Light emitting unit and optical sensor

Abstract

To provide a light emitting unit for securing accuracy in sensing a target.SOLUTION: A light emitting unit 1 includes: a light emitting diode 22 provided in a light emission branch route part Rl branched between an inductor 241 and a capacitor 242 in a resonance circuit part 240, so as to generate irradiation light by light emission; a discharge switching element 246 provided in the light emission branch route part Rl so as to turn on / off discharge from the capacitor 242 by switching; a charge switching element 247 provided on a side closer to the inductor 241 than to a branch point of the light emission branch route part Rl in the resonance circuit part 240, so as to turn on / off charge to the capacitor 242 by switching; and a drive circuit part 248 for controlling the discharge switching element 246 and the charge switching element 247 by individual on / off driving. The drive circuit part 248 controls an on-period of the charge switching element 247 before on-timing of the discharge switching element 246.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a light emitting technology in an optical sensor that senses a target by receiving reflected light from the target in response to light irradiated onto a sensing area. [Background technology]

[0002] In an optical sensor that receives reflected light from irradiated light, a light emitting technology that provides the irradiated light by emitting light is disclosed in Patent Document 1. In the technology disclosed in Patent Document 1, in a resonant circuit having an inductor and a capacitor, charging and discharging of the capacitor are switched by a switching element, so that a light emitting diode emits light in response to discharging of the capacitor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Pat. No. 9,368,936 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the technology disclosed in Patent Document 1, the peak intensity of the emitted light is constant, so that when the reflected intensity of the emitted light is high, for example, in the case of a nearby target or a highly reflective target, the received light intensity for the reflected light becomes saturated, which may lead to a decrease in sensing accuracy.

[0005] Therefore, an object of the present disclosure is to provide a light-emitting unit and an optical sensor that ensure the sensing accuracy of a target. [Means for solving the problem]

[0006] The technical means of the present disclosure for solving the problems will be described below. Note that the claims and the reference characters in parentheses in this section indicate the corresponding relationship with the specific means described in the embodiments described later in detail, and do not limit the technical scope of the present disclosure.

[0007] A first aspect of the present disclosure is An optical sensor (2) for sensing a target by receiving reflected light from the target in response to irradiation light irradiated onto a sensing area (As), the optical sensor (2) includes a light-emitting unit for emitting irradiation light, a resonant circuit section (240) having an inductor (241) and a capacitor (242); a light emission branch path section (Rl) branching out from between the inductor and the capacitor in the resonant circuit section; a light emitting diode (22) provided in the light emitting branch path section and configured to generate irradiation light by emitting light; a discharge switching element (246) provided in the light emission branch path section for switching on and off discharge from the capacitor; a charging switching element (247) that is provided on the inductor side of the branch point of the light emission branch path in the resonance circuit section and that switches on and off charging of the capacitor by switching; a drive circuit section (248) for controlling the discharge switching element and the charge switching element by individual on / off drive, The drive circuit section includes: Prior to the on-timing of the discharge switching element, the on-period of the charge switching element is controlled.

[0008] A second aspect of the present disclosure is The device includes a light-emitting unit (1) of the first embodiment and a light-receiving unit (45) that receives reflected light of the irradiated light emitted by the light-emitting unit.

[0009] According to the first and second aspects, the light-emitting branch path section branching from between the inductor and the capacitor in the resonant circuit section is provided with a light-emitting diode that generates irradiated light by emitting light, and a discharge switching element that switches on and off the discharge from the capacitor by switching. In particular, a charge switching element that switches on and off the charge to the capacitor by switching is provided on the inductor side of the branch point of the light-emitting branch path section in the resonant circuit section. With this, even if the light-receiving intensity of the reflected light relative to the irradiated light becomes saturated, the on-period of the charge switching element prior to the on-timing of the discharge switching element can be shortened to relatively reduce the light-receiving sensitivity. Therefore, such shortening control makes it possible to suppress the peak intensity of the irradiated light to a low intensity that matches the reception of the reflected light, thereby ensuring the sensing accuracy of the target. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing a configuration of an optical sensor according to an embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing a mechanical configuration of a light projection unit according to an embodiment. [Diagram 3] FIG. 2 is a schematic diagram illustrating a mechanical configuration of a light receiving unit according to an embodiment. [Figure 4] FIG. 2 is a circuit diagram showing an electrical configuration of a light-emitting unit according to an embodiment. [Diagram 5] 4 is a graph showing light emitting characteristics of a light emitting unit according to an embodiment. [Figure 6] 4 is a graph showing light emitting characteristics of a light emitting unit according to an embodiment. [Figure 7] 4 is a graph showing light emitting characteristics of a light emitting unit according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 1, one embodiment of the present disclosure relates to an optical sensor 2 including a light-emitting unit 1. The optical sensor 2 is mounted on a vehicle 5. The vehicle 5 is a moving body such as an automobile that can travel on a road with an occupant on board.

[0012] In the autonomous driving control mode, the vehicle 5 is capable of steady or temporary autonomous driving. Here, the autonomous driving control mode may be realized by autonomous driving control in which a system performs all driving tasks when activated, such as conditional driving automation, highly automated driving, or fully automated driving. The autonomous driving control mode may be realized in advanced driving assistance control in which a passenger performs some or all driving tasks, such as driving assistance or partial driving automation. The autonomous driving control mode may be realized by either one of the autonomous driving control and the advanced driving assistance control, or by a combination of them, or by switching between them.

[0013] In the following description, unless otherwise specified, the directions of front, rear, up, down, left, and right are defined with respect to the vehicle 5 on a horizontal plane. The horizontal direction refers to a direction parallel to the horizontal plane that serves as the directional reference for the vehicle 5. The vertical direction refers to a vertical direction that is also the up-down direction with respect to the horizontal plane that serves as the directional reference for the vehicle 5.

[0014] The optical sensor 2 is a so-called LiDAR (Light Detection and Ranging / Laser Imaging Detection and Ranging) for acquiring image data that can be used for driving control, including an automatic control driving mode, of the vehicle 5. The optical sensor 2 is disposed in at least one location of the vehicle 5, for example, the front portion, the left and right side portions, the rear portion, the upper roof, etc.

[0015] In the optical sensor 2, a three-dimensional orthogonal coordinate system is defined by an X-axis, a Y-axis, and a Z-axis as three mutually orthogonal axes. In particular, in this embodiment, the X-axis and the Z-axis are set along different horizontal directions of the vehicle 5, and the Y-axis is set along the vertical direction of the vehicle 5. Note that in Fig. 1, the left side of the dashed dotted line along the Y-axis (the side of a translucent panel 12 described later) actually illustrates a cross section perpendicular to the right side of the dashed dotted line (the side of modules 21 and 41 described later) where the three-dimensional orthogonal coordinate system is given.

[0016] The optical sensor 2 irradiates light toward a sensing area As corresponding to the installation location and viewing angle in the external space of the vehicle 5. The optical sensor 2 receives reflected light that is incident when the irradiated light is reflected from the sensing area As. In response to receiving reflected light from the irradiated light, the optical sensor 2 senses a target that reflects light within the sensing area As. Here, sensing means measuring at least the reflection point distance from the optical sensor 2 to the target and the reflection intensity from the target.

[0017] A representative sensing target in the optical sensor 2 applied to the vehicle 5 may be at least one of moving objects such as pedestrians, cyclists, animals other than humans, and other vehicles. A representative sensing target in the optical sensor 2 applied to the vehicle 5 may be at least one of stationary objects such as guardrails, road signs, roadside structures, and objects fallen on the road.

[0018] The optical sensor 2 includes a casing module 10, a light projecting module 21, a scanning module 31, a light receiving module 41, and a control module 51. The casing module 10 includes a housing 11 and a light-transmitting panel 12. The housing 11 is formed in a hollow box shape mainly made of a light-shielding material such as metal or synthetic resin. The housing 11 accommodates the light projecting module 21, the scanning module 31, and the light receiving module 41 inside. The housing 11 holds the light-transmitting panel 12 formed in a plate shape from a light-transmitting material such as glass or synthetic resin.

[0019] The light-projecting module 21 includes a light-emitting unit 1 and a light-projecting lens system 28. As shown in Fig. 2, the light-emitting unit 1 is constructed by mounting a plurality of light-emitting diodes 22 in an array on a substrate 21. Each light-emitting diode 22 generates pulsed infrared laser light that serves as light to be irradiated onto the sensing area As under the control of a control module 51. As each of the light-emitting diodes 22, for example, a laser diode such as an edge emitter laser or a vertical cavity surface emitting laser (VCSEL) is provided.

[0020] As shown in FIG. 1, the light projecting lens system 28 projects the illumination light emitted by the light-emitting unit 1 toward the scanning mirror 32 of the scanning module 31. The light projecting lens system 28 exerts at least one optical function, for example, focusing, collimating, shaping, and the like. The light projecting lens system 28 forms a light projection optical axis along the Z axis. The light projecting lens system 28 has at least one light projecting lens 29 on the light projection optical axis, the light projecting lens system 28 having a lens shape according to the optical function to be exerted. The light-emitting unit 1 is positioned on the light projection optical axis of the light projecting lens system 28. The illumination light emitted by each light-emitting diode 22 in the light-emitting unit 1 is guided along the light projection optical axis of the light projecting lens system 28.

[0021] The scanning module 31 includes a scanning mirror 32 and a scanning motor 35. The scanning mirror 32 is formed into a plate shape by depositing a reflective film on a reflective surface 33, which is one side of a base material. The scanning mirror 32 is supported by the housing 11 so as to be rotatable about a rotation center line along the Y axis. The scanning mirror 32 oscillates within a driving section that is finite due to the function of a mechanical or electrical stopper.

[0022] The scanning mirror 32 is provided in common to the light projecting module 21 and the light receiving module 41. The scanning mirror 32 irradiates the sensing area As through the light projecting lens system 28 of the light projecting module 21 by reflection from a reflecting surface 33 oriented in accordance with the rotation angle, through the light transmitting panel 12, thereby scanning the area As in time and space. Particularly in the optical sensor 2, the mechanical scanning of the sensing area As by the irradiated light is substantially limited to scanning in the horizontal direction.

[0023] Simultaneously with such scanning, the scanning mirror 32 further reflects the reflected light incident from the sensing area As through the light-transmitting panel 12 toward the light-receiving module 41 side by the reflecting surface 33 oriented according to the rotation angle. Here, the speeds of the irradiated light and the reflected light are sufficiently high compared to the rotational speed of the scanning mirror 32. As a result, the reflected light relative to the irradiated light is guided toward the light-receiving module 41 side so as to travel in the opposite direction to the irradiated light by the scanning mirror 32, which has approximately the same rotation angle as the irradiated light.

[0024] The scanning motor 35 is, for example, a voice coil motor, a brushed DC motor, or a stepping motor. The scanning motor 35 drives the scanning mirror 32 to rotate (i.e., swing) within the finite driving section under the control of the control module 51. At this time, the rotation angle of the scanning mirror 32 is sequentially changed in synchronization with the light emission period Pl (see FIG. 5 described later) of the light-emitting unit 1 of the light-projecting module 21.

[0025] The light receiving module 41 is disposed offset in the Y-axis direction with respect to the light projecting module 21. The light receiving module 41 includes a light receiving lens system 42 and a light receiving unit 45. The light receiving lens system 42 exerts an optical effect so as to form an image of the reflected light from the sensing area As on the light receiving unit 45. The light receiving lens system 42 forms a light receiving optical axis along the Z-axis. The light receiving lens system 42 has at least one light receiving lens 43 on the light receiving optical axis, the light receiving lens system 42 having a lens shape according to the optical effect it exerts. The reflected light incident from the reflecting surface 33 of the scanning mirror 32 is guided along the light receiving optical axis of the light receiving lens system 42, regardless of the rotation angle of the scanning mirror 32 within the driving section.

[0026] The light receiving unit 45 is positioned on the light receiving optical axis of the light receiving lens system 42. As shown in FIG. 3, the light receiving unit 45 is constructed by arranging a plurality of light receiving pixels 46 in an array on a substrate. Each of the light receiving pixels 46 is further constructed of a plurality of light receiving elements 460. The light receiving elements 460 of each of the light receiving pixels 46 are mainly composed of a photodiode such as a single photon avalanche diode (SPAD). With this configuration, each of the light receiving pixels 46 receives reflected light incident from the light receiving lens system 42 at each of the light receiving elements 460.

[0027] 1, the light receiving unit 45 is integrally provided with an output circuit 48. The output circuit 48 executes sampling processing according to control from the control module 51 for each scanning line associated with the rotation angle of the scanning mirror 32 according to the light emission period Pl. Thus, the output circuit 48 generates light receiving data for each scanning line based on the output signal from each light receiving pixel 46 of the light receiving unit 45 through the sampling processing. The light receiving data generated in this manner is output from the output circuit 48 to the control module 51.

[0028] The control module 51 is mainly composed of at least one computer having a processor 52 and a memory 53. The control module 51 may be entirely housed inside the housing 11 (example of FIG. 1). The control module 51 may be entirely disposed in the vehicle 5 outside the housing 11. The control module 51 may be distributed across the inside of the housing 11 and the external vehicle 5.

[0029] The control module 51 is connected to the light-emitting unit 1, the scanning motor 35, and the output circuit 48. The control module 51 controls these connected objects by executing a control program stored in the memory 53 using the processor 52. Specifically, the control module 51 synchronously controls the light emission of each light-emitting diode 22 in the light-emitting unit 1 and the rotation of the scanning mirror 32 by the scanning motor 35 for each light-emitting period Pl. In parallel with this, the control module 51 acquires light-receiving data from the output circuit 48 for each scanning line, which corresponds to each light-receiving period Pl, thereby sensing at least the reflection point distance from the optical sensor 2 to the target and generating sensing information based on the light-receiving data.

[0030] Next, a detailed configuration of the light-emitting unit 1 shown in Fig. 4 will be described. In the light-emitting unit 1, a plurality of light-emitting circuits 24 corresponding to the number of light-emitting diodes 22 are constructed. In addition to the light-emitting diodes 22, the light-emitting circuits 24 include a resonance circuit section 240, switching elements 246 and 247, and a drive circuit section 248. Note that Fig. 4 representatively shows a light-emitting circuit 24 corresponding to one light-emitting diode 22.

[0031] The resonant circuit section 240 is provided with a power supply terminal Ev to which a power supply voltage Vin is applied, and a ground terminal E0 to which a ground voltage is applied. The resonant circuit section 240 is a so-called LC series circuit having an inductor 241 and a capacitor 242 connected in series between the power supply terminal Ev and the ground terminal E0. The inductor 241 is mainly composed of an induction coil. The capacitor 242 is mainly composed of a heat-resistant capacitor such as an electrolytic type.

[0032] In the light-emitting circuit 24, a section from a midpoint E1 between the inductor 241 and the capacitor 242 in the resonant circuit section 240 to a ground terminal E0 is connected in parallel with the capacitor 242 by the light-emitting branch path section Rl. The light-emitting branch path section Rl is provided with a discharge switching element 246. The discharge switching element 246 is mainly composed of a field effect transistor such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). Due to such an arrangement and configuration in the light-emitting branch path section Rl, the discharge switching element 246 can turn on and off the discharge from the capacitor 242 by switching.

[0033] In the light-emitting circuit 24, in the light-emitting branch path section Rl from the midpoint E1 to the earth terminal E0, the light-emitting diode 22 is provided on the earth terminal E0 side relative to the discharge switching element 246. The forward direction in which the light-emitting diode 22 rectifies the current Io is set to the direction from the discharge switching element 246 side to the earth terminal E0 side. The light-emitting diode 22 generates irradiation light by emitting light due to discharge from the capacitor 242 in response to the discharge switching element 246 being turned on.

[0034] In the light-emitting circuit 24, a charging switching element 247 is provided at another intermediate point E2, which is closer to the inductor 241 than the intermediate point E1, which is a branch point where the light-emitting branch path section Rl branches off between the inductor 241 and the capacitor 242 in the resonance circuit section 240. The charging switching element 247 is mainly composed of a field-effect transistor such as a MOSFET. Due to such an arrangement and configuration at the intermediate point E2, the charging switching element 247 can turn the charging of the capacitor 242 on and off by switching.

[0035] In the light-emitting circuit 24, a drive circuit section 248 is connected to each of the switching elements 246, 247. The drive circuit section 248 is also connected to the control module 51. The drive circuit section 248 drives each of the switching elements 246, 247 to turn on and off individually in accordance with the control from the control module 51, as shown in Figs. 5 to 7. That is, the switching of each of the switching elements 246, 247 is controlled by the on / off drive function of the drive circuit section 248.

[0036] As shown by solid and dashed line graphs in each of the sub-diagrams (A) of Figures 5 to 7, in the drive circuit section 248, the reference ON timing Tn0 for switching the charge switching element 247 from the OFF drive state to ON drive is set to coincide with the start timing of each light emission period Pl. At the same time, in the drive circuit section 248, the reference OFF timing Tf0 for switching the charge switching element 247 from the ON drive state to OFF drive is set to a timing a certain period ΔTm has elapsed from the reference ON timing Tn0 for each light emission period Pl. By setting the period of the reference ON timing Tn0 and the reference OFF timing Tf0 in this way, the maximum ON period ΔTm of the charge switching element 247 is controlled to a time that is substantially equal to the time constant of the resonant circuit section 240.

[0037] In the drive circuit section 248, the on-period ΔT of the charging switching element 247 is controlled to a time equal to or shorter than the maximum on-period ΔTm for each light emission period Pl. At this time, for the charging switching element 247, the on-timing Tn may be adjusted to match the reference on-timing Tn0, while the off-timing Tf may be adjusted to a variable timing before the reference off-timing Tf0, as shown by the two-dot chain line graph in FIG. 5(A). For the charging switching element 247, the off-timing Tf may be adjusted to match the reference off-timing Tf0, while the on-timing Tn may be adjusted to a variable timing after the reference on-timing Tn0, as shown by the two-dot chain line graph in FIG. 6(A). For the charging switching element 247, the on-timing Tn may be adjusted to a variable timing after the reference on-timing Tn0, while the off-timing Tf may be adjusted to a variable timing before the reference off-timing Tf0 that is later than the on-timing Tn, as shown by the two-dot chain line graph in FIG. 7(A).

[0038] In this way, the more the drive circuit unit 248 controls to shorten the on-period ΔT of the charge switching element 247, the less the time that the current Ii (see also FIG. 4) flows through the inductor 241 in the resonant circuit unit 240, as shown by the solid line graphs and the two-dot chain line graphs corresponding to the other subdivisions in each of the subdivisions (B) of Figures 5 to 7. Correspondingly, in the resonant circuit unit 240, the voltage Vc (see also FIG. 4) charged to the capacitor 242 decreases, as shown by the solid line graphs and the two-dot chain line graphs corresponding to the other subdivisions in each of the subdivisions (C) of Figures 5 to 7. That is, the more the drive circuit unit 248 controls to shorten the on-period ΔT of the charge switching element 247, the less the charging voltage Vc of the capacitor 242 decreases.

[0039] 5 to 7, in the drive circuit section 248, the discharge switching element 246 in the OFF drive state is turned on at a timing later than the reference OFF timing Tf0 of the charge switching element 247 for each light emission period Pl. In other words, the control of the ON period ΔT for turning on the charge switching element 247 precedes the ON timing Td for switching the discharge switching element 246 in the OFF drive state to ON drive for each light emission period Pl.

[0040] In response to the ON driving of the discharge switching element 246, a discharge current discharged from the capacitor 242 in a state of a charging voltage Vc flows into the light emission branch path section Rl through the resonance circuit section 240. As a result, a current Io (see also FIG. 4) that rises and falls following the charging voltage Vc flows through the light emitting diode 22, and the light emitting diode 22 emits light with a peak intensity that follows the rise and fall of the current Io, as shown by the solid line graphs and the two-dot chain line graphs corresponding to the other division diagrams in each of FIGS. 5 to 7 (E).

[0041] Therefore, when the control module 51 recognizes an intensity saturation state, for example, where the received light intensity of reflected light from a nearby target or a highly reflective target exceeds the upper limit intensity at the light receiving unit 45, based on the light receiving data from the output circuit 48, the control module 51 issues a shortening control command to the drive circuit unit 248. As a result, the drive circuit unit 248 controls the on / off drive of the charge switching element 247 so as to shorten the on period ΔT to less than the maximum on period ΔTm, in accordance with the degree to which the received light intensity exceeds the upper limit intensity.

[0042] On the other hand, when the control module 51 recognizes an insufficient intensity state, for example, where the received light intensity of reflected light from a distant target falls below the lower limit intensity that ensures the sensing accuracy of the light receiving unit 45, based on the received light data from the output circuit 48, the control module 51 issues an extension control command to the drive circuit unit 248. As a result, the drive circuit unit 248 controls the on / off drive of the charge switching element 247 so as to increase the on-period ΔT within the range of the maximum on-period ΔTm, in accordance with the degree of insufficiency of the received light intensity from the lower limit intensity.

[0043] (Action and effect) The effects of the present embodiment described above will be described below.

[0044] According to this embodiment, the light-emitting diode 22 that generates irradiated light by emitting light and the discharge switching element 246 that switches on and off the discharge from the capacitor 242 are provided in the light-emitting branch path section Rl that branches off between the inductor 241 and the capacitor 242 in the resonant circuit section 240. In particular, a charge switching element 247 that switches on and off the charge to the capacitor 242 is provided on the inductor 241 side of the branch point of the light-emitting branch path section Rl in the resonant circuit section 240. With this, even if the light-receiving intensity of the reflected light relative to the irradiated light becomes saturated, the on-period ΔT of the charge switching element 247 prior to the on-timing Td of the discharge switching element 246 can be shortened to relatively reduce the light-receiving sensitivity. Therefore, such shortening control makes it possible to suppress the peak intensity of the irradiated light to a low intensity that matches the light-receiving reflected light, thereby ensuring the sensing accuracy of the target.

[0045] According to this embodiment, the off timing Tf of the charge switching element 247, which is turned on prior to the on timing Td of the discharge switching element 246, may be adjusted to be before the reference off timing Tf0, which is set periodically, to control the on period ΔT of the charge switching element 247. In this case, the on period ΔT of the charge switching element 247 can be stably shortened by adjusting the off timing Tf of the charge switching element 247 to be earlier than the reference off timing Tf0 from a state in which the intensity of the received reflected light is saturated. This is based on the fact that the off timing Tf of the charge switching element 247 is also advanced from the on timing Td of the discharge switching element 246, thereby reducing the influence of noise components generated when the charge switching element 247 is turned off on the current Io (see FIGS. 4, 5, and 7) flowing through the light-emitting diode 22 when the discharge switching element 246 is turned on. Therefore, such shortening control makes it possible to accurately stabilize the peak intensity of the irradiated light at a low intensity that matches the received reflected light, thereby ensuring sensing accuracy.

[0046] According to this embodiment, the on-timing Tn of the charge switching element 247, which is driven to be on prior to the on-timing Td of the discharge switching element 246, may be adjusted to be after the reference on-timing Tn0 that is periodically set, thereby controlling the on-period ΔT of the charge switching element 247. In this case, the on-period ΔT of the charge switching element 247 can be shortened by adjusting the on-timing Tn of the charge switching element 247 to be later than the reference on-timing Tn0 from a state in which the intensity of the received reflected light is saturated. Therefore, such shortening control makes it possible to accurately suppress the peak intensity of the irradiated light to a low intensity that matches the received reflected light, thereby improving the sensing accuracy.

[0047] According to this embodiment, the maximum on-period ΔTm of the charging switching element 247 is controlled by the time constant of the resonant circuit section 240. As a result, even if the received light intensity of the reflected light becomes insufficient rather than saturated, the peak intensity of the irradiated light can be increased to the maximum intensity according to the time constant of the resonant circuit section 240 so as to match the received reflected light, thereby making it possible to improve the sensing accuracy.

[0048] (Other embodiments) Although one embodiment has been described above, the present disclosure should not be construed as being limited to the embodiment described above, and can be applied to various embodiments within the scope not departing from the gist of the present disclosure.

[0049] In the modified example, the vehicle 5 to which the optical sensor 2 including the light-emitting unit 1 is applied may be, for example, an autonomous robot capable of transporting luggage or collecting information by autonomous or remote driving. In the modified example, the object to which the optical sensor 2 including the light-emitting unit 1 is applied may be, for example, a moving object other than the vehicle 5, or a stationary object such as a structure.

[0050] (Additional remarks) This specification discloses the following technical ideas and combinations thereof.

[0051] (Technical thought 1) In an optical sensor (2) that senses a target by receiving reflected light from the target in response to irradiation light irradiated onto a sensing area (As), a light-emitting unit that emits the irradiation light, a resonant circuit section (240) having an inductor (241) and a capacitor (242); a light emission branch path portion (Rl) branching from between the inductor and the capacitor in the resonance circuit portion; a light-emitting diode (22) provided in the light-emitting branch path section and generating the irradiation light by emitting light; a discharge switching element (246) provided in the light emission branch path section for switching on and off discharge from the capacitor; a charging switching element (247) that is provided on the inductor side of the branch point of the light emission branch path in the resonance circuit section and that switches on and off charging of the capacitor by switching; a drive circuit section (248) for controlling the discharge switching element and the charge switching element by individual on / off driving, The drive circuit unit includes: A light emitting unit that controls an on-period of the charge switching element prior to the on-timing of the discharge switching element.

[0052] (Technical thought 2) The drive circuit unit includes: The light-emitting unit described in technical idea 1 controls the on-period of the charge switching element by adjusting the off-timing of the charge switching element, which is turned on prior to the on-timing of the discharge switching element, to be before a reference off-timing that is periodically set.

[0053] (Technical Thought 3) The drive circuit unit includes: The light-emitting unit described in technical idea 1 or 2 controls the on-period of the charge switching element by adjusting the on-timing of the charge switching element, which is driven on prior to the on-timing of the discharge switching element, to a timing after a reference on-timing that is periodically set.

[0054] (Technical Thought 4) The drive circuit unit includes: The light-emitting unit according to any one of Technical Ideas 1 to 3, wherein a maximum on-period of the charging switching element is controlled to a time constant of the resonant circuit section.

[0055] (Technical Thought 5) A light-emitting unit (1) according to any one of Technical Concepts 1 to 4; and a light receiving unit (45) that receives the reflected light in response to the irradiated light emitted by the light emitting unit. [Explanation of symbols]

[0056] 1: light emitting unit, 2: optical sensor, 22: light emitting diode, 45: light receiving unit, 240: resonance circuit section, 241: inductor, 242: capacitor, 246: discharge switching element, 247: charge switching element, 248: drive circuit section, As: sensing area, Rl: light emitting branch path section

Claims

1. In an optical sensor (2) that senses a target by receiving reflected light from the target in response to irradiation light irradiated onto a sensing area (As), a light-emitting unit that emits the irradiation light, A resonant circuit section (240) having an inductor (241) and a capacitor (242); a light emission branch path portion (Rl) branching from between the inductor and the capacitor in the resonance circuit portion; a light-emitting diode (22) provided in the light-emitting branch path section and generating the irradiation light by emitting light; A discharge switching element (246) provided in the light emission branch path section for switching on and off the discharge from the capacitor; a charging switching element (247) that is provided on the inductor side of the branch point of the light emission branch path in the resonance circuit section and that switches on and off charging of the capacitor by switching; a drive circuit unit (248) that controls the discharge switching element and the charge switching element by individual on / off driving, The drive circuit unit includes: A light emitting unit that controls an on-period of the charge switching element prior to the on-timing of the discharge switching element.

2. The drive circuit unit includes: The light-emitting unit according to claim 1 , wherein the on-period of the charge switching element is controlled by adjusting the off-timing of the charge switching element, which is turned on prior to the on-timing of the discharge switching element, to be before a reference off-timing that is periodically set.

3. The drive circuit unit includes: The light-emitting unit according to claim 1 or 2, wherein the on-timing of the charge switching element, which is driven on prior to the on-timing of the discharge switching element, is adjusted to be after a reference on-timing that is periodically set, thereby controlling the on-period of the charge switching element.

4. The drive circuit unit includes:

2. The light-emitting unit according to claim 1, wherein a maximum on-period of the charging switching element is controlled to a time constant of the resonant circuit section.

5. A light-emitting unit (1) according to claim 1, and a light receiving unit (45) that receives the reflected light in response to the irradiated light emitted by the light emitting unit.

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