Detection device

Abstract

This detection device comprises: a light sensor; a light source that projects light to the light sensor; a detection signal amplifying circuit that coverts, to voltage, the fluctuations in the current supplied from the light sensor; and an A / D conversion circuit that converts the voltage-converted output voltage signal to a digital-value detection value (Raw). In a state where the light source is off, the A / D conversion circuit operates so that the detection value (Raw) is limited to the maximum gradient (Raw_max) or the minimum gradient (Raw_min) of the digital value.

Description

Detection device

[0001] The present invention relates to a detection device.

[0002] The oxygen saturation in the blood (hereinafter referred to as SpO2) is measured based on transcutaneous data acquired by irradiating light into the body through the skin and detecting light transmitted through or reflected from the arteries. ２ There are known detection devices that measure blood oxygen saturation (SpO ２ ) is the ratio of the amount of oxygen actually bound to hemoglobin to the total amount of oxygen that would be expected if all hemoglobin in the blood were oxygen-bound. ２ When acquiring the pulse wave, for example, a pulse wave acquired using red light and a pulse wave acquired using infrared light are used (for example, see Patent Document 1).

[0003] JP 2019-180861 A

[0004] In a configuration in which a pulse wave is acquired using an optical sensor such as an organic photodiode (OPD), fluctuations in current supplied from the optical sensor are converted into voltage fluctuations and amplified, and the output voltage signal after voltage conversion is converted into a digital value to acquire the pulse wave. In such a configuration, the fluctuation component of the pulse wave is small compared to the full-scale range of the digital value, and sufficient accuracy may not be achieved.

[0005] An object of the present disclosure is to provide a detection device that can improve the accuracy of detecting a pulse waveform.

[0006] A detection device according to one aspect of the present disclosure includes an optical sensor, a light source that irradiates the optical sensor with light, a detection signal amplifier circuit that converts fluctuations in current supplied from the optical sensor into a voltage, and an A / D conversion circuit that converts the voltage-converted output voltage signal into a digital detection value, wherein the A / D conversion circuit limits the detection value to the maximum or minimum gradation of the digital value when the light source is turned off.

[0007] A detection device according to one aspect of the present disclosure includes an optical sensor, a light source that irradiates the optical sensor with light, a detection signal amplification circuit that converts fluctuations in current supplied from the optical sensor into a voltage, and an output circuit that converts the voltage-converted output voltage signal into a detection value, wherein the output circuit limits the detection value to a maximum detection value or a minimum detection value when the light source is turned off.

[0008] FIG. 1 is a plan view showing a detection device according to the first embodiment. FIG. 2 is a block diagram showing an example of the configuration of the detection device according to the first embodiment. FIG. 3 is a circuit diagram showing the detection device according to the first embodiment. FIG. 4 is a circuit diagram showing an example of the configuration of an AFE circuit according to the first embodiment. FIG. 5 is a schematic partial cross-sectional view of an optical sensor according to the first embodiment. FIG. 6 is a timing waveform diagram showing an example of operation of a detection device according to a comparative example of the first embodiment. FIG. 7 is an enlarged view of a readout period for each optical sensor in the timing waveform diagram shown in FIG. 6. FIG. 8 is a view showing a correspondence relationship between a detection value of the AFE circuit and a light intensity received by an optical sensor in an example of operation of a detection device according to a comparative example of the first embodiment. FIG. 9 is a timing waveform diagram showing an example of operation of the detection device according to the first embodiment. FIG. 10 is an enlarged view of a readout period for each optical sensor in the timing waveform diagram shown in FIG. 9. FIG. 11 is a first diagram showing a correspondence relationship between a detection value of the AFE circuit and a light intensity received by an optical sensor in a first example of operation of the detection device according to the first embodiment. FIG. 12 is a second diagram showing the correspondence relationship between the detection value of the AFE circuit and the light intensity of the optical sensor in a first operation example of the detection device according to the first embodiment. FIG. 13 is a first diagram showing the correspondence relationship between the detection value of the AFE circuit and the light intensity of the optical sensor in a second operation example of the detection device according to the first embodiment. FIG. 14 is a second diagram showing the correspondence relationship between the detection value of the AFE circuit and the light intensity of the optical sensor in a second operation example of the detection device according to the first embodiment. FIG. 15 is a circuit diagram showing an example configuration of an AFE circuit according to a modified example of the first embodiment. FIG. 16 is a timing waveform diagram showing an example operation of the detection device according to a modified example of the first embodiment. FIG. 17 is an enlarged view of the readout period for each optical sensor in the timing waveform diagram shown in FIG. 16. FIG. 18 is a diagram showing the correspondence relationship between the detection value of the AFE circuit and the light intensity of the optical sensor in an operation example of the detection device according to the modified example of the first embodiment. FIG. 19 is a circuit diagram showing a detection device according to the second embodiment. FIG. 20 is a circuit diagram showing an example configuration of an AFE circuit according to the second embodiment. Fig. 21 is a diagram showing the correspondence relationship between the detection value of the AFE circuit and the intensity of light received by the optical sensor in an operation example of a detection device according to a comparative example of embodiment 2. Fig. 22 is a timing waveform diagram showing an operation example of the detection device according to embodiment 2. Fig. 23 is an enlarged view of a readout period for each optical sensor in the timing waveform diagram shown in Fig. 22.24 is a first diagram showing the correspondence relationship between the detection value of the AFE circuit and the intensity of light received by the optical sensor in an operation example of the detection device according to embodiment 2. FIG. 25 is a second diagram showing the correspondence relationship between the detection value of the AFE circuit and the intensity of light received by the optical sensor in an operation example of the detection device according to embodiment 2. FIG. 26 is a circuit diagram showing an example configuration of an AFE circuit according to a modified example of embodiment 2. FIG. 27 is a timing waveform diagram showing an operation example of the detection device according to a modified example of embodiment 2. FIG. 28 is an enlarged diagram of the readout period for each optical sensor in the timing waveform diagram shown in FIG. 27. FIG. 29 is a diagram showing the correspondence relationship between the detection value of the AFE circuit and the intensity of light received by the optical sensor in an operation example of the detection device according to the modified example of embodiment 2.

[0009] Modes (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the contents described in the following embodiments. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially identical. Furthermore, the components described below can be combined as appropriate. Furthermore, the disclosure is merely an example, and appropriate modifications that a person skilled in the art can easily conceive while maintaining the gist of the invention are naturally included within the scope of the present invention. Furthermore, for clarity of explanation, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual embodiment. However, these are merely examples and are not intended to limit the interpretation of the present invention. Furthermore, in this specification and each figure, elements similar to those described above with reference to the previous figures may be designated by the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0010] (Embodiment 1) FIG. 1 is a plan view showing a detection device according to embodiment 1. As shown in FIG. 1, the detection device 1 includes a sensor substrate 21, a sensor region 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. FIG. 1 illustrates an example in which 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. However, the arrangement of the first light sources 61 and the second light sources 62 shown in FIG. 1 is merely an example and can be modified as appropriate. For example, a plurality of first light sources 61 and a plurality of second light sources 62 may be provided on each of 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, or the first light sources 61 and the second light sources 62 may be arranged alternately in the second direction Dy. Furthermore, the number of light source substrates on which the first light sources 61 and the second light sources 62 are provided may be one or three or more.

[0011] The detection device 1 is electrically connected to a host 200. The host 200 is, for example, a higher-level control device of an apparatus (not shown) to which the detection device 1 is applied. The host 200 performs a predetermined process for acquiring biological information based on data output from the detection device 1.

[0012] A control board 121 is electrically connected to the sensor substrate 21 via a flexible printed circuit board 71. The flexible printed circuit board 71 is provided with an AFE circuit 48. The control board 121 is provided with a control circuit 122, a power supply circuit 123, and an output circuit 126.

[0013] The control circuit 122 is, for example, a control integrated circuit (IC) that outputs a logic control signal, or may be, for example, a programmable logic device (PLD) such as a field programmable gate array (FPGA).

[0014] The control circuit 122 supplies control signals to the sensor area 10, the gate line driving circuit 15, and the signal line selection circuit 16 to control the detection operation of the sensor area 10. The control circuit 122 also 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 are turned on or off.

[0015] The power supply circuit 123 supplies voltage signals such as a sensor power supply 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 supply circuit 123 also supplies a power supply voltage to the first light source 61 and the second light source 62.

[0016] The output circuit 126 is, for example, a USB controller IC, and controls communication between the control circuit 122 and the host 200 .

[0017] The sensor substrate 21 has a detection area AA and a peripheral area GA. The detection area AA is an area in which a plurality of optical sensors PD of the sensor area 10 are arranged in a matrix. The peripheral area GA is an area between the outer periphery of the detection area AA and the edge of the sensor substrate 21, and is an area in which no optical sensors PD are provided.

[0018] The gate line driving circuit 15 and the signal line selection circuit 16 are provided in the peripheral area GA. Specifically, the gate line driving circuit 15 is provided in a region of the peripheral area GA extending along the second direction Dy. The signal line selection circuit 16 is provided in a region of the peripheral area GA extending along the first direction Dx, and is provided between the sensor area 10 and the AFE circuit 48.

[0019] 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 perpendicular to the first direction Dx. The second direction Dy may intersect with the first direction Dx without being perpendicular to it. The third direction Dz is a direction perpendicular to the first direction Dx and the second direction Dy and is a normal direction of the sensor substrate 21.

[0020] The plurality of first light sources 61 are provided on the first light source substrate 51 and arranged along the second direction Dy. The 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 terminals 124 and 125 provided on the control board 121, respectively.

[0021] The first light sources 61 and the second light sources 62 may be, for example, inorganic light emitting diodes (LEDs) or organic light emitting diodes (OLEDs). The first light sources 61 and the second light sources 62 emit first light and second light of different wavelengths, respectively.

[0022] The first light emitted from the first light source 61 is reflected by the surface of the object to be detected, such as the subject's finger or wrist, and enters the sensor area 10. As a result, the sensor area 10 can detect a fingerprint by detecting the uneven shape of the surface of the finger Fg or the like. The second light emitted from the second light source 62 is reflected by the inside of the finger Fg or the like or passes through the finger Fg or the like and enters the sensor area 10. As a result, the sensor area 10 can detect information about the inside of the subject's finger, wrist, or the like. The information about the biological body is, for example, the subject's pulse wave, pulse rate, blood vessel image, etc. That is, the detection device 1 may be configured as a fingerprint detection device that detects fingerprints, or a vein detection device that detects blood vessel patterns such as veins.

[0023] The first light may have a wavelength of 420 nm or more and 600 nm or less, for example, approximately 500 nm, and the second light may have a wavelength of 780 nm or more and 950 nm or less, for example, approximately 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 a fingerprint based on the first light emitted from the first light source 61. The second light emitted from the second light source 62 is reflected or transmitted and absorbed inside the object to be detected and then enters the sensor area 10. This allows the sensor area 10 to detect biometric data such as a pulse wave and a blood vessel image (blood vessel pattern) as information about the internal living body of the subject's finger, wrist, etc.

[0024] Alternatively, the first light may have a wavelength of 600 nm or more and 700 nm or less, for example, about 660 nm, and the second light may have a wavelength of 780 nm or more and 950 nm or less, 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 region 10 can detect information about the living body, such as pulse waves, pulse rates, and blood vessel images, as well as blood oxygen levels. In this way, the detection device 1 has the first light source 61 and multiple second light sources 62, and can detect various pieces of information about the living body by performing detection based on the first light and detection based on the second light.

[0025] 2 is a block diagram showing an example of the configuration of the detection device according to embodiment 1. As shown in FIG. 2, the detection device 1 further includes a detection control circuit 11 and a detection circuit 40.

[0026] The sensor region 10 has a plurality of optical sensors PD. The optical sensors PD of the sensor region 10 are, for example, organic photodiodes (OPDs), and output electrical signals corresponding to irradiated light to the signal line selection circuit 16. The sensor region 10 also performs detection in accordance with gate drive signals supplied from the gate line drive circuit 15. The optical sensors PD may be, for example, silicon photodiodes (SiPDs).

[0027] The detection control circuit 11 is a circuit that supplies control signals to the gate line drive circuit 15, the signal line selection circuit 16, and the detection circuit 40, respectively, and controls their operations. The detection control circuit 11 also supplies various control signals to the first light source 61 and the second light source 62, and controls the lighting and non-lighting of each of them.

[0028] The gate line driving circuit 15 is a circuit that drives a plurality of gate lines GCL (see FIG. 3) based on various control signals. The gate line driving circuit 15 sequentially or simultaneously selects the plurality of gate lines GCL and supplies gate driving signals to the selected gate lines GCL. In this way, the gate line driving circuit 15 selects a plurality of photosensors PD connected to the gate lines GCL.

[0029] The signal line selection circuit 16 is a switch circuit that sequentially or simultaneously selects a plurality of signal lines SGL (see FIG. 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 a selection signal ASW supplied from the detection control circuit 11. As a result, the signal line selection circuit 16 outputs a detection signal of the photosensor PD to the detection circuit 40.

[0030] The detection circuit 40 includes an AFE circuit 48, a signal processing circuit 44, a memory 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 to operate in synchronization with each other based on a control signal supplied from the detection control circuit 11.

[0031] The AFE circuit 48 generates a detection value of each optical sensor PD based on the detection signal of each optical sensor PD output from the sensor area 10. The AFE circuit 48 is, for example, an analog front-end IC.

[0032] The AFE circuit 48 includes at least a detection signal amplifier circuit 42 and an A / D converter circuit 43 (output circuit). The detection signal amplifier circuit 42 converts fluctuations in current supplied from the optical sensor PD into voltage fluctuations and amplifies the voltage fluctuations. The A / D converter circuit 43 samples the voltage signal output from the detection signal amplifier circuit 42 and converts it into a digital detection value.

[0033] In the present disclosure, the signal processing circuit 44 and the memory circuit 46 are included in the control circuit 122 .

[0034] The signal processing circuit 44 acquires biological data for generating information about the living body based on the detection values ​​of the optical sensors PD output from the AFE circuit 48. In the present disclosure, the information about the living body includes a pulse wave acquired using infrared light or red light.

[0035] The memory circuitry 46 stores various setting information required when acquiring biological data in the signal processing circuitry 44. The memory circuitry 46 may include, for example, a random access memory (RAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), etc. The memory circuitry 46 may also be a register circuit, etc.

[0036] Next, a description will be given of an example of the circuit configuration of the detection device 1. Fig. 3 is a circuit diagram showing the detection device according to embodiment 1. As shown in Fig. 3, the sensor area 10 has a plurality of optical sensors PD arranged in a matrix within a detection area AA.

[0037] The gate line GCL extends in a first direction Dx and is connected to a plurality of photosensors PD arranged in the first direction Dx. The plurality of gate lines GCL1, GCL2, ..., GCL6 are arranged in a second direction Dy and are each connected to a gate line driving circuit 15. In the following description, when it is not necessary to distinguish between the plurality of gate lines GCL1, GCL2, ..., GCL6, they will be simply referred to as gate lines GCL. While FIG. 3 shows six gate lines GCL for ease of understanding, this is merely an example, and M gate lines GCL (M is a natural number) may be arranged.

[0038] The signal line SGL extends in the second direction Dy and is connected to a plurality of photosensors PD arranged in the second direction Dy. The 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 the following description, when it is not necessary to distinguish between the signal lines SGL1_1, SGL1_2, SGL1_3, ..., SGL3_3, they will be simply referred to as signal lines SGL. For ease of understanding, nine signal lines SGL are shown, but this is merely an example, and N signal lines SGL (N is a natural number) may be arranged.

[0039] The gate line driving circuit 15 receives various control signals from the control circuit 122 (see FIG. 1 ). Based on the various control signals, the gate line driving circuit 15 sequentially selects the multiple gate lines GCL1, GCL2, ..., GCL6 in a time-division manner. The gate line driving circuit 15 supplies a gate driving signal to the selected gate line GCL. This causes the gate driving signal to be supplied to a switch connected to each photosensor PD, thereby selecting the multiple photosensors PD arranged in the first direction Dx. The switch connected to each photosensor PD is a switching element formed, for example, of a thin film transistor, and is formed, for example, of an n-channel MOS (Metal Oxide Semiconductor) TFT (Thin Film Transistor).

[0040] The gate line driving circuit 15 may perform different driving for each detection mode of a fingerprint and a plurality of different pieces of biological information (such as pulse wave, pulse, blood vessel image, and blood oxygen concentration, hereinafter also simply referred to as "biometric information"). For example, the gate line driving circuit 15 may drive a plurality of gate lines GCL in a bundle.

[0041] The signal line selection circuit 16 is provided with a plurality of switches corresponding to the signal lines SGL1, SGL2, ..., SGL9, respectively. The switches provided corresponding to the signal lines SGL are switching elements formed of, for example, thin film transistors, and are formed of, for example, n-channel MOS (Metal Oxide Semiconductor) type TFTs (Thin Film Transistors).

[0042] The control circuit 122 (see FIG. 1) supplies selection signals ASW1, ASW2, and ASW3 to the signal line selection circuit 16. This causes the signal line selection circuit 16 to sequentially or simultaneously select the multiple signal lines SGL in a time-division manner. Specifically, in the configuration shown in FIG. 3, the signal line selection circuit 16 simultaneously selects signal lines SGL1_1, SGL2_1, and SGL3_1 and connects them to the AFE circuit 48. The signal line selection circuit 16 also simultaneously selects signal lines SGL1_2, SGL2_2, and SGL3_2 and connects them to the AFE circuit 48. The signal line selection circuit 16 also simultaneously selects signal lines SGL1_3, SGL2_3, and SGL3_3 and connects them to the AFE circuit 48. This configuration allows the detection device 1 to reduce the number of ICs including the AFE circuit 48 or the number of IC terminals. In addition, in order to make the explanation easier to understand, FIG. 3 shows an example in which three signal lines SGL are selected in a time-division manner, but this is merely an example, and the number of signal lines SGL selected in a time-division manner may be P (P is a natural number that is 1 / M, the number of equal divisions of the number of signal lines; for example, if the number of equal divisions of the number of signal lines M is Q, then P=M / Q).

[0043] Fig. 4 is a circuit diagram showing an example of the configuration of the AFE circuit according to embodiment 1. Fig. 4 also shows photosensors PD that are selected by gate drive signals supplied from the gate line drive circuit 15 to gate lines GCLn (n is a natural number from 1 to N (N=6 in the example shown in Fig. 3)) and connected to the AFE circuit 48 by the signal line selection circuit 16 via signal lines SGLq_1, SGLq_2, and SGLq_3 (q is a natural number from 1 to Q (Q=3 in the example shown in Fig. 3)).

[0044] A sensor power supply potential Vorg is applied to the cathode of each optical sensor PD from a power supply circuit 123. An anode of each optical sensor PD is connected to an AFE circuit 48 via a signal line selection circuit 16 in a time-division manner.

[0045] When the optical sensor PD is irradiated with light, a current corresponding to the intensity of the light irradiated onto the optical sensor PD flows through the optical sensor PD, and charge is accumulated in the capacitance element of the optical sensor PD. When the optical sensor PD is selected by the gate line drive circuit 15 and the signal line selection circuit 16, a current corresponding to the charge accumulated in the capacitance element of the optical sensor PD flows to the AFE circuit 48 via the signal line SGL.

[0046] The detection signal amplifier circuit 42 of the AFE circuit 48 converts fluctuations in the current supplied from the optical sensor PD via the signal line SGL into fluctuations in voltage and amplifies the voltage. The detection signal amplifier circuit 42 includes a differential amplifier circuit CA as a main component.

[0047] 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 a signal line selection circuit 16. The reference potential Vref is, for example, approximately half the value 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 a high potential voltage Vadh and a low potential voltage Vadl supplied to the A / D conversion circuit 43. The low potential voltage Vadl is, for example, the GND potential.

[0048] 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.

[0049] Next, the configuration of the optical sensor PD will be described. Fig. 5 is a schematic partial cross-sectional view of the optical sensor according to the first embodiment. 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, for example, an insulating substrate formed of a film-like resin.

[0050] The sensor structure 22 includes a TFT layer 221 , an anode electrode (lower electrode) 222 , a photosensor PD, and a cathode electrode (upper electrode) 226 .

[0051] 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 form a drive circuit that drives the sensor, and are also called a backplane.

[0052] The photosensor PD has an active layer 224, an electron transport layer (lower buffer layer) 223 provided between the active layer 224 and an anode electrode (lower electrode) 222, and a hole transport layer (upper buffer layer) 225 provided between the active layer 224 and a 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.

[0053] The characteristics (for example, voltage-current characteristics and resistance value) of the active layer 224 change depending on the light irradiated thereto. An organic material is used as the material of the active layer 224. Specifically, the active layer 224 has a bulk heterostructure in which a p-type organic semiconductor and an n-type organic semiconductor, an n-type fullerene derivative (PCBM), are mixed. For example, a low-molecular organic material, C ６０ (fullerene), PCBM (phenyl C61-butyric acid methyl ester), CuPc (copper phthalocyanine), F １６ CuPc (fluorinated copper phthalocyanine), rubrene (5,6,11,12-tetraphenyltetracene), PDI (a derivative of perylene), or the like can be used.

[0054] The active layer 224 can be formed by a vapor deposition (dry process) using these low molecular weight organic materials. In this case, the active layer 224 is formed by a vapor deposition (dry process) using, for example, CuPc and F １６ CuPc laminated film or rubrene and C ６０The active layer 224 may be a laminated film of the above-mentioned low molecular weight organic material and high molecular weight organic material. The active layer 224 may also be formed by a wet process. In this case, the active layer 224 is made of a material that combines the above-mentioned low molecular weight organic material and high molecular weight organic material. Examples of high molecular weight organic materials that can be used include P3HT (poly(3-hexylthiophene)) and F8BT (F8-alt-benzothiadiazole). The active layer 224 may be a film in which P3HT and PCBM are mixed, or a film in which F8BT and PDI are mixed.

[0055] 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 reaching 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 electron transport layer (lower buffer layer) 223 is made of ethoxylated polyethyleneimine (PEIE).

[0056] 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 a metal oxide layer. The metal oxide layer is made of tungsten oxide (WO ３ ), molybdenum oxide, etc. are used.

[0057] 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.

[0058] The anode electrode (lower electrode) 222 and the cathode electrode (upper electrode) 226 face each other with the photosensor PD interposed therebetween. The cathode electrode (upper electrode) 226 is made of a light-transmitting conductive material such as indium tin oxide (ITO). 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 made of an alloy material containing at least one of these metal materials.

[0059] By controlling the film thickness of the anode electrode (lower electrode) 222, the anode electrode (lower electrode) 222 can be formed as a semi-transparent electrode having light transmittance. For example, the anode electrode (lower electrode) 222 can be formed of a 10 nm thick Ag thin film to have a light transmittance of about 60%. In this case, the photosensor PD can detect the first light LD irradiated from the first surface FD side, for example.

[0060] The protective film 23 is provided on the second surface FU to cover the cathode electrode (upper electrode) 226. The protective film 23 is a passivation film, and is provided to protect the photosensor PD.

[0061] In the present disclosure, as a specific example of information about a living body acquired by the detection device 1, the oxygen saturation level in blood (hereinafter referred to as blood oxygen saturation (SpO ２ An example of acquiring a pulse wave, which is biological information for calculating the pulse wave amplitude (referred to as a pulse wave amplitude), will be described.

[0062] Here, for example, the first light emitted from the first light source 61 is red visible light (red light) having a wavelength of 600 nm or more and 700 nm or less, specifically, approximately 660 nm, and the second light emitted from the second light source 62 is infrared light having a wavelength of 780 nm or more and 950 nm or less, specifically, approximately 850 nm. ２ ), a first pulse wave acquired using the first light (red light) and a second pulse wave acquired using the second light (infrared light) are used.

[0063] Blood oxygen saturation (SpO ２) can be obtained by calculating the R value shown in the following equation (1) where the AC component of the first pulse wave is AC(Red), the DC component of the first pulse wave is DC(Red), the AC component of the second pulse wave is AC(IR), and the DC component of the second pulse wave is DC(IR), and applying the R value to the calibration curve shown in the following equation (2) (a and b are calibration coefficients):

[0064] R={AC(Red) / DC(Red)} / {AC(IR) / DC(IR)}...(1)

[0065] SpO ２ = b - a × R ... (2)

[0066] Since the amount of light absorbed by hemoglobin changes depending on the amount of oxygen absorbed by the hemoglobin, the amount of light detected by the optical sensor PD is the amount of light obtained by subtracting the amount of light absorbed by the blood (hemoglobin) from the first and second irradiated light. Most of the oxygen in the blood is reversibly bound to the hemoglobin in the red blood cells, and only a small portion is dissolved in the plasma. More specifically, the percentage of the blood's oxygen capacity that is bound to the blood is called the oxygen saturation (SpO ２ Using two wavelengths of first and second light, it is possible to calculate blood oxygen saturation from the amount of light emitted minus the amount of light absorbed by the blood (hemoglobin).

[0067] Oxygen saturation (SpO ２ ) is determined by the ratio of hemoglobin in the blood when it is bound to oxygen (O2Hb: oxygenated hemoglobin) to when it is not bound to oxygen (HHb: reduced hemoglobin). The absorption characteristics of red light are HHb >> O2Hb, with HHb having significantly greater absorbance, whereas the absorption characteristics of infrared light are HHb ≒ O2Hb, with O2Hb having slightly greater absorbance.

[0068] Next, an operation example of the detection device 1 will be described. First, an operation example according to a comparative example of embodiment 1 will be described. FIG. 6 is a timing waveform diagram showing an operation example of the detection device according to the comparative example of embodiment 1. Note that in the operation example of the detection device according to the comparative example of embodiment 1 shown in FIG. 6, a constant current source is not connected to the inverting input terminal (−) of the differential amplifier circuit CA.

[0069] 6, odd-numbered frame 1Fodd and even-numbered frame 1Feven have exposure periods Pex1 and Pex2 and readout periods Pdet1 and Pdet2, respectively. In the configuration shown in FIG. 3, during the readout periods Pdet1 and Pdet2, the gate line drive circuit 15 sequentially scans the gate lines GCL1 to GCL6.

[0070] 6, the control circuit 122 (detection control circuit 11) turns on the first light source 61 and turns off the second light source 62 during the exposure period Pex1 of odd-numbered frame 1Fodd. Also, during the exposure period Pex2 of even-numbered frame 1Feven, the control circuit 122 turns off the first light source 61 and turns on the second light source 62.

[0071] In this way, the first light source 61 and the second light source 62 are controlled to be turned on or off in a time-division manner for each frame. As a result, the detection value detected by the optical sensor PD using the first light and the detection value detected by the optical sensor PD using the second light are output in a time-division manner to the AFE circuit 48. Hereinafter, when it is not necessary to distinguish between the odd frame 1Fodd and the even frame 1Feven, the odd frame 1Fodd and the even frame 1Feven will be simply referred to as each frame 1F, the exposure periods Pex1 and Pex2 will be simply referred to as the exposure period Pex, and the readout periods Pdet1 and Pdet2 will be simply referred to as the readout period Pdet.

[0072] During the exposure period Pex, a current Iphoto corresponding to the intensity of light irradiating the photosensor PD flows through the photosensor PD, and charge is accumulated in the capacitance element of the photosensor PD. At this time, the charge Qphoto accumulated in the capacitance element of the photosensor PD is a value obtained by multiplying the current Iphoto flowing through the photosensor PD by the exposure period Pex (Qphoto = Iphoto x Pex).

[0073] During the selection period of the gate line GCLn, the selection signals ASW1, ASW2, and ASW3 are sequentially controlled to be high (hereinafter also referred to as "H control"), and each signal line SGL is sequentially connected to the AFE circuit 48. The high periods (hereinafter also referred to as "H periods") of the selection signals ASW1, ASW2, and ASW3 are used as readout periods for each optical sensor PD. FIG. 7 is an enlarged view of the readout periods for each optical sensor.

[0074] During a period including an exposure period Pex before time t1, the reset switch RSW is turned on and placed in a reset state. At time t1 during the readout period for each photosensor shown in FIG. 7 , the reset switch RSW is turned off and the reset state is released. Then, at time t2, the selection signal ASWp (p is a natural number ranging from 1 to P (P=3 in the example shown in FIG. 3 )) is turned high. A current corresponding to the charge accumulated in the capacitance element of the photosensor PD during the exposure period Pex flows through the signal line SGL to the AFE circuit 48, and charge accumulates in the negative feedback capacitance Cfb of the AFE circuit 48. At this time, the voltage signal Vout (hereinafter also referred to simply as the “output voltage signal Vout”) output from the detection signal amplifier circuit 42 drops from the reference potential Vref to a value corresponding to the charge accumulated in the negative feedback capacitance Cfb of the AFE circuit 48.

[0075] The output voltage signal Vout of the detection signal amplifier circuit 42 is taken in by the A / D conversion circuit 43 at the sampling timing of time t5 and converted into a digital detection value Raw.

[0076] Thereafter, at time t6, the reset switch RSW is controlled to be on, whereby the anode potential of the optical sensor 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 capacitance Cfb of the detection signal amplifier circuit 42 is reset. Then, at time t7, the selection signal ASWp is controlled to be low, and at time t8, the reset switch RSW is controlled to be off.

[0077] 8 is a diagram showing the correspondence relationship between the detection value of the AFE circuit and the light receiving intensity of the optical sensor in an operation example of a detection device according to a comparative example of embodiment 1. In Fig. 8, the vertical axis represents the digital detection value Raw [digit], and the horizontal axis represents the intensity of light (received light intensity) received by the optical sensor PD during the exposure period Pex.

[0078] In the configuration according to the first embodiment shown in FIGS. 3 and 4, as shown in FIG. 8, the smaller the intensity of received light during the exposure period Pex, the larger the detection value Raw. That is, the detection value Raw is a value that decreases in accordance with the intensity of received light during the exposure period Pex, with the detection value detected when the optical sensor PD is not exposed to light as the maximum value. In other words, the detection value Raw is a value that decreases in accordance with the intensity of received light during the exposure period Pex, with 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 the time of reset into a digital value as the maximum value. In the operation example according to the comparative example shown in FIGS. 6 and 7, the reference value Base_Raw is set to a value that decreases in accordance with the intensity of received light during the exposure period Pex, with the number of gradations of the A / D conversion circuit 43 being 2. ｎ (resolution n bits), 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 first embodiment shown in FIGS. 6 and 7 is expressed by the following equation (3).

[0079] Raw=Vout / (Vadc / 2 ｎ ) = (Vref-Qphoto / Cfb) / (Vadc / 2 ｎ ) … (3)

[0080] The number of gradations that can be output from the A / D conversion circuit 43 (output circuit) is 2. ｎ When this is set, the minimum gradation Raw_min (detected minimum value) is "0", and the maximum gradation Raw_max (detected maximum value) is "2 ｎ When the resolution of the A / D conversion circuit 43 is 12 bits (n=12), the minimum gradation Raw_min is "0" and the maximum gradation Raw_max is "4095". In addition, the reference value Base_Raw is set to, for example, "2048".

[0081] In the example shown in FIG. 8, the output range of the A / D conversion circuit 43 is set to approximately Vadc / (Vadc / 2 ｎ) In this case, the range in which the detection value Raw, which is the output value of the A / D conversion circuit 43, changes linearly with fluctuations in the output voltage signal Vout of the detection signal amplifier circuit 42 is limited to the range from the lower limit gradation Raw_lower_lim to the upper limit gradation 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 gradation Raw_lower_lim to the upper limit gradation Raw_upper_lim (Raw_lower_lim≦Raw≦Raw_upper_lim). Hereinafter, the range from the lower limit gradation Raw_lower_lim to the upper limit gradation Raw_upper_lim, in which the detection value Raw changes linearly with fluctuations in the output voltage signal Vout, is also referred to as the "detection range" of the detection device 1.

[0082] The detection range of 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 this disclosure) and the low potential voltage Vadl (e.g., GND potential) supplied to the A / D conversion circuit 43, and the like. The detection accuracy of the detection value Raw is also affected by the input / output characteristics and power supply voltage range of the detection signal amplifier circuit 42. 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.

[0083] Fig. 9 is a timing waveform diagram illustrating an example of the operation of the detection device according to embodiment 1. Fig. 10 is an enlarged view of a readout period for each optical sensor in the timing waveform diagram shown in Fig. 9 .

[0084] 9 and 10 , the reset switch RSW is turned on and reset during the period including the exposure period Pex before time t1. In the operation example shown in FIGS. 9 and 10 , the reset switch RSW is turned off and the reset state is released at time t1 during the readout period for each photosensor shown in FIG. 10 . Then, the selection signal ASWp is set to H at time t2. The offset switch ofsSW is turned on at time t3. At time t4, after the offset period Tofs has elapsed, the offset switch ofsSW is 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 from the photosensor PD, and the amount of charge stored in the negative feedback capacitance Cfb of the detection signal amplifier circuit 42 decreases. The charge ΔQofs that decreases at this time is Iofs×Tofs (ΔQofs=Iofs×Tofs). As a result, the detection value Raw in the operation example shown in FIGS. 9 and 10 is expressed by the following equation (4).

[0085] Raw=Vout / (Vadc / 2 ｎ ) = {Vref-(Qphoto-ΔQofs) / Cfb} / (Vadc / 2 ｎ ) … (4)

[0086] As a result, in the operation example shown in Figures 9 and 10, the detection value Raw is larger than the operation example of the comparative example shown in Figures 6 and 7 by the difference value ΔRaw (hereinafter also referred to as the "offset value ΔRaw") shown in the following equation (5).

[0087] ΔRaw=(ΔQofs / Cfb) / (Vadc / 2 ｎ ) = {(Iofs×Tofs) / Cfb} / (Vadc / 2 ｎ ) … (5)

[0088] That is, in the operation example of the detection device 1 according to the 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 formula (6) or (7).

[0089] Raw_upper_lim≧Vref / (Vadc / 2 ｎ )+ΔRaw=[Vref+{(Iofs×Tofs) / Cfb}] / (Vadc / 2 ｎ )…(6)

[0090] Raw_upper_lim×(Vadc / 2 ｎ ) ≧Vref+ΔRaw×(Vadc / 2 ｎ ) =Vref+{(Iofs×Tofs) / Cfb}…(7)

[0091] Fig. 11 is a first diagram showing the correspondence relationship between the detection value of the AFE circuit and the intensity of light received by the optical sensor in a first operation example of the detection device according to embodiment 1. Fig. 12 is a second diagram showing the correspondence relationship between the detection value of the AFE circuit and the intensity of light received by the optical sensor in the first operation example of the detection device according to embodiment 1. In the first operation example shown in Figs. 11 and 12, the dashed lines indicate the correspondence relationship between the detection value of the AFE circuit and the intensity of light received by the optical sensor in the operation example of the detection device according to the comparative example of embodiment 1 shown in Fig. 8.

[0092] 11 and 12 show an example in which the offset value ΔRaw is set so that the reference value Base_Raw is equal to the upper limit gradation Raw_upper_lim (Base_Raw=Raw_upper_lim), as shown in Fig. 11. As a result, as shown in Fig. 12, by increasing the received light intensity during the exposure period Pex (for example, by increasing the emission intensity of the light sources (first light source 61, second light source 62) or reducing the negative feedback capacitance Cfb), the AC components of the pulse wave within the detection range (AC(Red), AC(IR), see equation (1) above) can be increased compared to the example shown in Fig. 8, thereby improving the detection accuracy of the pulse waveform.

[0093] Here, for example, in a configuration for detecting the presence or absence of an object to be detected in the detection area AA, as shown in Figures 11 and 12, the reference value Base_Raw needs to be set within the detection range (Base_Raw≦Raw_upper_lim). However, in an example for acquiring a pulse wave, even if the reference value Base_Raw is set to match the upper limit gradation Raw_upper_lim (Base_Raw=Raw_upper_lim) as shown in Figures 11 and 12, the AC components of the pulse wave (AC(Red), AC(IR), see equation (1) above) are small relative to the detection range of the A / D conversion circuit 43 (Raw_lower_lim≦Raw≦Raw_upper_lim), and sufficient accuracy may not be obtained.

[0094] 13 is a first diagram showing the correspondence relationship between the detection value of the AFE circuit and the light intensity received by the optical sensor in a second operation example of the detection device according to embodiment 1. FIG. 14 is a second diagram showing the correspondence relationship 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 embodiment 1. In the second operation example of the detection device 1 according to embodiment 1 shown in FIGS. 13 and 14, the dashed line indicates the correspondence 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 embodiment 1 shown in FIG. 8, and the dot-dash line indicates the correspondence relationship 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 embodiment 1 shown in FIGS. 11 and 12.

[0095] In a second operation example of the detection device 1 according to the first embodiment, as shown in Fig. 13 , the offset value ΔRaw is set to be larger than that in the first operation example shown in Fig. 11 and Fig. 12 . Specifically, the offset value ΔRaw is set so as to satisfy the following equation (8) or (9). As a result, as shown in Fig. 14 , the upper limit of the range of detection values ​​Raw used to acquire a pulse wave can be brought closer to the upper limit gradation Raw_upper_lim, and the range of detection values ​​Raw used to acquire a pulse wave can be expanded to the upper limit of the detection range of the detection device 1.

[0096] Raw_upper_lim≦Vref / (Vadc / 2 ｎ )+ΔRaw=[Vref+{(Iofs×Tofs) / Cfb}] / (Vadc / 2 ｎ )…(8)

[0097] Raw_upper_lim×(Vadc / 2 ｎ ) ≦Vref+ΔRaw×(Vadc / 2 ｎ ) =Vref+{(Iofs×Tofs) / Cfb}…(9)

[0098] As a result, as shown in FIG. 14 , by increasing the light receiving intensity during the exposure period Pex compared to the examples shown in FIGS. 11 and 12 , the AC components of the pulse wave (AC(Red), AC(IR), see equation (1) above) within the detection range can be further increased, and the detection accuracy of the pulse waveform can be improved compared to the examples shown in FIGS. 11 and 12 .

[0099] 13 and 14 , in a region where the intensity of light received by the optical sensor PD during the exposure period Pex is smaller than a predetermined value S, the detection value Raw becomes nonlinear with respect to fluctuations in the output voltage signal Vout, and as the intensity of light received by the optical sensor PD during the exposure period Pex becomes smaller than the predetermined value S, the detection value Raw is limited to the maximum gradation Raw_max of the A / D conversion circuit 43. In other words, in a 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 fluctuations in the output voltage signal Vout, and as the intensity of light received by the optical sensor PD during the exposure period Pex becomes smaller than the predetermined value S, the detection value Raw is limited to the maximum gradation 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, when the light sources (first light source 61, second light source 62) are turned off, the detection value Raw is limited to the maximum gradation Raw_max (maximum detection value) of the A / D conversion circuit (output circuit) 43.

[0100] The region where the detection value Raw exceeds the upper limit gradation Raw_upper_lim and becomes nonlinear is outside the detection range of the detection device 1. If the detection range of the detection device 1 is assumed to be infinite, the detection value Raw will be linear over the entire range of the output voltage signal Vout. The two-dot chain lines shown in Figures 13 and 14 indicate hypothetical detection values ​​in the region where the detection value Raw exceeds the upper limit gradation Raw_upper_lim, assuming that the detection range of the detection device 1 is infinite. As described above, the detection value Raw is actually limited to the maximum gradation Raw_max of the A / D conversion circuit 43.

[0101] Blood oxygen saturation (SpO ２ In order to calculate the DC components (DC(Red), DC(IR), see equation (1) above) of the pulse wave used to calculate the base value Base_Raw, it is necessary to set a virtual base value Virtual_Base_Raw (hereinafter also referred to as the "virtual base value Virtual_Base_Raw") in place of the base value Base_Raw. Hereinafter, a method for setting the virtual base value Virtual_Base_Raw in a second operation example of the detection device 1 according to the first embodiment will be described.

[0102] (Virtual Reference Value Setting Method 1 According to First Embodiment) As shown in FIG. 13 , the virtual reference value Virtual_Base_Raw is set by subtracting an offset value ΔRaw (=(ΔQofs / Cfb) / (Vadc / 2)) from the reference value Base_Raw in the operation example according to the comparative example of the first embodiment when the optical sensor PD is not exposed to light during the exposure period Pex. 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 when the offset period Tofs is set to approximately zero in the second operation example of the detection device 1 according to the first embodiment, in a state where the optical sensor PD is not exposed to light during the exposure period Pex. The virtual reference value Virtual_Base_Raw in this case is expressed by the following equation (10).

[0103] Virtual_Base_Raw=Base_Raw+ΔRaw = [Vref+{(Iofs×Tofs) / Cfb}] / (Vadc / 2ｎ ) … (10)

[0104] (Virtual Reference Value Setting Method 2 According to First Embodiment) Considering the variation among the optical sensors PD, the reference value Base_Raw in the operation example of the comparative example of the first embodiment may be set to a value acquired for each optical sensor PD, for example, at the time of shipment of the detection device 1, in a state in which the optical sensors PD are not exposed to light during the exposure period Pex. In other words, considering the variation among the optical sensors PD, the reference value Base_Raw in the second operation example of the detection device 1 according to the first embodiment, in a state in which the optical sensors PD are not exposed to light during the exposure period Pex, may be set to a value acquired for each optical sensor PD, for example, at the time of shipment of the detection device 1. If the reference value of the optical sensor PD in m columns and n rows is Base_Raw(m, n), the virtual reference value Virtual_Base_Raw(m, n) for each optical sensor PD in m columns and n rows is expressed by the following equation (11):

[0105] Virtual_Base_Raw(m,n) =Base_Raw(m,n)+ΔRaw =Base_Raw(m,n) +{(Iofs×Tofs) / Cfb}] / (Vadc / 2 ｎ )…(11)

[0106] (Virtual Reference Value Setting Method 3 According to Embodiment 1) Considering variations in the offset current Iofs, the offset period Tofs, and the negative feedback capacitance Cfb of the detection signal amplifier circuit 42, for example, at the time of shipping the detection device 1, detection values ​​Raw at multiple points (four points in the example shown in FIG. 13 ) within the detection range (Raw_lower_lim≦Raw≦Raw_upper_lim) shown in FIG. 13 are acquired, and the virtual reference value Virtual_Base_Raw(m, n) for each optical sensor PD can be set by a method such as linear approximation (straight-line approximation) using the least squares method. The method for calculating the virtual reference value Virtual_Base_Raw(m, n) for each optical sensor PD is not limited to linear approximation.

[0107] 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 according to the first embodiment, the virtual reference value setting method 2 according to the first embodiment, 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 the memory circuit 46, the blood oxygen saturation (SpO ２ It is possible to calculate the DC components (DC(Red), DC(IR), see equation (1) above) of the pulse wave used to calculate the blood oxygen saturation (SpO ) using the first pulse wave acquired using the first light (red light) and the second pulse wave acquired using the second light (infrared light). ２ ) can be calculated with improved accuracy.

[0108] 15 is a circuit diagram showing an example of the configuration of an AFE circuit according to a modification of embodiment 1. In this embodiment, an offset voltage signal Vofs is input via an offset capacitance Cofs to the inverting input terminal (−) of the differential amplifier circuit CA of the detection signal amplifier circuit 42 that constitutes the AFE circuit 48a.

[0109] Fig. 16 is a timing waveform diagram illustrating an example of the operation of a detection device according to a modified example of embodiment 1. Fig. 17 is an enlarged view of a readout period for each optical sensor in the timing waveform diagram shown in Fig. 16 .

[0110] 16 and 17 , in a period including the exposure period Pex before time t1, the reference potential Vref is applied to the offset capacitance Cofs as the offset voltage signal Vofs, thereby resetting the offset capacitance Cofs, so that the potential difference across the offset capacitance Cofs becomes approximately zero.

[0111] 17, at time t1 during the readout period for each photosensor, the reset switch RSW is turned off to release the reset state, and after the selection signal ASWp is controlled to be high at time t2, a potential Vref-ΔVofs obtained by subtracting the offset potential ΔVofs from the reference potential Vref is applied to the offset capacitance Cofs during the period from time t3 to time t6 when the reset switch RSW is turned on. As a result, the offset potential ΔVofs is applied across the offset capacitance Cofs, and a portion of the charge accumulated in the capacitive element of the photosensor PD during the exposure period Pex moves to the offset capacitance Cofs. The charge ΔQofs that moves at this time is ΔVofs×Cofs (ΔQofs=ΔVofs×Cofs).

[0112] As a result, in the operational example of the detection device 1 according to the modified example of embodiment 1 shown in FIGS. 16 and 17, the detection value Raw is larger than the operational example according to the comparative example shown in FIGS. 6 and 7 by the offset value ΔRaw shown in the following equation (12).

[0113] ΔRaw=(ΔQofs / Cfb) / (Vadc / 2 ｎ ) = {(ΔVofs×Cofs) / Cfb} / (Vadc / 2 ｎ ) … (12)

[0114] That is, in the operation example of the detection device 1 according to the modified example of the first embodiment, the offset value ΔRaw can be set by adjusting the offset potential ΔVofs or the offset capacitance Cofs.

[0115] Fig. 18 is a diagram showing the correspondence relationship between the detection value of the AFE circuit and the intensity of light received by the optical sensor in an operation example of a detection device according to a modified example of embodiment 1. In Fig. 18, the dashed line indicates the correspondence relationship between the detection value of the AFE circuit and the intensity of light received by the optical sensor in the operation example of a detection device according to a comparative example of embodiment 1 shown in Fig. 8. Furthermore, the two-dot chain line shown in Fig. 18 indicates a virtual detection value that is actually limited to the maximum gradation Raw_max of the A / D conversion circuit 43 in a region where the detection value Raw exceeds the upper limit gradation Raw_upper_lim.

[0116] 18 , the offset value ΔRaw is set so as to satisfy the following equation (13) or (14). As a result, similarly to the second operation example of the detection device 1 according to embodiment 1, the upper limit of the range of the detection values ​​Raw used to acquire the pulse wave can be brought closer to the upper limit gradation Raw_upper_lim, and the range of the detection values ​​Raw used to acquire the pulse wave can be expanded to the upper limit of the detection range of the detection device 1.

[0117] Raw_upper_lim≦Vref / (Vadc / 2 ｎ )+ΔRaw = [Vref+{(ΔVofs×Cofs) / Cfb}] / (Vadc / 2 ｎ ) … (13)

[0118] Raw_upper_lim×(Vadc / 2 ｎ ) ≦Vref+ΔRaw×(Vadc / 2 ｎ ) =Vref+{(ΔVofs×Cofs) / Cfb}…(14)

[0119] As a result, similar to the second operation example of the detection device 1 according to the first embodiment shown in FIGS. 13 and 14 in the configuration according to the first embodiment shown in FIG. 4, by making the received light intensity during the exposure period Pex greater than that in the first operation example shown in FIGS. 11 and 12 (for example, by increasing the light emission intensity of the light sources (first light source 61, second light source 62) or reducing the negative feedback capacitance Cfb), it is possible to increase the AC components of the pulse wave within the detection range (AC(Red), AC(IR), see equation (1) above), and improve the detection accuracy of the pulse waveform.

[0120] 18 , in a region where the intensity of light received by the optical sensor PD during the exposure period Pex is smaller than a predetermined value S, similar to the second operation example of the detection device 1 according to the first embodiment, the detection value Raw becomes nonlinear with respect to fluctuations in the output voltage signal Vout, and as the intensity of light received by the optical sensor PD during the exposure period Pex becomes smaller than the predetermined value S, the detection value Raw is limited to the maximum gradation Raw_max of the A / D conversion circuit 43. In other words, in a region where the output voltage signal Vout of the detection signal amplifier circuit 42 exceeds the predetermined value, similar to the second operation example of the detection device 1 according to the first embodiment, the detection value Raw becomes nonlinear with respect to fluctuations in the output voltage signal Vout, and as the intensity of light received by the optical sensor PD during the exposure period Pex becomes smaller than the predetermined value S, the detection value Raw is limited to the maximum gradation Raw_max of the A / D conversion circuit 43. That is, in the detection device 1 according to the modified example of embodiment 1, as in the second operation example of the detection device 1 according to embodiment 1, when the light sources (first light source 61, second light source 62) are turned off, the detection value Raw is limited to the maximum gradation Raw_max (maximum detection value) of the A / D conversion circuit (output circuit) 43.

[0121] The region where the detection value Raw exceeds the upper limit gradation Raw_upper_lim and becomes nonlinear is outside the detection range of the detection device 1. Here, if the detection range of the detection device 1 is assumed to be infinite, the detection value Raw will be linear over the entire range of the output voltage signal Vout. The two-dot chain line shown in FIG. 18 indicates a hypothetical detection value in the region where the detection value Raw exceeds the upper limit gradation Raw_upper_lim, assuming that the detection range of the detection device 1 is infinite. As described above, the detection value Raw is actually limited to the maximum gradation Raw_max of the A / D conversion circuit 43.

[0122] Blood oxygen saturation (SpO ２ In order to calculate the DC components (DC(Red), DC(IR), see equation (1) above) of the pulse wave used to calculate Base_Raw, it is necessary to set a virtual reference value Virtual_Base_Raw in place of the reference value Base_Raw. Below, a method for setting the virtual reference value Virtual_Base_Raw will be described in an operation example of the detection device 1 according to a modified example of the first embodiment.

[0123] (Virtual Reference Value Setting Method 1 According to Modification of First Embodiment) As shown in FIG. 18 , the virtual reference value Virtual_Base_Raw is set by subtracting an offset value ΔRaw (=(ΔQofs / Cfb) / (Vadc / 2)) from the reference value Base_Raw in the operation example of the comparative example of the first embodiment when the optical sensor PD is not exposed to light during the exposure period Pex. 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 when the offset potential ΔVofs applied across the offset capacitance Cofs in the exemplary operation of the detection device 1 according to the modified example of the first embodiment is set to approximately zero in a state where the photosensor PD is not exposed to light during the exposure period Pex. The virtual reference value Virtual_Base_Raw in this case is expressed by the following equation (15).

[0124] Virtual_Base_Raw=Base_Raw+ΔRaw = [Vref+{(ΔVofs×Cofs) / Cfb}] / (Vadc / 2 ｎ ) … (15)

[0125] (Virtual Reference Value Setting Method 2 According to the Modification of the First Embodiment) Considering the variation among the optical sensors PD, the reference value Base_Raw in the operation example of the comparative example of the first embodiment may be set to a value acquired for each optical sensor PD, for example, at the time of shipping the detection device 1, when the optical sensor PD is not exposed to light during the exposure period Pex. In other words, considering the variation among the optical sensors PD, the reference value Base_Raw obtained when the offset potential ΔVofs applied across the offset capacitance Cofs in the operation example of the detection device 1 according to the modification of the first embodiment is set to approximately zero when the optical sensor PD is not exposed to light during the exposure period Pex may be set to a value acquired for each optical sensor PD, for example, at the time of shipping the detection device 1. If the reference value of the optical sensor PD in m columns and n rows is Base_Raw(m, n), the virtual reference value Virtual_Base_Raw(m, n) for each optical sensor PD in m columns and n rows is expressed by the following equation (16):

[0126] Virtual_Base_Raw(m,n) =Base_Raw(m,n)+ΔRaw =Base_Raw(m,n) +{(ΔVofs×Cofs) / Cfb}] / (Vadc / 2 ｎ ) … (16)

[0127] (Virtual Reference Value Setting Method 3 According to Modification of Embodiment 1) Considering variations in the offset potential ΔVofs, the offset capacitance Cofs, and the negative feedback capacitance Cfb of the detection signal amplifier circuit 42, for example, at the time of shipping the detection device 1, detection values ​​Raw at multiple points (four points in the example shown in FIG. 18 ) within the detection range (Raw_lower_lim≦Raw≦Raw_upper_lim) shown in FIG. 18 may be obtained, and the virtual reference value Virtual_Base_Raw(m, n) for each optical sensor PD may be set by a method such as linear approximation (straight-line approximation) using the least squares method. The method for calculating the virtual reference value Virtual_Base_Raw(m, n) for each optical sensor PD is not limited to linear approximation.

[0128] 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 the memory circuit 46, the blood oxygen saturation (SpO ２ It is possible to calculate the DC components (DC(Red), DC(IR), see equation (1) above) of the pulse wave used to calculate the blood oxygen saturation (SpO ) using the first pulse wave acquired using the first light (red light) and the second pulse wave acquired using the second light (infrared light). ２ ) can be calculated with improved accuracy.

[0129] 19 is a circuit diagram showing a detection device according to embodiment 2. FIG. 20 is a circuit diagram showing an example of the configuration of an AFE circuit according to embodiment 2.

[0130] 19 and 20 according to the second embodiment, a sensor power supply potential Vorg is applied to the anode of each optical sensor PD from a power supply circuit 123. The cathode of each optical sensor PD is connected to an AFE circuit 48 in a time-division manner via a signal line selection circuit 16.

[0131] In the above-described configuration, the configuration of the photosensor PD differs from that of the first embodiment shown in FIG. 5. Specifically, the anode electrode (lower electrode) 222 shown in FIG. 5 corresponds to the cathode electrode (lower electrode) in the configuration according to the second embodiment. The electron transport layer (lower buffer layer) 223 shown in FIG. 5 corresponds to the hole transport layer (lower buffer layer) in the configuration according to the second embodiment. The cathode electrode (upper electrode) 226 shown in FIG. 5 corresponds to the anode electrode (upper electrode) in the configuration according to the second embodiment.

[0132] When the optical sensor PD is irradiated with light, a current corresponding to the intensity of the light irradiated onto the optical sensor PD flows through the optical sensor PD, and charge is accumulated in the capacitance element of the optical sensor PD. When the optical sensor PD is selected by the gate line drive circuit 15 and the signal line selection circuit 16, a current corresponding to the charge accumulated in the capacitance element of the optical sensor PD flows to the AFE circuit 48 via the signal line SGL.

[0133] 21 is a diagram showing the correspondence relationship between the detection value of the AFE circuit and the light receiving intensity of the optical sensor in an operation example of a detection device according to a comparative example of embodiment 2. In Fig. 21, the vertical axis represents the digital detection value Raw [digit], and the horizontal axis represents the intensity of light received by the optical sensor PD during the exposure period Pex (received light intensity). The operation example of the detection device according to the comparative example of embodiment 2 is similar to the operation example of the detection device according to the comparative example of embodiment 1, and therefore detailed description thereof will be omitted here.

[0134] In the configuration according to the second embodiment shown in Figures 19 and 20, as shown in Figure 21, the smaller the intensity of received light during the exposure period Pex, the smaller the detection value Raw becomes. That is, the detection value Raw increases in accordance with the intensity of received light during the exposure period Pex, with the detection value when the optical sensor PD is not exposed to light as the minimum value. In other words, the detection value Raw increases in accordance with the intensity of received light during the exposure period Pex, with the reference value Base_Raw as the minimum value. In the operation example according to the comparative example of the second embodiment, the reference value Base_Raw is set to a value that is smaller than the number of gradations of the A / D conversion circuit 43 when the number of gradations is 2. ｎ (resolution n bits), 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).

[0135] Raw=Vout / (Vadc / 2 ｎ ) = (Vref+Qphoto / Cfb) / (Vadc / 2 ｎ ) … (17)

[0136] The number of gradations that can be output from the A / D conversion circuit 43 is 2. ｎ When this is set, the minimum gradation Raw_min is "0" and the maximum gradation Raw_max is "2 ｎ When the resolution of the A / D conversion circuit 43 is 12 bits (n=12), the minimum gradation Raw_min is "0" and the maximum gradation Raw_max is "4095".

[0137] In the example shown in FIG. 21, the output range of the A / D conversion circuit 43 is set to approximately Vadc / (Vadc / 2 ｎ) In this case, the range in which the detection value Raw, which is the output value of the A / D conversion circuit 43, changes linearly with the output voltage signal Vout of the detection signal amplifier circuit 42 is limited to the range from the lower limit gradation Raw_lower_lim to the upper limit gradation Raw_upper_lim. Therefore, in order to maintain the detection accuracy of the detection value Raw, it is necessary to perform detection within the detection range from the lower limit gradation Raw_lower_lim to the upper limit gradation Raw_upper_lim (Raw_lower_lim≦Raw≦Raw_upper_lim), as in the first embodiment.

[0138] Fig. 22 is a timing waveform diagram illustrating an example of the operation of the detection device according to embodiment 2. Fig. 23 is an enlarged view of a readout period for each optical sensor in the timing waveform diagram shown in Fig. 22.

[0139] 22 and 23 , the reset switch RSW is turned on and placed in a reset state during a period including the exposure period Pex before time t1. In the operation example of the detection device 1 according to the second embodiment shown in FIG. 22 and 23 , the reset switch RSW is turned off and the reset state is released at time t1 during the readout period for each photosensor shown in FIG. 23 . After that, the selection signal ASWp is set to H at time t2. The offset switch ofSW is turned on at time t3. At time t4, after the offset period Tofs has elapsed, the offset switch ofSW is turned off. As a result, during the offset period Tofs from time t2 to time t4, an offset current Iofs flows into the negative feedback capacitance Cfb of the detection signal amplifier circuit 42, and the amount of charge stored in the negative feedback capacitance Cfb of the detection signal amplifier circuit 42 decreases. The charge ΔQofs that is reduced at this time is Iofs×Tofs (ΔQofs=Iofs×Tofs). As a result, the detection value Raw in the operation example shown in FIGS.

[0140] Raw=Vout / (Vadc / 2 ｎ ) = {Vref+(Qphoto-ΔQofs) / Cfb} / (Vadc / 2 ｎ ) … (18)

[0141] As a result, in the operational example of the detection device 1 according to embodiment 2 shown in Figures 22 and 23, the detection value Raw is smaller than the operational example according to the comparative example of embodiment 2 by the offset value ΔRaw shown in the following equation (19).

[0142] ΔRaw=(ΔQofs / Cfb) / (Vadc / 2 ｎ ) = {(Iofs×Tofs) / Cfb} / (Vadc / 2 ｎ ) … (19)

[0143] 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.

[0144] Fig. 24 is a first diagram showing the correspondence relationship between the detection value of the AFE circuit and the intensity of light received by the optical sensor in an operation example of the detection device according to embodiment 2. Fig. 25 is a second diagram showing the correspondence relationship between the detection value of the AFE circuit and the intensity of light received by the optical sensor in an operation example of the detection device according to embodiment 2. In Figs. 24 and 25, the dashed lines indicate the correspondence relationship between the detection value of the AFE circuit and the intensity of light received by the optical sensor in an operation example of the detection device according to the comparative example of embodiment 2 shown in Fig. 21.

[0145] 24 and 25 indicate a virtual detection value that is actually limited to the minimum gradation Raw_min of the A / D conversion circuit 43 in a region where the detection value Raw falls below the lower limit gradation Raw_lower_lim.

[0146] 24 shows an example of operation of the detection device 1 according to the second embodiment, in which the offset value ΔRaw is set larger than that of the operation example of the detection device according to the comparative example of the second embodiment, indicated by the dashed line. Specifically, the offset value ΔRaw is set so as to satisfy the following equation (20) or (21). As a result, as shown in FIG. 25, the lower limit of the range of the detection values ​​Raw used to acquire the pulse wave can be brought closer to the upper limit gradation Raw_lower_lim, and the range of the detection values ​​Raw used to acquire the pulse wave can be expanded to the lower limit of the detection range of the detection device 1.

[0147] Raw_lower_lim≧Vref / (Vadc / 2 ｎ )-ΔRaw = [Vref-{(Iofs×Tofs) / Cfb}] / (Vadc / 2 ｎ ) … (20)

[0148] Raw_lower_lim×(Vadc / 2 ｎ ) ≧Vref−ΔRaw×(Vadc / 2 ｎ ) =Vref-{(Iofs×Tofs) / Cfb}…(21)

[0149] As a result, by increasing the light receiving intensity during the exposure period Pex (for example, by increasing the light emission intensity of the light sources (first light source 61, second light source 62) or by reducing the negative feedback capacitance Cfb), the AC components of the pulse wave within the detection range (AC(Red), AC(IR), see equation (1) above) can be increased, thereby improving the detection accuracy of the pulse waveform.

[0150] 24 and 25 , in a region where the intensity of light received by the optical sensor PD during the exposure period Pex is smaller than a predetermined value S, the detection value Raw becomes nonlinear with respect to fluctuations in the output voltage signal Vout, and as the intensity of light received by the optical sensor PD during the exposure period Pex becomes smaller than the predetermined value S, the detection value Raw is limited to the minimum gradation Raw_min of the A / D conversion circuit 43. In other words, in a region where the output voltage signal Vout of the detection signal amplifier circuit 42 is below the predetermined value, the detection value Raw becomes nonlinear with respect to fluctuations in the output voltage signal Vout, and as the intensity of light received by the optical sensor PD during the exposure period Pex becomes smaller than the predetermined value S, the detection value Raw is limited to the minimum gradation Raw_min of the A / D conversion circuit 43. That is, in an example of operation of the detection device 1 according to the second embodiment, when the light sources (first light source 61, second light source 62) are turned off, the detection value Raw is limited to the minimum gradation Raw_min (minimum detection value) of the A / D conversion circuit (output circuit) 43.

[0151] The region where the detection value Raw exceeds the lower limit gradation Raw_lower_lim and becomes nonlinear is outside the detection range of the detection device 1. If the detection range of the detection device 1 is assumed to be infinite, the detection value Raw will be linear over the entire range of the output voltage signal Vout. The two-dot chain lines shown in Figures 24 and 25 indicate hypothetical detection values ​​in the region where the detection value Raw falls below the lower limit gradation Raw_lower_lim, assuming that the detection range of the detection device 1 is infinite. As described above, the detection value Raw is actually limited to the minimum gradation Raw_min of the A / D conversion circuit 43.

[0152] Blood oxygen saturation (SpO ２ In order to calculate the DC components (DC(Red), DC(IR), see equation (1) above) of the pulse wave used to calculate Base_Raw, it is necessary to set a virtual reference value Virtual_Base_Raw in place of the reference value Base_Raw. Hereinafter, a method for setting the virtual reference value Virtual_Base_Raw will be described in an operation example of the detection device 1 according to the second embodiment.

[0153] (Virtual Reference Value Setting Method 1 According to Second Embodiment) As shown in FIG. 24 , the virtual reference value Virtual_Base_Raw is calculated by subtracting an offset value ΔRaw (=(ΔQofs / Cfb) / (Vadc / 2)) from the reference value Base_Raw when the offset period Tofs is set to approximately zero in the operation example of the detection device 1 according to the second embodiment, while the optical sensor PD is not exposed to light during the exposure period Pex. ｎ )) can be calculated. 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 set to approximately zero in the operation example of the detection device 1 of embodiment 2, in a state where the photosensor PD is not exposed to light during the exposure period Pex. The virtual reference value Virtual_Base_Raw in this case is expressed by the following equation (22).

[0154] Virtual_Base_Raw=Base_Raw−ΔRaw=[Vref−{(Iofs×Tofs) / Cfb}] / (Vadc / 2 ｎ ) … (22)

[0155] (Virtual Reference Value Setting Method 2 According to Second Embodiment) Considering the variation among the optical sensors PD, the reference value Base_Raw in the operation example of the comparative example of the second embodiment may be set to a value acquired for each optical sensor PD, for example, at the time of shipment of the detection device 1, when the optical sensor PD is not exposed to light during the exposure period Pex. In other words, considering the variation among the optical sensors PD, the reference value Base_Raw when the offset period Tofs is set to approximately zero in the operation example of the detection device 1 according to the second embodiment may be set to a value acquired for each optical sensor PD, for example, at the time of shipment of the detection device 1, when the optical sensor PD is not exposed to light during the exposure period Pex. If the reference value of the optical sensor PD in m columns and n rows is Base_Raw(m, n), the virtual reference value Virtual_Base_Raw(m, n) for each optical sensor PD in m columns and n rows is expressed by the following equation (23).

[0156] Virtual_Base_Raw(m,n) =Base_Raw(m,n)-ΔRaw =Base_Raw(m,n)-{(Iofs×Tofs) / Cfb}] / (Vadc / 2 ｎ )…(23)

[0157] (Virtual Reference Value Setting Method 3 According to Embodiment 2) Considering variations in the offset current Iofs, the offset period Tofs, and the negative feedback capacitance Cfb of the detection signal amplifier circuit 42, for example, at the time of shipping the detection device 1, detection values ​​Raw at multiple points (four points in the example shown in FIG. 24 ) within the detection range (Raw_lower_lim≦Raw≦Raw_upper_lim) shown in FIG. 24 may be obtained, and the virtual reference value Virtual_Base_Raw(m, n) for each optical sensor PD may be set by a method such as linear approximation (straight-line approximation) using the least squares method. The method for calculating the virtual reference value Virtual_Base_Raw(m, n) for each optical sensor PD is not limited to linear approximation.

[0158] 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 methods 1, 2, and 3 according to the second embodiment. The virtual reference value Virtual_Base_Raw thus set is stored in the memory circuit 46, whereby the blood oxygen saturation (SpO ２ It is possible to calculate the DC components (DC(Red), DC(IR), see equation (1) above) of the pulse wave used to calculate the blood oxygen saturation (SpO ) using the first pulse wave acquired using the first light (red light) and the second pulse wave acquired using the second light (infrared light). ２ ) can be calculated with improved accuracy.

[0159] 26 is a circuit diagram showing an example of the configuration of an AFE circuit according to a modification of embodiment 2. In this embodiment, an 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 an offset capacitance Cofs.

[0160] Fig. 27 is a timing waveform diagram showing an example of the operation of a detection device according to a modification of embodiment 2. Fig. 28 is an enlarged view of a readout period for each optical sensor in the timing waveform diagram shown in Fig. 27.

[0161] 27 and 28 , in a period including the exposure period Pex before time t1, the reference potential Vref is applied to the offset capacitance Cofs as the offset voltage signal Vofs, thereby resetting the offset capacitance Cofs, so that the potential difference across the offset capacitance Cofs becomes approximately zero.

[0162] 28 , at time t1 during the readout period for each photosensor, the reset switch RSW is turned off to release the reset state, and after the selection signal ASWp is controlled to be high at time t2, a potential Vref+ΔVofs, which is the reference potential Vref plus an offset potential ΔVofs, is applied to the offset capacitance Cofs during the period from time t3 to time t6 when the reset switch RSW is turned on. As a result, the offset potential ΔVofs is applied across the offset capacitance Cofs, and a portion of the charge accumulated in the capacitive element of the photosensor PD during the exposure period Pex moves to the offset capacitance Cofs. The charge ΔQofs that moves at this time is ΔVofs×Cofs (ΔQofs=ΔVofs×Cofs).

[0163] As a result, in the operational example of the detection device 1 according to the modified example of embodiment 2 shown in Figures 27 and 28, the detection value Raw is smaller than the operational example according to the comparative example of embodiment 2 by the offset value ΔRaw shown in the following equation (24).

[0164] ΔRaw=(ΔQofs / Cfb) / (Vadc / 2 ｎ ) = {(ΔVofs×Cofs) / Cfb} / (Vadc / 2 ｎ ) … (24)

[0165] That is, in the operation example of the detection device 1 according to the modified example of the second embodiment, the offset value ΔRaw can be set by adjusting the offset potential ΔVofs or the offset capacitance Cofs.

[0166] Fig. 29 is a diagram showing the correspondence relationship between the detection value of the AFE circuit and the intensity of light received by the optical sensor in an operation example of a detection device according to a modified example of embodiment 2. In Fig. 29, the dashed line indicates the correspondence relationship between the detection value of the AFE circuit and the intensity of light received by the optical sensor in the operation example of a detection device according to a comparative example of embodiment 2 shown in Fig. 21. Furthermore, the two-dot chain line shown in Fig. 29 indicates a virtual detection value that is actually limited to the maximum gradation Raw_max of the A / D conversion circuit 43 in a region where the detection value Raw is below the lower limit gradation Raw_lower_lim.

[0167] 29 , the offset value ΔRaw is set so as to satisfy the following equation (25) or (26). As a result, similar to the operation example of the detection device 1 according to embodiment 2, the lower limit of the range of the detection values ​​Raw used to acquire the pulse wave can be brought closer to the upper limit gradation Raw_lower_lim, and the range of the detection values ​​Raw used to acquire the pulse wave can be expanded to the lower limit of the detection range of the detection device 1.

[0168] Raw_lower_lim≧Vref / (Vadc / 2 ｎ )-ΔRaw = [Vref-{(ΔVofs×Cofs) / Cfb}] / (Vadc / 2 ｎ ) … (25)

[0169] Raw_lower_lim×(Vadc / 2 ｎ ) ≧Vref−ΔRaw×(Vadc / 2 ｎ ) =Vref-{(ΔVofs×Cofs) / Cfb}...(26)

[0170] As a result, similarly to the operational example of the detection device 1 according to the second embodiment shown in FIG. 24 , by increasing the light receiving intensity during the exposure period Pex (for example, by increasing the light emission intensity of the light sources (first light source 61, second light source 62) or by reducing the negative feedback capacitance Cfb), the AC components of the pulse wave within the detection range (AC(Red), AC(IR), see equation (1) above) can be increased, thereby improving the detection accuracy of the pulse waveform.

[0171] 29 , in a region where the intensity of light received by the optical sensor PD during the exposure period Pex is smaller than a predetermined value S, the detection value Raw becomes nonlinear with respect to fluctuations in the output voltage signal Vout, similar to the operation example of the detection device 1 according to the second embodiment, and as the intensity of light received by the optical sensor PD during the exposure period Pex becomes smaller than the predetermined value S, the detection value Raw is limited to the minimum gradation Raw_min of the A / D conversion circuit 43. In other words, in a region where the output voltage signal Vout of the detection signal amplifier circuit 42 is below the predetermined value, the detection value Raw becomes nonlinear with respect to fluctuations in the output voltage signal Vout, similar to the operation example of the detection device 1 according to the second embodiment, and as the intensity of light received by the optical sensor PD during the exposure period Pex becomes smaller than the predetermined value S, the detection value Raw is limited to the minimum gradation Raw_min of the A / D conversion circuit 43. That is, in the detection device 1 according to the modified example of embodiment 2, similar to the operation example of the detection device 1 according to embodiment 2, when the light sources (first light source 61, second light source 62) are turned off, the detection value Raw is limited to the minimum gradation Raw_min (minimum detection value) of the A / D conversion circuit (output circuit) 43.

[0172] The region where the detection value Raw exceeds the lower limit gradation Raw_lower_lim and becomes nonlinear is outside the detection range of the detection device 1. Here, if the detection range of the detection device 1 is assumed to be infinite, the detection value Raw will be linear over the entire range of the output voltage signal Vout. The two-dot chain line shown in Figure 29 indicates a hypothetical detection value in the region where the detection value Raw falls below the lower limit gradation Raw_lower_lim, assuming that the detection range of the detection device 1 is infinite. As described above, the detection value Raw is actually limited to the minimum gradation Raw_min of the A / D conversion circuit 43.

[0173] Blood oxygen saturation (SpO ２ In order to calculate the DC components (DC(Red), DC(IR), see equation (1) above) of the pulse wave used to calculate Base_Raw, it is necessary to set a virtual reference value Virtual_Base_Raw in place of the reference value Base_Raw. Below, a method for setting the virtual reference value Virtual_Base_Raw will be described in an operation example of the detection device 1 according to the modified example of embodiment 2.

[0174] (Virtual Reference Value Setting Method 1 According to Modification of Second Embodiment) As shown in FIG. 29 , the virtual reference value Virtual_Base_Raw is calculated by subtracting an offset value ΔRaw (=(ΔQofs / Cfb) / (Vadc / 2)) from the reference value Base_Raw in the operation example of the comparative example of the second embodiment when the optical sensor PD is not exposed to light during the exposure period Pex. ｎ )) can be calculated. 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 potential ΔVofs applied across the offset capacitance Cofs in the operation example according to the modified example of the second embodiment is set to approximately zero in a state where the photosensor PD is not exposed to light during the exposure period Pex. The virtual reference value Virtual_Base_Raw in this case is expressed by the following equation (27).

[0175] Virtual_Base_Raw=Base_Raw-ΔRaw = [Vref-{(ΔVofs×Cofs) / Cfb}] / (Vadc / 2 ｎ ) … (27)

[0176] (Virtual Reference Value Setting Method 2 According to the Modification of the Second Embodiment) Considering the variation among the optical sensors PD, the reference value Base_Raw in the operation example of the comparative example of the second embodiment may be set to a value acquired for each optical sensor PD, for example, at the time of shipping the detection device 1, when the optical sensor PD is not exposed to light during the exposure period Pex. In other words, considering the variation among the optical sensors PD, the reference value Base_Raw obtained when the offset potential ΔVofs applied across the offset capacitance Cofs in the operation example of the modification of the second embodiment is set to approximately zero during the exposure period Pex, may be set to a value acquired for each optical sensor PD, for example, at the time of shipping the detection device 1. If the reference value of the optical sensor PD in m columns and n rows is Base_Raw(m, n), the virtual reference value Virtual_Base_Raw(m, n) for each optical sensor PD in m columns and n rows is expressed by the following equation (28).

[0177] Virtual_Base_Raw(m,n) =Base_Raw(m,n)-ΔRaw =Base_Raw(m,n)-{(ΔVofs×Cofs) / Cfb}] / (Vadc / 2 ｎ ) … (28)

[0178] (Virtual Reference Value Setting Method 3 According to Modification of Embodiment 2) Considering variations in the offset potential ΔVofs, the offset capacitance Cofs, and the negative feedback capacitance Cfb of the detection signal amplifier circuit 42, for example, at the time of shipping the detection device 1, detection values ​​Raw at multiple points (four points in the example shown in FIG. 29 ) within the detection range (Raw_lower_lim≦Raw≦Raw_upper_lim) shown in FIG. 29 may be obtained, and the virtual reference value Virtual_Base_Raw(m, n) for each optical sensor PD may be set by a method such as linear approximation (straight-line approximation) using the least squares method. The method for calculating the virtual reference value Virtual_Base_Raw(m, n) for each optical sensor PD is not limited to linear approximation.

[0179] In the modification 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 modification of the second embodiment, the virtual reference value setting method 2 according to the modification of the second embodiment, and the virtual reference value setting method 3 according to the modification of the second embodiment. By storing the virtual reference value Virtual_Base_Raw thus set in the memory circuit 46, the blood oxygen saturation (SpO ２ It is possible to calculate the DC components (DC(Red), DC(IR), see equation (1) above) of the pulse wave used to calculate the blood oxygen saturation (SpO ) using the first pulse wave acquired using the first light (red light) and the second pulse wave acquired using the second light (infrared light). ２ ) can be calculated with improved accuracy.

[0180] In the above-described embodiment, a configuration in which multiple optical sensors PD are arranged in a matrix within the detection area AA of the sensor area 10 is described, but the configuration according to the present disclosure is not limited to this and can also be applied to a configuration having, for example, one or several optical sensors PD.

[0181] Although preferred embodiments of the present invention have been described above, the present invention is not limited to such embodiments. The contents disclosed in the embodiments are merely examples, and various modifications are possible without departing from the spirit of the present invention. Appropriate modifications made without departing from the spirit of the present invention naturally fall within the technical scope of the present invention. At least one of various omissions, substitutions, and modifications of components can be made without departing from the gist of each of the above-described embodiments and modifications.

[0182] REFERENCE SIGNS LIST 1 Detector 10 Sensor region 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 amplifier circuit 43 A / D conversion circuit 44 Signal processing circuit 46 Memory 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 region CA Differential amplifier circuit Cfb Negative feedback capacitance Cofs Offset capacitance GA Peripheral area GCL Gate line Iofs Offset current ofsSW Offset switch PD Optical 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. An optical sensor; A light source that irradiates the optical sensor with light; a detection signal amplifier circuit for converting a fluctuation in current supplied from the optical sensor into a voltage; an A / D conversion circuit for converting the output voltage signal after the voltage conversion into a detection value of a digital value; Equipped with The A / D conversion circuit includes: When the light source is turned off, the detection value is limited to a maximum or minimum gradation of a digital value. Detection device.

2. the light sensor is an organic photodiode; An active layer; an upper electrode provided with an upper buffer layer sandwiched between the upper electrode and the active layer; a lower electrode provided with a lower buffer layer sandwiched between the lower electrode and the active layer; having The detection device according to claim 1 .

3. an exposure period during which light is irradiated from the light source to the optical sensor; a readout period in which the detection value is acquired based on the charge accumulated in the optical sensor during the exposure period; having The detection signal amplifier circuit includes: a differential amplifier circuit having a non-inverting input terminal to which a reference potential is applied and an inverting input terminal to which the optical sensor is connected; a negative feedback capacitance connected between the inverting input terminal and an output terminal of the differential amplifier circuit; Equipped with 3. A detection device according to claim 1 or 2.

4. the inverting input terminal of the differential amplifier circuit is connected to the anode of the optical sensor; 4. The detection device according to claim 3.

5. The differential amplifier circuit includes: an offset period in which a predetermined offset current is discharged from the non-inverting input terminal is provided within the readout period; 5. The detection device according to claim 4.

6. A signal processing circuit for acquiring a pulse wave based on the detection value is further provided. The signal processing circuit includes: Calculating a DC component of the pulse wave based on a preset virtual reference value.

6. The detection device according to claim 5.

7. The signal processing circuit includes: and setting the virtual reference value by adding an offset value determined by the offset period and the offset current to a reference value acquired in a readout period in which the offset period is set to substantially zero in a state in which the optical sensor is not exposed to light during the exposure period.

7. The detection device according to claim 6.

8. The signal processing circuit includes: obtaining detection values ​​at a plurality of points within a detection range in which detection values ​​that change linearly with respect to fluctuations in the output voltage signal can be obtained, and setting the virtual reference value based on the detection values ​​at the plurality of points; 7. The detection device according to claim 6.

9. The differential amplifier circuit includes: an offset voltage signal is input to the non-inverting input terminal via an offset capacitance; An offset potential is applied across the offset capacitance during a predetermined period of the readout period.

5. The detection device according to claim 4.

10. A signal processing circuit for acquiring a pulse wave based on the detection value is further provided. The signal processing circuit includes: Calculating a DC component of the pulse wave based on a preset virtual reference value.

10. The detection device according to claim 9.

11. The signal processing circuit includes: setting 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 set to approximately zero in a state in which the optical sensor is not exposed to light during the exposure period; 11. The detection device of claim 10.

12. The signal processing circuit includes: obtaining detection values ​​at a plurality of points within a detection range in which detection values ​​that change linearly with respect to fluctuations in the output voltage signal can be obtained, and setting the virtual reference value based on the detection values ​​at the plurality of points; 11. The detection device of claim 10.

13. the inverting input terminal of the differential amplifier circuit is connected to the cathode of the optical sensor; 4. The detection device according to claim 3.

14. The differential amplifier circuit includes: an offset period is provided within the readout period, in which a predetermined offset current is caused to flow into the non-inverting input terminal; 14. The detection device according to claim 13.

15. A signal processing circuit for acquiring a pulse wave based on the detection value is further provided. The signal processing circuit includes: Calculating a DC component of the pulse wave based on a preset virtual reference value.

15. The detection device of claim 14.

16. The signal processing circuit includes: setting 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 set to substantially zero in a state in which the optical sensor is not exposed to light during the exposure period; 16. The detection device of claim 15.

17. The signal processing circuit includes: obtaining detection values ​​at a plurality of points within a detection range in which detection values ​​that change linearly with respect to fluctuations in the output voltage signal can be obtained, and setting the virtual reference value based on the detection values ​​at the plurality of points; 16. The detection device of claim 15.

18. The differential amplifier circuit includes: an offset voltage signal is input to the non-inverting input terminal via an offset capacitance; An offset potential is applied across the offset capacitance during a predetermined period of the readout period.

14. The detection device according to claim 13.

19. A signal processing circuit for acquiring a pulse wave based on the detection value is further provided. The signal processing circuit includes: Calculating a DC component of the pulse wave based on a preset virtual reference value.

20. The detection device of claim 18.

20. The signal processing circuit includes: setting 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 set to approximately zero in a state in which the optical sensor is not exposed to light during the exposure period; 20. The detection device of claim 19.

21. The signal processing circuit includes: obtaining detection values ​​at a plurality of points within a detection range in which detection values ​​that change linearly with respect to fluctuations in the output voltage signal can be obtained, and setting the virtual reference value based on the detection values ​​at the plurality of points; 20. The detection device of claim 19.

22. A plurality of the optical sensors are provided, the plurality of optical sensors are sequentially connected to the detection signal amplifier circuit during the readout period; 5. The detection device according to claim 4.

23. a plurality of the detection signal amplifier circuits and the A / D converter circuits; a first optical sensor connected to a first detection signal amplifier circuit and a second optical sensor connected to a second detection signal amplifier circuit are simultaneously selected during the readout period; 23. The detection device of claim 22.

24. a sensor region in which a plurality of the optical sensors are arranged in a matrix within a detection region; A plurality of gate lines are connected to the photosensors arranged in the row direction and arranged in the column direction; a gate line driving circuit that sequentially selects a plurality of the gate lines during the readout period; Equipped with 24. The detection device of claim 23.

25. An optical sensor; A light source that irradiates the optical sensor with light; a detection signal amplifier circuit for converting a fluctuation in current supplied from the optical sensor into a voltage; an output circuit for converting the output voltage signal into a detection value; Equipped with The output circuit includes: The detection value is limited to a maximum detection value or a minimum detection value when the light source is turned off. Detection device.