049] The output circuit 126 is, for example, a USB controller IC, and controls communication between the control circuit 122 and the host 200 .

[0050] The sensor substrate 21 has a detection area AA and a peripheral area GA. The detection area AA is an area where a plurality of optical sensors PD included in the sensor area 10 are arranged in a matrix. The peripheral area GA is an area between the periphery of the detection area AA and the end of the sensor substrate 21, and is an area where no optical sensors PD are arranged.

[0051] The gate line drive circuit 15 and the signal line selection circuit 16 are provided in the peripheral area GA. Specifically, the gate line drive circuit 15 is provided in a region extending along the second direction Dy in the peripheral area GA. The signal line selection circuit 16 is provided in a region extending along the first direction Dx in the peripheral area GA and is provided between the sensor area 10 and the AFE circuit 48.

[0052] In addition, the first direction Dx is a direction in a plane parallel to the sensor substrate 21. The second direction Dy is a direction in a plane parallel to the sensor substrate 21, and is a direction orthogonal to the first direction Dx. In addition, the second direction Dy may cross the first direction Dx non-orthogonally. In addition, the third direction Dz is a direction orthogonal to the first direction Dx and the second direction Dy, and is a normal direction of the sensor substrate 21.

[0053] A plurality of first light sources 61 are provided on the first light source substrate 51 and arranged along the second direction Dy. A plurality of second light sources 62 are provided on the second light source substrate 52 and arranged along the second direction Dy. The first light source substrate 51 and the second light source substrate 52 are electrically connected to the control circuit 122 and the power supply circuit 123 via the terminal portions 124 and 125 provided on the control substrate 121, respectively.

[0054] The first light sources 61 and the second light sources 62 may be inorganic LEDs (Light Emitting Diodes), organic ELs (OLEDs), etc. The first light sources 61 and the second light sources 62 emit first light and second light of different wavelengths, respectively.

[0055] The first light emitted from the first light source 61 is reflected by the surface of the subject's finger, wrist, etc. and enters the sensor area 10. Therefore, the sensor area 10 can detect the fingerprint by detecting the concavo-convex shape of the surface of the finger Fg, etc. The second light emitted from the second light source 62 is reflected by the inside of the finger Fg, etc. or passes through the finger Fg, etc. and enters the sensor area 10. Therefore, the sensor area 10 can detect the biological information related to the inside of the subject's finger, wrist, etc. The biological information is, for example, the subject's pulse wave, pulse, blood vessel image, etc. That is, the detection device 1 can also be configured as a fingerprint detection device for detecting fingerprints, or a vein detection device for detecting blood vessel patterns such as veins.

[0056] The first light may have a wavelength of 420 nm to 600 nm, for example, about 500 nm, and the second light may have a wavelength of 780 nm to 950 nm, for example, about 850 nm. In this case, the first light is blue or green visible light (blue light or green light), and the second light is infrared light. The sensor area 10 can detect fingerprints based on the first light emitted from the first light source 61. The second light emitted from the second light source 62 is reflected inside the object to be detected or is transmitted through the object to be detected / absorbed by the object to be detected and enters the sensor area 10. Thus, the sensor area 10 can detect biological data such as pulse waves, blood vessel images (vascular patterns), etc. as biological information related to the inside of the subject's fingers, wrists, etc.

[0057] Alternatively, the first light may have a wavelength of 600 nm to 700 nm, for example, about 660 nm, and the second light may have a wavelength of 780 nm to 950 nm, for example, about 850 nm. In this case, based on the first light emitted from the first light source 61 and the second light emitted from the second light source 62, the sensor area 10 can detect the blood oxygen concentration as information related to the living body in addition to the pulse wave, pulse, and blood vessel image. In this way, the detection device 1 has the first light source 61 and the plurality of second light sources 62, and can detect various information related to the living body by performing detection based on the first light and detection based on the second light.

[0058] Figure 2 is a block diagram showing a configuration example of a detection device according to Embodiment 1. Figure 2 As shown, the detection device 1 further comprises a detection control circuit 11 and a detection circuit 40 .

[0059] The sensor region 10 has a plurality of light sensors PD. The light sensors PD in the sensor region 10 are, for example, organic photodiodes (OPDs), and output electrical signals corresponding to the irradiated light to the signal line selection circuit 16. In addition, the sensor region 10 performs detection based on the gate drive signal supplied from the gate line drive circuit 15. The light sensors PD may be, for example, silicon photodiodes (SiPDs).

[0060] The detection control circuit 11 supplies control signals to the gate line driving circuit 15, the signal line selection circuit 16 and the detection circuit 40 to control their operations. In addition, the detection control circuit 11 supplies various control signals to the first light source 61 and the second light source 62 to control their respective light emission and non-light emission.

[0061] The gate line driving circuit 15 drives a plurality of gate lines GCL based on various control signals (see Figure 3 ) circuit. The gate line driving circuit 15 selects a plurality of gate lines GCL sequentially or simultaneously and supplies a gate driving signal to the selected gate line GCL. Thus, the gate line driving circuit 15 selects a plurality of light sensors PD connected to the gate lines GCL.

[0062] The signal line selection circuit 16 selects a plurality of signal lines SGL in sequence or simultaneously (see Figure 3 ). The signal line selection circuit 16 is, for example, a multiplexer. The signal line selection circuit 16 electrically connects the selected signal line SGL to the AFE circuit 48 based on the selection signal ASW supplied from the detection control circuit 11. Thus, the signal line selection circuit 16 outputs the detection signal of the optical sensor PD to the detection circuit 40.

[0063] The detection circuit 40 includes an AFE circuit 48, a signal processing circuit 44, a storage circuit 46, and a detection timing control circuit 47. The detection timing control circuit 47 controls the AFE circuit 48 and the signal processing circuit 44 based on a control signal supplied from the detection control circuit 11 so as to operate synchronously.

[0064] The AFE circuit 48 generates a detection value of each photosensor PD based on the detection signal of each photosensor PD output from the sensor region 10. The AFE circuit 48 is, for example, an analog front end IC.

[0065] The AFE circuit 48 includes at least a detection signal amplifier circuit 42 and an A / D conversion circuit 43 (output circuit). The detection signal amplifier circuit 42 converts the change of the current supplied from the photosensor PD into a change of voltage and amplifies it. The A / D conversion circuit 43 samples the voltage signal output from the detection signal amplifier circuit 42 and converts it into a detection value of a digital value.

[0066] In the present disclosure, the signal processing circuit 44 and the storage circuit 46 are included in the control circuit 122 .

[0067] The signal processing circuit 44 acquires biological data for generating information related to the living body based on the detection values ​​of the photosensors PD output from the AFE circuit 48. In the present disclosure, the information related to the living body includes a pulse wave acquired by infrared light or red light.

[0068] The storage circuit 46 stores various setting information required for acquiring biological data in the signal processing circuit 44. The storage circuit 46 may be in the form of, for example, a RAM (Random Access Memory), a ROM (Read Only Memory), an EEPROM (Electrically Erasable Programmable ReadOnly Memory), etc. In addition, the storage circuit 46 may be a register circuit or the like.

[0069] Next, a circuit configuration example of the detection device 1 will be described. Figure 3 is a circuit diagram showing a detection device according to Embodiment 1. Figure 3 As shown, the sensor region 10 has a plurality of photosensors PD arranged in a matrix in the detection area AA.

[0070] The gate line GCL extends in the first direction Dx and is connected to a plurality of light sensors PD arranged in the first direction Dx. In addition, a plurality of gate lines GCL1, GCL2, ..., GCL6 are arranged in the second direction Dy and are respectively connected to the gate line driving circuit 15. In addition, in the following description, when it is not necessary to distinguish between the plurality of gate lines GCL1, GCL2, ..., GCL6, they are simply referred to as the gate line GCL. In addition, in Figure 3 In order to make the description easier to understand, six gate lines GCL are shown, but this is just an example, and M (M is a natural number) gate lines GCL may be arranged.

[0071] The signal line SGL extends in the second direction Dy and is connected to a plurality of light sensors PD arranged in the second direction Dy. In addition, a plurality of signal lines SGL1_1, SGL1_2, SGL1_3, ..., SGL3_3 are arranged in the first direction Dx and are connected to the signal line selection circuit 16 and the reset circuit 17, respectively. In addition, in the following description, when it is not necessary to distinguish between the plurality of signal lines SGL1_1, SGL1_2, SGL1_3, ..., SGL3_3, they are simply represented as signal lines SGL. In addition, for easy understanding of the description, 9 signal lines SGL are shown, but this is just an example, and N (N is a natural number) signal lines SGL may also be arranged.

[0072] The gate line driving circuit 15 is driven by the control circuit 122 (see Figure 1 ) receives various control signals. The gate line driving circuit 15 selects a plurality of gate lines GCL1, GCL2, ..., GCL6 in sequence in a time-sharing manner based on the various control signals. The gate line driving circuit 15 supplies a gate driving signal to the selected gate line GCL. Thus, a gate driving signal is supplied to the switch connected to each photo sensor PD, and a plurality of photo sensors PD arranged in the first direction Dx are selected. The switch connected to each photo sensor PD is, for example, a switching element composed of a thin film transistor, for example, a TFT (Thin Film Transistor) of an n-channel MOS (Metal Oxide Semiconductor: Metal Oxide Semiconductor) type.

[0073] In addition, the gate line driving circuit 15 may also perform different driving according to the detection modes of fingerprint detection and information related to different multiple biological bodies (pulse wave, pulse, blood vessel image, blood oxygen concentration, etc., hereinafter referred to as "biological body information"). For example, the gate line driving circuit 15 may also drive multiple gate lines GCL in a bundle.

[0074] The plurality of switches of the signal line selection circuit 16 are provided corresponding to the signal lines SGL1, SGL2, ..., SGL9. The switches provided corresponding to the signal lines SGL are switching elements composed of thin film transistors, for example, n-channel MOS (Metal Oxide Semiconductor) type TFTs (Thin Film Transistors).

[0075] Control circuit 122 (see Figure 1 ) supplies selection signals ASW1, ASW2, and ASW3 to the signal line selection circuit 16. As a result, the signal line selection circuit 16 selects the plurality of signal lines SGL sequentially or simultaneously in a time-division manner. Specifically, Figure 3In the structure shown, the signal line selection circuit 16 simultaneously selects the signal lines SGL1_1, SGL2_1, and SGL3_1, and connects them to the AFE circuit 48 respectively. In addition, the signal line selection circuit 16 simultaneously selects the signal lines SGL1_2, SGL2_2, and SGL3_2, and connects them to the AFE circuit 48 respectively. In addition, the signal line selection circuit 16 simultaneously selects the signal lines SGL1_3, SGL2_3, and SGL3_3, and connects them to the AFE circuit 48 respectively. With such a structure, the detection device 1 can reduce the number of ICs including the AFE circuit 48 or the number of IC terminals. In addition, in Figure 3 In order to facilitate the understanding of the description, an example of selecting three signal lines SGL in a time-sharing manner is shown, but this is just an example, and the number of signal lines SGL selected in a time-sharing manner may also be P (P is a natural number that is one-half of the number of equal divisions of the number of signal lines M. For example, when the number of equal divisions of the number of signal lines M is Q, P=M / Q).

[0076] Figure 4 is a circuit diagram showing a configuration example of an AFE circuit according to Embodiment 1. Figure 4 In the figure, a light sensor PD is also shown. The light sensor PD is driven by a gate line driving circuit 15 to a gate line GCLn (n is 1 to N (in Figure 3 In the example shown, N = 6) (a natural number) is selected by the gate drive signal supplied, and the gate drive signal is selected by the signal line selection circuit 16 through the signal lines SGLq_1, SGLq_2, SGLq_3 (q is 1 to Q (in Figure 3 In the example shown, a natural number (Q=3) is connected to the AFE circuit 48.

[0077] A sensor power supply potential Vorg is applied to the cathode of each photosensor PD from the power supply circuit 123. The anode of each photosensor PD is connected to the AFE circuit 48 via the signal line selection circuit 16 in a time-division manner.

[0078] When light irradiates the photosensor PD, a current corresponding to the intensity of the light irradiating the photosensor PD flows through the photosensor PD, and charges are accumulated in the capacitor element of the photosensor PD. When selected by the gate line drive circuit 15 and the signal line selection circuit 16, a current corresponding to the charges accumulated in the capacitor element of the photosensor PD flows to the AFE circuit 48 via the signal line SGL.

[0079] The detection signal amplifier circuit 42 of the AFE circuit 48 converts the variation of the current supplied from the photosensor PD via the signal line SGL into the variation of the voltage and amplifies the voltage. The detection signal amplifier circuit 42 includes a differential amplifier circuit CA as a main component.

[0080] A reference potential Vref having a fixed potential is applied to the non-inverting input terminal (+) of the differential amplifier circuit CA, and a signal line SGL is connected to the inverting input terminal (-) of the differential amplifier circuit CA via the signal line selection circuit 16. The reference potential Vref is, for example, approximately half of the power supply voltage Vadc of the A / D conversion circuit 43 (Vref≈Vadc / 2). The power supply voltage Vadc of the A / D conversion circuit 43 is given by the potential difference between the high potential voltage Vadh and the low potential voltage Vadl supplied to the A / D conversion circuit 43. The low potential voltage Vadl is, for example, the GND potential.

[0081] A negative feedback capacitor Cfb and a reset switch RSW are connected between the inverting input terminal (-) and the output terminal of the differential amplifier circuit CA. In this embodiment, a constant current source is connected to the inverting input terminal (-) via an offset switch ofsSW.

[0082] Next, the structure of the photosensor PD will be described. Figure 5 1 is a schematic partial cross-sectional view of the optical sensor according to Embodiment 1. The sensor region 10 of the detection device 1 includes a sensor substrate 21, a sensor structure 22, and a protective film 23. The sensor substrate 21 is an insulating substrate formed of, for example, a film-like resin.

[0083] The sensor structure 2 includes a TFT layer 221 , an anode electrode (lower electrode) 222 , a photosensor PD, and a cathode electrode (upper electrode) 226 .

[0084] Various wirings such as gate lines GCL and signal lines SGL are provided on the TFT layer 221. The sensor substrate 21 and the TFT layer 221 are a driving circuit for driving the sensor, and are also called a backplane.

[0085] The photosensor PD includes an active layer 224, an electron transport layer (lower buffer layer) 223 provided between the active layer 224 and the anode electrode (lower electrode) 222, and a hole transport layer (upper buffer layer) 225 provided between the active layer 224 and the cathode electrode (upper electrode) 226. In other words, the electron transport layer (lower buffer layer) 223, the active layer 224, and the hole transport layer (upper buffer layer) 225 of the photosensor PD are stacked in this order in a direction perpendicular to the sensor substrate 21.

[0086] The characteristics of the active layer 224 (e.g., voltage-current characteristics, resistance value) change according to the irradiated light. As the material of the active layer 224, an organic material is used. Specifically, the active layer 224 has a bulk heterostructure in which a p-type organic semiconductor and an n-type fullerene derivative (PCBM) as an n-type organic semiconductor are mixed. As the active layer 224, for example, C as a low molecular weight organic material can be used. 60(fullerene), PCBM (phenyl C61-butyric acidmethyl ester), CuPc (copper phthalocyanine), F 16 CuPc (fluorinated copper phthalocyanine), rubrene (rubrene: 5,6,11,12-tetraphenyltetraphenyl), PDI (derivative of perylene), etc.

[0087] The active layer 224 can be formed by using these low molecular weight organic materials through a dry process. In this case, the active layer 224 can be, for example, CuPc and F. 16 CuPc laminated film, or rubrene and C 60 The active layer 224 can also be formed by a coating type (Wet Process). In this case, the active layer 224 uses a material that combines the above-mentioned low-molecular organic material and the high-molecular organic material. As the high-molecular organic material, for example, P3HT (poly (3-hexylthiophene): poly (3-hexylthiophene)), F8BT (F8-alt-benzothiadiazole: poly (9,9-dioctylfluorene-co-benzothiadiazole)), etc. can be used. The active layer 224 can be a film in a state where P3HT and PCBM are mixed, or a film in a state where F8BT and PDI are mixed.

[0088] The electron transport layer (lower buffer layer) 223 and the hole transport layer (upper buffer layer) 225 are provided to facilitate the electrons and holes generated in the active layer 224 to reach the anode electrode (lower electrode) 222 or the cathode electrode (upper electrode) 226. The electron transport layer (lower buffer layer) 223 is in direct contact with the anode electrode (lower electrode) 222. The active layer 224 is in direct contact with the electron transport layer (lower buffer layer) 223. The material of the electron transport layer (lower buffer layer) 223 uses ethoxylated polyethyleneimine (PEIE).

[0089] The hole transport layer (upper buffer layer) 225 is in direct contact with the active layer 224, and the cathode electrode (upper electrode) 226 is in direct contact with the hole transport layer (upper buffer layer) 225. The hole transport layer (upper buffer layer) 225 is an oxidized metal layer. As the oxidized metal layer, tungsten oxide (WO 3 ), molybdenum oxide, etc.

[0090] The materials and manufacturing methods of the electron transport layer (lower buffer layer) 223 , the active layer 224 , and the hole transport layer (upper buffer layer) 225 are merely examples, and other materials and manufacturing methods may be used.

[0091] The anode electrode (lower electrode) 222 and the cathode electrode (upper electrode) 226 are opposed to each other with the light sensor PD interposed therebetween. The cathode electrode (upper electrode) 226 is made of a light-transmitting conductive material such as ITO (Indium Tin Oxide). The anode electrode (lower electrode) 222 is made of a metal material such as silver (Ag) or aluminum (Al). Alternatively, the anode electrode (lower electrode) 222 may be an alloy material containing at least one of these metal materials.

[0092] By controlling the film thickness of the anode electrode (lower electrode) 222, the anode electrode (lower electrode) 222 can be formed as a semi-transmissive electrode having light transmittance. For example, the anode electrode (lower electrode) 222 is formed of a 10 nm thick Ag thin film, thereby having a light transmittance of about 60%. In this case, the light sensor PD can detect the first light LD irradiated from the first surface FD side, for example.

[0093] The protective film 23 is provided on the second surface FU so as to cover the cathode electrode (upper electrode) 226. The protective film 23 is a passivation film and is provided to protect the photosensor PD.

[0094] In the present disclosure, as a specific example of the information related to the living body acquired by the detection device 1, the information used to calculate the oxygen saturation in the blood (hereinafter referred to as blood oxygen saturation (SpO2)) is acquired. 2 )) is explained with the example of biological information, namely the pulse wave.

[0095] Here, for example, as the first light emitted from the first light source 61, red visible light (red light) of 600 nm or more and 700 nm or less, specifically, about 660 nm is used, and as the second light emitted from the second light source 62, infrared light of 780 nm or more and 950 nm or less, specifically, about 850 nm is used. 2 ), a first pulse wave obtained using a first light (red light) and a second pulse wave obtained using a second light (infrared light) are used.

[0096] Blood oxygen saturation (SpO 2 ) can be obtained as follows: set the AC component of the first pulse wave to AC(Red), set the DC component of the first pulse wave to DC(Red), set the AC component of the second pulse wave to AC(IR), set the DC component of the second pulse wave to DC(IR), calculate the R value shown in the following formula (1), and apply it to the calibration curve shown in the following formula (2) (a and b are calibration coefficients).

[0097] R={AC(Red) / DC(Red)} / {AC(IR) / DC(IR)}…(1)

[0098] SpO 2 =ba×R…(2)

[0099] Since the amount of light absorbed changes according to the amount of oxygen absorbed by hemoglobin, the light sensor PD detects the amount of light obtained by subtracting the light absorbed by blood (hemoglobin) from the irradiated first light and second light. Most of the blood oxygen is reversibly bound to hemoglobin in red blood cells, and a very small part is dissolved in plasma. More specifically, the value of how much percentage of the allowed amount of oxygen is bound to the blood as a whole is called oxygen saturation (SpO 2 ). The blood oxygen saturation can be calculated by subtracting the amount of light absorbed by the blood (hemoglobin) from the irradiated light at the two wavelengths of the first light and the second light.

[0100] Oxygen saturation (SpO 2 ) is determined by the ratio of hemoglobin in the blood to oxygen (O2Hb: oxygenated hemoglobin) and unbound hemoglobin (HHb: reduced hemoglobin). The absorption characteristics of red light are HHb>>O2Hb, and the absorbance of HHb is significantly larger. In contrast, the absorption characteristics of infrared light are HHb≈O2Hb, and the absorbance of O2Hb is slightly larger.

[0101] Next, an operation example of the detection device 1 will be described. Here, first, an operation example according to a comparative example of the first embodiment will be described. Figure 6 is a timing waveform diagram showing an operation example of the detection device involved in the comparative example of the first embodiment. Figure 6 In the operation example of the detection device according to the comparative example of the first embodiment shown, the constant current source is not connected to the inverting input terminal (−) of the differential amplifier circuit CA.

[0102] exist Figure 6 In the example shown, in the odd-numbered frame 1Fodd and the even-numbered frame 1Feven, exposure periods Pex1 and Pex2 and readout periods Pdet1 and Pdet2 are provided, respectively. Figure 3 In the illustrated structure, during the readout periods Pdet1 and Pdet2 , the gate line driving circuit 15 sequentially scans the gate lines GCL1 to GCL6 .

[0103] like Figure 6As shown, the control circuit 122 (detection control circuit 11) makes the first light source 61 emit light and does not make the second light source 62 emit light during the exposure period Pex1 of the odd frame 1Fodd. Also, the first light source 61 does not emit light and makes the second light source 62 emit light during the exposure period Pex2 of the even frame 1Feven.

[0104] In this way, the first light source 61 and the second light source 62 are controlled to emit light / not emit light in a time-sharing manner in units of frames. As a result, the detection value detected by the light sensor PD using the first light and the detection value detected by the light sensor PD using the second light are output to the AFE circuit 48 in a time-sharing manner. In the following, when there is no need to distinguish between the odd frame 1Fodd and the even frame 1Feven for explanation, the odd frame 1Fodd and the even frame 1Feven are simply represented as each frame 1F, the exposure periods Pex1 and Pex2 are simply represented as the exposure periods Pex, and the readout periods Pdet1 and Pdet2 are simply represented as the readout periods Pdet.

[0105] During the exposure period Pex, a current Iphoto corresponding to the intensity of the light irradiating the photosensor PD flows through the photosensor PD, and charges are accumulated in the capacitor element of the photosensor PD. At this time, the charge Qphoto accumulated in the capacitor element of the photosensor PD becomes the value obtained by multiplying the current Iphoto flowing through the photosensor PD by the exposure period Pex (Qphoto=Iphoto×Pex).

[0106] During the selection period of the gate line GCLn, the selection signals ASW1, ASW2, and ASW3 are sequentially controlled to a high level (hereinafter also referred to as "H control"), and each signal line SGL is sequentially connected to the AFE circuit 48. The high level period (hereinafter also referred to as "H period") of the selection signals ASW1, ASW2, and ASW3 is the readout period of each photosensor PD. Figure 7 is an enlarged view of the readout period of each photosensor.

[0107] During the period including the exposure period Pex before time t1, the reset switch RSW is controlled to be turned on and brought into the reset state. Figure 7 At time t1 during the readout period of each photosensor shown in FIG. 1 , the reset switch RSW is turned off to release the reset state. Thereafter, at time t2, when the selection signal ASWp (p is 1 to P (in Figure 3In the example shown, when H control is performed (P=3), a current corresponding to the charge accumulated in the capacitor element of the photosensor PD during the exposure period Pex flows to the AFE circuit 48 via the signal line SGL, and the charge is accumulated in the negative feedback capacitor Cfb of the AFE circuit 48. At this time, the voltage signal Vout (hereinafter also referred to as "output voltage signal Vout") output from the detection signal amplifier circuit 42 is reduced from the reference potential Vref to a value corresponding to the charge accumulated in the negative feedback capacitor Cfb of the AFE circuit 48.

[0108] The output voltage signal Vout of the detection signal amplifier circuit 42 is acquired by the A / D converter circuit 43 at the sampling timing of time t5 and converted into a detection value Raw of a digital value.

[0109] When the reset switch RSW is turned on at time t6, the anode potential of the photosensor PD and the output voltage of the detection signal amplifier circuit 42 are reset to the reference potential Vref, and the charge accumulated in the negative feedback capacitor Cfb of the detection signal amplifier circuit 42 is reset. Then, at time t7, the selection signal ASWp is controlled to be L, and at time t8, the reset switch RSW is turned off.

[0110] Figure 8 1 is a diagram showing the correspondence between the detection value of the AFE circuit and the light intensity received by the optical sensor in the operation example of the detection device according to the comparative example of the first embodiment. Figure 8 In FIG. 1 , the vertical axis represents the detection value Raw [digit] of the digital value, and the horizontal axis represents the intensity of light (received light intensity) received by the photosensor PD during the exposure period Pex.

[0111] exist Figure 3 as well as Figure 4 In the structure involved in the embodiment 1 shown in FIG. Figure 8 As shown, the smaller the light intensity during the exposure period Pex, the larger the detection value Raw. That is, the detection value Raw is a value that takes the detection value when the light sensor PD is not exposed as the maximum value, and decreases according to the light intensity during the exposure period Pex. In other words, the detection value Raw is a value that takes the value Base_Raw (hereinafter also referred to as "reference value Base_Raw") obtained by converting the output voltage of the detection signal amplifier circuit 42 at reset into a digital value as the maximum value, and decreases according to the light intensity during the exposure period Pex. Figure 6 as well as Figure 7 In the operation example according to the comparative example shown, the number of grayscales of the A / D conversion circuit 43 is set to 2. n (resolution n bits), the reference value Base_Raw is approximately Vref / (Vadc / 2 n)(Base_Raw≈Vref / (Vadc / 2 n )). Figure 6 as well as Figure 7 The detection value Raw in the operation example of the detection device according to the comparative example of the first embodiment shown is expressed by the following equation (3).

[0112] Raw=Vout / (Vadc / 2 n )=(Vref-Qphoto / Cfb) / (Vadc / 2 n )…(3)

[0113] Furthermore, when the number of grayscales that can be output from the A / D conversion circuit 43 (output circuit) is set to 2 n When the minimum grayscale Raw_min (detection minimum value) is "0", the maximum grayscale Raw_max (detection maximum value) is "2 n -1". When the resolution of the A / D conversion circuit 43 is 12 bits (n=12), the minimum grayscale Raw_min is "0" and the maximum grayscale Raw_max is "4095". In addition, the reference value Base_Raw is, for example, "2048".

[0114] exist Figure 8 In the example shown, the output range of the A / D conversion circuit 43 is roughly set to Vadc / (Vadc / 2 n ). At this time, the range in which the detection value Raw, which is the output value of the A / D conversion circuit 43, changes linearly with respect to the change of the output voltage signal Vout of the detection signal amplification circuit 42 is limited to the range from the lower limit grayscale Raw_lower_lim to the upper limit grayscale Raw_upper_lim. Therefore, in order to maintain the detection accuracy of the detection value Raw, it is necessary to perform detection within the range from the lower limit grayscale Raw_lower_lim to the upper limit grayscale Raw_upper_lim (Raw_lower_lim≤Raw≤Raw_upper_lim). Hereinafter, the range from the lower limit grayscale Raw_lower_lim to the upper limit grayscale Raw_upper_lim in which the detection value Raw changes linearly with respect to the change of the output voltage signal Vout is also referred to as the "detection range" in the detection device 1.

[0115] In addition, the detection range in the detection device 1 is determined by the input-output characteristics of the A / D conversion circuit 43, the power supply voltage range given by the potential difference between the high potential voltage Vadh (power supply voltage Vadc in the present disclosure) and the low potential voltage Vadl (for example, GND potential) supplied to the A / D conversion circuit 43, and the like. In addition, the detection accuracy of the detection value Raw also acts on the input-output characteristics and the power supply voltage range of the detection signal amplifier circuit 42. In order to maintain the detection accuracy of the detection value Raw, the power supply voltage range of the detection signal amplifier circuit 42 needs to be at least within the power supply voltage range of the A / D conversion circuit 43.

[0116] Fig. 9 This is a timing waveform diagram showing an operation example of the detection device according to the first embodiment. Fig.10 yes Fig. 9 The timing waveform diagram shown is an enlarged view of the readout period of each photosensor.

[0117] exist Fig. 9 as well as Fig.10 In the operation example shown, the reset switch RSW is also controlled to be turned on and placed in the reset state during the exposure period Pex before time t1. Fig. 9 as well as Fig.10 In the example shown, Fig.10 At time t1 during the readout period of each photosensor shown, the reset switch RSW is controlled to be turned off to release the reset state, and then at time t2, the selection signal ASWp is controlled to be H, and then at time t3, the offset switch ofsSW is controlled to be turned on, and at time t4 after the offset period Tofs has passed, the offset switch ofsSW is controlled to be turned off. As a result, during the offset period Tofs from time t2 to time t4, a constant current Iofs (hereinafter also referred to as "offset current Iofs") flows out from the photosensor PD, and the amount of charge accumulated in the negative feedback capacitor Cfb of the detection signal amplification circuit 42 decreases. At this time, the reduced charge ΔQofs is set to Iofs×Tofs (ΔQofs=Iofs×Tofs). As a result, Fig. 9 as well as Fig.10 The detection value Raw in the illustrated operation example is expressed by the following equation (4).

[0118] Raw=Vout / (Vadc / 2 n )={Vref-(Qphoto-ΔQofs) / Cfb} / (Vadc / 2 n )… (4)

[0120] As a result, in Fig. 9 as well as Fig.10 In the operation example shown, the detection value Raw becomes relative to Figure 6 as well as Figure 7 The operation example according to the comparative example shown here only increases the value of the difference value ΔRaw (hereinafter also referred to as “offset value ΔRaw”) shown in the following equation (5).

[0121] ΔRaw=(ΔQofs / Cfb) / (Vadc / 2 n )={(Iofs×Tofs) / Cfb} / (Vadc / 2 n )… (5)

[0123] That is, in the operation example of the detection device 1 according to Embodiment 1, the offset value ΔRaw can be set by adjusting the offset current Iofs or the offset period Tofs. Specifically, the offset value ΔRaw is set so as to satisfy the following equation (6) or equation (7).

[0124] Raw_upper_lim≥Vref / (Vadc / 2 n )+ΔRaw=[Vref+{(Iofs×Tofs) / Cfb}] /

[0125] (Vadc / 2 n )…(6)

[0126] Raw_upper_lim×(Vadc / 2 n )≥Vref+ΔRaw×(Vadc / 2 n )=Vref+{(Iofs×Tofs)

[0127] / Cfb}…(7)

[0128] Fig.11 This is a first diagram showing the correspondence between the detection value of the AFE circuit and the light receiving intensity of the photosensor in the first operation example of the detection device according to the first embodiment. Fig.12 2 is a second diagram showing the correspondence between the detection value of the AFE circuit and the light intensity received by the optical sensor in the first operation example of the detection device according to the first embodiment. Fig.11 as well as Fig.12 In the first operation example shown, the dotted line shows Figure 8 The correspondence relationship between the detection value of the AFE circuit and the light receiving intensity of the photosensor in the operation example of the detection device according to the comparative example of the first embodiment is shown.

[0129] exist Fig.11 as well as Fig.12 In Fig.11As shown in FIG. 1 , an example is shown in which the offset value ΔRaw is set so that the reference value Base_Raw becomes the upper grayscale Raw_upper_lim (Base_Raw=Raw_upper_lim). Fig.12 As shown, by increasing the light intensity during the exposure period Pex (for example, increasing the light intensity of the light source (the first light source 61, the second light source 62) or reducing the negative feedback capacitor Cfb), Figure 8 Compared with the example shown in the figure, the AC component of the pulse wave within the detection range (AC(Red), AC(IR), refer to the above-mentioned formula (1)) can be increased, and the detection accuracy of the pulse wave waveform can be improved.

[0130] Here, for example, in a structure for detecting whether or not there is a detected object in the detection area AA, Fig.11 as well as Fig.12 As shown, the reference value Base_Raw needs to be set within the detection range (Base_Raw≤Raw_upper_lim), but in the example of obtaining the pulse wave, Fig.11 as well as Fig.12 As shown, even when the reference value Base_Raw is made consistent with the upper grayscale Raw_upper_lim (Base_Raw=Raw_upper_lim), the AC component of the pulse wave (AC(Red), AC(IR), refer to the above formula (1)) is small relative to the detection range of the A / D conversion circuit 43 (Raw_lower_lim≤Raw≤Raw_upper_lim), and sometimes sufficient accuracy cannot be obtained.

[0131] Fig.13 This is a first diagram showing the correspondence between the detection value of the AFE circuit and the light receiving intensity of the photosensor in the second operation example of the detection device according to the first embodiment. Fig.14 2 is a second diagram showing the correspondence between the detection value of the AFE circuit and the light intensity received by the optical sensor in the second operation example of the detection device according to the first embodiment. Fig.13 as well as Fig.14 In the second operation example of the detection device 1 according to the embodiment 1 shown in FIG. Figure 8 The corresponding relationship between the detection value of the AFE circuit and the light intensity received by the optical sensor in the operation example of the detection device according to the comparative example of the first embodiment shown in FIG. Fig.11 as well as Fig.12 FIG. 1 is a diagram showing a correspondence relationship between a detection value of the AFE circuit and the light receiving intensity of the photosensor in the first operation example of the detection device according to the first embodiment.

[0132] In the second operation example of the detection device 1 according to the first embodiment, Fig.13 As shown, it shows that the offset value ΔRaw is Fig.11 as well as Fig.12 Specifically, the offset value ΔRaw is set to satisfy the following equation (8) or equation (9). Fig.14 As shown, the upper limit of the range of the detection value Raw for acquiring the pulse wave can be brought close to the upper limit grayscale Raw_upper_lim, and the range of the detection value Raw for acquiring the pulse wave can be expanded to the upper limit of the detection range of the detection device 1 .

[0133] Raw_upper_lim≤Vref / (Vadc / 2 n )+ΔRaw=[Vref+{(Iofs×Tofs) / Cfb}] /

[0134] (Vadc / 2 n )…(8)

[0135] Raw_upper_lim×(Vadc / 2 n )≤Vref+ΔRaw×(Vadc / 2 n )=Vref+{(Iofs×Tofs)

[0136] / Cfb}…(9)

[0137] Therefore, if Fig.14 As shown in the figure, by making the light intensity ratio within the exposure period Pex Fig.11 as well as Fig.12 The example shown is large, which can further increase the AC component of the pulse wave within the detection range (AC (Red), AC (IR), refer to the above formula (1)), and Fig.11 as well as Fig.12 Compared with the example shown, the detection accuracy of the pulse waveform can be improved.

[0138] exist Fig.13 as well as Fig.14In the second operation example of the detection device 1 according to the first embodiment shown, in the region where the light intensity of the photosensor PD during the exposure period Pex is less than the predetermined value S, the detection value Raw becomes nonlinear with respect to the change of the output voltage signal Vout, and as the light intensity of the photosensor PD during the exposure period Pex becomes less than the predetermined value S, the detection value Raw is limited to the maximum grayscale Raw_max of the A / D conversion circuit 43. In other words, in the region where the output voltage signal Vout of the detection signal amplifier circuit 42 exceeds the predetermined value, the detection value Raw becomes nonlinear with respect to the change of the output voltage signal Vout, and as the light intensity of the photosensor PD during the exposure period Pex becomes less than the predetermined value S, the detection value Raw is limited to the maximum grayscale Raw_max of the A / D conversion circuit 43. That is, in the second operation example of the detection device 1 according to the first embodiment, in the state where the light sources (the first light source 61 and the second light source 62) are turned off, the detection value Raw is limited to the maximum grayscale Raw_max (detection maximum value) of the A / D conversion circuit (output circuit) 43.

[0139] The region where the detection value Raw exceeds the upper grayscale Raw_upper_lim and becomes nonlinear is a region outside the detection range of the detection device 1. Here, assuming that the detection range of the detection device 1 is infinite, the detection value Raw becomes linear in the entire region of the output voltage signal Vout. Fig.13 as well as Fig.14 The double-dashed line shows a virtual detection value when the detection range of the detection device 1 is assumed to be infinite in the region where the detection value Raw exceeds the upper grayscale Raw_upper_lim. As described above, the detection value Raw is actually limited to the maximum grayscale Raw_max of the A / D conversion circuit 43.

[0140] To calculate the blood oxygen saturation (SpO 2 ) of the pulse wave (DC(red), DC(IR), refer to the above formula (1)), it is necessary to set a virtual reference value Virtual_Base_Raw (hereinafter also referred to as "virtual reference value Virtual_Base_Raw") instead of the reference value Base_Raw. Hereinafter, in the second operation example of the detection device 1 involved in the first embodiment, the method of setting the virtual reference value Virtual_Base_Raw is described.

[0141] (Virtual reference value setting method 1 according to embodiment 1)

[0142] like Fig.13As shown, the virtual reference value Virtual_Base_Raw can be calculated as follows: when the photosensor PD is not exposed during the exposure period Pex, the offset value ΔRaw (=(ΔQofs / Cfb) / (Vadc / 2 n )). In other words, the virtual reference value Virtual_Base_Raw can be calculated by adding the offset value ΔRaw to the reference value Base_Raw obtained when the offset period Tofs is substantially zero in the second operation example of the detection device 1 according to the first embodiment when the light sensor PD is not exposed during the exposure period Pex. The virtual reference value Virtual_Base_Raw in this case is represented by the following formula (10).

[0143] Virtual_Base_Raw=Base_Raw+ΔRaw=[Vref+{(Iofs×Tofs) / Cfb}] / (Vadc / 2 n )…(10)

[0144] (Virtual reference value setting method 2 according to embodiment 1)

[0145] When the deviation of each photosensor PD is taken into account, the reference value Base_Raw in the operation example of the comparative example of the first embodiment may be set to a value obtained for each photosensor PD, for example, when the photosensor PD is not exposed during the exposure period Pex. In other words, when the deviation of each photosensor PD is taken into account, the reference value Base_Raw in the second operation example of the detection device 1 according to the first embodiment when the offset period Tofs is made substantially zero during the exposure period Pex may be set to a value obtained for each photosensor PD, for example, when the detection device 1 is shipped from the factory. When the reference value of the photosensor PD of the m columns and n rows is set to Base_Raw(m, n), the virtual reference value Virtual_Base_Raw(m, n) of each photosensor PD of the m columns and n rows is expressed by the following formula (11).

[0146] Virtual_Base_Raw(m,n)=Base_Raw(m,n)+ΔRaw=Base_Raw(m,n)+{(Iofs×Tofs) / Cfb}] / (Vadc / 2 n )…(11)

[0147] (Virtual reference value setting method 3 according to embodiment 1)

[0148] When considering the deviation of the offset current Iofs, the offset period Tofs, and the negative feedback capacitance Cfb of the detection signal amplifier circuit 42, for example, when the detection device 1 is shipped, the value of Fig.13 Multiple points within the detection range (Raw_lower_lim≤Raw≤Raw_upper_lim) shown in Fig.13 In the example shown, the detection values ​​Raw of 4 points (in the example shown) can be set by, for example, using a linear approximation (straight line approximation) using the least squares method, a virtual reference value Virtual_Base_Raw (m, n) of each photosensor PD. The method of calculating the virtual reference value Virtual_Base_Raw (m, n) of each photosensor PD is not limited to linear approximation.

[0149] In the first embodiment, the signal processing circuit 44 calculates the virtual reference value Virtual_Base_Raw using any one of the virtual reference value setting method 1, the virtual reference value setting method 2, and the virtual reference value setting method 3 according to the first embodiment. By storing the virtual reference value Virtual_Base_Raw thus set in advance in the storage circuit 46, it is possible to calculate the blood oxygen saturation (SpO 2 ) of the pulse wave (DC(Red), DC(IR), refer to the above formula (1)). Thus, the blood oxygen saturation (SpO2) using the first pulse wave obtained by the first light (red light) and the second pulse wave obtained by the second light (infrared light) can be improved. 2 ) calculation accuracy.

[0150] (Variation Example)

[0151] Fig.15 1 is a circuit diagram showing a configuration example of an AFE circuit according to a modification of the first embodiment. Fig.15 As shown, in this embodiment, the offset voltage signal Vofs is input to the inverting input terminal (−) of the differential amplifier circuit CA of the detection signal amplifier circuit 42 constituting the AFE circuit 48 a via the offset capacitor Cofs.

[0152] Fig.16 This is a timing waveform diagram showing an operation example of the detection device involved in the modification of the first embodiment. Fig.17 yes Fig.16 The timing waveform diagram shown is an enlarged view of the readout period of each photosensor.

[0153] exist Fig.16 as well as Fig.17In the operation example of the detection device 1 according to the modification of the first embodiment shown, during the exposure period Pex before time t1, the reference potential Vref is applied as the offset voltage signal Vofs to the offset capacitor Cofs, and the offset capacitor Cofs is reset. As a result, the potential difference between both ends of the offset capacitor Cofs is substantially zero.

[0154] Then, in Fig.17 At time t1 during the readout period of each photosensor shown, the reset switch RSW is turned off to release the reset state, and at time t2, the selection signal ASWp is controlled to be H. Thereafter, from time t3 to time t6 when the reset switch RSW is turned on, a potential Vref-ΔVofs obtained by subtracting the offset potential ΔVofs from the reference potential Vref is applied to the offset capacitor Cofs. As a result, the offset potential ΔVofs is applied between the two ends of the offset capacitor Cofs, and a part of the charge accumulated in the capacitor element of the photosensor PD during the exposure period Pex moves to the offset capacitor Cofs. The charge ΔQofs moved at this time is ΔVofs×Cofs (ΔQofs=ΔVofs×Cofs).

[0155] As a result, in Fig.16 as well as Fig.17 In the operation example of the detection device 1 according to the modification of the first embodiment shown in FIG. 1 , the detection value Raw becomes relative to Figure 6 as well as Figure 7 The operation example according to the comparative example shown here is to increase only the value of the offset value ΔRaw expressed by the following equation (12).

[0156] ΔRaw=(ΔQofs / Cfb) / (Vadc / 2 n )={(ΔVofs×Cofs) / Cfb} / (Vadc / 2 n )… (12)

[0158] That is, in the operation example of the detection device 1 according to the modification of the first embodiment, the offset value ΔRaw can be set by adjusting the offset potential ΔVofs or the offset capacitance Cofs.

[0159] Fig.18 1 is a diagram showing the correspondence between the detection value of the AFE circuit and the light intensity received by the optical sensor in the operation example of the detection device according to the modification of the first embodiment. Fig.18 The dotted line shows Figure 8 The correspondence between the detection value of the AFE circuit and the light intensity received by the optical sensor in the operation example of the detection device according to the comparative example of the first embodiment shown in FIG. Fig.18The two-dot chain line shows that in the region where the detection value Raw exceeds the upper limit grayscale Raw_upper_lim, the virtual detection value is actually limited to the maximum grayscale Raw_max of the A / D conversion circuit 43.

[0160] exist Fig.18 In the example of the second operation of the detection device 1 according to the first embodiment, the upper limit of the range of the detection value Raw for obtaining the pulse wave can be made close to the upper limit grayscale Raw_upper_lim, and the range of the detection value Raw for obtaining the pulse wave can be expanded to the upper limit of the detection range of the detection device 1.

[0161] Raw_upper_lim≤Vref / (Vadc / 2 n )+ΔRaw=[Vref+{(ΔVofs×Cofs) / Cfb}] /

[0162] (Vadc / 2 n )…(13)

[0163] Raw_upper_lim×(Vadc / 2 n )≤Vref+ΔRaw×(Vadc / 2 n )

[0164] =Vref+{(ΔVofs×Cofs) / Cfb}…(14)

[0165] Therefore, with Figure 4 In the structure of the embodiment 1 shown in FIG. Fig.13 as well as Fig.14 Similarly, in the second operation example of the detection device 1 according to the first embodiment shown in FIG. 1 , the light intensity ratio in the exposure period Pex is set to Fig.11 as well as Fig.12 The first action example shown is large (for example, increasing the luminous intensity of the light source (first light source 61, second light source 62) or reducing the negative feedback capacitor Cfb), which can increase the AC component of the pulse wave within the detection range (AC (Red), AC (IR), refer to the above formula (1)), and can improve the detection accuracy of the pulse wave waveform.

[0166] exist Fig.18In the example shown, in the region where the light intensity of the photosensor PD during the exposure period Pex is less than the predetermined value S, the detection value Raw becomes nonlinear with respect to the change in the output voltage signal Vout, similarly to the second operation example of the detection device 1 according to the first embodiment, and as the light intensity of the photosensor PD during the exposure period Pex becomes less than the predetermined value S, the detection value Raw is limited to the maximum Raw grayscale Raw_max of the A / D conversion circuit 43. In other words, in the region where the output voltage signal Vout of the detection signal amplifier circuit 42 exceeds the predetermined value, similarly to the second operation example of the detection device 1 according to the first embodiment, the detection value Raw becomes nonlinear with respect to the change in the output voltage signal Vout, and as the light intensity of the photosensor PD during the exposure period Pex becomes less than the predetermined value S, the detection value Raw is limited to the maximum grayscale Raw_max of the A / D conversion circuit 43. That is, in the detection device 1 involved in the variation example of implementation mode 1, similarly to the second action example of the detection device 1 involved in implementation mode 1, when the light sources (first light source 61, second light source 62) are extinguished, the detection value Raw is limited to the maximum grayscale Raw_max (detection maximum value) of the A / D conversion circuit (output circuit) 43.

[0167] The region where the detection value Raw exceeds the upper grayscale Raw_upper_lim and becomes nonlinear is a region outside the detection range of the detection device 1. Here, assuming that the detection range of the detection device 1 is infinite, the detection value Raw becomes linear in the entire region of the output voltage signal Vout. Fig.18 The double-dashed line shows a virtual detection value when the detection range of the detection device 1 is assumed to be infinite in the region where the detection value Raw exceeds the upper grayscale Raw_upper_lim. As described above, the detection value Raw is actually limited to the maximum grayscale Raw_max of the A / D conversion circuit 43.

[0168] To calculate the blood oxygen saturation (SpO 2 ) of the pulse wave (DC(Red), DC(IR), refer to the above formula (1)), it is necessary to set a virtual reference value Virtual_Base_Raw instead of the reference value Base_Raw. Hereinafter, in the operation example of the detection device 1 involved in the modification of the first embodiment, the method of setting the virtual reference value Virtual_Base_Raw is described.

[0169] (Virtual Reference Value Setting Method 1 According to Modification Example of Embodiment 1)

[0170] like Fig.18As shown, the virtual reference value Virtual_Base_Raw can be calculated as follows: when the photosensor PD is not exposed in the exposure period Pex, the offset value ΔRaw (=(ΔQofs / Cfb) / (Vadc / 2 n )). In other words, the virtual reference value Virtual_Base_Raw can be calculated as follows: in the state where the light sensor PD is not exposed during the exposure period Pex, the offset value ΔRaw is added to the reference value Base_Raw when the offset potential ΔVofs applied between the two ends of the offset capacitor Cofs is substantially zero in the operation example of the detection device 1 involved in the modified example of the first embodiment. The virtual reference value Virtual_Base_Raw in this case is represented by the following formula (15).

[0171] Virtual_Base_Raw=Base_Raw+ΔRaw=[Vref+{(ΔVofs×Cofs) / Cfb}] / (Vadc / 2 n )…(15)

[0172] (Virtual Reference Value Setting Method 2 According to Modification Example of Embodiment 1)

[0173] When the deviation of each photosensor PD is taken into account, the reference value Base_Raw in the operation example of the comparative example of the first embodiment may be set to a value obtained for each photosensor PD, for example, when the photosensor PD is not exposed during the exposure period Pex. In other words, when the deviation of each photosensor PD is taken into account, the reference value Base_Raw when the bias potential ΔVofs applied between the two ends of the bias capacitor Cofs is substantially zero in the operation example of the detection device 1 according to the modified example of the first embodiment may be set to a value obtained for each photosensor PD, for example, when the photosensor PD is not exposed during the exposure period Pex. When the reference value of the photosensor PD of the m column and n row is set to Base_Raw(m, n), the virtual reference value Virtual_Base_Raw(m, n) of each photosensor PD of the m column and n row is expressed by the following formula (16).

[0174] Virtual_Base_Raw(m,n)=Base_Raw(m,n)+ΔRaw=Base_Raw(m,n)+{(ΔVofs×Cofs) / Cfb}] / (Vadc / 2 n )…(16)

[0175] (Virtual Reference Value Setting Method 3 According to Modification Example of Embodiment 1)

[0176] When considering the deviation of the offset potential ΔVofs, the offset capacitance Cofs, and the negative feedback capacitance Cfb of the detection signal amplifier circuit 42, for example, when the detection device 1 is shipped, the value Fig.18 Multiple points within the detection range (Raw_lower_lim≤Raw≤Raw_upper_lim) shown in Fig.18 In the example shown, the detection values ​​Raw of 4 points (in the example shown) can be set by, for example, using a linear approximation (straight line approximation) using the least squares method, a virtual reference value Virtual_Base_Raw (m, n) of each photosensor PD. The method of calculating the virtual reference value Virtual_Base_Raw (m, n) of each photosensor PD is not limited to linear approximation.

[0177] In the modification of the first embodiment, the signal processing circuit 44 calculates the virtual reference value Virtual_Base_Raw using any one of the virtual reference value setting method 1 according to the modification of the first embodiment, the virtual reference value setting method 2 according to the modification of the first embodiment, and the virtual reference value setting method 3 according to the modification of the first embodiment. By storing the virtual reference value Virtual_Base_Raw thus set in advance in the storage circuit 46, the signal processing circuit 44 can calculate the blood oxygen saturation (SpO 2 ) of the pulse wave (DC(Red), DC(IR), refer to the above formula (1)). Thus, the blood oxygen saturation (SpO2) using the first pulse wave obtained by the first light (red light) and the second pulse wave obtained by the second light (infrared light) can be improved. 2 ) calculation accuracy.

[0178] (Implementation Method 2)

[0179] Fig.19 1 is a circuit diagram showing a detection device according to the second embodiment. Fig. 20 : is a circuit diagram showing a configuration example of an AFE circuit according to the second embodiment.

[0180] exist Fig.19 as well as Fig. 20 In the configuration according to the second embodiment shown, the sensor power supply potential Vorg is applied to the anode of each photosensor PD from the power supply circuit 123. The cathode of each photosensor PD is connected to the AFE circuit 48 via the signal line selection circuit 16 in a time-division manner.

[0181] In the above structure, the structure of the light sensor PD is the same as Figure 5 The structure of the embodiment 1 shown is different. Specifically, Figure 5 The anode electrode (lower electrode) 222 shown corresponds to the cathode electrode (lower electrode) in the structure according to Embodiment 2. Figure 5 The electron transport layer (lower buffer layer) 223 shown corresponds to the hole transport layer (lower buffer layer) in the structure according to Embodiment 2. Figure 5 The cathode electrode (upper electrode) 226 shown corresponds to the anode electrode (upper electrode) in the structure according to the second embodiment.

[0182] When light irradiates the photosensor PD, a current corresponding to the intensity of the light irradiating the photosensor PD flows through the photosensor PD, and charges are accumulated in the capacitor element of the photosensor PD. When selected by the gate line driving circuit 15 and the signal line selection circuit 16, a current corresponding to the charges accumulated in the capacitor element of the photosensor PD flows to the AFE circuit 48 via the signal line SGL.

[0183] Fig.21 : is a diagram showing the correspondence between the detection value of the AFE circuit and the light intensity received by the optical sensor in the operation example of the detection device according to the comparative example of the second embodiment. Fig.21 , the vertical axis represents the detection value Raw [digit] of the digital value, and the horizontal axis represents the intensity of light received by the light sensor PD during the exposure period Pex (received light intensity). The operation example of the detection device involved in the comparative example of embodiment 2 is the same as the operation example of the detection device involved in the comparative example of embodiment 1, so the detailed description is omitted here.

[0184] exist Fig.19 as well as Fig. 20 In the structure involved in the embodiment 2 shown in FIG. Fig.21 As shown in FIG. 1 , the smaller the light intensity during the exposure period Pex is, the smaller the detection value Raw is. That is, the detection value Raw is a value that takes the detection value of the light sensor PD in the unexposed state as the minimum value and increases according to the light intensity during the exposure period Pex. In other words, the detection value Raw is a value that takes the reference value Base_Raw as the minimum value and increases according to the light intensity during the exposure period Pex. In the operation example involved in the comparative example of the second embodiment, the grayscale number of the A / D conversion circuit 43 is set to 2. n (resolution n bits), the reference value Base_Raw is approximately Vref / (Vadc / 2 n )(Base_Raw≈Vref / (Vadc / 2 n )). The detection value Raw in the operation example of the detection device according to the comparative example of the second embodiment is expressed by the following equation (17).

[0185] Raw=Vout / (Vadc / 2 n )=(Vref+Qphoto / Cfb) / (Vadc / 2 n )…(17)

[0186] In addition, when the number of grayscales that can be output from the A / D conversion circuit 43 is set to 2 n When the minimum grayscale Raw_min is "0", the maximum grayscale Raw_max is "2 n -1". When the resolution of the A / D conversion circuit 43 is 12 bits (n=12), the minimum grayscale Raw_min is "0" and the maximum grayscale Raw_max is "4095".

[0187] exist Fig.21 In the example shown, the output range of the A / D conversion circuit 43 is roughly set to Vadc / (Vadc / 2 n ). At this time, the range in which the output value of the A / D conversion circuit 43, i.e., the detection value Raw, changes linearly with respect to the output voltage signal Vout of the detection signal amplifier circuit 42 is limited to the range from the lower grayscale Raw_lower_lim to the upper grayscale Raw_upper_lim. Therefore, in order to maintain the detection accuracy of the detection value Raw, as in the first embodiment, it is necessary to perform detection within the detection range from the lower grayscale Raw_lower_lim to the upper grayscale Raw_upper_lim (Raw_lower_lim≤Raw≤Raw_upper_lim).

[0188] Fig. 22 This is a timing waveform diagram showing an operation example of the detection device involved in the second embodiment. Fig.23 yes Fig. 22 The timing waveform diagram shown is an enlarged view of the readout period of each photosensor.

[0189] exist Fig. 22 as well as Fig.23 In the operation example of the detection device 1 according to the second embodiment shown in FIG. 1 , the reset switch RSW is controlled to be turned on and placed in the reset state even during the period including the exposure period Pex before the time t1. Fig. 22 as well as Fig.23 In the example of operation of the detection device 1 according to the second embodiment shown in FIG. Fig.23At time t1 during the readout period of each photosensor shown, the reset switch RSW is controlled to be turned off to release the reset state, and then at time t2, the selection signal ASWp is controlled to be H, and then at time t3, the offset switch ofsSW is controlled to be turned on, and at time t4 after the offset period Tofs has passed, the offset switch ofsSW is controlled to be turned off. As a result, during the offset period Tofs from time t2 to time t4, the offset current Iofs flows into the negative feedback capacitor Cfb of the detection signal amplifier circuit 42, and the amount of charge accumulated in the negative feedback capacitor Cfb of the detection signal amplifier circuit 42 decreases. The reduced charge ΔQofs at this time is set to Iofs×Tofs (ΔQofs=Iofs×Tofs). As a result, Fig. 22 as well as Fig.23 The detection value Raw in the illustrated operation example is expressed by the following equation (18).

[0190] Raw=Vout / (Vadc / 2 n )={Vref+(Qphoto-ΔQofs) / Cfb} / (Vadc / 2 n )… (18)

[0192] As a result, in Fig. 22 as well as Fig.23 In the operation example of the detection device 1 according to the second embodiment shown, the detection value Raw becomes a value smaller than the operation example according to the comparative example of the second embodiment by the offset value ΔRaw expressed by the following equation (19).

[0193] ΔRaw=(ΔQofs / Cfb) / (Vadc / 2 n )={(Iofs×Tofs) / Cfb} / (Vadc / 2 n )… (19)

[0195] That is, in the operation example of the detection device 1 according to the second embodiment, the offset value ΔRaw can be set by adjusting the offset current Iofs or the offset period Tofs.

[0196] Fig.24 This is a first diagram showing the correspondence between the detection value of the AFE circuit and the light receiving intensity of the photosensor in the operation example of the detection device according to the second embodiment. Fig.25 2 is a second diagram showing the correspondence between the detection value of the AFE circuit and the light intensity received by the optical sensor in the operation example of the detection device according to the second embodiment. Fig.24 as well as Fig.25 The dotted line shows Fig.21The correspondence relationship between the detection value of the AFE circuit and the light receiving intensity of the photosensor in the operation example of the detection device according to the comparative example of the second embodiment is shown.

[0197] also, Fig.24 as well as Fig.25 The two-dot chain line shows that in the region where the detection value Raw is lower than the lower limit grayscale Raw_lower_lim, a virtual detection value is actually limited to the minimum grayscale Raw_min of the A / D conversion circuit 43 .

[0198] In the operation example of the detection device 1 according to the second embodiment, Fig.24 As shown in FIG. 1 , an example in which the offset value ΔRaw is increased compared to the operation example of the detection device involved in the comparative example of embodiment 2 shown by the dotted line is shown. Specifically, the offset value ΔRaw is set in a manner that satisfies the following equation (20) or equation (21). Thus, Fig.25 As shown, the lower limit of the range of the detection value Raw for acquiring the pulse wave can be brought close to the upper grayscale Raw_lower_lim, and the range of the detection value Raw for acquiring the pulse wave can be expanded to the lower limit of the detection range of the detection device 1 .

[0199] Raw_lower_lim≥Vref / (Vadc / 2 n )-ΔRaw=[Vref-{(Iofs×Tofs) / Cfb}] /

[0200] (Vadc / 2 n )…(20)

[0201] Raw_lower_lim×(Vadc / 2 n )≥Vref-ΔRaw×(Vadc / 2 n )=Vref-{(Iofs×Tofs)

[0202] / Cfb}…(21)

[0203] Therefore, by increasing the light intensity during the exposure period Pex (for example, increasing the luminous intensity of the light source (first light source 61, second light source 62) or reducing the negative feedback capacitor Cfb), the AC component of the pulse wave within the detection range (AC (Red), AC (IR), refer to the above formula (1)) can be increased, thereby improving the detection accuracy of the pulse wave waveform.

[0204] exist Fig.24 as well as Fig.25In the example of operation of the detection device 1 according to the second embodiment shown, in the region where the light intensity of the photosensor PD during the exposure period Pex is less than the predetermined value S, the variation of the detection value Raw with respect to the output voltage signal Vout becomes nonlinear, and as the light intensity of the photosensor PD during the exposure period Pex becomes less than the predetermined value S, the detection value Raw is limited to the minimum grayscale Raw_min of the A / D conversion circuit 43. In other words, in the region where the output voltage signal Vout of the detection signal amplifier circuit 42 is less than the predetermined value, the variation of the detection value Raw with respect to the output voltage signal Vout becomes nonlinear, and as the light intensity of the photosensor PD during the exposure period Pex becomes less than the predetermined value S, the detection value Raw is limited to the minimum grayscale Raw_min of the A / D conversion circuit 43. That is, in the example of operation of the detection device 1 according to the second embodiment, in the state where the light sources (the first light source 61 and the second light source 62) are turned off, the detection value Raw is limited to the minimum grayscale Raw_min (detection minimum value) of the A / D conversion circuit (output circuit) 43.

[0205] The region where the detection value Raw exceeds the lower grayscale limit Raw_lower_lim and becomes nonlinear is a region outside the detection range of the detection device 1. Here, assuming that the detection range of the detection device 1 is infinite, the detection value Raw becomes linear in the entire region of the output voltage signal Vout. Fig.24 as well as Fig.25 The double-dashed line shows a virtual detection value when the detection range of the detection device 1 is assumed to be infinite in the region where the detection value Raw is lower than the lower limit grayscale Raw_lower_lim. As described above, the detection value Raw is actually limited to the minimum grayscale Raw_min of the A / D conversion circuit 43.

[0206] To calculate the blood oxygen saturation (SpO 2 ) of the pulse wave (DC(Red), DC(IR), refer to the above formula (1)), it is necessary to set a virtual reference value Virtual_Base_Raw instead of the reference value Base_Raw. The following describes a method of setting the virtual reference value Virtual_Base_Raw in the operation example of the detection device 1 involved in the second embodiment.

[0207] (Virtual reference value setting method 1 according to embodiment 2)

[0208] like Fig.24As shown in FIG. 1 , the virtual reference value Virtual_Base_Raw can be calculated as follows: in the state where the light sensor PD is not exposed during the exposure period Pex, the offset value ΔRaw (= (ΔQofs / Cfb) / (Vadc / 2 n )). In other words, the virtual reference value Virtual_Base_Raw can be calculated by subtracting the offset value ΔRaw from the reference value Base_Raw when the offset period Tofs is substantially zero in the operation example of the detection device 1 in Embodiment 2 when the light sensor PD is not exposed during the exposure period Pex. The virtual reference value Virtual_Base_Raw in this case is represented by the following formula (22).

[0209] Virtual_Base_Raw=Base_Raw-ΔRaw=[Vref-{(Iofs×Tofs) / Cfb}] / (Vadc / 2 n )…(twenty two)

[0210] (Virtual reference value setting method 2 according to embodiment 2)

[0211] When the deviation of each photosensor PD is taken into account, the reference value Base_Raw in the operation example of the comparative example of the second embodiment may be set to a value obtained for each photosensor PD, for example, when the detection device 1 is shipped from the factory, when the photosensor PD is not exposed during the exposure period Pex. In other words, when the deviation of each photosensor PD is taken into account, the reference value Base_Raw in the operation example of the detection device 1 involved in the second embodiment may be set to a value obtained for each photosensor PD, for example, when the detection device 1 is shipped from the factory, when the photosensor PD is not exposed during the exposure period Pex. When the reference value of the photosensor PD of the m column and n row is set to Base_Raw(m, n), the virtual reference value Virtual_Base_Raw(m, n) of each photosensor PD of the m column and n row is expressed by the following formula (23).

[0212] Virtual_Base_Raw(m,n)=Base_Raw(m,n)-ΔRaw=Base_Raw(m,n)-{(Iofs×Tofs) / Cfb}] / (Vadc / 2 n )…(twenty three)

[0213] (Virtual reference value setting method 3 according to embodiment 2)

[0214] When considering the deviation of the offset current Iofs, the offset period Tofs, and the negative feedback capacitance Cfb of the detection signal amplifier circuit 42, for example, when the detection device 1 is shipped, the value of Fig.24 Multiple points within the detection range (Raw_lower_lim≤Raw≤Raw_upper_lim) shown in Fig.24 In the example shown, the detection values ​​Raw of 4 points (in the example shown) can be set by, for example, using a linear approximation (straight line approximation) using the least squares method, a virtual reference value Virtual_Base_Raw (m, n) of each photosensor PD. The method of calculating the virtual reference value Virtual_Base_Raw (m, n) of each photosensor PD is not limited to linear approximation.

[0215] In the second embodiment, the signal processing circuit 44 calculates the virtual reference value Virtual_Base_Raw using any one of the virtual reference value setting method 1 according to the second embodiment, the virtual reference value setting method 2 according to the second embodiment, and the virtual reference value setting method 3 according to the second embodiment. By storing the virtual reference value Virtual_Base_Raw thus set in advance in the storage circuit 46, it is possible to calculate the blood oxygen saturation (SpO 2 ) of the pulse wave (DC(Red), DC(IR), refer to the above formula (1)). Thus, the blood oxygen saturation (SpO2) using the first pulse wave obtained by the first light (red light) and the second pulse wave obtained by the second light (infrared light) can be improved. 2 ) calculation accuracy.

[0216] (Variation Example)

[0217] Fig.26 1 is a circuit diagram showing a configuration example of an AFE circuit according to a modification of the second embodiment. Fig.26 As shown, in this embodiment, the offset voltage signal Vofs is input to the inverting input terminal (−) of the differential amplifier circuit CA of the detection signal amplifier circuit 42 constituting the AFE circuit 48 a via the offset capacitor Cofs.

[0218] Fig. 27 It is a timing waveform diagram showing an operation example of the detection device involved in the modification example of the second embodiment. Fig.28 yes Fig. 27 The timing waveform diagram shown is an enlarged view of the readout period of each photosensor.

[0219] exist Fig. 27 as well as Fig.28In the operation example of the detection device 1 according to the variation of the second embodiment shown, during the exposure period Pex before time t1, the reference potential Vref is applied as the offset voltage signal Vofs to the offset capacitor Cofs, and the offset capacitor Cofs is reset. As a result, the potential difference between the two ends of the offset capacitor Cofs is substantially zero.

[0220] Then, in Fig.28 At time t1 of the readout period of each photosensor shown, the reset switch RSW is turned off to release the reset state, and at time t2, the selection signal ASWp is controlled to be H. Thereafter, from time t3 to time t6 when the reset switch RSW is turned on, a potential Vref+ΔVofs obtained by adding an offset potential ΔVofs to a reference potential Vref is applied to the offset capacitor Cofs. As a result, an offset potential ΔVofs is applied between both ends of the offset capacitor Cofs, and a portion of the charge accumulated in the capacitor element of the photosensor PD during the exposure period Pex moves to the offset capacitor Cofs. The charge ΔQofs moved at this time is ΔVofs×Cofs (ΔQofs=ΔVofs×Cofs).

[0221] As a result, in Fig. 27 as well as Fig.28 In the operation example of the detection device 1 according to the modification of the second embodiment shown, the detection value Raw becomes a value smaller than the operation example according to the comparative example of the second embodiment by the offset value ΔRaw shown in the following equation (24).

[0222] ΔRaw=(ΔQofs / Cfb) / (Vadc / 2 n )={(ΔVofs×Cofs) / Cfb} / (Vadc / 2 n )… (twenty four)

[0224] That is, in the operation example of the detection device 1 according to the modification of the second embodiment, the offset value ΔRaw can be set by adjusting the offset potential ΔVofs or the offset capacitance Cofs.

[0225] Fig.29 : is a diagram showing the correspondence between the detection value of the AFE circuit and the light intensity received by the photosensor in the operation example of the detection device according to the modification of the second embodiment. Fig.29 The dotted line shows Fig.21 The correspondence between the detection value of the AFE circuit and the light intensity received by the optical sensor in the operation example of the detection device according to the comparative example of the second embodiment shown in FIG. Fig.29The two-dot chain line shows that in the region where the detection value Raw is lower than the lower limit grayscale Raw_lower_lim, the virtual detection value is actually limited to the maximum grayscale Raw_max of the A / D conversion circuit 43.

[0226] exist Fig.29 In the example of the operation of the detection device 1 according to the second embodiment, the lower limit of the range of the detection value Raw for obtaining the pulse wave can be made close to the upper limit grayscale Raw_lower_lim, and the range of the detection value Raw for obtaining the pulse wave can be expanded to the lower limit of the detection range of the detection device 1.

[0227] Raw_lower_lim≥Vref / (Vadc / 2 n )-ΔRaw=[Vref-{(ΔVofs×Cofs) / Cfb}] /

[0228] (Vadc / 2 n )…(25)

[0229] Raw_lower_lim×(Vadc / 2 n )≥Vref-ΔRaw×(Vadc / 2 n )

[0230] =Vref-{(ΔVofs×Cofs) / Cfb}…(26)

[0231] Therefore, with Fig.24 Similarly, the operation example of the detection device 1 involved in the embodiment 2 shown can increase the light intensity within the exposure period Pex (for example, increase the luminous intensity of the light source (first light source 61, second light source 62) or reduce the negative feedback capacitor Cfb), thereby increasing the AC component (AC (Red), AC (IR), refer to the above formula (1)) of the pulse wave within the detection range, thereby improving the detection accuracy of the pulse wave waveform.

[0232] exist Fig.29In the example of operation of the detection device 1 according to the variation of the second embodiment shown, in the region where the light intensity of the photosensor PD during the exposure period Pex is less than the predetermined value S, the detection value Raw becomes nonlinear with respect to the change in the output voltage signal Vout, as in the example of operation of the detection device 1 according to the second embodiment, and as the light intensity of the photosensor PD during the exposure period Pex becomes less than the predetermined value S, the detection value Raw is limited to the minimum grayscale Raw_min of the A / D conversion circuit 43. In other words, in the region where the output voltage signal Vout of the detection signal amplifier circuit 42 is lower than the predetermined value, the detection value Raw becomes nonlinear with respect to the change in the output voltage signal Vout, as in the example of operation of the detection device 1 according to the second embodiment, and as the light intensity of the photosensor PD during the exposure period Pex becomes less than the predetermined value S, the detection value Raw is limited to the minimum grayscale Raw_min of the A / D conversion circuit 43. That is, in the detection device 1 involved in the variant example of embodiment 2, similarly to the operation example of the detection device 1 involved in embodiment 2, when the light sources (first light source 61, second light source 62) are extinguished, the detection value Raw is limited to the minimum grayscale Raw_min (detection minimum value) of the A / D conversion circuit (output circuit) 43.

[0233] The region where the detection value Raw exceeds the lower grayscale limit Raw_lower_lim and becomes nonlinear is a region outside the detection range of the detection device 1. Here, assuming that the detection range of the detection device 1 is infinite, the detection value Raw becomes linear in the entire region of the output voltage signal Vout. Fig.29 The double-dashed line shows a virtual detection value when the detection range of the detection device 1 is assumed to be infinite in the region where the detection value Raw is lower than the lower limit grayscale Raw_lower_lim. As described above, the detection value Raw is actually limited to the minimum grayscale Raw_min of the A / D conversion circuit 43.

[0234] To calculate the blood oxygen saturation (SpO 2 ) of the pulse wave (DC(Red), DC(IR), refer to the above formula (1)), it is necessary to set a virtual reference value Virtual_Base_Raw instead of the reference value Base_Raw. Hereinafter, in the operation example of the detection device 1 involved in the modification of the second embodiment, the method of setting the virtual reference value Virtual_Base_Raw is described.

[0235] (Virtual Reference Value Setting Method 1 According to Modification Example of Embodiment 2)

[0236] like Fig.29As shown, the virtual reference value Virtual_Base_Raw can be calculated as follows: when the light sensor PD is not exposed during the exposure period Pex, the offset value ΔRaw (= (ΔQofs / Cfb) / (Vadc / 2n)) is subtracted from the reference value Base_Raw in the action example of the comparative example of the second embodiment. In other words, the virtual reference value Virtual_Base_Raw can be calculated as follows: when the light sensor PD is not exposed during the exposure period Pex, the offset value ΔRaw is subtracted from the reference value Base_Raw in the action example involved in the modified example of the second embodiment, in which the offset potential ΔVofs applied between the two ends of the offset capacitor Cofs is substantially zero. The virtual reference value Virtual_Base_Raw in this case is represented by the following formula (27).

[0237] Virtual_Base_Raw=Base_Raw-ΔRaw=[Vref-{(ΔVofs×Cofs) / Cfb}] / (Vadc / 2 n )…(27)

[0238] (Virtual Reference Value Setting Method 2 According to Modification Example of Implementation 2)

[0239] When the deviation of each photosensor PD is taken into account, the reference value Base_Raw in the operation example of the comparative example of the second embodiment may be set to a value obtained for each sensor PD, for example, when the detection device 1 is shipped from the factory, when the photosensor PD is not exposed during the exposure period Pex. In other words, when the deviation of each photosensor PD is taken into account, the reference value Base_Raw when the offset potential ΔVofs applied between the two ends of the offset capacitor Cofs is substantially zero in the operation example according to the modified example of the second embodiment may be set to a value obtained for each photosensor PD, for example, when the detection device 1 is shipped from the factory, when the photosensor PD is not exposed during the exposure period Pex. When the reference value of the photosensor PD of the m column and n row is set to Base_Raw(m, n), the virtual reference value Virtual_Base_Raw(m, n) of each photosensor PD of the m column and n row is expressed by the following equation (28).

[0240] Virtual_Base_Raw(m,n)=Base_Raw(m,n)-ΔRaw=Base_Raw(m,n)-{(ΔVofs×Cofs) / Cfb}] / (Vadc / 2 n )…(28)

[0241] (Virtual reference value setting method 3 according to variation of embodiment 2)

[0242] When considering the deviation of the offset potential ΔVofs, the offset capacitance Cofs, and the negative feedback capacitance Cfb of the detection signal amplifier circuit 42, for example, when the detection device 1 is shipped, the value Fig.29 Multiple points within the detection range (Raw_lower_lim≤Raw≤Raw_upper_lim) shown in Fig.29 In the example shown, the detection values ​​Raw of 4 points (in the example shown) can be set by, for example, using a linear approximation (straight line approximation) using the least squares method, a virtual reference value Virtual_Base_Raw (m, n) of each photosensor PD. The method of calculating the virtual reference value Virtual_Base_Raw (m, n) of each photosensor PD is not limited to linear approximation.

[0243] In the variation of the second embodiment, the signal processing circuit 44 calculates the virtual reference value Virtual_Base_Raw using any one of the virtual reference value setting method 1 according to the variation of the second embodiment, the virtual reference value setting method 2 according to the variation of the second embodiment, and the virtual reference value setting method 3 according to the variation of the second embodiment. By storing the virtual reference value Virtual_Base_Raw thus set in advance in the storage circuit 46, the signal processing circuit 44 can calculate the blood oxygen saturation (SpO2) in the same manner as in the second embodiment. 2 )'s DC component (DC(Red), DC(IR), refer to the above formula (1)). This can improve the calculation accuracy of the blood oxygen saturation (SpO2) using the first pulse wave obtained using the first light (red light) and the second pulse wave obtained using the second light (infrared light).

[0244] In the above embodiment, a structure in which a plurality of optical sensors PD are arranged in a matrix in the detection area AA of the sensor region 10 is described. However, the structure of the present disclosure is not limited thereto, and for example, it can also be applied to a structure having one or more optical sensors PD.

[0245] The preferred embodiments of the present invention have been described above, but the present invention is not limited to such embodiments. The contents disclosed in the embodiments are only examples, and various changes can be made without departing from the gist of the present invention. Appropriate changes made without departing from the gist of the present invention certainly also belong to the technical scope of the present invention. Without departing from the gist of the above-mentioned embodiments and the gist of the various modifications, at least one of the various omissions, substitutions and changes of the constituent elements can be made.

[0246] Description of Reference Numerals

[0247] 1: detection device; 10: sensor area; 11: detection control circuit; 15: gate line driving circuit; 16: signal line selection circuit; 21: sensor substrate; 22: sensor structure; 23: protective film; 40: detection circuit; 42: detection signal amplification circuit; 43: A / D conversion circuit; 44: signal processing circuit; 46: storage circuit; 47: detection timing control circuit; 48, 48a: AFE circuit; 61: first light source (light source); 62: second light source (light source); 122: control circuit; 123: power supply circuit; 126: output circuit; 200: host; 221: TFT layer; 222: anode electrode (lower electrode); 223: electron transport layer (lower buffer layer); 224: active layer; 225: hole transport layer (upper buffer layer); 226: cathode electrode (upper electrode); AA: detection area; CA: differential amplifier circuit; Cfb: negative feedback capacitor; Cofs: offset capacitor; GA: peripheral area; GCL: gate line; Iofs: offset current; ofsSW: offset switch; PD: light sensor; Pdet, Pdet1, Pdet2: readout period; Pex, Pex1, Pex2: exposure period; Raw: detection value (AFE circuit); RSW: reset switch; SGL: signal line; Tofs: offset period; Vadc: power supply voltage (A / D conversion circuit); Vorg: sensor power supply potential; Vout: output voltage signal (detection signal amplifier circuit); Vref: reference potential; ΔVofs: offset potential.

Claims

1. A detection device, characterized in that: have: Light sensor; a light source for irradiating light toward the light sensor; a detection signal amplifying circuit that converts a change in current supplied from the optical sensor into a voltage; and The A / D conversion circuit converts the output voltage signal after voltage conversion into a digital detection value. The A / D conversion circuit limits the detection value to a maximum grayscale or a minimum grayscale of a digital value when the light source is off.

2. The detection device according to claim 1, wherein: The light sensor is an organic photodiode having: Active layer; an upper electrode disposed with an upper buffer layer interposed between the upper electrode and the active layer; and The lower electrode is provided with a lower buffer layer interposed between the lower electrode and the active layer.

3. The detection device according to claim 1 or 2, wherein: The detection device comprises: During exposure, light is irradiated from the light source toward the light sensor; and During the readout period, the detection value is acquired based on the charge accumulated in the photosensor during the exposure period. The detection signal amplifying circuit comprises: a differential amplifier circuit, applying a reference potential to a non-inverting input terminal and connecting the optical sensor to an inverting input terminal; and The negative feedback capacitor is connected between the inverting input terminal and the output terminal of the differential amplifier circuit.

4. The detection device according to claim 3, wherein: The inverting input terminal of the differential amplifier circuit is connected to the anode of the photosensor.

5. The detection device according to claim 4, wherein: The differential amplifier circuit is provided with an offset period during the read period for causing a predetermined offset current to flow from the non-inverting input terminal.

6. The detection device according to claim 5, wherein: The detection device further includes a signal processing circuit that acquires a pulse wave based on the detection value. The signal processing circuit calculates a DC component of the pulse wave based on a preset virtual reference value.

7. The detection device according to claim 6, wherein: The signal processing circuit sets the virtual reference value by adding an offset value determined by the offset period and the offset current to a reference value acquired during a readout period in which the offset period is substantially zero when the photosensor is not exposed during the exposure period.

8. The detection device according to claim 6, wherein: The signal processing circuit acquires detection values ​​at a plurality of points within a detection range capable of acquiring detection values ​​that change linearly with respect to a change in the output voltage signal, and sets the virtual reference value based on the detection values ​​at the plurality of points.

9. The detection device according to claim 4, wherein: The differential amplifier circuit inputs an offset voltage signal to the non-inverting input terminal via an offset capacitor. An offset potential is applied between both ends of the offset capacitor during a predetermined period of the readout period.

10. The detection device according to claim 9, wherein: The detection device further includes a signal processing circuit that acquires a pulse wave based on the detection value. The signal processing circuit calculates a DC component of the pulse wave based on a preset virtual reference value.

11. The detection device according to claim 10, wherein: The signal processing circuit sets the virtual reference value by adding an offset value determined by the offset capacitance and the offset potential to a reference value acquired in a readout period in which the offset potential is substantially zero when the photosensor is not exposed in the exposure period.

12. The detection device according to claim 10, wherein: The signal processing circuit acquires detection values ​​at a plurality of points within a detection range capable of acquiring detection values ​​that change linearly with respect to a change in the output voltage signal, and sets the virtual reference value based on the detection values ​​at the plurality of points.

13. The detection device according to claim 3, wherein: The inverting input terminal of the differential amplifier circuit is connected to a cathode of the photosensor.

14. The detection device according to claim 13, wherein: The differential amplifier circuit is provided with an offset period during the read period for flowing a predetermined offset current into the non-inverting input terminal.

15. The detection device according to claim 14, wherein: The detection device further includes a signal processing circuit that acquires a pulse wave based on the detection value. The signal processing circuit calculates a DC component of the pulse wave based on a preset virtual reference value.

16. The detection device according to claim 15, wherein: The signal processing circuit sets the virtual reference value by subtracting an offset value determined by the offset period and the offset current from a reference value acquired in a readout period in which the offset period is substantially zero when the photosensor is not exposed in the exposure period.

17. The detection device according to claim 15, wherein: The signal processing circuit acquires detection values ​​at a plurality of points within a detection range capable of acquiring detection values ​​that change linearly with respect to a change in the output voltage signal, and sets the virtual reference value based on the detection values ​​at the plurality of points.

18. The detection device according to claim 13, wherein: The differential amplifier circuit inputs an offset voltage signal to the non-inverting input terminal via an offset capacitor. An offset potential is applied between both ends of the offset capacitor during a predetermined period of the readout period.

19. The detection device according to claim 18, wherein: The detection device further includes a signal processing circuit that acquires a pulse wave based on the detection value. The signal processing circuit calculates a DC component of the pulse wave based on a preset virtual reference value.

20. The detection device according to claim 19, wherein: The signal processing circuit sets the virtual reference value by subtracting an offset value determined by the offset capacitance and the offset potential from a reference value acquired in a readout period in which the offset potential is substantially zero when the photosensor is not exposed in the exposure period.

21. The detection device according to claim 19, wherein: The signal processing circuit acquires detection values ​​at a plurality of points within a detection range capable of acquiring detection values ​​that change linearly with respect to a change in the output voltage signal, and sets the virtual reference value based on the detection values ​​at the plurality of points.

22. The detection device according to any one of claims 4 to 21, wherein: The detection device includes a plurality of the optical sensors. The plurality of photosensors are sequentially connected to the detection signal amplifying circuit during the readout period.

23. The detection device according to claim 22, wherein: The detection device includes a plurality of the detection signal amplifying circuits and the A / D conversion circuits. During the readout period, the first photosensor connected to the first detection signal amplifying circuit and the second photosensor connected to the second detection signal amplifying circuit are simultaneously selected.

24. The detection device according to claim 23, wherein: The detection device comprises: A sensor area, in which a plurality of the optical sensors are arranged in a matrix shape within the detection area; A plurality of gate lines are connected to the light sensors arranged side by side in the row direction and arranged in the column direction; as well as The gate line driving circuit sequentially selects the plurality of gate lines during the readout period.

25. A detection device, characterized in that: have: Light sensor; a light source for irradiating light toward the light sensor; a detection signal amplifying circuit that converts a change in current supplied from the optical sensor into a voltage; and The output circuit converts the output voltage signal after voltage conversion into a detection value. The output circuit limits the detection value to a detection maximum value or a detection minimum value when the light source is off.

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