Detection device

Abstract

This detection device comprises: an optical sensor; a light source for emitting light to the optical sensor; and a detection circuit including an integrating circuit connected to the optical sensor. The integrating circuit is provided so as to be capable of changing a gain corresponding to the slope of an output voltage characteristic indicating the relationship between the intensity of light emitted to the optical sensor and an output voltage of the integrating circuit. The optical sensor measures the intensity of light both when the light source is off and when the light source is on. The greater the light intensity of external light measured when the light source is off, the more the integrating circuit reduces the gain.

Description

Detection Device

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

[0002] Optical sensors capable of detecting fingerprint patterns and vein patterns are known (see, for example, Patent Document 1). Such optical sensors include a plurality of photodiodes that use an organic semiconductor material as an active layer.

[0003] Japanese Patent Application Laid-Open No. 2009-32005

[0004] In such a detection device, the amount of light incident on the optical sensor varies depending on measurement conditions such as the presence or absence of external light, the amount of light from the external light and the light source, the measurement location on the object to be detected, the distance between the object to be detected and the light source, etc. This may result in a decrease in the detection accuracy of the detection device.

[0005] An object of the present invention is to provide a detection device that can improve detection accuracy.

[0006] A detection device according to one embodiment of the present disclosure includes an optical sensor, a light source that irradiates light onto the optical sensor, and a detection circuit including an integrating circuit connected to the optical sensor, wherein the integrating circuit is configured to change a gain corresponding to a slope of an output voltage characteristic that indicates the relationship between the amount of light irradiated onto the optical sensor and the output voltage of the integrating circuit, the optical sensor measures the amount of light when the light source is turned off and when the light source is turned on, and the integrating circuit reduces the gain as the amount of external light measured when the light source is turned off increases.

[0007] FIG. 1 is a plan view schematically illustrating a detection device according to an embodiment. FIG. 2 is a cross-sectional view taken along line II-II' of FIG. 1. FIG. 3 is a block diagram illustrating an example of the configuration of a detection device according to an embodiment. FIG. 4 is a circuit diagram illustrating an example of the configuration of a detection device according to an embodiment. FIG. 5 is a timing chart illustrating a detection method of the detection device according to an embodiment. FIG. 6 is an explanatory diagram illustrating the relationship between the integrated light amount and the output voltage of an integrating circuit in a detection device according to a comparative example. FIG. 7 is a flowchart illustrating a method of adjusting output voltage characteristics showing the relationship between the integrated light amount and the output voltage of an integrating circuit in a detection device according to an embodiment. FIG. 8 is a graph illustrating a method of calculating a virtual photocurrent from a light source in step ST2 of FIG. 7. FIG. 9 is an explanatory diagram illustrating a method of calculating an exposure period in step ST3 of FIG. 7. FIG. 10 is a graph illustrating a method of adjusting a gain and an offset amount in steps ST4 and ST5 of FIG. 7. FIG. 11 is a graph illustrating the waveforms of the output voltages and the measurement range in FIG. 10. FIG. 12 is a graph illustrating a method of calculating a drive current supplied to a photosensor. Fig. 13 is a schematic diagram showing an example of the appearance of a detection device according to a modified example when a finger is placed inside the detection device as viewed from the side of the housing. Fig. 14 is a cross-sectional view taken along line XIV-XIV' in Fig. 13.

[0008] Modes (embodiments) for carrying out the present disclosure will be described in detail with reference to the drawings. The present disclosure 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. Note that the disclosure is merely an example, and any appropriate modifications that a person skilled in the art can easily conceive while maintaining the gist of the present disclosure are naturally included within the scope of the present disclosure. Furthermore, for clarity of explanation, the drawings may schematically depict the width, thickness, shape, etc. of each part compared to the actual embodiment. However, these are merely examples and are not intended to limit the interpretation of the present disclosure. Furthermore, in this disclosure 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.

[0009] In this specification and claims, when expressing an aspect of placing another structure on top of a certain structure, the term "on top" is used, unless otherwise specified, to include both a case in which another structure is placed directly on top of a certain structure so as to be in contact with the certain structure, and a case in which another structure is placed above a certain structure via yet another structure.

[0010] 1 is a plan view schematically illustrating a detection device according to an embodiment. As shown in FIG. 1, the detection device 1 includes a substrate 21, a plurality of photodiodes PD (optical sensors), a plurality of signal lines SL, a plurality of shield layers 26, power supply lines CL1, CL2, and CL3, and a control circuit 50.

[0011] In the following description, the first direction Dx is a direction in a plane parallel to the substrate 21. The second direction Dy is a direction in a plane parallel to the substrate 21, and is a direction perpendicular to the first direction Dx. The second direction Dy may intersect 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. The third direction Dz is the normal direction of the substrate 21. Furthermore, "planar view" refers to the positional relationship when viewed from a direction perpendicular to the substrate 21.

[0012] The substrate 21 has a detection area AA and a peripheral area GA. The detection area AA is an area in which multiple photodiodes PD are provided. The peripheral area GA is an area between the periphery of the detection area AA and the edge of the substrate 21, and is an area in which multiple photodiodes PD are not provided. Multiple signal lines SL and a control circuit 50 are provided in the peripheral area GA of the substrate 21.

[0013] The detection device 1 has a plurality of photodiodes PD as optical sensor elements. Each photodiode PD outputs an electrical signal corresponding to the light incident thereon. More specifically, the photodiodes PD are organic photodiodes (OPDs) using organic semiconductors. The plurality of photodiodes PD are arranged side by side in the second direction Dy in the detection area AA.

[0014] The photodiodes PD each include an organic semiconductor layer 30 (a lower buffer layer 32, an active layer 31, and an upper buffer layer 33 (see FIG. 2 )), a lower electrode 23 disposed below the organic semiconductor layer 30, and an upper electrode 24 disposed above the organic semiconductor layer 30. The lower electrodes 23 are provided for each of the photodiodes PD and are arranged side by side in the second direction Dy in the detection area AA. The lower electrodes 23 are also spaced apart from each other in the second direction Dy. The organic semiconductor layer 30 and the upper electrode 24 are provided across the photodiodes PD and are continuous in the detection area AA. Note that in FIG. 1 , for ease of viewing, the organic semiconductor layer 30 and the upper electrode 24 provided above the lower electrode 23 are represented by dashed lines and two-dot chain lines, respectively. The stacked configuration of the photodiodes PD, the lower electrodes 23, and the upper electrodes 24 will be described later with reference to FIG. 2 .

[0015] One ends of the signal lines SL are electrically connected to the lower electrodes 23 of the photodiodes PD, respectively. The other ends of the signal lines SL are connected to a detection circuit 51 included in the control circuit 50. In other words, the detection circuit 51 is electrically connected to the lower electrodes 23 of the photodiodes PD via the signal lines SL.

[0016] The multiple shield layers 26 are arranged to overlap the multiple signal lines SL in a plan view. More specifically, the multiple shield layers 26 overlap portions of the multiple signal lines SL that extend in the first direction Dx, and extend in the first direction Dx along the multiple signal lines SL. The multiple shield layers 26 are also arranged in the second direction Dy.

[0017] The multiple shield layers 26 are connected to a power supply circuit 52 of the control circuit 50 via power supply lines CL1 and CL2 extending in the second direction Dy. More specifically, the power supply line CL1 is provided in the same layer as the multiple shield layers 26 and intersects with the multiple shield layers 26. The power supply line CL2 is provided in the same layer as the multiple signal lines SL. One end of the power supply line CL2 is electrically connected to the power supply line CL1 via a contact hole CH2. The other end of the power supply line CL2 is electrically connected to the power supply circuit 52.

[0018] With this configuration, the power supply circuit 52 supplies a reference voltage VCOM to the multiple shield layers 26 via the power supply lines CL1 and CL2. The reference voltage VCOM is a voltage signal having a fixed, predetermined potential. The reference voltage VCOM is, for example, a voltage signal having a potential equivalent to the first reference potential Vref supplied to the lower electrode 23. The first reference potential Vref is a fixed, predetermined potential. Note that the connection between the multiple shield layers 26 and the power supply circuit 52 may be configured in any manner, and the arrangement, number, etc. of the power supply lines CL1 and CL2 may be changed as appropriate.

[0019] The upper electrode 24 extends in the second direction Dy across the detection area AA and the peripheral area GA. The upper electrode 24 is electrically connected to the power supply line CL3 in the peripheral area GA via the contact hole CH3 and the terminal portion 24a. The power supply line CL3 is connected to the power supply circuit 52.

[0020] With this configuration, the upper electrodes 24 of the multiple photodiodes PD are connected to the power supply circuit 52 included in the control circuit 50 via the terminal portions 24a and the power supply wiring CL3. The power supply circuit 52 supplies a second reference potential Vorg (see FIG. 4) to the upper electrodes 24 of the photodiodes PD. The second reference potential Vorg is a fixed, predetermined potential.

[0021] The control circuit 50 (detection circuit 51 and power supply circuit 52) ​​is disposed adjacent to the photodiodes PD in the second direction Dy in the peripheral area GA of the substrate 21. The control circuit 50 is a circuit that supplies control signals to the multiple photodiodes PD to control their detection operations. The multiple photodiodes PD output electrical signals (photocurrents Id) corresponding to the light irradiating each of them to the detection circuit 51. As a result, the detection device 1 detects information about the object to be detected based on the photocurrents Id from the multiple photodiodes PD.

[0022] Note that detailed configuration examples of the control circuit 50 and the detection operation of the photodiode PD will be described later with reference to Figures 3 to 12. The control circuit 50 is provided on the same substrate 21 as the multiple photodiodes PD, but this is not limiting. The control circuit 50 may be provided on a separate control substrate connected to the substrate 21 via, for example, a flexible printed circuit board. Furthermore, the detection circuit 51 and the power supply circuit 52 of the control circuit 50 may each be formed as separate circuits.

[0023] Although not shown in FIG. 1 , the detection device 1 also includes a first light source 61 and a second light source 62 (see FIG. 3 ). The first light source 61 and the second light source 62 may be, for example, an inorganic light-emitting diode (LED) or an organic light-emitting diode (OLED). The first light source 61 and the second light source 62 emit light of different wavelengths. For example, the first light source 61 emits near-infrared light or infrared light. The second light source 62 emits green light or red light. The green light has a wavelength of, for example, 490 nm or more and 550 nm or less. The red light has a wavelength of, for example, 640 nm or more and 770 nm or less. The infrared light has a wavelength of, for example, approximately 2500 nm or more and approximately 25 μm or less. Near-infrared light has a wavelength of, for example, about 770 nm or more and about 2500 nm or less.

[0024] The light emitted from the first light source 61 and the second light source 62 is reflected by the surface of the object to be detected, such as a finger, and enters the multiple photodiodes PD. This allows the detection device 1 to detect a fingerprint by detecting the uneven shape of the surface of the finger or the like. Alternatively, the light emitted from the first light source 61 and the second light source 62 may be reflected inside the finger or the like or pass through the finger or the like and enter the multiple photodiodes PD. This allows the detection device 1 to detect information about a living body inside the finger or the like. The information about the living body includes, for example, the pulse wave, pulse rate, and blood vessel image of the finger or palm. In other words, 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.

[0025] The detection device 1 of this embodiment detects information about a living body, such as a pulse wave, pulse rate, and blood vessel image, based on the light emitted from the first light source 61 and the light emitted from the second light source 62, and also detects blood oxygen saturation (SpO ２ ) can be detected. In this way, the detection device 1 has the first light source 61 and the second light source 62, and can detect information about various living organisms by performing detection based on light of different wavelengths emitted from the first light source 61 and the second light source 62. Note that the above-mentioned emission colors of the first light source 61 and the second light source 62 are merely examples, and the present disclosure is not limited to the emission colors of the first light source 61 and the second light source 62.

[0026] Next, a description will be given of the laminated structure of the photodiode PD and the shield layer 26. Fig. 2 is a cross-sectional view taken along line II-II' in Fig. 1.

[0027] In the following description, the direction from the substrate 21 toward the sealing film 28 in a direction perpendicular to the surface of the substrate 21 will be referred to as the "upper side" or simply "upper." The direction from the sealing film 28 toward the substrate 21 will be referred to as the "lower side" or simply "lower."

[0028] 2, the substrate 21 is an insulating substrate, and is made of, for example, glass or a resin material. The substrate 21 is not limited to a flat plate shape and may have a curved surface. In this case, the substrate 21 may be a film-like resin.

[0029] The signal line SL is provided on the substrate 21. The signal line SL is formed, for example, of a metal wiring, and is formed of a material having better conductivity than the lower electrode 23 of the photodiode PD. The insulating film 27 is provided on the substrate 21 to cover the signal line SL. The insulating film 27 may be an inorganic insulating film or an organic insulating film. Furthermore, the insulating film 27 may be a single layer or a multilayer film.

[0030] The photodiode PD is provided on the insulating film 27. More specifically, the photodiode PD has a lower electrode 23, a lower buffer layer 32, an active layer 31, an upper buffer layer 33, and an upper electrode 24. In the photodiode PD, the lower electrode 23, the lower buffer layer 32, the active layer 31, the upper buffer layer 33, and the upper electrode 24 are stacked in this order in a direction perpendicular to the substrate 21.

[0031] The lower electrode 23 is provided on the insulating film 27 and is electrically connected to the signal line SL through a contact hole CH1 provided in the insulating film 27. The lower electrode 23 is a cathode electrode of the photodiode PD and is formed of a light-transmitting conductive material such as ITO (Indium Tin Oxide).

[0032] The characteristics (for example, voltage-current characteristics and resistance value) of the active layer 31 change depending on the light irradiated thereto. An organic material is used as the material of the active layer 31. Specifically, the active layer 31 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 C ６１ 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.

[0033] The active layer 31 can be formed by a vapor deposition (dry process) using these low molecular weight organic materials. In this case, the active layer 31 is formed by, for example, CuPc and F １６ CuPc laminated film or rubrene and C ６０The active layer 31 may be a laminated film of the above-mentioned low molecular weight organic material and high molecular weight organic material. The active layer 31 may also be formed by a coating process (wet process). In this case, the active layer 31 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 31 may be a film in which P3HT and PCBM are mixed, or a film in which F8BT and PDI are mixed.

[0034] The lower buffer layer 32 is an electron transport layer, and the upper buffer layer 33 is a hole transport layer. The lower buffer layer 32 and the upper buffer layer 33 are provided to facilitate the holes and electrons generated in the active layer 31 reaching the lower electrode 23 or the upper electrode 24. Ethoxylated polyethyleneimine (PEIE) is used as the material for the electron transport layer. A metal oxide layer is used as the material for the hole transport layer. Tungsten oxide (WO ３ ), molybdenum oxide, etc. are used.

[0035] The materials and manufacturing methods of the lower buffer layer 32, the active layer 31, and the upper buffer layer 33 are merely examples, and other materials and manufacturing methods may be used. For example, the lower buffer layer 32 and the upper buffer layer 33 are not limited to single-layer films, and may be formed as multilayer films including an electron blocking layer and a hole blocking layer.

[0036] The upper electrode 24 is provided on the upper buffer layer 33. The upper electrode 24 is an anode electrode of the photodiode PD, and is formed continuously over the entire detection area AA. In other words, the upper electrode 24 is provided continuously over the multiple photodiodes PD. The upper electrode 24 is formed of a light-transmitting conductive material such as ITO or IZO.

[0037] The sealing film 28 is provided on the upper electrode 24. The sealing film 28 is made of an inorganic film such as a silicon nitride film or an aluminum oxide film, or a resin film such as acrylic. The sealing film 28 is not limited to a single layer, but may be a laminated film of two or more layers combining the inorganic film and the resin film. The sealing film 28 effectively seals the photodiode PD and can prevent moisture from entering from the upper surface side.

[0038] The shield layer 26 is provided on the insulating film 27 in the same layer as the lower electrode 23. The shield layer 26 is formed of the same material as the lower electrode 23, for example, a light-transmitting conductive material such as ITO. However, without being limited to this, the shield layer 26 may be formed of a material different from that of the lower electrode 23, for example, a metal material.

[0039] As described above, the reference voltage VCOM is supplied to the multiple shield layers 26. The shield layers 26 suppress the parasitic capacitance between the upper electrode 24 of the photodiode PD and the signal line SL, and suppress unintended capacitive coupling between the photodiode PD (upper electrode 24) and the signal line SL.

[0040] The detection device 1 of this embodiment may not be provided with the shield layer 26. Furthermore, although an example in which the lower electrode 23 is a cathode electrode and the upper electrode 24 is an anode electrode has been described, the present invention is not limited to this, and the lower electrode 23 may be an anode electrode and the upper electrode 24 may be a cathode electrode. In this case, the lower buffer layer 32 may be a hole transport layer and the upper buffer layer 33 may be an electron transport layer.

[0041] Next, an example of a detection method of the detection device 1 of this embodiment will be described. Fig. 3 is a block diagram showing an example of the configuration of the detection device according to this embodiment. As shown in Fig. 3, the control circuit 50 includes a detection circuit 51, a power supply circuit 52, a light source drive circuit 53, a memory circuit 54, and an adjustment circuit 55.

[0042] The detection circuit 51 is a current detection circuit that measures the photocurrent Id output from the photodiode PD. The detection circuit 51 includes, for example, an integration circuit 46 and an A / D conversion circuit 47 (see FIG. 4 ). The detection circuit 51 measures the photocurrent Id output from the photodiode PD, performs signal processing such as A / D conversion, and outputs a sensor value So corresponding to the photocurrent Id to the host 101.

[0043] The power supply circuit 52 supplies a second reference potential Vorg to the anode of the photodiode PD, and also supplies a first reference potential Vref to the cathode of the photodiode PD. In the case of the circuit shown in FIG. 4, when the reset switch rsw is on, a reference potential equivalent to the first reference potential Vref is supplied from the power supply circuit 52 to the cathode of the photodiode PD via the output of the operational amplifier 45. The first reference potential Vref has a higher potential than the second reference potential Vorg. This causes the photodiode PD to be reverse-biased.

[0044] The light source drive circuit 53 supplies a light source control signal LED1 to the first light source 61 and a light source control signal LED2 to the second light source 62. In this way, the light source drive circuit 53 controls the lighting and non-lighting of each of the first light source 61 and the second light source 62. The first light source 61 and the second light source 62 irradiate the photodiode PD with light amounts corresponding to the light source control signals LED1 and LED2.

[0045] The memory circuit 54 temporarily stores information about the photocurrent Id measured by the detection circuit 51. The memory circuit 54 also stores in advance various pieces of information (coefficients r_th, r_A, margins r_margin1, r_margin2, etc.) used to adjust the output voltage characteristics of the integrating circuit 46, which will be described later.

[0046] The adjustment circuit 55 includes an exposure period setting circuit 56, a gain adjustment circuit 57, an offset adjustment circuit 58, and an arithmetic circuit 59. The adjustment circuit 55 adjusts the exposure period Texp (see FIG. 5 ) in detection of the photodiode PD, and various parameters such as the gain and offset of the integration circuit 46 of the detection circuit 51. The operations of the exposure period setting circuit 56, the gain adjustment circuit 57, the offset adjustment circuit 58, and the arithmetic circuit 59 will be described later with reference to FIG. 7 and subsequent figures. In addition, for ease of understanding, the exposure period setting circuit 56, the gain adjustment circuit 57, the offset adjustment circuit 58, and the arithmetic circuit 59 are depicted as separate circuits in FIG. 3 , but these circuits may be configured as a common circuit (for example, an integrated circuit (IC)).

[0047] 4 is a circuit diagram showing an example of the configuration of a detection device according to an embodiment. As shown in FIG. 4, a plurality of photodiodes PD1, PD2, PD3, and PD4 are connected to an integrating circuit 46 included in a detection circuit 51 via connection switches SSW1, SSW2, SSW3, and SSW4. The detection device 1 also has a constant current source 48. The constant current source 48 is connected to a connection node N1 between the plurality of photodiodes PD1, PD2, PD3, and PD4 and the integrating circuit 46 via an offset switch ofs.

[0048] In the following description, when it is not necessary to distinguish between the photodiodes PD1, PD2, PD3, and PD4, they will simply be referred to as photodiodes PD. Furthermore, when it is not necessary to distinguish between the connection switches SSW1, SSW2, SSW3, and SSW4, they will simply be referred to as connection switches SSW.

[0049] The anode of the photodiode PD is supplied with a second reference potential Vorg from the power supply circuit 52. The cathode of the photodiode PD is connected to the detection circuit 51 via the connection switch SSW.

[0050] The sensor capacitance Cd is connected in parallel to the photodiode PD and is formed between the upper electrode 24 and the lower electrode 23 of the photodiode PD.

[0051] The detection circuit 51 includes an integration circuit 46 and an A / D conversion circuit 47. The integration circuit 46 converts fluctuations in the photocurrent Id output from the photodiode PD into fluctuations in voltage. The A / D conversion circuit 47 converts the analog signal output from the integration circuit 46 into a digital signal.

[0052] The integrator circuit 46 includes an operational amplifier 45, a feedback capacitor Cfb, and a reset switch rsw. The inverting input (-) of the operational amplifier 45 is connected to the photodiode PD via a connection switch SSW. The multiple photodiodes PD1, PD2, PD3, and PD4 are connected in parallel to the inverting input (-) of the integrator circuit 46 via multiple connection switches SSW1, SSW2, SSW3, and SSW4.

[0053] A first reference potential Vref is supplied to the non-inverting input (+) of the operational amplifier 45 from the power supply circuit 52. The output of the operational amplifier 45 is connected to the A / D conversion circuit 47. The output voltage Vout of the integrating circuit 46 is the voltage value at a connection node N2 between the operational amplifier 45 and the A / D conversion circuit 47.

[0054] The gain of the integrating circuit 46 is configured to be changeable. That is, the gain of the integrating circuit 46 can be adjusted by changing the capacitance value of the feedback capacitance Cfb. The feedback capacitance Cfb may be configured as a variable capacitance element, or may be configured to have a plurality of different capacitance elements that can be switched by a switch (not shown). In addition, the reset switch rsw is provided to reset the charge of the feedback capacitance Cfb of the integrating circuit 46 during a reset period.

[0055] 5 is a timing chart illustrating a detection method of the detection device according to the embodiment. As shown in FIG. 5, the detection device 1 includes a measurement cycle adjustment period T0, an external light measurement period T1, and measurement periods T2, T3, and T4. One cycle of measurement including the measurement cycle adjustment period T0, the external light measurement period T1, and the measurement periods T2, T3, and T4 is repeatedly performed multiple times at a predetermined cycle.

[0056] The measurement cycle adjustment period T0 is provided to adjust the measurement cycle for performing one cycle of measurement. During the measurement cycle adjustment period T0, the connection switches SSW and the reset switch rsw are turned on, and the offset switch ofs is turned off.

[0057] During the external light measurement period T1, the detection circuit 51 measures external light irradiated onto the multiple photodiodes PD. During the external light measurement period T1, the first light source 61 and the second light source 62 are turned off, and only external light is irradiated onto the multiple photodiodes PD. At time t1, the multiple connection switches SSW1, SSW2, SSW3, and SSW4 are sequentially turned on. While the connection switch SSW1 is on, a photocurrent Id flows that corresponds to the charge accumulated in the sensor capacitance Cd of the photodiode PD1. The photocurrent Id during the external light measurement period T1 has a current value that corresponds to the intensity of the external light.

[0058] While the connection switch SSW1 is on, the reset switch rsw is repeatedly turned on and off multiple times. In Fig. 5, the period while the connection switch SSW1 is on includes two periods Tchk during which the reset switch rsw is on. However, the number of periods Tchk is simplified to make the drawing easier to understand, and the period Tchk may be provided three or more times depending on the required measurement accuracy of the external light intensity.

[0059] During the ambient light measurement period T1, the offset switch ofs is turned on. The constant current source 48 changes the setting of the offset current Idac for each period Tchk. During the period when the reset switch rsw is off, the offset current Idac having the changed current value flows from the constant current source 48. The output voltage Vout of the integrating circuit 46 changes for each period Tchk according to the offset current Idac. The detection circuit 51 determines the offset current Idac at which the output voltage Vout is equal to the first reference potential Vref as the photocurrent Id_ol due to ambient light. That is, the detection circuit 51 determines the offset current Idac at which the output voltage Vout maintains the first reference potential Vref even after a predetermined time has elapsed since the reset switch rsw was changed from on to off as the photocurrent Id_ol due to ambient light.

[0060] 5, the photocurrent Id_ol due to external light is measured in a time-division manner for each of the photodiodes PD1, PD2, PD3, and PD4 during the external light measurement period T1. The measured photocurrent Id_ol due to external light is stored in the memory circuit 54 for each of the photodiodes PD1, PD2, PD3, and PD4. However, this is not limited to this. During the external light measurement period T1, multiple connection switches SSW1, SSW2, SSW3, and SSW4 may be turned on, and the photocurrent Id_ol due to external light may be measured simultaneously for each of the photodiodes PD1, PD2, PD3, and PD4. In this case, the average value of the photocurrent Id_ol due to external light may be used as the photocurrent Id_ol due to external light for each photodiode PD.

[0061] The adjustment circuit 55 (see FIG. 3) adjusts various parameters such as the gain and offset amount in the output voltage characteristics of the integration circuit 46 based on the external light intensity measured during the external light measurement period T1. The light source drive circuit 53 (see FIG. 3) sets the light intensities of the first light source 61 and the second light source 62 based on the external light intensity measured during the external light measurement period T1.

[0062] Next, during measurement periods T2, T3, and T4, the detection device 1 measures the detectable substance by switching the first light source 61 and the second light source 62 on and off. During measurement period T2, the first light source 61 and the second light source 62 are turned off, and the detectable substance is measured using only external light. During measurement period T3, the first light source 61 is turned on and the second light source 62 is turned off, and the detectable substance is measured using the first light source 61 and external light. During measurement period T4, the first light source 61 is turned off and the second light source 62 is turned on, and the detectable substance is measured using the second light source 62 and external light.

[0063] Each of the measurement periods T2, T3, and T4 includes an exposure period Texp and a readout period Tread. In the following explanation, of the measurement periods T2, T3, and T4, only the measurement period T2 will be explained. However, the measurement method for the measurement periods T3 and T4 is the same as that for the measurement period T2. At time t2, the connection switch SSW1 is turned on, and after a predetermined period has elapsed, the connection switch SSW1 is turned off. The actual exposure period Texp begins when the connection switch SSW1 is turned off. While the light source is on, a current corresponding to the amount of light flows through the photodiode PD1. At this time, if the connection switch SSW1 is on, the potential on the cathode side of the photodiode PD1 maintains a potential equivalent to the first reference potential Vref. When the connection switch SSW1 is turned off, a current corresponding to the amount of light flowing through the photodiode PD1 flows through the sensor capacitance Cd. This causes charge to accumulate in the sensor capacitance Cd.

[0064] After the connection switch SSW1 is turned off, the connection switches SSW2, SSW3, and SSW4 are sequentially controlled to be turned on and off in a time-division manner, and the effective exposure periods Texp of the photodiodes PD2, PD3, and PD4 start sequentially at different timings.

[0065] The reset switch rsw is turned on during a period including the exposure period Texp, and the integration circuit 46 is in a reset state. The reset switch rsw is turned off at a timing before the readout period Tread, and the integration circuit 46 is released from the reset state.

[0066] When the connection switch SSW1 is turned on at time t3, the readout period Tread begins, and a current corresponding to the charge accumulated in the sensor capacitance Cd flows to the feedback capacitance Cfb of the integration circuit 46. An offset period Tdac is set to overlap with the readout period Tread. During the offset period Tdac, the offset switch ofs is turned on, and an offset current Idac set by the adjustment circuit 55 (see FIG. 3) flows from the constant current source 48. The integration circuit 46 converts the current flowing through the capacitance Cd during the readout period Tread and the offset current Idac into a voltage, and outputs the output voltage Vout.

[0067] After the connection switch SSW1 is turned off, the connection switches SSW2, SSW3, and SSW4 are sequentially turned on, and the readout periods Tread of the photodiodes PD2, PD3, and PD4 start sequentially at different timings. The principle of reading from the photodiodes PD2, PD3, and PD4 is the same as the principle of reading from the photodiode PD1 described above.

[0068] The A / D conversion circuit 47 performs signal processing on the output voltage Vout output from the integrating circuit 46 and outputs a sensor value So corresponding to the photocurrent Id to the host 101. Here, the detection circuit 51 outputs, as the sensor value So (measured value), data on the difference between the output voltage Vout of the integrating circuit 46 measured during the measurement period T3 when the first light source 61 is on and the output voltage Vout measured during the measurement period T2 when the first light source 61 and the second light source 62 are off. In other words, the sensor value So (measured value) is data on the difference obtained by subtracting the output voltage Vout based only on external light during the measurement period T2 from the output voltage Vout based on the first light source 61 and external light during the measurement period T3.

[0069] Similarly, the detection circuit 51 outputs, as a sensor value So (measured value), data representing the difference between the output voltage Vout of the integrating circuit 46 measured during the measurement period T4 when the second light source 62 is on and the output voltage Vout measured during the measurement period T2 when the first light source 61 and the second light source 62 are off. That is, the sensor value So (measured value) is the data representing the difference obtained by subtracting the output voltage Vout based only on external light during the measurement period T2 from the output voltage Vout based on the second light source 62 and external light during the measurement period T4. This allows the detection device 1 to remove the component due to external light from the output voltage Vout in the sensor value So, and to accurately measure the object to be detected based on each of the first light source 61 and the second light source 62.

[0070] Next, a method for adjusting the output voltage characteristics of the integrating circuit 46 will be described. FIG. 6 is an explanatory diagram showing the relationship between the integrated light amount and the output voltage of the integrating circuit in a detection device according to a comparative example. The horizontal axis of the graph shown in FIG. 6 represents the integrated light amount, and the vertical axis represents the output voltage Vout of the integrating circuit 46. The integrated light amount is the product of the amount of light irradiated from the light source and the exposure period Texp. Note that in FIG. 6, the exposure period Texp will be described as having a constant length. In the following description, when it is not necessary to distinguish between the first light source 61 and the second light source 62, they will simply be referred to as light sources.

[0071] FIG. 6 also shows a pulse wave graph that shows the relationship between the output voltage Vout (Vout=V1, V2, V3, V4) and time t for each of the integrated light amounts L1, L2, L3, and L4.

[0072] As shown in FIG. 6 , the photodiode PD may be irradiated with different amounts of light, ranging from an integrated light amount L1 when there is no external light and the light source is off to an integrated light amount L4 when there is external light and the light source is on. In the comparative example, the gain and offset are set so that the output voltage Vout (=V1) based on the integrated light amount L1 to the output voltage Vout (=V4) based on the integrated light amount L4 fall within the effective range Da of the integrating circuit. That is, the gain and offset of the integrating circuit are set so that the minimum value of the expected output voltage Vout (output voltage V1) is equal to or greater than the minimum value Vmin of the effective range Da, and the maximum value of the expected output voltage Vout (output voltage V4) is equal to or less than the maximum value Vmax of the effective range Da. As a result, the output voltage Vout output from the integrating circuit 46 may be measured with a small amplitude, potentially reducing detection accuracy.

[0073] FIG. 7 is a flowchart showing a method for adjusting the output voltage characteristics, which show the relationship between the integrated light amount and the output voltage of the integrating circuit, in a detection device according to an embodiment. As shown in FIG. 7 , the detection device 1 measures the photocurrent Id_ol due to external light (step ST1). The measurement of the photocurrent Id_ol due to external light is similar to the method described for the external light measurement period T1 in FIG. 5 , and therefore a repeated description will be omitted. The photocurrent Id_ol due to external light may be measured at each predetermined measurement period, which involves multiple cycles of measurement. However, the photocurrent Id_ol due to external light may be measured every cycle, or at a predetermined timing (e.g., when the detection device 1 is powered on).

[0074] Next, the detection device 1 calculates a virtual photocurrent Id_pl(a) due to the light source (step ST2). Fig. 8 is a graph for explaining a method for calculating the virtual photocurrent Id_pl(a) due to the light source in step ST2 of Fig. 7. The horizontal axis of the graph shown in Fig. 8 represents the photocurrent Id_ol due to external light, and the vertical axis represents the virtual photocurrent Id_pl(a) due to the light source.

[0075] 8, the coefficient r_th indicates the ratio of the light intensity of the light source to the light intensity of external light. The coefficient r_th is set in advance based on past measurement results and the like, and is stored in the memory circuit 54. The coefficient r_th is, for example, approximately 0.3. The coefficient r_th is set so that the photocurrent Id_pl due to the light source can be measured in the detection circuit 51 even when external light is present.

[0076] As shown in Figure 8, the virtual photocurrent Id_pl(a) due to the light source is calculated by multiplying the photocurrent Id_ol due to external light measured in step ST1 (for example, the photocurrent Id_ol due to external light = A2) by a coefficient r_th based on the following equation (1).

[0077] Id_pl(a)=(Id_ol)×(r_th)... (1)

[0078] When the photocurrent Id_ol due to external light is equal to or greater than A1 and equal to or less than A3, the virtual photocurrent Id_pl(a) due to the light source is calculated based on equation (1). When the photocurrent Id_ol due to external light is smaller than A1, the virtual photocurrent Id_pl(a) due to the light source is set to the minimum photocurrent min-Id_pl. When the photocurrent Id_ol due to external light is larger than A3, the virtual photocurrent Id_pl(a) due to the light source is set to the maximum photocurrent max-Id_pl.

[0079] Here, the minimum photocurrent min-Id_pl is the photocurrent Id_pl from the light source that provides a predetermined amplitude of the output voltage Vout in the detection circuit 51 in the absence of external light. The maximum photocurrent max-Id_pl is the photocurrent Id_pl from the light source that flows in the photodiode PD when maximum currents (rated currents) are passed through the first light source 61 and the second light source 62. The minimum photocurrent min-Id_pl and the maximum photocurrent max-Id_pl are set in advance and stored in the memory circuit 54.

[0080] Next, the detection device 1 calculates the exposure period Texp (step ST3). Fig. 9 is an explanatory diagram for explaining the method of calculating the exposure period in step ST3 of Fig. 7. In Fig. 9, the threshold value Cd-max is the maximum value of the integrated light amount corresponding to the saturation capacity of the sensor capacitance Cd of the photodiode PD.

[0081] 9, when the photocurrent Id_ol due to external light and the virtual photocurrent Id_pl(a) due to the light source flow over the exposure period Texp(d) before adjustment, the integrated light amount B4 may exceed the threshold value Cd-max. Here, the integrated light amount B3 of the photocurrent Id_ol due to external light is expressed as B3 = (Id_ol) × (Texp(d)). Furthermore, the integrated light amount B4 is expressed as B4 = (Id_ol) × (Texp(d)) + (Id_pl(a)) × (Texp(d)).

[0082] The exposure period setting circuit 56 (see FIG. 3) sets the adjusted exposure period Texp(s) based on the photocurrent Id_ol due to external light obtained in steps ST1 and ST2 and the virtual photocurrent Id_pl(a) due to the light source so that the sensor capacitance Cd does not saturate. More specifically, the exposure period setting circuit 56 (see FIG. 3) determines the adjusted exposure period Texp(s) based on the following equation (2):

[0083] Texp(s)=(Cd×(Vref-Vorg)×r_margin1) / ((Id_ol)+(Id_pl(a)))+Tread... (2)

[0084] Here, in equation (2), r_margin1 is a margin for the saturated capacitance of the sensor capacitance Cd. The margin r_margin1 is a preset parameter and is stored in the memory circuit 54. For example, the margin r_margin1 is set to about 0.7.

[0085] Next, the detection device 1 determines the gain of the integrating circuit 46 (step ST4). Fig. 10 is a graph for explaining the method of adjusting the gain and offset amount in steps ST4 and ST5 of Fig. 7. Fig. 11 is a graph for explaining the waveforms of each output voltage and the measurement range in Fig. 10.

[0086] The horizontal axis of the graph shown in Fig. 10 represents the integrated light amount, and the vertical axis represents the output voltage Vout of the integrating circuit 46. Output voltage characteristics G1, G2, and G3 shown in Fig. 10 each represent the relationship between the amount of light irradiated onto the photodiode PD and the output voltage Vout of the integrating circuit 46. Furthermore, the integrated light amounts B1 and B2 in Fig. 10 are the integrated light intensities corresponding to the exposure period Texp (s) after adjustment obtained in step ST3.

[0087] FIG. 11 shows a schematic diagram of the waveforms (pulse waves) of the output voltage Vout (=V15, V16) of the output voltage characteristic G1 in FIG. 10, the output voltage Vout (=V13, V14) of the output voltage characteristic G2, and the output voltage Vout (=V11, V12) of the output voltage characteristic G3 on the same time axis.

[0088] 10, in the output voltage characteristic G1 corresponding to the feedback capacitance Cfb(d) before adjustment, the output voltage Vout of the integrating circuit 46 at the integrated light amount B1 when the light source is off (external light only) is Vout=V15. The output voltage Vout of the integrating circuit 46 at the integrated light amount B2 when the light source is on (external light and light source) is Vout=V16.

[0089] 11, the measurement range D(d) before adjustment is represented by the difference between the output voltage Vout (=V16) at the integrated light amount B2 (when the light source is on) and the output voltage Vout (=V15) at the integrated light amount B1 (when the light source is off). More specifically, the measurement range D(d) before adjustment is the difference between the maximum amplitude of the output voltage V16 and the minimum amplitude of the output voltage V15.

[0090] The measurement range D(d) before adjustment is greater than the effective range Dmax. Here, the effective range Dmax is determined by multiplying the effective range Da (see FIG. 6) of the integrating circuit 46 by a margin r_margin2 (Dmax = Da × (r_margin2)). The margin r_margin2 is a parameter that is set in advance in consideration of time fluctuations in the DC component of the output voltage Vout, and is stored in the memory circuit 54. For example, the margin r_margin2 is set to approximately 0.6.

[0091] In step ST4, the integration circuit 46 reduces the gain as the photocurrent Id_ol (amount of external light) due to external light measured in step ST1 when the light source is off increases. More specifically, the gain adjustment circuit 57 (see FIG. 3) is configured to include a feedback capacitance Cfb of the integration circuit 46, and can adjust the gain of the integration circuit 46 by changing the capacitance value of the feedback capacitance Cfb.

[0092] 10 and 11, the gain adjustment circuit 57 (see FIG. 3) adjusts the feedback capacitance Cfb so that the measurement range D(d) before adjustment falls within the effective range Dmax. Specifically, the gain adjustment circuit 57 (see FIG. 3) determines the adjusted feedback capacitance Cfb(s) based on the following equation (3):

[0093] Cfb(s)=(Id_pl(a)+(Id_ol+Id_pl(a))×(r_ac))×Texp(s) / Dmax... (3)

[0094] In equation (3), the coefficient r_ac is the maximum value of the ratio (=ac / dc) of the AC component (ac) to the DC component (dc) of the output voltage Vout, and is set to, for example, about 0.05 (5%).

[0095] 10, the output voltage characteristic G2 after gain adjustment has a smaller slope than the output voltage characteristic G1 before adjustment. In the output voltage characteristic G2 after gain adjustment, the output voltage Vout of the integrating circuit 46 at the integrated light amount B1 is Vout=V13. The output voltage Vout of the integrating circuit 46 at the integrated light amount B2 is Vout=V14. The difference (V14-V13) between the output voltage V14 and the output voltage V13 is smaller than the difference (V16-V15) between the output voltage V16 and the output voltage V15 in the output voltage characteristic G1 before adjustment.

[0096] 11, the adjusted measurement range D(s) is the difference between the maximum amplitude of the output voltage V14 at the integrated light amount B2 and the minimum amplitude of the output voltage V13 at the integrated light amount B1. The adjusted measurement range D(s) is set to be equal to the effective range Dmax.

[0097] Next, the detection device 1 determines the offset amount of the integrating circuit 46 (step ST5). The offset amount of the output voltage characteristic G2 of the integrating circuit 46 can be adjusted by changing the offset current Idac of the constant current source 48 (see FIG. 4). In other words, the offset adjustment circuit 58 (see FIG. 3) includes the constant current source 48 connected to the photodiode PD and the connection node N1 with the detection circuit 51.

[0098] 10 , the offset adjustment circuit 58 determines the adjusted offset current Idac(s) for the gain-adjusted output voltage characteristic G2 obtained in step ST4 so that the output voltage Vout of the integrating circuit 46 at the integrated light intensity B1 (when the light source is off) becomes the target voltage Vtgt. More specifically, the offset adjustment circuit 58 determines the offset current Idac(s) based on the component (voltage value) of the photocurrent Id_ol due to external light and the difference between the first reference potential Vref and the target voltage Vtgt. The offset adjustment circuit 58 shifts the gain-adjusted output voltage characteristic G2 obtained in step ST4 toward a lower voltage as the photocurrent Id_ol due to external light (the amount of external light) becomes larger.

[0099] The adjusted offset current Idac(s) is expressed by the following equation (4): In equation (4), Tdac is the offset period Tdac shown in FIG.

[0100] Idac(s)=((Id_ol)×Texp(s)+Cfb(s)×(Vtgt-Vref)) / Tdac... (4)

[0101] As shown in FIGS. 10 and 11 , in the output voltage characteristic G3 after the offset adjustment, the output voltage Vout of the integrating circuit 46 at the integrated light amount B1 is shifted to Vout=V11. The output voltage V11 has a voltage value equivalent to the target voltage Vtgt. Furthermore, the output voltage Vout of the integrating circuit 46 at the integrated light amount B2 is shifted to Vout=V12. The output voltage V12 has a voltage value equivalent to the first reference potential Vref. The difference (V12−V11) between the output voltage V12 and the output voltage V11 is ideally equivalent to the difference (V14−V13) between the output voltage V14 and the output voltage V13 in the output voltage characteristic G2.

[0102] Furthermore, the measurement range D(s) in the output voltage characteristic G3 after offset adjustment is located within the effective range Da of the integrating circuit 46. As shown in Fig. 11, the minimum value of the amplitude of the output voltage V11 of the integrating circuit 46 at the integrated light amount B1 (when the light source is off) is equal to or greater than the minimum value Vmin of the effective range Da. Furthermore, the maximum value of the amplitude of the output voltage V12 of the integrating circuit 46 at the integrated light amount B2 (when the light source is on) is equal to or less than the maximum value Vmax of the effective range Da.

[0103] Next, the detection device 1 measures the object to be detected under the conditions of the gain and offset of the integration circuit 46 and the exposure period Texp in the detection circuit 51 determined in steps ST3 to ST5 (step ST6). In measuring the object to be detected in step ST6, the light intensities of the first light source 61 and the second light source 62 are determined according to the photocurrent Id_ol due to external light.

[0104] 12 is a graph illustrating a method for calculating the drive current supplied to the optical sensor. The horizontal axis of the graph shown in FIG. 12 represents the photocurrent Id_ol due to external light, and the vertical axis represents the light source drive current ILED supplied to the first light source 61 and the second light source 62.

[0105] 12, the light source drive current ILED is calculated based on the following equation (5) by multiplying the photocurrent Id_ol due to external light measured in step ST1 (for example, the photocurrent Id_ol due to external light is E2) by a coefficient r_A. In FIG. 12, the coefficient r_A indicates the ratio of the light amount of the light source (light source drive current ILED) to the amount of external light. The coefficient r_A is set in advance and stored in the memory circuit 54.

[0106] ILED=(Id_ol)×(r_A)... (5)

[0107] As shown in equation (5), the greater the amount of external light, the greater the light source drive current ILED. That is, the greater the amount of external light, the greater the light amounts of the first light source 61 and the second light source 62. Furthermore, the smaller the amount of external light, or when there is no external light, the smaller the light source drive current ILED. That is, the smaller the amount of external light, the smaller the light amounts of the first light source 61 and the second light source 62. This allows the detection device 1 to reduce the power consumption of the first light source 61 and the second light source 62 compared to when the first light source 61 and the second light source 62 irradiate light at a fixed, constant amount regardless of the amount of external light.

[0108] More specifically, when the photocurrent Id_ol due to external light is in the range of E1 to E3, the light source drive current ILED is calculated based on equation (5). When the photocurrent Id_ol due to external light is smaller than E1, the light source drive current ILED is set to the minimum value min-ILED. When the photocurrent Id_ol due to external light is larger than E3, the light source drive current ILED is set to the maximum value max-ILED.

[0109] Here, the minimum value min-ILED of the light source drive current ILED is a minimum current value that is set in advance corresponding to the photocurrent Id_pl (e.g., minimum photocurrent min-Id_pl (see FIG. 8)) from the light source that can be measured by the detection circuit 51 in the absence of external light. The maximum value max-ILED of the light source drive current ILED is the maximum current value (rated current) that can be passed through each of the first light source 61 and the second light source 62.

[0110] During measurement periods T3 and T4 (see FIG. 5), the light source drive circuit 53 supplies the light source drive current I determined based on FIG. 12 and equation (5) to the first light source 61 and the second light source 62. The photodiode PD is irradiated with external light and light corresponding to the light source drive current I set in step ST6 from the first light source 61 and the second light source 62.

[0111] During measurement periods T3 and T4 (see FIG. 5), the connection switch SSW is turned on and off based on the adjusted exposure period Texp (s) set in step ST3. This causes a charge corresponding to the adjusted exposure period Texp (s) to accumulate in the sensor capacitance Cd. During the readout period Tread, the integration circuit 46 of the detection circuit 51 measures the photocurrent Id_ol due to external light and the photocurrent Id_pl due to the light source, using the gain and offset determined in steps ST4 and ST5.

[0112] As a result, compared to the comparative example described above, the detection device 1 of this embodiment can appropriately adjust the output voltage characteristics of the integrating circuit 46 by determining the exposure period Texp, the gain of the integrating circuit 46, and the offset amount according to the intensity of external light. Therefore, regardless of the intensity of external light, the amplitude of the output voltage Vout can be measured within the effective range Da of the integrating circuit 46, and the effective range Da of the integrating circuit 46 can be used widely. Therefore, the detection device 1 can improve detection accuracy.

[0113] Furthermore, since the detection device 1 of this embodiment can measure a large amplitude of the output voltage Vout regardless of the intensity of external light, it is possible to suppress signal processing of the output voltage Vout, such as increasing the number of bits of the A / D conversion circuit 47, compared to the comparative example described above. As a result, the detection device 1 of this embodiment can suppress the generation of noise due to signal processing.

[0114] 7 to 12 are merely examples of the methods for adjusting various parameters, and may be modified as appropriate. For example, the values ​​of the coefficient r_th, the coefficient r_A, the margins r_margin1, r_margin2, etc. are merely exemplary and are not limited to these. Alternatively, the exposure period Texp, the gain of the integration circuit 46, and the offset amount may be determined without using the margins r_margin1 and r_margin2.

[0115] 13 is a schematic diagram showing an example of the appearance of a detection device according to a modification when a finger is placed inside the detection device as viewed from the side of the housing. FIG. 14 is a cross-sectional view taken along the line XIV-XIV′ in FIG.

[0116] As shown in FIG. 13 , the detection device 1A according to the modified example can be applied to a ring-shaped device that can be attached to and detached from the human body. The detection device 1A is worn on a finger Fg of the human body. The finger Fg includes the thumb, index finger, middle finger, ring finger, little finger, etc. The human body is an individual to be authenticated, whose identity is verified by the detection device 1A. The detection device 1A can detect biometric information about a living body from the finger Fg on which it is worn. The finger Fg is an example of a measurement target. The measurement target is a living body or part of a living body, and is the measurement target. The detection device 1A is made into a ring or wristband, making it easy for the user to carry. In the following description, it is assumed that the detection device 1A is used as a ring.

[0117] 14 , the detection device 1A includes a housing 200, a light source 60, a first optical sensor 10A, a second optical sensor 10B, and a flexible printed circuit board 70. The detection device 1A includes a battery (not shown) inside the housing 200 and operates on power from the battery.

[0118] The housing 200 is formed in a ring shape (annular shape) that can be worn on a finger Fg and is a wearable member that is worn on a living body. In the example shown in FIG. 14 , the housing 200 includes a first housing 210 and a second housing 220. The first housing 210 and the second housing 220 are integrally formed into a ring shape. The first housing 210 is a member that comes into contact with the human body on which the housing 200 is worn. The first housing 210 houses the light source 60, the first optical sensor 10A, the second optical sensor 10B, etc. The first housing 210 is formed in a ring shape using a housing material such as a transparent synthetic resin or silicone. The second housing 220 has a surface of the housing 200 that covers the outer peripheral surface 210A of the first housing 210. The second housing 220 is formed in a ring shape using a material such as a metal or a non-transparent synthetic resin. The housing 200 accommodates the flexible printed circuit board 70, on which the light source 60, the first optical sensor 10A, the second optical sensor 10B, etc. are mounted, inside the first housing 210. The flexible printed circuit board 70 is accommodated inside the housing 200, for example, by forming the housing 200 in a ring shape using a mold and filling the surrounding area with a filling material.

[0119] In this modification, the first optical sensor 10A and the second optical sensor 10B each include the above-described photodiode PD. The first optical sensor 10A and the second optical sensor 10B are arranged to sandwich the light source 60 in the circumferential direction 200C. That is, the detection device 1A is arranged in the circumferential direction 200C with the first optical sensor 10A, the light source 60, and the second optical sensor 10B lined up in this order. By arranging the first optical sensor 10A and the second optical sensor 10B to sandwich the light source 60 in the circumferential direction 200C, the light emitted by the light source 60 can be detected over a wide range of the housing 200.

[0120] The detection device 1A according to the modified example can also apply the same methods for adjusting the exposure period Texp, the gain of the integration circuit 46, and the offset amount as in the detection device 1 of the embodiment. The configurations shown in Figures 13 and 14 are merely examples and can be modified as appropriate. For example, while Figure 14 shows one light source 60, the present invention is not limited to this, and multiple light sources 60 (first light source 61 and second light source 62) may be provided so as to be able to irradiate near-infrared light, red light, and green light.

[0121] Although preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to such embodiments. The contents disclosed in the embodiments are merely examples, and various modifications are possible within the scope of the present disclosure. Appropriate modifications made within the scope of the present disclosure naturally fall within the technical scope of the present disclosure. At least one of various omissions, substitutions, and modifications of components can be made within the scope of the gist of each of the above-described embodiments and modifications.

[0122] 1, 1A Detector 21 Substrate 23 Lower electrode 24 Upper electrode 30 Organic semiconductor layer 31 Active layer 32 Lower buffer layer 33 Upper buffer layer 45 Operational amplifier 46 Integration circuit 47 A / D conversion circuit 48 Constant current source 50 Control circuit 51 Detection circuit 52 Power supply circuit 55 Adjustment circuit 57 Gain adjustment circuit 58 Offset adjustment circuit 61 First light source 62 Second light source Cfb Feedback capacitance Vref First reference potential Vorg Second reference potential PD, PD1, PD2, PD3, PD4 Photodiodes (photosensors)

Claims

1. A detection device comprising: an optical sensor; a light source which irradiates light onto the optical sensor; and a detection circuit including an integrating circuit connected to the optical sensor, wherein the integrating circuit is configured to change a gain corresponding to a slope of an output voltage characteristic which indicates the relationship between the amount of light irradiated onto the optical sensor and the output voltage of the integrating circuit, the optical sensor measures the amount of light when the light source is turned off and when the light source is turned on, and the integrating circuit reduces the gain as the amount of external light measured when the light source is turned off increases.

2. The detection device according to claim 1, wherein the detection circuit outputs, as a measured value, data on the difference between the output voltage of the integrating circuit when the light source is turned off and the output voltage of the integrating circuit when the light source is turned on.

3. The detection device according to claim 1, wherein the amount of light from the light source is increased as the amount of external light increases.

4. The detection device according to claim 1, further comprising an offset adjustment circuit, the offset adjustment circuit shifting the output voltage characteristics to a lower voltage side as the amount of external light increases.

5. The detection device according to claim 4, wherein the offset adjustment circuit includes a constant current source connected to a connection node between the optical sensor and the detection circuit.

6. A detection device according to claim 1, further comprising a gain adjustment circuit, the gain adjustment circuit including a feedback capacitance of the integrating circuit, and adjusting the gain in the integrating circuit by changing a capacitance value of the feedback capacitance.

7. The detection device according to claim 1, wherein the optical sensor is an OPD (Organic Photodiode).

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