Detection device

Abstract

A detection device disclosed herein comprises: a photodiode; a light source that irradiates the photodiode with light; a detection circuit that is connected to the photodiode, measures the current output from the photodiode, and outputs a sensor output; and a control circuit that controls the detection operation of the photodiode and the detection circuit. The control circuit has a first period, in which the sensor output from the detection circuit is not used as detection data, and a second period, in which the sensor output from the detection circuit is used as detection data, and performs detection by switching to the second period after the first period has elapsed from the measurement start timing of the photodiode and the detection circuit.

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 have multiple photodiodes that use an organic semiconductor material as an active layer. As described in Patent Document 2, the photodiodes are disposed between a lower electrode and an upper electrode, and the lower electrode, an electron transport layer, an active layer, a hole transport layer, and the upper electrode are stacked in this order, for example.

[0003] JP 2009-32005 A International Publication No. 2020 / 188959

[0004] There is a demand for improved detection accuracy in optical sensors using OPDs (organic photodiodes).

[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 aspect of the present disclosure includes a photodiode, a light source that irradiates the photodiode with light, a detection circuit connected to the photodiode that measures a current output from the photodiode and outputs a sensor output, and a control circuit that controls the detection operation of the photodiode and the detection circuit, wherein the control circuit has a first period in which the sensor output from the detection circuit is not used as detection data and a second period in which the sensor output from the detection circuit is used as detection data, and after the first period has elapsed from the timing at which the photodiode and the detection circuit start measurement, the control circuit switches to the second period and performs detection.

[0007] FIG. 1 is a schematic diagram showing an example of the external appearance of a detection device according to the first embodiment, when a finger is placed inside the detection device, as viewed from the side of the housing. FIG. 2 is a cross-sectional view taken along line II-II' in FIG. 1. FIG. 3 is a development view showing an example of the development of a flexible substrate of the detection device according to the first embodiment. FIG. 4 is a plan view showing an example of the configuration of the sensor substrate shown in FIG. 3. FIG. 5 is a cross-sectional view taken along line V-V' in FIG. 4. FIG. 6 is a cross-sectional view taken along line VI-VI' in FIG. 4. FIG. 7 is a block diagram showing an example of the configuration of the detection device according to the first embodiment. FIG. 8 is a circuit diagram showing an example of the configuration of a detection circuit. FIG. 9 is a timing waveform diagram showing an example of the operation of a detection device according to a comparative example. FIG. 10 is a graph schematically showing the relationship between the drive time and the sensor output of a detection device according to a comparative example. FIG. 11 is a timing waveform diagram showing an example of the operation of the detection device according to the first embodiment. FIG. 12 is a timing waveform diagram showing an example of the operation of a detection device according to a second embodiment. FIG. 13 is a graph schematically showing the relationship between the drive time and the sensor output of a detection device according to the second embodiment. FIG. 14 is a timing waveform diagram showing an example of the operation of a detection device according to a third embodiment. Fig. 15 is a graph schematically showing the relationship between the drive time and the sensor output of the detection device according to the third embodiment. Fig. 16 is a timing waveform diagram showing an example of the operation of the detection device according to the fourth embodiment. Fig. 17 is a graph schematically showing the relationship between the drive time and the sensor output of the detection device according to the fourth embodiment.

[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 the present disclosure, 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 schematic diagram showing an example of the appearance of a detection device according to a first embodiment, when a finger is placed inside the detection device, as viewed from the side of the housing. FIG. 2 is a cross-sectional view taken along line II-II′ of FIG. 1.

[0011] As shown in FIG. 1 , the detection device 1 according to the first embodiment is a ring-shaped device that can be attached to and detached from the human body. The detection device 1 is worn on, for example, 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 1. The detection device 1 can detect biometric information about a living organism 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 organism or a part of a living organism, and is a measurement target. The detection device 1 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 1 is used as a ring.

[0012] Although the detection device 1 is a ring-shaped device, the invention is not limited to this, and the detection device 1 may be built into a wristwatch or a wristband to be configured as a wearable device.

[0013] 2, the detection device 1 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 1 includes a battery (not shown) inside the housing 200 and operates on power from the battery.

[0014] The housing 200 is formed in a ring shape (annular shape) that can be worn on a finger Fg, and is a wearing member that is worn on a living body. As shown in Fig. 2, the housing 200 includes a first housing 210 and a second housing 220. The housing 200 is formed in a ring shape by integrating the first housing 210 and the second housing 220.

[0015] 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 from a housing material such as a transparent synthetic resin or silicone.

[0016] 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 from a material such as metal or non-transparent synthetic resin. The housing 200 accommodates a 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 by, for example, forming the housing 200 in a ring shape in a mold and filling the surrounding area with a filling material.

[0017] In this embodiment, the first optical sensor 10A and the second optical sensor 10B are provided so as to sandwich the light source 60 in the circumferential direction 200C. That is, the detection device 1 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 so as to sandwich the light source 60 in the circumferential direction 200C, the first optical sensor 10A and the second optical sensor 10B can detect light emitted by the light source 60 over a wide range of the housing 200.

[0018] Each of the first optical sensor 10A and the second optical sensor 10B detects light emitted by the light source 60 and reflected by a finger Fg or the like, directly incident light, etc. The first optical sensor 10A and the second optical sensor 10B are organic photodiodes (OPDs). The first optical sensor 10A is provided on the housing 200 so as to be adjacent to one end 61 of the light source 60 in the circumferential direction 200C of the housing 200. The second optical sensor 10B is provided on the housing 200 so as to be adjacent to the other end 62 of the light source 60 in the circumferential direction 200C of the housing 200.

[0019] As shown in FIG. 2 , the light source 60 is provided inside the first housing 210 of the housing 200 and is configured to be able to irradiate light toward the finger Fg wearing the housing 200. For example, an inorganic LED (Light Emitting Diode) or an organic EL (OLED) is used as the light source 60. The light source 60 irradiates light of a predetermined wavelength. In this embodiment, the light source 60 has multiple light sources so as to be able to irradiate near-infrared light, red light, and green light. However, the present invention is not limited thereto, and the light source 60 may have a light source of at least one color.

[0020] Light emitted from the light source 60 is reflected by the surface of the object to be detected, such as a finger Fg, and enters the first optical sensor 10A and the second optical sensor 10B. This allows the detection device 1 to detect a fingerprint by detecting the shape of the projections and recesses on the surface of the finger Fg. Alternatively, the light emitted from the light source 60 may be reflected inside the finger Fg or pass through the finger Fg before entering the first optical sensor 10A and the second optical sensor 10B. This allows the detection device 1 to detect information about a living body inside the finger Fg. Examples of information about a living body include pulse waves, pulse rates, and blood vessel images of the finger or palm. That is, the detection device 1 may be configured as a fingerprint detection device that detects fingerprints, or a vein detection device that detects vascular patterns such as veins.

[0021] 3 is a development view showing an example of the development of the flexible substrate of the detection device according to the first embodiment. As shown in FIG. 3, the flexible printed circuit board 70 is formed in a deformable band shape, and is formed into a ring shape by bringing one end 71 and the other end 72 close to each other or connecting them. The flexible printed circuit board 70 has a first mounting area 73 and a second mounting area 74. The first mounting area 73 is an area where the light source 60 and the like are mounted. The second mounting area 74 is an area where the control circuit 51, the power supply circuit 52, and the like are mounted.

[0022] The sensor board 21 is mounted on the flexible printed circuit board 70 so as to straddle the vicinity of the light source 60 in the first mounting area 73. The first optical sensor 10A, the second optical sensor 10B, etc. are mounted on the sensor board 21. The sensor board 21 is an insulating board, and is formed, for example, in a strip shape using a film-like resin or the like, making it a deformable board. The sensor board 21 is provided inside the housing 200 and curves to fit the shape of the housing 200. The flexible printed circuit board 70 electrically connects the first optical sensor 10A and the second optical sensor 10B on the sensor board 21, the light source 60, and the control circuit 51.

[0023] 2 , the flexible printed circuit board 70 is housed inside the housing 200 so that the surface on which the first optical sensor 10A, the second optical sensor 10B, and the light source 60 are mounted is located on the inner periphery of the housing 200. If the flexible printed circuit board 70 is translucent, the first optical sensor 10A, the second optical sensor 10B, and the light source 60 may be mounted on the side facing the outer periphery of the ring, opposite to the side facing the inner periphery of the ring. In this case, the light source 60 may be disposed so that it emits light toward the flexible printed circuit board 70 and that the light that has passed through the flexible printed circuit board 70 is emitted toward the side facing the inner periphery of the housing 200.

[0024] Next, the detailed configuration of the sensor substrate will be described with reference to Fig. 4. Fig. 4 is a plan view showing an example of the configuration of the sensor substrate shown in Fig. 3. Fig. 4 shows a plan view of the sensor substrate 21 when it is developed into a flat plate.

[0025] In the following description, 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 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 sensor substrate 21. Furthermore, "planar view" refers to the positional relationship when viewed from a direction perpendicular to the sensor substrate 21.

[0026] As shown in FIG. 4 , the sensor board 21 has a cutout portion 22 between both ends in the circumferential direction 200C of the housing 200, i.e., in the longitudinal direction (first direction Dx) of the sensor board 21. The sensor board 21 has a plurality of first optical sensors 10A mounted on one end 21A of the cutout portion 22, and a plurality of second optical sensors 10B mounted on the other end 21B of the cutout portion 22. In other words, the cutout portion 22 is located between the first optical sensors 10A and the second optical sensors 10B in the first direction Dx. The terminal portion 40 is provided at one end 21A of the sensor board 21 in the longitudinal direction. The terminal portion 40 supplies power from a power supply circuit 52 (see FIG. 3 ) to the first optical sensors 10A and the second optical sensors 10B.

[0027] The sensor substrate 21 also includes a connecting portion 23 corresponding to the portion where the cutout portion 22 is provided. The connecting portion 23 contacts the cutout portion 22 and connects the region of the sensor substrate 21 where the first optical sensor 10A is provided and the region of the sensor substrate 21 where the second optical sensor 10B is provided. This allows the region of the sensor substrate 21 where the first optical sensor 10A is provided and the region of the sensor substrate 21 where the second optical sensor 10B is provided to be integrally formed.

[0028] The light source 60 is disposed in an area overlapping with the cutout portion 22. The cutout portion 22 is formed over a distance in the first direction Dx that is longer than the length of the light source 60. The cutout portion 22 is formed over a distance in the second direction Dy that is longer than the length of the light source 60 and shorter than the length (width) of the sensor substrate 21. This allows the cutout portion 22 of the sensor substrate 21 to secure a space for disposing the light source 60.

[0029] Next, the configurations of the first optical sensor 10A and the second optical sensor 10B will be described with reference to Figures 4 to 6. Figure 5 is a cross-sectional view taken along line VV' in Figure 4. Figure 6 is a cross-sectional view taken along line VI-VI' in Figure 4.

[0030] 4, the first optical sensor 10A has a stacked configuration in which two lower electrodes 11 aligned in the first direction Dx are covered by one upper electrode 15A. The second optical sensor 10B has a stacked configuration in which two lower electrodes 11 aligned in the first direction Dx are covered by one upper electrode 15B. The upper electrode 15 includes the upper electrode 15A of the first optical sensor 10A and the upper electrode 15B of the second optical sensor 10B. The upper electrodes 15A and 15B have rectangular surfaces and are independent electrodes that are not electrically connected.

[0031] The first power supply electrode 25A and the second power supply electrode 25B are provided on the sensor substrate 21 and extend along the second direction Dy. The first power supply electrode 25A is provided between one end 21A of the sensor substrate 21 and the first optical sensor 10A in the first direction Dx. The second power supply electrode 25B is provided between the other end 21B of the sensor substrate 21 and the second optical sensor 10B in the first direction Dx. The first power supply electrode 25A is electrically connected to a terminal 40 of the sensor substrate 21 via a first wiring 26A, and receives a power supply potential from a power supply circuit 52 (see FIG. 3 ) via the terminal 40. The second power supply electrode 25B is electrically connected to a terminal 40 of the sensor substrate 21 via a second wiring 26B, and receives a power supply potential from the power supply circuit 52 via the terminal 40.

[0032] The upper electrode 15A of the first optical sensor 10A is connected to the first power supply electrode 25A via the conductive material 24 and is electrically connected to the terminal 40 via the first wiring 26A connected to the first power supply electrode 25A. The upper electrode 15B of the second optical sensor 10B is connected to the second power supply electrode 25B via the conductive material 24 and is electrically connected to the terminal 40 via the second wiring 26B connected to the second power supply electrode 25B. As a result, the upper electrode 15A and the upper electrode 15B are each supplied with power from the independent power systems of the first power supply electrode 25A and the second power supply electrode 25B. The conductive material 24 is made of a conductive material and covers the entire surface of the first power supply electrode 25A or the second power supply electrode 25B, electrically connecting the first power supply electrode 25A to the upper electrode 15A and the second power supply electrode 25B to the upper electrode 15B. The upper electrode 15A and the first power supply electrode 25A, and the upper electrode 15B and the second power supply electrode 25B may be directly connected without the conductive material 24 therebetween.

[0033] The third wiring 26C connects each of the lower electrodes 11 of the first optical sensor 10A and the second optical sensor 10B to a terminal 40 provided on the sensor substrate 21. The third wiring 26C connected to the lower electrode 11 of the first optical sensor 10A is connected to the terminal 40 through a region along one of the long sides of the sensor substrate 21 (the lower long side in FIG. 4 ). The third wiring 26C connected to the lower electrode 11 of the second optical sensor 10B is connected to the terminal 40 through a region along the other of the long sides of the sensor substrate 21 (the upper long side in FIG. 4 ) and the connecting portion 23. The multiple third wirings 26C are connected to the detection circuit 48 (see FIG. 7 ) via the terminal 40 and signal lines of the flexible printed circuit board 70. In other words, the detection circuit 48 (see FIG. 7 ) is electrically connected to the lower electrodes 11 of the first optical sensor 10A and the second optical sensor 10B via the signal lines.

[0034] The first power supply electrode 25A and the second power supply electrode 25B are supplied with a power supply potential from a power supply circuit 52 via the terminal portion 40, and supply the power supply potential to the upper electrode 15A and the upper electrode 15B. In the example shown in Fig. 4, the first power supply electrode 25A and the second power supply electrode 25B are formed in a substantially rectangular shape extending in the second direction Dy in a plan view, and have the same area (size).

[0035] As shown in FIG. 5, the photodiode PD constituting the first optical sensor 10A is provided on the sensor substrate 21 via an insulating layer 27.

[0036] The third wiring 26C is provided on the upper surface of the sensor substrate 21. The third wiring 26C is formed, for example, of a metal wiring, and is formed of a material having better conductivity than the lower electrode 11 of the first optical sensor 10A. The third wiring 26C is provided in a layer between the sensor substrate 21 and the photodiode PD in the third direction Dz. The third wiring 26C is electrically connected to the terminal portion 40 on the sensor substrate 21 (see FIG. 4 ). Note that the third wiring 26C may be formed, for example, in the same layer as the lower electrode 11, or may be formed of metal. The insulating layer 27 is provided on the sensor substrate 21, covering the third wiring 26C. The insulating layer 27 may be an inorganic insulating film or an organic insulating film.

[0037] The photodiode PD is provided as a sensor element on the insulating layer 27. The photodiode PD has a lower electrode 11, a lower buffer layer 12, an active layer 13, an upper buffer layer 14, and an upper electrode 15 (upper electrode 15A). In the photodiode PD, the lower electrode 11, the lower buffer layer 12, the active layer 13, the upper buffer layer 14, and the upper electrode 15 are stacked in this order in a third direction Dz perpendicular to the sensor substrate 21.

[0038] The lower electrode 11 is made of a light-transmitting conductive material such as ITO (Indium Tin Oxide).

[0039] The characteristics (for example, voltage-current characteristics and resistance value) of the active layer 13 change depending on the light irradiated thereto. An organic material is used as the material of the active layer 13. Specifically, the active layer 13 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.

[0040] The active layer 13 can be formed by a vapor deposition (dry process) using these low molecular weight organic materials. In this case, the active layer 13 is formed by, for example, CuPc and F １６ CuPc laminated film or rubrene and C ６０The active layer 13 may be a laminated film of the above-mentioned low molecular weight organic material and high molecular weight organic material. The active layer 13 may also be formed by a coating process (wet process). In this case, the active layer 13 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 13 may be a film in which P3HT and PCBM are mixed, or a film in which F8BT and PDI are mixed.

[0041] The lower buffer layer 12 and the upper buffer layer 14 are provided to facilitate the holes and electrons generated in the active layer 13 reaching the lower electrode 11 or the upper electrode 15. One of the lower buffer layer 12 and the upper buffer layer 14 is a hole transport layer. The other of the lower buffer layer 12 and the upper buffer layer 14 is an electron transport layer. The material of the hole transport layer is a metal oxide layer. As the metal oxide layer, tungsten oxide (WO ３ ), molybdenum oxide, etc. The material of the electron transport layer is ethoxylated polyethyleneimine (PEIE).

[0042] The materials and manufacturing methods of the lower buffer layer 12, the active layer 13, and the upper buffer layer 14 are merely examples, and other materials and manufacturing methods may be used. For example, the lower buffer layer 12 and the upper buffer layer 14 are not limited to single-layer films, and may be formed as multilayer films including an electron blocking layer and a hole blocking layer.

[0043] The upper electrode 15 is provided on the upper buffer layer 14. The upper electrode 15 is continuously formed over the entire photodiode PD of the first optical sensor 10A. In other words, the upper electrode 15 is continuously provided over the multiple photodiodes PD. The upper electrode 15 faces the multiple lower electrodes 11, with the lower buffer layer 12, the active layer 13, and the upper buffer layer 14 sandwiched between them. The upper electrode 15 is formed of a light-transmitting conductive material such as ITO or IZO. A portion of the end of the upper surface 15a of the upper electrode 15 is electrically connected to a conductive material 24. The conductive material 24 is electrically connected to a first power supply electrode 25A and supplies a power supply potential from the first power supply electrode 25A to the upper electrode 15.

[0044] The sealing film 90 is provided on the upper electrode 15. The sealing film 90 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 90 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 90 effectively seals the photodiode PD and can prevent moisture from entering from the upper surface side. In this embodiment, the photodiode PD is configured to protect the terminal portion 40, the sensor substrate 21, etc. by covering the sealing film 90 to a part of the terminal portion 40 with a resin 91.

[0045] As shown in FIG. 6 , the two lower electrodes 11 of the second optical sensor 10B are provided in a different region of the sensor substrate 21 from the lower electrodes 11 of the first optical sensor 10A. The lower electrodes 11 are covered with a lower buffer layer 12, an active layer 13, an upper buffer layer 14, and an upper electrode 15B. The photodiode PD constituting the second optical sensor 10B has the same configuration as the photodiode PD of the first optical sensor 10A. That is, the photodiode PD of the second optical sensor 10B has a lower electrode 11, a lower buffer layer 12, an active layer 13, an upper buffer layer 14, and an upper electrode 15B. In this embodiment, the first optical sensor 10A and the second optical sensor 10B are organic photodiodes.

[0046] In the second optical sensor 10B, a portion of an end of the upper surface 15a of the upper electrode 15 is electrically connected to the conductive material 24, and the conductive material 24 is electrically connected to the second power supply electrode 25B. In the second optical sensor 10B, a power supply potential is supplied from the second power supply electrode 25B to the upper electrode 15. In the second optical sensor 10B, a sealing film 90 is provided on the upper electrode 15, the conductive material 24, etc., so that the photodiode PD is well sealed.

[0047] Next, an example of a detection method of the detection device 1 of this embodiment will be described. FIG. 7 is a block diagram showing an example of the configuration of the detection device according to the first embodiment. As shown in FIG. 7, the control circuit 51 controls the detection operation of the photodiode PD and the light source 60 based on a control signal Sc from the host 101. The control circuit 51 also receives the sensor output So output from the detection circuit 48 in response to the current (photocurrent Id) output from the photodiode PD. The control circuit 51 outputs the sensor output So measured during the data use period DT after a predetermined data non-use period NDT has elapsed since the start of measurement to the host 101. The host 101 may be, for example, a host IC, a host CPU, or the like. Details of the data use period DT and the data non-use period NDT will be described later with reference to FIG. 11 and subsequent figures.

[0048] The control circuit 51 includes a detection drive circuit 53, a counter 54, a mode switching circuit 55, a data processing circuit 56, a memory circuit 57, and a timing controller 58. The detection drive circuit 53 outputs various signals such as a start control signal STV, a clock signal CK, and a read control signal CH (see FIG. 11 ) to control the detection operation of the photodiode PD. The detection drive circuit 53 also outputs a power supply control signal CL to the power supply circuit 52 to supply a drive power supply VDD_ORG and a light source drive power supply VLED to the photodiode PD and the light source, respectively.

[0049] The counter 54 is a circuit that counts the number of pulses of the clock signal CK from the detection drive circuit 53. More specifically, the number of pulses of the clock signal CK corresponding to the period from the timing of the start of measurement to the end of a predetermined data non-use period NDT (see FIG. 11) is set in advance, and the counter 54 outputs an output signal to the mode switching circuit 55 when it has counted the preset number of pulses from the timing of the start of measurement.

[0050] The mode switching circuit 55 switches between the data non-use period NDT and the data use period DT based on the output signal from the counter 54. Specifically, the mode switching circuit 55 switches between a high-level voltage mode switching signal DE and a low-level voltage mode switching signal DE based on the output signal from the counter 54, and outputs the switched signal to the detection drive circuit 53 and the data processing circuit 56.

[0051] The detection drive circuit 53 can change various conditions, such as the frame rate, the drive current ILED supplied to the light source 60, and the length of the readout period INT, between the data use period DT and the data non-use period NDT in accordance with the mode switching signal DE from the mode switching circuit 55.

[0052] Furthermore, the data processing circuit 56 performs predetermined processing on the sensor output So received from the detection circuit 48 in response to the mode switching signal DE from the mode switching circuit 55. Details of the data processing circuit 56 will be described later with reference to FIG.

[0053] The memory circuit 57 temporarily stores the sensor output So processed by the data processing circuit 56. The memory circuit 57 also stores various conditions related to the detection operation of the detection device 1. For example, the memory circuit 57 stores in advance various conditions such as the length of the data non-use period NDT (the number of pulses of the clock signal CK), the frame rate at which one frame is detected, the length of the readout period INT of the detection circuit 48, and the drive current ILED supplied to the light source 60.

[0054] The timing controller 58 controls the detection and driving circuit 53, the counter 54, the mode switching circuit 55, the data processing circuit 56, and the memory circuit 57 so that they operate in synchronization with or asynchronous to one another.

[0055] 8 is a circuit diagram showing an example of the configuration of the detection circuit. As shown in Fig. 8, four photodiodes PD1, PD2, PD3, and PD4 are connected to the detection circuit 48. Of the four photodiodes PD1, PD2, PD3, and PD4, for example, the photodiodes PD1 and PD2 form a first optical sensor 10A (see Fig. 4), and the photodiodes PD3 and PD4 form a second optical sensor 10B (see Fig. 4).

[0056] The detection circuit 48 includes a plurality of connection switches SSW1, SSW2, SSW3, and SSW4, operational amplifiers 63a and 63b, transistors Tr1 and Tr2, and A / D conversion circuits 64a and 64b. The power supply circuit 52 includes constant current sources 65a and 65b.

[0057] In the following description, when it is not necessary to distinguish between the multiple photodiodes PD1, PD2, PD3, and PD4, they will simply be referred to as photodiodes PD. When it is not necessary to distinguish between the multiple connection switches SSW1, SSW2, SSW3, and SSW4, they will simply be referred to as connection switches SSW. The operational amplifiers 63a and 63b, transistors Tr1 and Tr2, and A / D conversion circuits 64a and 64b may also be simply referred to as operational amplifier 63, transistor Tr, and A / D conversion circuit 64, respectively.

[0058] A drive power supply VDD_ORG is supplied from a power supply circuit 52 to the cathodes of the multiple photodiodes PD1, PD2, PD3, and PD4. The anodes of the photodiodes PD1, PD2, PD3, and PD4 are connected to one end of connection switches SSW1, SSW2, SSW3, and SSW4, respectively. The other end of either connection switch SSW1 or SSW3 is connected to the inverting input of an operational amplifier 63a and the source of transistor Tr1. The other end of either connection switch SSW2 or SSW4 is connected to the inverting input of an operational amplifier 63b and the source of transistor Tr2. The drains of transistors Tr1 and Tr2 are connected to A / D conversion circuits 64a and 64b, respectively. However, for example, the drains of transistors Tr1 and Tr2 may be connected to a power supply potential via resistors, and both ends of the resistors may be measured by the A / D conversion circuits 64a and 64b, respectively. As a result, the A / D conversion circuits 64a and 64b output to the control circuit 51 a sensor output So corresponding to the current (photocurrent Id) output from the photodiodes PD1, PD2, PD3, and PD4.

[0059] More specifically, connection switches SSW1 and SSW3, an operational amplifier 63a, a transistor Tr1, and an A / D conversion circuit 64a are provided corresponding to the two photodiodes PD1 and PD3. The photodiodes PD1 and PD3 connected to the A / D conversion circuit 64a are switched depending on whether the connection switches SSW1 and SSW3 are on (connected state) or off (disconnected state). When one of the connection switches SSW1 and SSW3 is on, the other of the connection switches SSW1 and SSW3 is off.

[0060] Corresponding to the two photodiodes PD2 and PD4, connection switches SSW2 and SSW4, an operational amplifier 63b, a transistor Tr2, and an A / D conversion circuit 64b are provided. The photodiodes PD2 and PD4 connected to the A / D conversion circuit 64b are switched by turning the connection switches SSW2 and SSW4 on and off. When one of the connection switches SSW2 and SSW4 is on, the other of the connection switches SSW2 and SSW4 is off.

[0061] In the following description, the circuit configuration corresponding to the photodiodes PD1 and PD3 will be described. However, the circuit configuration corresponding to the photodiodes PD1 and PD3 is the same as the circuit configuration corresponding to the photodiodes PD2 and PD4. The description of the circuit configuration corresponding to the photodiodes PD1 and PD3 can also be applied to the circuit configuration corresponding to the photodiodes PD2 and PD4.

[0062] As shown in FIG. 8, the operational amplifier 63 and the transistor Tr are connected between the A / D conversion circuit 64 and the connection switches SSW1 and SSW3 connected to the photodiodes PD1 and PD3.

[0063] One end of each of the connection switches SSW1 and SSW3 is connected to the anodes of the photodiodes PD1 and PD3, respectively. The other ends of the connection switches SSW1 and SSW3 are connected to the inverting input (-) of the operational amplifier 63 and the source of the transistor Tr. That is, the inverting input (-) of the operational amplifier 63 is connected to the photodiodes PD1 and PD3 via the connection switches SSW1 and SSW2. A reference potential VREF is supplied to the non-inverting input (+) of the operational amplifier 63 from the power supply circuit 52. The output of the operational amplifier 63 is connected to the gate of the transistor Tr.

[0064] The transistor Tr is a source-follower transistor. The source of the transistor Tr is connected to the inverting input (−) of the operational amplifier 63 and is also connected to a reference potential (e.g., ground potential GND) via a constant current source 65. The drain of the transistor Tr is connected to the A / D conversion circuit 64.

[0065] The A / D conversion circuit 64 performs signal processing such as A / D conversion based on the current flowing through the drain of the transistor Tr and outputs the sensor output So. In other words, the detection circuit 48 is a current detection circuit that measures the current flowing through the drain of the transistor Tr. The detection circuit 48 is not limited to the A / D conversion circuit 64 and may be configured to include other signal processing circuits, etc.

[0066] With this configuration, for example, when the connection switch SSW1 is on and the connection switch SSW3 is off, the photodiode PD1 is connected to the A / D conversion circuit 64 via the connection switch SSW1, the operational amplifier 63, and the transistor Tr. Also, the photodiode PD3 is disconnected from the transistor Tr and the A / D conversion circuit 64. Due to an imaginary short of the operational amplifier 63, the anode of the photodiode PD1 becomes the same reference potential VREF as the non-inverting input (+).

[0067] The drive power supply VDD_ORG has a potential higher than the reference potential REF. As a result, when the connection switch SSW1 is turned on, the photodiode PD1 is reverse-bias driven. At this time, when light is irradiated onto the photodiode PD1, a photocurrent Id flows from the photodiode PD1 to the constant current source 65. Because the bias current PDBIAS of the constant current source 65 is constant, the current flowing to the drain of the transistor Tr is the bias current PDBIAS minus the photocurrent Id. In other words, the A / D conversion circuit 64 outputs a sensor output So corresponding to the photocurrent Id output from the photodiode PD1. In other words, if the output current flowing to the drain of the transistor Tr is Io, then Io = PDBIAS - Id. The bias current PDBIAS is a preset constant current.

[0068] Similarly, when the connection switch SSW1 is off and the connection switch SSW3 is on, the photodiode PD3 is connected to the A / D conversion circuit 64 via the connection switch SSW3, the operational amplifier 63, and the transistor Tr. Furthermore, the photodiode PD1 is disconnected from the A / D conversion circuit 64. Due to an imaginary short in the operational amplifier 63, the anode of the photodiode PD3 is at the same reference potential VREF as the non-inverting input (+). This causes the photodiode PD3 to be reverse-biased. Similarly, a current Io corresponding to the light irradiating the photodiode PD3 flows through the drain of the transistor Tr. In other words, the A / D conversion circuit 64 outputs a sensor output So corresponding to the photocurrent Id output from the photodiode PD3.

[0069] 8, the photodiodes PD1 and PD3 connected to the operational amplifier 63, the transistor Tr, and the A / D conversion circuit 64 are switched in a time-division manner by turning on and off the connection switches SSW1 and SSW3. Therefore, the detection device 1 can reduce the circuit size compared to when the operational amplifier 63, the transistor Tr, and the A / D conversion circuit 64 are provided corresponding to each of the photodiodes PD1 and PD3. Furthermore, the detection device 1 can improve the degree of detection flexibility by, for example, performing detection using light of different wavelengths corresponding to each of the photodiodes PD1 and PD3.

[0070] Next, a detection method of the detection device 100 according to the comparative example will be described with reference to Fig. 9 and Fig. 10. Fig. 9 is a timing waveform diagram showing an example of the operation of the detection device according to the comparative example. Fig. 10 is a graph schematically showing the relationship between the drive time of the detection device according to the comparative example and the sensor output.

[0071] The detection device 100 according to the comparative example has a similar configuration to the detection device 1 of the first embodiment described above, but differs in the method of detecting the sensor output So. As shown in Fig. 9, in the detection device 100 according to the comparative example, the detection drive circuit 53 outputs a start control signal STV of a high-level voltage at time t1, and detection of one frame (1F) begins. One frame (1F) is the period required to detect the photocurrent Id output from each of the photodiodes PD1, PD2, PD3, and PD4.

[0072] The detection drive circuit 53 sets the start control signal STV to a low-level voltage at time t2. The mode switching circuit 55 sets the mode switching signal DE to a low-level voltage at time t2. As a result, the data non-use period NDT is switched to the data use period DT at approximately the same timing as the start of measurement of one frame (1F), and detection of the data use period DT begins. The data non-use period NDT is a period during which the control circuit 51 does not use the sensor output So received from the detection circuit 48 as detection data. The data use period DT is a period during which the control circuit 51 uses the sensor output So received from the detection circuit 48 as detection data and outputs it to the host 101.

[0073] At time t3, a predetermined period after time t2, the readout period INT of the photodiodes PD1 and PD2 begins. That is, at time t3, the detection drive circuit 53 outputs high-level voltage readout control signals CH1 and CH2, turning on the connection switches SSW1 and SSW2. Also at time t3, the detection drive circuit 53 supplies a drive current ILED to the light source 60, turning on the light source 60.

[0074] As a result, during the readout period INT, the photodiodes PD1 and PD2 are connected to the operational amplifiers 63a and 63b via the connection switches SSW1 and SSW2, respectively. During the readout period INT, a photocurrent Id corresponding to the light irradiated on the photodiodes PD1 and PD2 flows, and the detection circuit 48 outputs a sensor output So corresponding to the photocurrent Id.

[0075] At time t4, the readout period INT for photodiodes PD1 and PD2 ends. At time t5, a predetermined period after time t4, the readout period INT for photodiodes PD3 and PD4 begins. That is, at time t5, the detection drive circuit 53 outputs high-level voltage readout control signals CH3 and CH4, turning on the connection switches SSW3 and SSW4. Also at time t5, the detection drive circuit 53 supplies a drive current ILED to the light source 60, turning on the light source 60.

[0076] As a result, during the readout period INT, the photodiodes PD3 and PD4 are connected to the operational amplifiers 63a and 63b via the connection switches SSW3 and SSW4, respectively. During the readout period INT, a photocurrent Id corresponding to the light irradiated to the photodiodes PD3 and PD4 flows, and the detection circuit 48 outputs a sensor output So corresponding to the photocurrent Id.

[0077] At time t6, the readout period INT of the photodiodes PD3 and PD4 ends, and detection of one frame (1F) is completed. After time t7, detection of the next frame (1F) is repeatedly executed.

[0078] The graph in Fig. 10 shows the relationship between the sensor output So and the drive time for different waiting times. The waiting time is the time from the end of the previous measurement to the start of detection of one frame (1F). As shown in Fig. 10, due to the characteristics of the OPD, the sensor output So output from the photodiode PD shows a large value immediately after drive starts, and requires a predetermined period (approximately 10 seconds in the example shown in Fig. 10) to stabilize.

[0079] In the detection device 100 according to the comparative example, the data use period DT starts at approximately the same timing as the start of measurement for one frame (1F). Therefore, noise components immediately after the start of measurement are detected as included in the sensor output So. As a result, the detection accuracy may be reduced in the comparative example.

[0080] 11 is a timing waveform diagram showing an example of the operation of the detection device 1 according to the first embodiment. As shown in Fig. 11, in the detection device 1 according to the first embodiment, the control circuit 51 has a data non-use period NDT (first period) in which the sensor output So from the detection circuit 48 is not used as detection data, and a data use period DT (second period) in which the sensor output So from the detection circuit 48 is used as detection data.

[0081] After the data non-use period NDT (first period) has elapsed from the timing (e.g., time t21) when the photodiode PD and the detection circuit 48 start measuring, the control circuit 51 switches to the data use period DT (second period) and performs detection.

[0082] More specifically, at time t21, the detection drive circuit 53 outputs a high-level voltage start control signal STV, thereby starting detection of one frame (1F). At time t22, the detection drive circuit 53 sets the start control signal STV to a low-level voltage. At time t23, a predetermined period after time t22, the readout period INT of the photodiodes PD1 and PD2 begins. That is, at time t23, the detection drive circuit 53 outputs high-level voltage readout control signals CH1 and CH2, thereby turning on the connection switches SSW1 and SSW2. Also at time t23, the power supply circuit 52 supplies a drive current ILED to the light source 60, thereby turning on the light source 60.

[0083] At time t24, the readout period INT for photodiodes PD1 and PD2 ends. At time t25, a predetermined period after time t24, the readout period INT for photodiodes PD3 and PD4 begins. That is, at time t25, the detection drive circuit 53 outputs high-level voltage readout control signals CH3 and CH4, turning on the connection switches SSW3 and SSW4. Also at time t25, the detection drive circuit 53 supplies a drive current ILED to the light source 60, turning on the light source 60.

[0084] After time t26, detection of the next frame (1F) is repeatedly executed multiple times.

[0085] The mode switching circuit 55 sets the mode switching signal DE to a high-level voltage for a predetermined period from the start of measurement at time t21. This causes a non-data use period NDT to continue for a predetermined period from the start of measurement of one frame (1F). In this embodiment, the non-data use period NDT is, for example, 10 seconds. As described above, during the non-data use period NDT, the control circuit 51 does not use the sensor output So received from the detection circuit 48 as detection data. Specifically, the data processing circuit 56 of the control circuit 51 does not use the sensor output So received from the detection circuit 48 as detection data during the non-data use period NDT. In this case, the control circuit 51 does not output the sensor output So during the non-data use period NDT to the host 101. Alternatively, the control circuit 51 does not store the sensor output So during the non-data use period NDT in the memory circuit 57.

[0086] After a predetermined data non-use period NDT (e.g., 10 seconds) has elapsed since the start of measurement, the detection drive circuit 53 sets the start control signal STV to a high-level voltage at time t27. The counter 54 outputs an output signal to the mode switching circuit 55 when it has counted the number of pulses of the clock signal CK, which is preset according to the data non-use period NDT, from the timing of the start of measurement. The mode switching circuit 55 receives the output signal from the counter 54 and sets the mode switching signal DE to a low-level voltage at time t28, a predetermined period after time t27. As a result, at time t28, a predetermined period (e.g., 10 seconds) after the start of measurement (time t21), the data non-use period NDT is switched to the data use period DT, and detection of the data use period DT begins.

[0087] From time t29 to time t32, a readout period INT is performed in which the photocurrent Id flowing through the photodiode PD is measured, similar to the period from time t23 to time t26. The detection circuit 48 outputs a sensor output So corresponding to the photocurrent Id. The data processing circuit 56 of the control circuit 51 uses the sensor output So received from the detection circuit 48 as detection data during the data use period DT. In this case, the control circuit 51 outputs the sensor output So during the data use period DT to the host 101 as detection data. Alternatively, the control circuit 51 may store the sensor output So during the data use period DT in the memory circuit 57 as detection data.

[0088] As described above, the detection device 1 according to the first embodiment does not use the sensor output So measured during the predetermined data non-use period NDT from the start of measurement of one frame (1F). That is, even if the sensor output So contains noise components immediately after measurement of the photodiode PD begins during the data non-use period NDT, the sensor output So during the data non-use period NDT is not used as detection data. The detection device 1 then uses the sensor output So output from the detection circuit 48 during the data use period DT after a predetermined period has elapsed since measurement began and the characteristics of the photodiode PD have stabilized. This sensor output So does not substantially contain noise components immediately after measurement of the photodiode PD begins. This allows the detection device 1 to achieve improved detection accuracy compared to the comparative example described above.

[0089] The detection method shown in FIG. 11 is merely an example and can be modified as appropriate. For example, the data non-use period NDT is not limited to 10 seconds and can be modified depending on various conditions, such as the characteristics of the photodiode PD and the light intensity of the light source 60. Also, in FIG. 11 , the timing at which the photodiode PD and the detection circuit 48 start measurement is the rising edge of the start control signal STV, but this is not limiting. For example, the timing at which the photodiode PD and the detection circuit 48 start measurement may be the start of the first readout period INT after the start control signal STV, or the timing at which the light source 60 is first turned on. In this case, the control circuit 51 turns on the light source 60 at the start of measurement, and after the data non-use period NDT (first period) has elapsed since the light source 60 was turned on, switches to the data use period DT (second period) and performs detection.

[0090] Second Embodiment Fig. 12 is a timing waveform diagram showing an example of the operation of a detection device according to a second embodiment. Fig. 13 is a graph schematically showing the relationship between the drive time and the sensor output of the detection device according to the second embodiment.

[0091] As shown in FIG. 12 , in the detection device 1 according to the second embodiment, the frame rate at which the multiple photodiodes PD are detected during the data non-use period NDT (first period) is higher than the frame rate during the data use period DT (second period). During the data non-use period NDT, the period required to detect one frame (1F) is, for example, 10 ms. That is, the frame rate during the data non-use period NDT is preferably 100 Hz or higher. During the data use period DT, the period required to detect one frame (1F) is, for example, 40 ms. That is, the frame rate during the data use period DT is approximately 25 Hz.

[0092] Specifically, the detection drive circuit 53 of the control circuit 51 controls the read control signal CH and the lighting of the light source 60 during the data unused period NDT to have different cycles from the read control signal CH and the lighting of the light source 60 during the data used period DT, in response to the mode switching signal DE from the mode switching circuit 55. Note that the length of one read period INT and the lighting time of one light source 60 during the data unused period NDT are equivalent to the length of one read period INT and the lighting time of one light source 60 during the data used period DT. Also, the read period INT of the photodiode PD and the lighting of the light source 60 from time t41 to time t46 and from time t47 to time t52 shown in FIG. 12 are the same as those in the first embodiment described above, and therefore repeated description will be omitted.

[0093] As shown in FIG. 13, compared to the sensor output So when multiple photodiodes PD are driven at a frame rate of 25 Hz, the sensor output So when multiple photodiodes PD are driven at a frame rate of 100 Hz stabilizes within a short drive time from the start of measurement.

[0094] As a result, as shown in FIG. 12 , in the detection device 1 according to the second embodiment, by increasing the frame rate during the data non-use period NDT (for example, 100 Hz or higher), the data non-use period NDT can be made shorter than in the first embodiment described above. The control circuit 51 can set the length of the data non-use period NDT from the timing of measurement start until switching to the data use period DT. For example, the control circuit 51 can set the length of the data non-use period NDT by setting the number of pulses of the clock signal CK counted by the counter 54. In the example shown in FIG. 12 , the data non-use period NDT is, for example, about 3 seconds.

[0095] In the second embodiment, the mode switching circuit 55 of the control circuit 51 sets the mode switching signal DE to a low-level voltage at time t48, a predetermined period (e.g., 3 seconds) after the start of measurement (time t41), thereby starting the data use period DT.

[0096] The frame rates of the data non-use periods NDT and data use periods DT, the length of the data non-use periods NDT, etc. shown in FIGS. 12 and 13 are merely examples and can be changed as appropriate.

[0097] (Third embodiment) Fig. 14 is a timing waveform diagram showing an example of the operation of a detection device according to a third embodiment. Fig. 15 is a graph schematically showing the relationship between the drive time and the sensor output of the detection device according to the third embodiment.

[0098] 14, in the detection device 1 according to the third embodiment, the drive current I supplied to the light source 60 during the data non-use period NDT (first period) is greater than the drive current I supplied to the light source 60 during the data use period DT (second period). For example, the drive current I supplied to the light source 60 during the data non-use period NDT is 50 mA or more. The drive current I supplied to the light source 60 during the data use period DT is approximately 25 mA.

[0099] Specifically, the detection drive circuit 53 of the control circuit 51 outputs a power supply control signal CL to the power supply circuit 52 in response to a mode switching signal DE from the mode switching circuit 55, and controls the light source drive power VLED supplied to the light source 60 during the data non-use period NDT to be different from the light source drive power VLED supplied to the light source 60 during the data use period DT. A drive current ILED flows through the light source 60 in each period in accordance with the light source drive power VLED. Note that, except for the magnitude of the drive current ILED, the readout period INT of the photodiode PD and the lighting of the light source 60 from time t61 to time t66 and from time t67 to time t72 shown in FIG. 14 are the same as those in the first embodiment described above, and therefore repeated description will be omitted.

[0100] 15, the sensor output So when a drive current ILED of 50 mA is supplied to the light source 60 stabilizes in a shorter time from the start of driving than the sensor output So when a drive current ILED of 25 mA is supplied to the light source 60. In other words, the stronger the intensity of light irradiated onto the photodiode PD during the non-data use period NDT after the start of measurement, the shorter the time it takes for the sensor output So to stabilize.

[0101] 14, in the detection device 1 according to the third embodiment, the drive current ILED supplied to the light source 60 during the non-use-of-data period NDT is increased, thereby making it possible to shorten the non-use-of-data period NDT compared to the first embodiment described above. In the example shown in FIG. 14, the non-use-of-data period NDT is, for example, about 3 seconds.

[0102] In the third embodiment, the mode switching circuit 55 sets the mode switching signal DE to a low-level voltage at time t68, which is a time when the data non-use period NDT (e.g., 3 seconds) has elapsed since the start of measurement at time t61. This causes the data use period DT to start at time t68.

[0103] The values ​​of the drive current ILED in the data non-use period NDT and the data use period DT, the length of the data non-use period NDT, etc. shown in FIGS. 14 and 15 are merely examples and can be changed as appropriate.

[0104] (Fourth embodiment) Fig. 16 is a timing waveform diagram showing an example of the operation of a detection device according to a fourth embodiment. Fig. 17 is a graph schematically showing the relationship between the drive time and the sensor output of the detection device according to the fourth embodiment.

[0105] As shown in FIG. 16 , in the detection device 1 according to the fourth embodiment, the readout period INT of the detection circuit 48 during the data unused period NDT (first period) is longer than the readout period INT of the detection circuit 48 during the data used period DT (second period). The readout period INT is the period during which the photodiode PD and the operational amplifier 63 of the detection circuit 48 are connected via the connection switch SSW. For example, the readout period INT of the detection circuit 48 during the data unused period NDT is 100 μs or more (117.3 μs in FIG. 16 ). The readout period INT of the detection circuit 48 during the data used period DT is approximately 14.8 μs.

[0106] Specifically, the detection drive circuit 53 of the control circuit 51 controls the period during which the read control signal CH is at a high level voltage in the data non-use period NDT and the period during which the read control signal CH is at a high level voltage in the data use period DT to be different lengths in response to the mode switching signal DE from the mode switching circuit 55.

[0107] Furthermore, in the fourth embodiment, the length of the readout period INT in the data non-use period NDT is longer than the period during which the light source 60 is turned on. Specifically, the readout period INT of the photodiodes PD1 and PD2 begins at time t83. Also at time t83, a drive current ILED is supplied to the light source 60, turning the light source 60 on. At time t84, the supply of the drive current ILED ends, turning the light source 60 off. The readout period INT continues even after the light source 60 is turned off, and ends at time t85, a predetermined period after time t84.

[0108] At time t85, the readout period INT of the photodiodes PD3 and PD4 begins. Also at time t85, the drive current ILED is supplied to the light source 60, turning the light source 60 on. At time t86, the supply of the drive current ILED ends, turning the light source 60 off. The readout period INT continues even after the light source 60 is turned off, and ends at time t87, a predetermined period after time t86.

[0109] The readout period INT of the photodiode PD and the lighting of the light source 60 from time t88 to time t93 shown in FIG. 16 are the same as those in the first embodiment described above, and a repeated description will be omitted.

[0110] 17 , compared to the sensor output So when the readout period INT is short (e.g., 14.8 μs), the sensor output So when the readout period INT is long (e.g., 117.3 μs) stabilizes in a short time from the start of driving. In other words, in the detection device 1 of the fourth embodiment, the charge generated in response to light irradiated on the photodiode PD flows sufficiently to the operational amplifier 63 side during the readout period INT, so that the sensor output So stabilizes in a short time. Alternatively, in the detection device 1 of the fourth embodiment, by lengthening the readout period INT, the operation of the operational amplifier 63 and the constant current source 65 of the detection circuit 48 becomes stable, and as a result, the sensor output So stabilizes in a short time.

[0111] 16, in the detection device 1 according to the fourth embodiment, the readout period INT of the photodiode PD is lengthened during the data non-use period NDT, thereby making it possible to shorten the data non-use period NDT compared to the first embodiment described above. In the example shown in FIG. 16, the data non-use period NDT is, for example, about 3 seconds.

[0112] The lengths of the read period INT and the data non-use period NDT shown in FIGS. 16 and 17 are merely examples and can be changed as appropriate.

[0113] The second to fourth embodiments described above may be combined as appropriate. For example, the detection device 1 may increase the frame rate during the non-data use period NDT (second embodiment) and increase the drive current I LED supplied to the light source 60 during the non-data use period NDT (third embodiment).

[0114] Alternatively, the detection device 1 may increase the frame rate during the data non-use period NDT (second embodiment) and lengthen the readout period INT of the detection circuit 48 during the data non-use period NDT (fourth embodiment). Alternatively, the detection device 1 may increase the drive current ILED supplied to the light source 60 during the data non-use period NDT (third embodiment) and lengthen the readout period INT of the detection circuit 48 during the data non-use period NDT (fourth embodiment).

[0115] Although the detection device 1 has been described as containing the sensor substrate 21 and the like inside the ring-shaped housing 200, the present invention is not limited to this. The detection device 1 may be, for example, contained in a rectangular housing, or may be attached to the object to be measured without being contained in a housing.

[0116] 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.

[0117] 1, 100 Detection device 10A First optical sensor 10B Second optical sensor 11 Lower electrode 12 Lower buffer layer 13 Active layer 14 Upper buffer layer 15, 15A, 15B Upper electrode 21 Sensor substrate 48 Detection circuit 51 Control circuit 52 Power supply circuit 60 Light source 63, 63a, 63b Operational amplifier 64, 64a, 64b A / D conversion circuit 65, 65a, 65b Constant current source 70 Flexible printed circuit board 200 Housing DE Mode switching signal DT Data use period ILED Drive current INT Readout period NDT Data non-use period PD Photodiode

Claims

1. A detection device comprising: a photodiode; a light source that irradiates light onto the photodiode; a detection circuit connected to the photodiode that measures a current output from the photodiode and outputs a sensor output; and a control circuit that controls the detection operation of the photodiode and the detection circuit, wherein the control circuit has a first period in which the sensor output from the detection circuit is not used as detection data, and a second period in which the sensor output from the detection circuit is used as detection data, and after the first period has elapsed from the timing when the photodiode and the detection circuit start measurement, the control circuit switches to the second period and performs detection.

2. The detection device according to claim 1, wherein the control circuit turns on the light source at the start of measurement, and switches to the second period after the first period has elapsed since the light source was turned on.

3. The detection device according to claim 1, comprising a plurality of said photodiodes, wherein the frame rate at which detection is performed by said plurality of photodiodes during said first period is higher than the frame rate during said second period, and said frame rate during said first period is 100 Hz or higher.

4. The detection device according to claim 1, wherein the drive current supplied to the light source in the first period is greater than the drive current supplied to the light source in the second period, and the drive current in the first period is 50 mA or more.

5. The detection device according to claim 1, wherein the photodiode and the operational amplifier of the detection circuit have a readout period during which they are connected via a connection switch, the readout period in the first period is longer than the readout period in the second period, and the readout period in the first period is 100 μs or more.

6. The detection device according to claim 1, wherein the control circuit is capable of setting the length of the first period from the timing of starting measurement until switching to the second period.

7. The detection device of claim 1, wherein the first period is 10 seconds.

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