Light emitting unit, and optical sensor

Abstract

A light emitting unit (1) comprises: a light emitting diode (22) that is provided in a light emission branch route portion (Rl) which branches from between an inductor (241) and a capacitor (242) in a resonance circuit portion (240) and that generates emitted light by light emission; a discharge switching element (246) that is provided in the light emission branch route portion (Rl) and that switches to turn discharge from the capacitor (242) on and off; a charge switching element (247) that is provided in a control branch route portion (Rc) which branches from the resonance circuit portion (240) on the inductor (241) side of the branch point of the light emission branch route portion (Rl), and that switches to turn charging to the capacitor (242) on and off; and a drive circuit portion (248) that controls the discharge switching element (246) and the charge switching element (247) by means of on / off drive operations. The drive circuit portion (248) controls an ON period of the charge switching element (247) prior to an ON timing of the discharge switching element (246).

Description

Light-emitting unit, optical sensor CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Patent Application No. 2023-196232 filed in Japan on November 17, 2023, and the contents of the original application are incorporated by reference in their entirety.

[0002] The present disclosure relates to a light emitting technology in an optical sensor that senses a target by receiving light reflected from the target in response to light irradiated onto a sensing area.

[0003] In an optical sensor that receives reflected light from irradiated light, a light-emitting technology that emits light to emit the irradiated 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, and a light-emitting diode emits light in response to the discharge of the capacitor.

[0004] U.S. Pat. No. 9,368,936

[0005] However, in the technology disclosed in Patent Document 1, the peak intensity of the emitted light remains constant. Therefore, when the reflected intensity of the emitted light is low, for example, as in the case of a distant target, the received light intensity may be insufficient relative to the reflected light, which may result in a decrease in sensing accuracy.

[0006] Therefore, an object of the present disclosure is to provide a light-emitting unit and an optical sensor that ensure target sensing accuracy.

[0007] The technical means of the present disclosure for solving the problems will be described below.

[0008] a control branch path section that branches off from the inductor side of the resonant circuit section at a point closer to the inductor than the branch point of the light-emitting branch path section; a charge switching element that is provided in the control branch path section and switches on and off charging of the capacitor; and a drive circuit section that controls the discharge switching element and the charge switching element by individual on / off driving, wherein the drive circuit section controls the on period of the charge switching element prior to the on timing of the discharge switching element.

[0009] According to a first aspect, the light-emitting branch path section branching from the resonant circuit section between the inductor and the capacitor includes 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. In particular, the control branch path section branching from the resonant circuit section closer to the inductor than the branch point of the light-emitting branch path includes a charge switching element that switches on and off the charge from the capacitor. This allows the on-period of the charge switching element prior to the on-timing of the discharge switching element to be extended, even if the received light intensity of the reflected light relative to the irradiated light is insufficient. Therefore, this extension control increases the peak intensity of the irradiated light to a high intensity that matches the received light of the reflected light, ensuring target sensing accuracy.

[0010] A second aspect of the present disclosure is a light-emitting unit of the first aspect, further comprising: a second charging switching element, which is provided in the resonant circuit section on the inductor side of the branch point of the light-emitting branch path section, separate from the first charging switching element as a charging switching element, and which switches on and off charging of the capacitor; a drive circuit section controls the discharge switching element, the first charging switching element, and the second charging switching element by individual on / off driving, and the drive circuit section switches between a first control mode in which the on period of the first charging switching element is controlled during the on period of the second charging switching element prior to the on timing of the discharge switching element, and a second control mode in which the on period of the second charging switching element is controlled during the off period of the first charging switching element prior to the on timing of the discharge switching element.

[0011] According to a second aspect, a first charge switching element that switches on and off charging to the capacitor is provided in the control branch path section that branches off from the inductor side of the branch point of the light emission branch path section in the resonant circuit section, and a second charge switching element that switches on and off charging to the capacitor is provided in the resonant circuit section on the inductor side of the branch point of the light emission branch path section.

[0012] Therefore, in the first control mode, even if the received light intensity of the reflected light is insufficient compared to the emitted light, the on-period of the first charge switching element prior to the on-timing of the discharge switching element is extended during the on-period of the second charge switching element, thereby relatively increasing the light-receiving sensitivity. Therefore, in a sensing scene that requires increasing the peak intensity of the emitted light to a high intensity that matches the received reflected light, such extension control can impart a high peak intensity to the emitted light, thereby ensuring the sensing accuracy of the target.

[0013] On the other hand, in the second control mode, even if saturation occurs in the received light intensity of reflected light relative to the irradiated light, the on-period of the second charge switching element prior to the on-timing of the discharge switching element is shortened during the off-period of the first charge switching element, thereby relatively lowering the light-receiving sensitivity. Therefore, in sensing scenes where it is necessary to suppress the peak intensity of the irradiated light to a low intensity that matches the received reflected light, such shortening control can provide the irradiated light with a low peak intensity, thereby ensuring the accuracy of sensing the target.

[0014] A third aspect of the present disclosure includes the light-emitting unit of the first or second aspect, and a light-receiving unit that receives reflected light of the irradiated light emitted by the light-emitting unit.

[0015] According to the third aspect, the sensing accuracy can be improved by the effect exerted by the light-emitting unit of the first or second aspect.

[0016] FIG. 1 is a cross-sectional view showing the configuration of an optical sensor according to a first embodiment. FIG. 2 is a schematic diagram showing the mechanical configuration of a light-emitting unit according to the first embodiment. FIG. 3 is a schematic diagram showing the mechanical configuration of a light-receiving unit according to the first embodiment. FIG. 4 is a circuit diagram showing the electrical configuration of a light-emitting unit according to the first embodiment. FIG. 5 is a graph showing the light-emitting characteristics of a light-emitting unit according to the first embodiment. FIG. 6 is a graph showing the light-emitting characteristics of a light-emitting unit according to the first embodiment. FIG. 7 is a circuit diagram showing the configuration of a light-emitting unit according to a second embodiment. FIG. 8 is a graph showing the light-emitting characteristics of a light-emitting unit according to the second embodiment in a first control mode. FIG. 9 is a graph showing the light-emitting characteristics of a light-emitting unit according to the second embodiment in the first control mode. FIG. 10 is a graph showing the light-emitting characteristics of a light-emitting unit according to the second embodiment in the second control mode. FIG. 11 is a circuit diagram showing the configuration of a light-emitting unit according to a modified example of the second embodiment. FIG. 12 is a graph showing the light-emitting characteristics of a light-emitting unit according to a modified example of the second embodiment. 10A and 10B are graphs showing the light emitting characteristics of a light emitting unit according to a modification of the second embodiment, respectively.

[0017] Hereinafter, multiple embodiments of the present disclosure will be described with reference to the drawings. Note that corresponding components in each embodiment are designated by the same reference numerals, and redundant description may be omitted. Furthermore, when only a portion of the configuration is described in each embodiment, the configuration of another previously described embodiment may be applied to the remaining portions of the configuration. Furthermore, in addition to the combinations of configurations explicitly stated in the description of each embodiment, configurations of multiple embodiments may be partially combined together even if not explicitly stated, provided that there is no particular problem with the combination.

[0018] First Embodiment As shown in Fig. 1 , a first embodiment of the present disclosure relates to an optical sensor 2 configured to include a light-emitting unit 1. The optical sensor 2 is mounted on a vehicle 5. The vehicle 5 is a mobile body such as an automobile that can travel on a road with an occupant on board.

[0019] The vehicle 5 is capable of steady or temporary autonomous driving in an autonomous driving control mode. Here, the autonomous driving control mode may be realized by autonomous driving control, such as conditional driving automation, highly automated driving, or fully automated driving, in which a system performs all driving tasks when activated. The autonomous driving control mode may also be realized by advanced driving assistance control, such as driving assistance or partial driving automation, in which a passenger performs some or all driving tasks. The autonomous driving control mode may be realized by either autonomous driving control or advanced driving assistance control, or by a combination of these, or by switching between them.

[0020] 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.

[0021] 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 automatic driving mode, of the vehicle 5. The optical sensor 2 is disposed in at least one location on the vehicle 5, such as the front, left and right side portions, rear portion, or upper roof.

[0022] In the optical sensor 2, a three-dimensional Cartesian coordinate system is defined by three mutually orthogonal axes: an X axis, a Y axis, and a Z axis. 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 below) actually illustrates a cross section perpendicular to the right side of the dashed dotted line (the side of modules 21 and 41 described below) where the three-dimensional Cartesian coordinate system is defined.

[0023] The optical sensor 2 emits light toward a sensing area As corresponding to the installation location and field of view angle in the external space of the vehicle 5. The optical sensor 2 receives reflected light that enters the sensing area As when the emitted light is reflected from the sensing area As. In response to receiving the reflected light of the emitted 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.

[0024] A typical sensing target in the optical sensor 2 applied to the vehicle 5 may be at least one of moving objects such as a pedestrian, a cyclist, a non-human animal, and another vehicle. A typical sensing target in the optical sensor 2 applied to the vehicle 5 may be at least one of stationary objects such as a guardrail, a road sign, a roadside structure, and an object fallen on the road.

[0025] 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 and is mainly made of a light-blocking material such as metal or synthetic resin. The housing 11 houses 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, which is formed in a plate shape from a light-transmitting material such as glass or synthetic resin.

[0026] 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 210. Each light-emitting diode 22 generates pulsed infrared laser light that is used to irradiate the sensing area As under the control of the control module 51. Each of these light-emitting diodes 22 is provided as a laser diode, such as an edge-emitter laser or a vertical cavity surface-emitting laser (VCSEL).

[0027] As shown in FIG. 1 , the light projection 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 projection lens system 28 performs at least one optical function, such as focusing, collimating, and shaping. The light projection lens system 28 forms a projection optical axis along the Z axis. The light projection lens system 28 has at least one projection lens 29 on the projection optical axis, the lens shape of which corresponds to the optical function to be performed. The light-emitting unit 1 is positioned on the projection optical axis of the light projection lens system 28. The illumination light emitted by each light-emitting diode 22 in the light-emitting unit 1 is guided along the projection optical axis of the light projection lens system 28.

[0028] 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 around a rotation center line along the Y axis. The scanning mirror 32 oscillates within a driving range that is finite due to the function of a mechanical or electrical stopper.

[0029] 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 with the irradiated light incident from 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 both temporally and spatially. In particular, in the optical sensor 2, the mechanical scanning of the sensing area As with the irradiated light is substantially limited to scanning in the horizontal direction.

[0030] Simultaneously with this 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 by the reflecting surface 33 oriented according to the rotation angle. Here, the speeds of the irradiated light and 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 by the scanning mirror 32, which has approximately the same rotation angle as the irradiated light, so as to travel in the opposite direction to the irradiated light.

[0031] 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 range 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.

[0032] The light-receiving module 41 is disposed offset in the Y-axis direction relative 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 function to image the light reflected from the sensing area As onto 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 lens shape of which corresponds to the optical function to be exerted. 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.

[0033] 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 light receiving pixel 46 is further constructed from a plurality of light receiving elements 460. The light receiving elements 460 of each light receiving pixel 46 are mainly composed of photodiodes such as single photon avalanche diodes (SPADs). With this configuration, each light receiving pixel 46 receives reflected light incident from the light receiving lens system 42 with each light receiving element 460.

[0034] 1 , the light receiving unit 45 is integrally provided with an output circuit 48. The output circuit 48 performs sampling processing under control of 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, through the sampling processing, the output circuit 48 generates light reception data for each scanning line based on the output signal from each light receiving pixel 46 of the light receiving unit 45. The light reception data generated in this manner is output from the output circuit 48 to the control module 51.

[0035] 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.

[0036] 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 components 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.

[0037] Next, the 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 resonant 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.

[0038] 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.

[0039] In the light-emitting circuit 24, the section from the midpoint E1 between the inductor 241 and the capacitor 242 in the resonant circuit section 240 to the ground terminal E0 is connected in parallel with the capacitor 242 by the light-emitting branch path section RI. The light-emitting branch path section RI 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 this arrangement and configuration in the light-emitting branch path section RI, the discharge switching element 246 can turn on and off the discharge from the capacitor 242 by switching.

[0040] In the light-emitting circuit 24, the light-emitting branch path Rl extending from the midpoint E1 to the ground terminal E0 is provided with a light-emitting diode 22 on the ground 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 toward the ground terminal E0 side. The light-emitting diode 22 generates illumination light by emitting light due to discharge from the capacitor 242 in response to the discharge switching element 246 being turned on.

[0041] In the light-emitting circuit 24, the resonant circuit section 240 is connected from another midpoint E2, which is closer to the inductor 241 than the midpoint E1, which is the branch point where the light-emitting branch path section RI branches from the inductor 241 and the capacitor 242, to the ground terminal E0 via the control branch path section Rc. Thus, the control branch path section Rc, which is connected in parallel with the capacitor 242 and the light-emitting branch path section RI, is provided with a charge switching element 247. The charge switching element 247 is primarily composed of a field-effect transistor such as a MOSFET. Due to its placement and configuration in the control branch path section Rc, the charge switching element 247 can switch on and off the charging of the capacitor 242. A backflow prevention diode 249 is provided between the inductor 241 and the midpoint E2 in the resonant circuit section 240 to prevent a drop in the charging voltage Vc to the capacitor 242.

[0042] In the light-emitting circuit 24, a drive circuit unit 248 is connected to each of the switching elements 246, 247. The drive circuit unit 248 is also connected to the control module 51. The drive circuit unit 248 drives each of the switching elements 246, 247 to turn on and off individually, as shown in FIGS. 5 to 7, in accordance with control from the control module 51. That is, the switching of each of the switching elements 246, 247 is controlled by the on / off drive function of the drive circuit unit 248.

[0043] 5 to 7 , the drive circuit unit 248 sets a reference ON timing tn0 for switching the charge switching element 247 from an OFF state to an ON state at the start of each light emission cycle P1. At the same time, the drive circuit unit 248 sets a reference OFF timing tf0 for switching the charge switching element 247 from an ON state to an OFF state at a timing a certain period Δtm after the reference ON timing tn0 for each light emission cycle P1. By setting the reference ON timing tn0 and the reference OFF timing tf0 in this manner, a minimum ON period Δtm is defined for the charge switching element 247.

[0044] In the drive circuit unit 248, the on-period Δt of the charge switching element 247 is controlled to be equal to or longer than the minimum on-period Δtm for each light-emitting period Pl. In this case, as shown by the dashed-two-dot line graph in FIG. 5A , the on-timing tn of the charge switching element 247 may be adjusted to match the reference on-timing tn0, while the off-timing tf may be adjusted to a variable timing after the reference off-timing tf0. As shown by the dashed-two-dot line graph in FIG. 6A , the off-timing tf of the charge switching element 247 may be adjusted to match the reference off-timing tf0, while the on-timing tn may be adjusted to a variable timing before the reference on-timing tn0, as long as it is after the initial timing of each light-emitting period Pl. As shown by the dashed-two-dot line graph in FIG. 7A , the on-timing tn of the charge switching element 247 may be adjusted to a variable timing before the reference on-timing tn0, as long as it is after the initial timing of each light-emitting period Pl, while the off-timing tf may be adjusted to a variable timing after the reference off-timing tf0.

[0045] As the drive circuit unit 248 extends the on-period Δt of the charge switching element 247 from the minimum on-period Δtm by adjusting either of these, the duration and magnitude of the current Ii (see also FIG. 4) flowing through the inductor 241 in the resonant circuit unit 240 increases, as shown by the solid line graphs and two-dot chain line graphs corresponding to the other subdivisions in each of FIGS. 5 to 7 (B). Accordingly, the voltage Vc (see also FIG. 4) charged to the capacitor 242 increases in the resonant circuit unit 240, as shown by the solid line graphs and two-dot chain line graphs corresponding to the other subdivisions in each of FIGS. 5 to 7 (C). That is, the more the drive circuit unit 248 extends the on-period Δt of the charge switching element 247 from the minimum on-period Δtm, the greater the charging voltage Vc of the capacitor 242. Here, the charging voltage Vc of the capacitor 242 when the charge switching element 247 remains off is, at most, expressed by the following equation (1) using the power supply voltage Vin: On the other hand, when the charging switching element 247 is turned on and its on period Δt is extended, the charging voltage Vc of the capacitor 242 increases within the range defined by the following equation 2 using the power supply voltage Vin.

[0046] 5 to 7, in the drive circuit unit 248, the discharge switching element 246 in the OFF drive state is turned on at a timing that is later than the OFF timing tf 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 occurs prior to the ON timing td for switching the discharge switching element 246 in the OFF drive state to ON for each light emission period Pl.

[0047] In response to the ON driving of the discharge switching element 246, a discharge current discharged from the capacitor 242, which is in a state of a charging voltage Vc, flows into the light-emitting branch path section RI through the resonant 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 two-dot chain line graphs corresponding to the other subdivisions in each of FIGS.

[0048] Therefore, when the control module 51 recognizes, for example, based on the light reception data from the output circuit 48, a state in which the received light intensity of reflected light from a distant target falls below the lower limit intensity at which sensing accuracy is guaranteed in the light receiving unit 45, the control module 51 issues an extension control command to the drive circuit section 248. As a result, the drive circuit section 248 controls the on / off driving of the charge switching element 247 so as to extend the on period Δt within a range after the start timing of each light emission cycle Pl, for example, in accordance with the degree to which the received light intensity is insufficient from the lower limit intensity.

[0049] (Operational Effects) The operational effects of the first embodiment described above are described below. According to the first embodiment, the light-emitting branch path section RI, which branches off between the inductor 241 and the capacitor 242 in the resonant circuit section 240, is provided with a light-emitting diode 22 that generates irradiated light by emitting light and a discharge switching element 246 that switches on and off the discharge from the capacitor 242. Therefore, in particular, the control branch path section Rc, which branches off from the resonant circuit section 240 closer to the inductor 241 than the branch point of the light-emitting branch path section RI, is provided with a charge switching element 247 that switches on and off the charge to the capacitor 242. This allows the on-period Δt of the charge switching element 247 prior to the on-timing td of the discharge switching element 246 to be extended, thereby relatively increasing the light-receiving sensitivity, even if the received light intensity of the reflected light relative to the irradiated light is insufficient. Therefore, this extension control increases the peak intensity of the irradiated light to a high intensity that matches the received light of the reflected light, ensuring target sensing accuracy.

[0050] According to the first embodiment, the on-period Δt of the charge switching element 247 may be controlled by adjusting 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, to a timing after the periodically set reference off-timing tf0. In this case, when the received light intensity of the reflected light is insufficient, the on-period Δt of the charge switching element 247 can be extended by adjusting the off-timing tf of the charge switching element 247 to be later than the reference off-timing tf0. Therefore, such extension control makes it possible to accurately increase the peak intensity of the irradiated light to a high intensity that matches the received light of the reflected light, thereby ensuring sensing accuracy.

[0051] According to the first embodiment, the on-timing tn 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 earlier than the periodically set reference on-timing tn0, thereby controlling the on-period Δt of the charge switching element 247. In this case, when the received light intensity of the reflected light is insufficient, the on-period Δt of the charge switching element 247 can be extended by adjusting the on-timing tn of the charge switching element 247 to be earlier than the reference on-timing tn0. Therefore, such extension control makes it possible to accurately increase the peak intensity of the irradiated light to a high intensity that matches the received light of the reflected light, thereby improving sensing accuracy.

[0052] Second Embodiment As shown in FIG. 8, the second embodiment is a modification of the first embodiment.

[0053] In the light-emitting circuit 2024 of the second embodiment, a charge switching element 247 on the control branch path section Rc similar to that of the first embodiment is provided as a first charge switching element 247. In addition, in the light-emitting circuit 2024, a second charge switching element 2247 is provided between the inductor 241 and the capacitor 242 of the resonant circuit section 2240.

[0054] Specifically, the second charging switching element 2247 is provided at another intermediate point E3 in the resonant circuit section 2240, which is closer to the inductor 241 than intermediate points E1 and E2, which are branch points where the branch path sections Rl and Rc branch from between the inductor 241 and the capacitor 242. The second charging switching element 2247 is mainly composed of a field-effect transistor such as a MOSFET. This arrangement and configuration at intermediate point E3 allows the second charging switching element 2247 to turn on and off the charging of the capacitor 242 by switching. In the resonant circuit section 2240 of the second embodiment, a backflow prevention diode 249 is provided between the inductor 241 and intermediate point E3, thereby suppressing a drop in the charging voltage to the capacitor 242.

[0055] 9 to 14, the second charge switching element 2247 is driven on and off separately from the other switching elements 246, 247 by the drive circuit unit 2248 in accordance with control from the control module 51. That is, not only the discharge switching element 246 and the first charge switching element 247, but also the second charge switching element 2247 is controlled by the on / off drive function of the drive circuit unit 2248. Therefore, the on / off drive function of the drive circuit unit 2248 follows a switching command between control modes M1 and M2, which are switched depending on the peak intensity of irradiated light that the control module 51 determines is necessary based on the light reception data from the output circuit 48.

[0056] Specifically, when the control module 51 determines that a high-intensity condition requiring a high peak intensity of the irradiated light is met, including an insufficient intensity condition in which the received light intensity of the reflected light falls below a lower limit intensity at the light-receiving unit 45, the control module 51 commands the drive circuit unit 2248 to switch to a first control mode M1, which increases the peak intensity more than the second control mode M2, described below. As a result, as shown by the solid and dashed lines in each of the sub-diagrams (B) in Figures 9 to 11, the drive circuit unit 2248 in the first control mode M1 holds the second charge switching element 2247 in the on state while the high-intensity condition is met. Here, the insufficient intensity condition included in the high-intensity condition is a condition that is met, for example, when the received light intensity of the reflected light from a distant target or the like falls below a lower limit intensity at the light-receiving unit 45. Therefore, the high-intensity condition may be met when the received light intensity is higher than the lower limit intensity, which is the criterion for determining whether the insufficient intensity condition is met, but when it becomes necessary to adjust the peak intensity of the irradiated light to a range higher than the second control mode M2, described below.

[0057] 9 to 11 , in the drive circuit unit 2248 in the first control mode M1, the reference ON timing tn0 for switching the first charging switching element 247 from the OFF driving state to ON driving is set to coincide with the start timing of each light emission cycle P1. At the same time, in the drive circuit unit 2248 in the first control mode M1, the reference OFF timing tf0 for switching the first charging switching element 247 from the ON driving state to OFF driving is set to a timing that is a certain period Δtm after the reference ON timing tn0 for each light emission cycle P1. By setting the periods of the reference ON timing tn0 and the reference OFF timing tf0 in this way, a minimum ON period Δtm is defined for the first charging switching element 247.

[0058] In the drive circuit unit 2248 in the first control mode M1 during the on-period ΔT of the second charging switching element 2247, the on-period Δt of the first charging switching element 247 is controlled to be equal to or longer than the minimum on-period Δtm for each light-emitting period P1. In this case, for the first 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 after the reference off-timing tf0, as shown by the two-dot chain line graph in FIG. 10(A). For the first 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 before the reference on-timing tn0, as long as it is after the start of each light-emitting period P1. For the first charging switching element 247, as shown by the dashed-dotted line graph in Figure 11 (A), the on-timing tn may be adjusted to a variable timing before the reference on-timing tn0 as long as it is after the initial timing of each light-emitting period Pl, and the off-timing tf may be adjusted to a variable timing after the reference off-timing tf0.

[0059] In the first control mode M1, as a result of any of these adjustments, the more the drive circuit unit 2248 controls the on-period Δt of the first charging switching element 247 to be extended from the minimum on-period Δtm, the longer and larger the current Ii (see also FIG. 8) flows through the inductor 241 in the resonant circuit unit 2240, as shown by the solid line graphs and two-dot chain line graphs corresponding to the other subdivisions in each of the subdivisions (C) in FIGS. 9 to 11. Accordingly, in the resonant circuit unit 2240, the voltage Vc (see also FIG. 8) charged to the capacitor 242 increases, as shown by the solid line graphs and two-dot chain line graphs corresponding to the other subdivisions in each of the subdivisions (D) in FIGS. 9 to 11. That is, the more the drive circuit unit 2248 controls the on-period Δt of the first charging switching element 247 to be extended from the minimum on-period Δtm, the greater the charging voltage Vc of the capacitor 242 increases within the range defined by equation 2, the same as in the first embodiment.

[0060] 9 to 11 , in the drive circuit unit 2248, during the on-period ΔT of the second charge switching element 2247, the discharge switching element 246 in the off-drive state is turned on at a timing that is later than the off-timing tf of the first charge switching element 247 for each light emission period Pl. In other words, the control of the on-period Δt for turning on the first 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 in the on-period ΔT of the second charge switching element 2247.

[0061] In response to the ON-driving of the discharge switching element 246, a discharge current discharged from the capacitor 242, which is in a state of a charging voltage Vc, flows into the light-emitting branch path section R1 through the resonant circuit section 2240. As a result, a current Io (see also FIG. 8 ) 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 two-dot chain line graphs corresponding to the other subdivisions in each of FIGS. 9 to 11 (F).

[0062] When the control module 51 determines that a low-intensity condition, which requires a low peak intensity of irradiated light and includes an intensity saturation condition in which the received light intensity of reflected light exceeds an upper limit intensity at the light-receiving unit 45, is satisfied, the control module 51 commands the drive circuit unit 2248 to switch to a second control mode M2, which reduces the peak intensity below that of the first control mode M1. As a result, as shown by the solid and dashed lines in each of the sub-diagrams (A) in Figures 12 to 14, the drive circuit unit 2248 in the second control mode M2 ​​holds the first charge switching element 247 in the off state while the low-intensity condition is satisfied. Here, the intensity saturation condition included in the low-intensity condition is a condition that is satisfied when, for example, the received light intensity of reflected light from a nearby target or a highly reflective target exceeds an upper limit intensity at the light-receiving unit 45. Therefore, the low-intensity condition may be satisfied when the received light intensity is lower than the upper limit intensity, which is the criterion for determining whether the intensity saturation condition is satisfied, but when it becomes necessary to adjust the peak intensity of irradiated light to a range lower than that of the first control mode M1.

[0063] 12 to 14, in the drive circuit unit 2248 in the second control mode M2, the reference ON timing Tn0 for switching the second charge switching element 2247 from the OFF drive state to ON drive is set to coincide with the start of each light emission cycle Pl. At the same time, in the drive circuit unit 2248 in the second control mode M2, the reference OFF timing Tf0 for switching the second charge switching element 2247 from the ON drive state to OFF drive is set to a timing that is a certain period ΔTm after the reference ON timing Tn0 for each light emission cycle Pl. By setting the periods of the reference ON timing Tn0 and the reference OFF timing Tf0 in this way, the maximum ON period ΔTm of the second charge switching element 2247 is controlled to a time that is substantially equal to the time constant of the resonant circuit unit 2240.

[0064] In the drive circuit unit 2248 in the second control mode M2 ​​during the off period ωt of the first charge switching element 247, the on period ΔT of the second charge switching element 2247 is controlled to be equal to or shorter than the maximum on period ΔTm for each light emission period Pl. In this case, for the second charge switching element 2247, 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. 12(B). For the second charge switching element 2247, 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. For the second charging switching element 2247, the on timing Tn may be adjusted to a variable timing after the reference on timing Tn0, as shown by the dashed-dotted line graph in Figure 14 (B), and 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.

[0065] In the second control mode M2, as a result of any of these adjustments, the more the drive circuit unit 2248 controls the on-period ΔT of the second charging switching element 2247 to be shortened from the maximum on-period ΔTm, the more the duration and magnitude of the current Ii flowing through the inductor 241 in the resonant circuit unit 2240 decrease, as shown by the solid line graphs and two-dot chain line graphs corresponding to the other subdivisions in each of the subdivisions (C) in Figures 12 to 14. Accordingly, in the resonant circuit unit 2240, the voltage Vc charged to the capacitor 242 decreases, as shown by the solid line graphs and two-dot chain line graphs corresponding to the other subdivisions in each of the subdivisions (D) in Figures 12 to 14. In other words, the more the drive circuit unit 2248 controls the on-period ΔT of the second charging switching element 2247 to be shortened from the maximum on-period ΔTm, the more the charging voltage Vc of the capacitor 242 decreases within the range defined by Equation 3, where Vc in Equation 1 of the first embodiment is the maximum charging voltage.

[0066] 12 to 14, in the drive circuit unit 2248, during the off period ωt of the first charge switching element 247, 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 second charge switching element 2247 for each light emission period Pl. In other words, the control of the on period ΔT for turning on the second charge switching element 2247 precedes the on timing Td for switching the discharge switching element 246 in the off-drive state to on for each light emission period Pl in the off period ωt of the first charge switching element 247.

[0067] In response to the ON driving of the discharge switching element 246, a discharge current discharged from the capacitor 242, which is in a state of a charging voltage Vc, flows into the light-emitting branch path section RI through the resonant circuit section 2240. As a result, a current Io 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 two-dot chain line graphs corresponding to the other subdivisions in each of Figures 12 to 14 (F).

[0068] (Operations and Effects) Operations and effects specific to the second embodiment described above will be described below.

[0069] According to the second embodiment, a first charge switching element 247 that switches on and off the charging of the capacitor 242 is provided in the control branch path section Rc that branches off from the inductor 241 side of the branch point of the light emission branch path section Rl in the resonant circuit section 2240. At the same time, a second charge switching element 2247 that switches on and off the charging of the capacitor 242 is provided in the resonant circuit section 2240 on the inductor 241 side of the branch point of the light emission branch path section Rl.

[0070] Therefore, in the first control mode M1, even if the received light intensity of the reflected light relative to the emitted light is insufficient, the light receiving sensitivity can be relatively increased by extending the on-period Δt of the first charge switching element 247 prior to the on-timing td of the discharge switching element 246 during the on-period ΔT of the second charge switching element 2247. Therefore, in a sensing scene where it is necessary to increase the peak intensity of the emitted light to a high intensity that matches the received reflected light, such extension control can impart a high peak intensity to the emitted light, thereby ensuring the accuracy of sensing the target.

[0071] On the other hand, in the second control mode M2, even if saturation occurs in the received light intensity of reflected light relative to the irradiated light, the on-period ΔT of the second charge switching element 2247 prior to the on-timing td of the discharge switching element 246 can be shortened during the off-period ωt of the first charge switching element 247, thereby relatively lowering the light-receiving sensitivity. Therefore, in a sensing scene where it is necessary to suppress the peak intensity of the irradiated light to a low intensity that matches the received reflected light, such shortening control can be used to give the irradiated light a low peak intensity, thereby ensuring the target sensing accuracy. Moreover, by combining this second control mode M2 ​​with the first control mode M1 described above, it is also possible to increase the dynamic range of received light.

[0072] According to the first control mode M1 in which the second charge switching element 2247 is controlled to be held in the on state as in the second embodiment, the peak intensity of the irradiated light can be accurately matched to the received reflected light by controlling the on period Δt of the first charge switching element 247. This makes it possible to improve the sensing accuracy.

[0073] According to the second embodiment, when a high-intensity condition is met in which the peak intensity of the irradiated light is made higher than that of the second control mode M2, the second control mode M2 ​​is switched to the first control mode M1. This makes it possible to respond in a timely manner to a sensing scene in which a peak intensity of the irradiated light that is higher than that of the second control mode M2 ​​is required for receiving reflected light by switching to the first control mode M1, thereby ensuring sensing accuracy.

[0074] According to the second control mode M2 ​​of the second embodiment, the off timing Tf of the second charge switching element 2247, which is turned on prior to the on timing Td of the discharge switching element 246, may be adjusted to be earlier than the periodically set reference off timing Tf0, thereby controlling the on period ΔT of the second charge switching element 2247. In this case, when the received light intensity of reflected light is saturated, the on period ΔT of the second charge switching element 2247 can be stably shortened by adjusting the off timing Tf of the second charge switching element 2247 to be earlier than the reference off timing Tf0, thereby controlling the on period ΔT of the second charge switching element 2247. Therefore, such shortening control accurately stabilizes the peak intensity of the irradiated light at a low intensity that matches the received reflected light, thereby ensuring sensing accuracy.

[0075] According to the second control mode M2 ​​of the second embodiment, the on-timing Tn of the second charge switching element 2247, which is turned on prior to the on-timing Td of the discharge switching element 246, may be adjusted to a timing after the periodically set reference on-timing Tn0, thereby controlling the on-period ΔT of the second charge switching element 2247. In this case, when the intensity of the received reflected light is saturated, the on-period ΔT of the second charge switching element 2247 can be shortened by adjusting the on-timing Tn of the second charge switching element 2247 to be later than the reference on-timing Tn0. Therefore, such shortening control accurately suppresses the peak intensity of the irradiated light to a low intensity that matches the received reflected light, thereby improving sensing accuracy.

[0076] (Other Embodiments) Although multiple embodiments have been described above, the present disclosure should not be construed as being limited to those embodiments, and can be applied to various embodiments and combinations within the scope that does not deviate from the gist of the present disclosure.

[0077] 15 , in a modification of the second embodiment, the control branch path section Rc in which the first charging switching element 247 is provided may branch off from an intermediate point E4 between the inductor 241 and the second charging switching element 2247 at the intermediate point E3 in the resonant circuit section 2240. In the resonant circuit section 2240 of this modification, a backflow prevention diode 249 is provided between the inductor 241 and the intermediate point E4, thereby suppressing a decrease in the charging voltage Vc to the capacitor 242.

[0078] In a modification of the second embodiment as shown in FIG. 16 , the second charging switching element 2247 may be constantly held in the ON state during activation of the vehicle 5 and / or the optical sensor 2, thereby substantially realizing only the first control mode M1, which is equivalent to the first embodiment. In a modification of the second embodiment as shown in FIG. 17 , the second charging switching element 2247 may be repeatedly turned on and off within the maximum ON period ΔTm in the second control mode M2, thereby controlling the total time ΣΔT of the intermittent ON periods ΔT of the second charging switching element 2247 to be shorter than the maximum ON period ΔTm. In a modification of the second embodiment as shown in FIG. 18 and a further modification of FIG. 17 (not shown), the first charging switching element 247 may be constantly held in the OFF state during activation of the vehicle 5 and / or the optical sensor 2, thereby substantially realizing only the second control mode M2.

[0079] In the modifications of the first and second embodiments, the vehicle 5 to which the optical sensor 2 including the light-emitting unit 1 is applied may be, for example, an autonomous robot that is capable of autonomously or remotely traveling to transport luggage or collect information, etc. In the modifications of the first and second embodiments, the object to which the optical sensor 2 including the light-emitting unit 1 is applied may be, for example, a moving body other than the vehicle 5, or a stationary object such as a structure.

[0080] (Additional Remarks) This specification discloses the following technical ideas and combinations thereof.

[0081] (Technical Idea 1) In an optical sensor (2) that senses a target by receiving light reflected from the target in response to illumination light illuminated onto a sensing area (As), the light emitting unit provides the illumination light by emitting light, comprising: a resonance circuit section (240, 2240) having an inductor (241) and a capacitor (242); an illumination branch path section (Rl) that branches off from between the inductor and the capacitor in the resonance circuit section; a light emitting diode (22) that is provided in the illumination branch path section and generates the illumination light by emitting light; a discharge switching element (246) that is provided in the illumination branch path section and switches on / off discharge from the capacitor; a control branch path section (Rc) that branches off from the inductor side of the branch point of the illumination branch path section in the resonance circuit section; and a charge switching element (247) that is provided in the control branch path section and switches on / off charging of the capacitor by switching. A light-emitting unit comprising a drive circuit section (248, 2248) that controls the discharge switching element and the charge switching element by individual on / off driving, wherein the drive circuit section controls the on period of the charge switching element prior to the on timing of the discharge switching element.

[0082] (Technical Idea 2) The driving circuit section 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 a time after a periodically set reference off timing, in the light-emitting unit described in Technical Idea 1.

[0083] (Technical Idea 3) The driving circuit section controls the on period of the charge switching element by adjusting the on timing of the charge switching element, which is turned on prior to the on timing of the discharge switching element, to a value before a periodically set reference on timing. This is the light-emitting unit described in Technical Idea 1 or 2.

[0084] (Technical Idea 4) A light-emitting unit described in any one of Technical Ideas 1 to 3, which is provided with a second charging switching element (2247) that is provided in the resonant circuit section (2240) on the inductor side of the branch point of the light-emitting branch path section, separate from the first charging switching element (247) as the charging switching element, and which switches the charging of the capacitor on and off by switching; and the drive circuit section (2248) controls the discharge switching element, the first charging switching element, and the second charging switching element by individual on / off driving, and the drive circuit section switches between a first control mode that controls the on period of the first charging switching element during the on period of the second charging switching element prior to the on timing of the discharge switching element, and a second control mode that controls the on period of the second charging switching element during the off period of the first charging switching element prior to the on timing of the discharge switching element.

[0085] (Technical Concept 5) The light-emitting unit according to Technical Concept 4, wherein in the first control mode, the drive circuit section controls to hold the second charge switching element in an ON state.

[0086] (Technical Idea 6) The light-emitting unit described in Technical Idea 4 or 5, wherein the drive circuit section switches from the second control mode to the first control mode when a high-intensity condition is met that increases the peak intensity of the irradiation light higher than that of the second control mode.

[0087] (Technical Idea 7) In the second control mode, the drive circuit section controls the on period of the second charge switching element by adjusting the off timing of the second charge switching element, which is turned on prior to the on timing of the discharge switching element, to a value before a periodically set reference off timing, to be an illuminating unit described in any one of Technical Ideas 4 to 6.

[0088] (Technical Idea 8) In the second control mode, the drive circuit section controls the on period of the second charge switching element by adjusting the on timing of the second charge switching element, which is turned on prior to the on timing of the discharge switching element, to a time after a periodically set reference on timing. This is a light-emitting unit described in any one of Technical Ideas 4 to 7.

[0089] (Technical Idea 9) An optical sensor comprising: a light-emitting unit (1) according to any one of Technical Ideas 1 to 8; and a light-receiving unit (45) that receives the reflected light of the irradiated light emitted by the light-emitting unit.

Claims

1. In an optical sensor (2) that senses a target by receiving reflected light from the target in response to irradiated light irradiated onto a sensing area (As), a light emitting unit that emits the irradiated light, a resonant circuit section (2240) having an inductor (241) and a capacitor (242); a light-emitting branch path portion (Rl) branching from between the inductor and the capacitor in the resonant 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 discharge from the capacitor; a control branch path section (Rc) that branches from the inductor side relative to a branch point of the light emission branch path section in the resonance circuit section; a first charging switching element (247) provided in the control branch path section and switching on and off charging of the capacitor; a second charging switching element (2247) that is provided in the resonance circuit unit on the inductor side of the branch point of the light emission branch path unit, separate from the first charging switching element, and that switches on and off charging of the capacitor; a drive circuit unit (2248) that controls the discharge switching element, the first charge switching element, and the second charge switching element by individual on / off driving, The drive circuit unit A light-emitting unit that switches between a first control mode in which the on period of the first charge switching element is controlled during the on period of the second charge switching element prior to the on timing of the discharge switching element, and a second control mode in which the on period of the second charge switching element is controlled during the off period of the first charge switching element prior to the on timing of the discharge switching element.

2. The drive circuit unit 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 a timing after a periodically set reference off-timing.

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

4. In the first control mode, the drive circuit unit The light-emitting unit according to claim 1 , wherein the second charging switching element is controlled to be held in an on state.

5. The drive circuit unit The light-emitting unit according to claim 1 , wherein the second control mode is switched to the first control mode when a high-intensity condition is met in which the peak intensity of the irradiated light is made higher than that in the second control mode.

6. In the second control mode, the drive circuit unit: The light-emitting unit described in claim 1, wherein the on-period of the second charge switching element is controlled by adjusting the off-timing of the second charge switching element, which is turned on prior to the on-timing of the discharge switching element, to be before a periodically set reference off-timing.

7. In the second control mode, the drive circuit unit: The light-emitting unit described in claim 1 or 6 controls the on-period of the second charge switching element by adjusting the on-timing of the second charge switching element, which is turned on prior to the on-timing of the discharge switching element, to a timing after a periodically set reference on-timing.

8. A light-emitting unit (1) according to claim 1; and a light receiving unit (45) that receives the reflected light of the irradiated light emitted by the light emitting unit.