Optical sensor

Abstract

The optical sensor includes: a light projecting unit that generates a projected light beam by a light source element; a light receiving unit that outputs a detection signal by receiving the reflected light beam; and a control unit that controls the light projecting unit and the light receiving unit. The control unit is configured so as to execute: monitoring a heat transfer temperature (Tt) transferred to the surroundings of the light source element in the light projection unit; and controlling a light emission output (P1) in the light source element so as to absorb a temperature change amount of a junction temperature (Tj) in the light source element, the temperature change amount being related to an efficiency change amount of the light emission efficiency and a heat transfer change amount of the heat transfer temperature (Tt), the efficiency change amount of the light emission efficiency being reduced in accordance with an increase in the heat transfer temperature (Tt) in the light source element.

Description

[0001] Cross-reference to related applications

[0002] This application is based on patent application No. 2023-016177 filed in Japan on February 6, 2023, and the entire contents of the basic application are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to optical sensors. Background Art

[0004] Optical sensors that project a light beam and receive a reflected light beam are widely known. Patent Document 1 discloses a sensor that outputs a detection signal based on a reflected light beam received by a light receiving unit in response to a light beam generated by a light source element in a light projecting unit.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: U.S. Patent No. 10,677,898 Summary of the Invention

[0008] In the optical sensor disclosed in Patent Document 1, the radiation energy from the light source element is increased while the detection signal is lower than the reference signal and not saturated. As a result, when the ambient temperature of the light source element increases, the temperature of the light source element continues to rise in accordance with the increase in radiation energy, potentially leading to durability issues such as a shortened lifespan of the light source element.

[0009] An object of the present disclosure is to provide an optical sensor with ensured durability.

[0010] Hereinafter, the technical solution of the present disclosure for solving the technical problem will be described.

[0011] One embodiment of the present disclosure is an optical sensor that projects a light beam and receives a reflected light beam reflected from the light beam, and is characterized in that it comprises: a light projecting unit that generates a light beam from a light source element; a light receiving unit that outputs a detection signal by receiving the reflected light beam; and a control unit that controls the light projecting unit and the light receiving unit, the control unit being configured to perform the following control: monitoring the heat transfer temperature transferred from the light projecting unit to the surroundings of the light source element; and controlling the light output in the light source element in a manner that absorbs a temperature change in the junction temperature in the light source element that is related to an efficiency change in the luminous efficiency that decreases in the light source element due to an increase in the heat transfer temperature and a heat transfer change in the heat transfer temperature.

[0012] Thus, in the light projection unit of one embodiment of the present disclosure, the control unit monitors the heat transfer temperature transmitted to the surrounding area of ​​the light source element. Therefore, the control unit also monitors the temperature change of the junction temperature of the light source element, which is related to the change in efficiency of the luminous efficiency and the heat transfer change in the heat transfer temperature, which decreases in the light source element as the heat transfer temperature rises. Thus, the control unit controls the light output of the light source element in a manner that absorbs the temperature change of the junction temperature. This can suppress the reduction in the life of the light source element caused by the temperature rise, thereby ensuring durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a cross-sectional view showing the overall structure of the optical sensor according to the first embodiment.

[0014] Figure 2 It is a schematic diagram showing the light projection light source unit according to the first embodiment.

[0015] Figure 3 This is a timing chart for explaining the operation of the light projection light source unit according to the first embodiment.

[0016] Figure 4 It is a schematic diagram showing the light receiving detection unit according to the first embodiment.

[0017] Figure 5 This is a block diagram showing the circuit configuration of the light projection light source unit according to the first embodiment.

[0018] Figure 6 This is a circuit diagram showing the detailed configuration of the power supply circuit according to the first embodiment.

[0019] Figure 7 This is a circuit diagram showing the detailed configuration of the adjustment circuit according to the first embodiment.

[0020] Figure 8 This is a circuit diagram showing the detailed configuration of the temperature measurement circuit according to the first embodiment.

[0021] Figure 9 This is a graph for explaining the control principle of the control unit in the first embodiment.

[0022] Figure 10 This is a graph for explaining the control principle of the control unit in the second embodiment.

[0023] Figure 11 This is a graph showing the characteristics of the power supply circuit according to the third embodiment.

[0024] Figure 12 Yes Figure 7 A circuit diagram showing a detailed configuration of an adjustment circuit according to a modified example. DETAILED DESCRIPTION

[0025] Hereinafter, multiple embodiments of the present disclosure will be described based on the accompanying drawings. In addition, in each embodiment, by marking the corresponding components with the same reference numerals, repeated descriptions are sometimes omitted. In addition, when only a part of the structure is described in each embodiment, the structure of other embodiments previously described can be applied to the other parts of the structure. Furthermore, not only the combination of structures explicitly described in the description of each embodiment, but also the structures of multiple embodiments can be partially combined with each other even if not explicitly described, as long as the combination does not particularly cause obstacles.

[0026] (First embodiment)

[0027] like Figure 1 As shown, the optical sensor 10 of the first embodiment of the present disclosure is a LiDAR (Light Detection and Ranging / Laser Imaging Detection and Ranging) configured on a mobile body to optically detect the outside world. The mobile body to which the optical sensor 10 is configured is a vehicle such as a car that can be driven by at least one of manual driving, automatic driving, and remote driving. In addition, in the following description, unless otherwise specified, the directions shown as front, rear, up, down, left, and right are defined with respect to the vehicle on a horizontal plane. In addition, in the following description, the horizontal direction and the vertical direction refer to the parallel direction and the perpendicular direction relative to the horizontal plane in the vehicle on the horizontal plane, respectively.

[0028] The optical sensor 10 is placed, for example, at at least one location on the vehicle, such as the front, left or right sides, rear, or roof. The optical sensor 10 projects a projection beam Bp toward a detection area Ad corresponding to the location on the vehicle. The optical sensor 10 detects the return light reflected from the external projection beam Bp by a target in the detection area Ad as a reflected light beam Br. Thus, the projection beam Bp, which becomes the reflected light beam Br, is selected to be in the near-infrared region, which is difficult for humans to visually perceive.

[0029] The optical sensor 10 detects external targets in the detection area Ad by receiving a reflected light beam Br that is reflected from the projected light beam Bp. Such detection of external targets refers to one or more types of detection, including at least the distance, such as the distance from the optical sensor 10 to the target, the direction in which the target is located, and the reflection intensity of the reflected light beam Br from the target. Representative targets that are detected by the optical sensor 10 for vehicles may be, for example, at least one of moving objects such as pedestrians, cyclists, animals other than humans, and other vehicles. Representative targets that are detected by the optical sensor 10 for vehicles may also be, for example, at least one of stationary objects such as guardrails, road signs, structures beside the road, and fallen objects on the road.

[0030] In the optical sensor 10, a three-dimensional coordinate system is defined by the three axes of X-axis, Y-axis, and Z-axis that are orthogonal to each other. In particular, in the three-dimensional coordinate system of this embodiment, the Y-axis direction is defined along the vertical direction of the vehicle, and the X-axis direction and the Z-axis direction are defined along different horizontal directions of the vehicle. Figure 1 In the figure, the portion on the left side of the one-dot chain line along the Y-axis direction (the cover plate 12 side described later) actually shows a cross section perpendicular to the portion on the right side of the one-dot chain line (the portions 21 and 41 side described later).

[0031] The optical sensor 10 includes a housing 11, a light projecting unit 21, a scanner 31, a light receiving unit 41, and a control unit 51. The housing 11 is a light-shielding box-shaped structure made of, for example, metal or resin. The housing 11 houses the light projecting unit 21, the scanner 31, the light receiving unit 41, and the control unit 51. An opening extending through the housing 11 is sealed by a cover 12. The light-transmitting cover 12 is made of, for example, resin or glass, and separates the interior and exterior of the housing 11.

[0032] The light projection unit 21 includes a light projection light source unit 22 and a light projection lens unit 26. Figure 2 As shown, the light source unit 22 is constructed by mounting a plurality of light source elements 24 in an array on a substrate. In particular, in this embodiment, each light source element 24 is a laser diode arranged in a single row along the Y-axis. Each light source element 24 can be an edge-emitting laser or a vertical cavity surface-emitting laser (VCSEL).

[0033] Each light source element 24 is controlled by a control signal from the control unit 51. Figure 3 As shown in FIG, each light emitting element 24 generates a laser beam Bp in a common pulse emission time. Figure 3 In the detection frame Fd of each scanning line shown in FIG, each light source element 24 is arranged in the order i to iv in the Y-axis direction (see FIG. Figure 2 ) light up in sequence.

[0034] like Figure 1 As shown, the light-projecting lens unit 26 is constructed as a structure in which at least one light-projecting lens 27 is held in a lens barrel 28. The light-transmitting light-projecting lens 27 is mainly made of a base material such as resin or glass, and is formed into a lens shape corresponding to the optical effect to be performed. The light-projecting lens 27 performs at least one optical effect such as focusing, collimating, and shaping on the light beam Bp from the light-projecting light source unit 22. The light-projecting lens 27 is positioned in a light-shielding lens barrel 28 formed of, for example, metal or resin. The light-projecting lens unit 26 constructed in this manner forms a light-projecting optical axis Op that guides the light beam Bp to the side of the scanning unit 31 by aligning with the light-projecting light source unit 22.

[0035] The scanning unit 31 includes a scanning mirror 32 and a scanning motor 35. The scanning mirror 32 is formed in the shape of a plate with a reflective film deposited on one side of a substrate, namely, a reflective surface 33. The scanning mirror 32 is supported by the frame 11 so as to be rotatable about a rotation centerline along the Y-axis. The scanning mirror 32 swings within a driving range defined by mechanical or electrical stoppers.

[0036] The scanning motor 35 is, for example, a voice coil motor, a brushed DC motor, or a stepping motor. The output shaft of the scanning motor 35 is coupled to the scanning mirror 32 directly or indirectly via a drive mechanism such as a speed reducer. The scanning motor 35 is held by the housing 11 so as to rotate the scanning mirror 32 along with the output shaft. The scanning motor 35 rotationally drives (i.e., swings) the scanning mirror 32 within a limited drive range in response to a control signal from the control unit 51.

[0037] The scanning mirror 32 causes the projected light beam Bp incident from the light projecting unit 21 to be reflected by the reflecting surface 33 and irradiated toward the detection area Ad through the cover plate 12, thereby scanning the detection area Ad according to the rotation angle of the scanning motor 35. At this time, the scanning of the detection area Ad by the projected light beam Bp is substantially limited to scanning in the horizontal direction as the scanning mirror 32 is driven by rotation.

[0038] Scanning mirror 32 uses reflective surface 33 to reflect reflected light beam Br, which enters from an object in detection area Ad through cover plate 12, toward light receiving unit 41, based on the rotational angle of scan motor 35. At this time, the speeds of projected light beam Bp and reflected light beam Br are sufficiently greater than the rotational speed of scanning mirror 32. Consequently, reflected light beam Br is reflected from scanning mirror 32, which can assume a substantially identical rotational angle relative to projected light beam Bp, and is guided toward light receiving unit 41 in the opposite direction to projected light beam Bp.

[0039] The light receiving section 41 has a light receiving lens unit 42 and a light receiving detection unit 45. The light receiving lens unit 42 is constructed as a structure in which at least one light receiving lens 43 is held by a lens barrel 44. The light transmitting light receiving lens 43 is mainly made of a base material such as resin or glass, and is formed into a lens shape corresponding to the optical effect to be performed. The light receiving lens 43 performs an optical effect so that the reflected light beam Br from the scanning mirror 32 is imaged toward the light receiving detection unit 45. The light receiving lens 43 is positioned in a light shielding lens barrel 44 formed of metal or resin, for example. The light receiving lens unit 42 of such a structure is formed by aligning with the light receiving detection unit 45 so that the light receiving optical axis Or that guides the reflected light beam Br from the scanning section 31 to the side of the unit 45 is offset from the light projection optical axis Op of the light projection lens unit 26 in the Y-axis direction.

[0040] like Figure 4 As shown, the light-receiving detection unit 45 is constructed by installing a plurality of light-receiving pixels 46 in an array on a substrate. Each light-receiving pixel 46 is arranged at least along the Y-axis direction. The light-receiving detection unit 45 is formed with a light-receiving surface 45a on a single side of the substrate, and the light-receiving surface 45a has a rectangular outline that is long along the Y-axis direction and short along the X-axis direction. The light-receiving surface 45a is constituted as an aggregate of the incident surfaces in each light-receiving pixel 46. Here, further, each light-receiving pixel 46 is respectively composed of the same number of multiple light-receiving elements 460, such as single photon avalanche diodes (Single Photon Avalanche Diodes). As shown Figure 1 As shown, each of the light-receiving pixels 46 receives the reflected light beam Br incident on the light-receiving surface 45 a from the light-receiving lens unit 42 .

[0041] The light receiving detection unit 45 is provided with an output circuit 47. The output circuit 47 generates a detection frame Fd (see FIG. 4 ) of each scanning line in synchronization with the light emission cycle of the light emission light source unit 22 and corresponding to the rotation angle of the scanning mirror 32. Figure 3 ), sampling processing is performed in each control cycle according to the control signal from the control unit 51. At this time, the output circuit 47 synthesizes the response outputs from the light receiving elements 460 of each light receiving pixel 46 in each control cycle to generate a detection signal. The detection signal generated in this way is output from the output circuit 47 to the control unit 51 for each scanning line.

[0042] The control unit 51 controls the detection of target objects in the detection area Ad of the outside world. The control unit 51 is mainly composed of at least one of a computer including a processor and a memory. The control unit 51 is connected to the light projection light source unit 22, the scanning motor 35, and the light receiving detection unit 45. The control unit 51 controls the light projection light source unit 22 to generate a light projection beam Bp in each light projection cycle. In addition, the control unit 51 controls the scanning motor 35 to control the scanning and reflection of the scanning mirror 32 in synchronization with the light projection cycle of the light projection light source unit 22. Furthermore, the control unit 51 processes the detection signal output from the light receiving detection unit 45 in the detection frame Fd corresponding to the light projection cycle of the light projection light source unit 22 and the scanning and reflection of the scanning mirror 32, thereby generating detection data of the target objects in the detection area Ad.

[0043] (Circuit Configuration of Light Source Unit)

[0044] Next, the circuit structure of the light source unit 22 will be described. Figure 5 As shown, the light projection light source unit 22 includes a power supply circuit 2, a regulating circuit 4, and a temperature measuring circuit 6. Of these circuits 2, 4, and 6, at least the regulating circuit 4 and the temperature measuring circuit 6 are mounted on the same substrate.

[0045] The power supply circuit 2 generates a power supply voltage Vs supplied to the regulator circuit 4 by boosting the input voltage Vb from the vehicle battery. Figure 6 As shown, in the power supply circuit 2, the feedback terminal of the DC-DC regulator 220 is connected to the output terminal of the regulator 220 and the output node of the digital-to-analog converter 221. Thus, the digital-to-analog converter 221 controls the set voltage Vd output from the output node according to the control signal from the control unit 51. As a result, the DC-DC regulator 220 adjusts the power supply voltage Vs output from the output terminal according to the input voltage Vb.

[0046] Such a power supply circuit 2 may also supply the power supply voltage Vs to the temperature measuring circuit 6. The power supply circuit 2 may be shared by the light projecting light source unit 22 and the light receiving detection unit 45, thereby also supplying the power supply voltage Vs to the light receiving detection unit 45.

[0047] Figure 5 The regulating circuit 4 shown is based on the power supply voltage Vs supplied by the power supply circuit 2, as shown in FIG. Figure 9 As shown in FIG. 1 , the voltage V1 applied to each light source element 24 is adjusted, thereby controlling the light output P1 of each light source element 24. Figure 7As shown, in adjustment circuit 4, inductor 240 and capacitor 241 are connected in series in the path from power supply circuit 2 to the ground terminal at ground potential. That is, adjustment circuit 4 is a resonant circuit of the LC series connection type. In such adjustment circuit 4, inductor 240 is primarily composed of an induction coil. Furthermore, in adjustment circuit 4, capacitor 241 is primarily composed of a heat-resistant capacitor, such as an electrolytic capacitor.

[0048] In the adjustment circuit 4, a rectifier element 242 and a first switching element 243 are connected in series in the path from the inductor 240 to the capacitor 241. Furthermore, in the adjustment circuit 4, a second switching element 244 is provided in one of three or more branch paths that branch from the path between the first switching element 243 and the capacitor 241 and are connected to the ground terminal. In such an adjustment circuit 4, the rectifier element 242 is mainly composed of a rectifier diode that provides a current rectification function from the inductor 240 side to the capacitor 241 side. Furthermore, in the adjustment circuit 4, the first and second switching elements 243 and 244 are respectively mainly composed of field effect transistors such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) that are turned on and off according to individual control signals from the control unit 51.

[0049] In the adjustment circuit 4, a group of a third switch element 245 and a light source element 24 is provided on a branch path that branches from the path between the first switch element 243 and the capacitor 241 and is connected to the ground terminal, and is different from the second switch element 244. In such an adjustment circuit 4, each group of the third switch element 245 is mainly composed of a field effect transistor such as a MOSFET that is turned on and off according to a separate control signal from the control unit 51. In addition, Figure 7 The Greek numerals for the branch paths of the group in which the third switching element 245 and the light source element 24 are provided represent the same as above. Figure 2 、 Figure 3 The light emission order of each light source element 24 is shown as i to iv.

[0050] exist Figure 3In the detection frame Fd for each scanning line shown, in the adjustment circuit 4, the conduction state of the second switching element 244 for a fixed time is repeated according to the light emission order i to iv of each light source element 24. Furthermore, in the adjustment circuit 4, the conduction state of the first switching element 243 for a variable time, in response to the individual control signal from the control unit 51, is repeated according to the light emission order i to iv of each light source element 24. At this time, the timing of the start of conduction of the first switching element 243 is adjusted to be synchronized with the timing of the start of conduction of the second switching element 244. Thus, in the adjustment circuit 4, the charging voltage Vc of the capacitor 241 via the coil current Ic is adjusted according to the light emission order i to iv of each light source element 24.

[0051] In the detection frame Fd, further in the adjustment circuit 4, according to the light-emitting sequence i to iv of each light source element 24, after a fixed time from the timing of the end of conduction of the second switch element 244 (i.e., the timing of cutoff), the third switch element 245 in the same group as the light source element 24 of the corresponding light-emitting sequence is switched to the conduction state within the pulse light-emitting time. At this time, for any of the light source elements 24, the timing of the start of conduction of the third switch element 245 is also adjusted to be later than the timing of the end of conduction of the first switch element 243 (i.e., the timing of cutoff) according to the corresponding light-emitting sequence. Therefore, in the adjustment circuit 4, as Figure 3 As shown, the charging voltage Vc adjusted individually according to the light emission order i to iv of each light source element 24 is applied as the applied voltage Vl to the light source element 24 in the corresponding light emission order.

[0052] Figure 5 The temperature measuring circuit 6 shown measures the heat transfer temperature Tt (the unit of temperature in the following description is ° C.) of heat transferred from each light source element 24 to the common surrounding area, and outputs it to the control unit 51. Figure 8 As shown, in the temperature measuring circuit 6, the thermistor element 260 and the series resistor 261 are connected in series in the reverse order in the path from the battery of the input voltage Vb or the power supply circuit 2 of the power supply voltage Vs to the ground terminal. Figure 2 As shown, at least the thermistor element 260 is disposed at one location in the peripheral region common to each light source element 24 in the adjustment circuit 4 .

[0053] In this temperature measurement circuit 6, thermistor element 260 is primarily composed of a thermistor with a large temperature coefficient of resistance, so that its resistance value changes according to the amount of heat transferred from the junction of each light source element 24 through the mounting substrate of the circuits 4 and 6. Furthermore, in the temperature measurement circuit 6, the series resistor 261 is primarily composed of a high-precision resistor with a small temperature coefficient of resistance, in order to output the resistance value of thermistor element 260 related to the voltage across its terminals. Therefore, a conversion circuit 262 is also connected to the temperature measurement circuit 6 to convert the resistance value of thermistor element 260 related to the voltage across the series resistor 261 into a digital signal representing the heat transfer temperature Tt transmitted from each light source element 24 to the thermistor element 260.

[0054] (Control principle of the control unit)

[0055] Next, the control principle of the control unit 51 on the light projection light source unit 22 is described. The control principle of the control unit 51 is constructed as follows: Figure 5 、 Figure 9 The heat transfer temperature Tt outputted from the temperature measuring circuit 6 is monitored and based on the monitoring result, as shown in FIG. Figure 3 、 Figure 9 In this manner, the light emission outputs Pl are controlled according to the applied voltage Vl in accordance with the light emission orders i to iv of the light source elements 24 .

[0056] Specifically, if Figure 9 As shown, as the temperature range allowed for the junction temperature Tj of each light source element 24, an allowable temperature range τj up to and including the upper limit temperature Tju is defined for each light source element 24. The upper limit temperature Tju of the allowable temperature range τj is set to be lower than the rated temperature shared by each light source element 24. Furthermore, as the temperature range for the heat transfer temperature Tt corresponding to the allowable temperature range τj, a reference heat transfer range τt is defined for each light source element 24. On the high temperature side of the reference heat transfer range τt, the boundary temperature Ttb separating the inside and outside is set as the heat transfer temperature Tt corresponding to the upper limit temperature Tju of the allowable temperature range τj according to the correlation equation 1, and is set for each light source element 24.

[0057] [Number 1]

[0058]

[0059] In equation 1, ηb is the luminous efficiency at the boundary temperature Ttb in the heat transfer temperature Tt, and is commonly set for each light source element 24. In equation 1, Rjt is the thermal resistance in the heat transfer path from the junction of the light source element 24 through the mounting substrate of the circuits 4 and 6 (see Figure 5 ), the relative position relationship between each light source element 24 and the thermistor element 260 is set (refer to Figure 2 In equation 1, P1b is the light emission output Pl at the boundary temperature Ttb in the heat transfer temperature Tt, and is set to a separate value for each light source element 24.

[0060] like Figure 9 As shown, the commonly allowed output range for the luminous output Pl of each light source element 24 is defined as the allowable output range ρl, and the luminous output Plb at the boundary temperature Ttb is set to the middle value within this range ρl. Within the allowable output range ρl, the maximum output Plu on the upper limit is defined to ensure the safety of the projected light beam Bp for human eyes, while the minimum output Pll on the lower limit is defined to ensure the accuracy of the detection signal by ensuring the intensity of the reflected light beam Br. Based on the above, the applied voltage Vl used to control the luminous output Pl to the luminous output Plb within the allowable output range ρl is set as a separate applied voltage Vlb for each light source element 24, according to a correlation of two, with the electrostatic capacitance C of the capacitor 241 as a constant.

[0061] [Number 2]

[0062]

[0063] Therefore, when the heat transfer temperature Tt monitored by each light source element 24 is Figure 9 When the temperature is within the reference heat transfer range τt, the control unit 51 maintains the applied voltage Vl at a separate applied voltage Vlb for each light source element 24 at the boundary temperature Ttb. However, at a heat transfer temperature Tt below the boundary temperature Ttb within the reference heat transfer range τt, the applied voltage Vlb is maintained according to the relationship shown in Equations 3 and 4, thereby keeping the junction temperature Tj of each light source element 24 within the allowable temperature range τj. Furthermore, by maintaining the applied voltage Vlb according to the relationship shown in Equations 3 and 4 at a heat transfer temperature Tt below the boundary temperature Ttb within the reference heat transfer range τt, the luminous output Pl of each light source element 24 is individually controlled to be within the allowable output range ρl. Here, η in Equations 3 and 4 is defined as a function of the decrease in luminous efficiency as the heat transfer temperature Tt increases, and is defined by a common equation, table, or map for each light source element 24.

[0064] [Number 3]

[0065]

[0066] [Number 4]

[0067]

[0068] On the other hand, the heat transfer temperature Tt commonly monitored in each light source element 24 is as follows: Figure 9If the temperature rises outside the reference heat transfer range τt, the control unit 51 adjusts the applied voltage Vl of each light source element 24 so that the temperature change ΔTj of the junction temperature Tj from the upper limit temperature Tju is absorbed under the correlation relationship of Equations 5 and 6. Thus, the light emission output Pl of each light source element 24 is individually controlled so that the temperature change ΔTj is absorbed under the correlation relationship of Equations 5 and 6.

[0069] [Number 5]

[0070]

[0071] [Number 6]

[0072]

[0073] In Equations 5 and 6, ΔTt is defined as the amount of change in heat transfer temperature Tt from the boundary temperature Ttb, i.e., the heat transfer change. In Equations 5 and 6, Δη is defined as a function of the efficiency change from the luminous efficiency ηb at the boundary temperature Ttb according to the heat transfer change ΔTt, and is defined by a common equation, table, or map for each light source element 24. Thus, in order to absorb the temperature change ΔTj associated with the heat transfer change ΔTt and the efficiency change Δη in accordance with Equations 5 and 6, each light source element 24 performs individual control of the light emission output Pl by individually adjusting the applied voltage Vl so that the temperature change ΔTj becomes substantially zero (0).

[0074] Based on the above, at the heat transfer temperature Tt outside the reference heat transfer range τt, the generation of the temperature change ΔTj in each light source element 24 is suppressed according to the correlation relationship of Figures 5 and 6, so that the junction temperature Tj of each light source element 24 is as follows: Figure 9 Thus, the upper limit temperature Tju of the allowable temperature range τj is maintained. Furthermore, at a heat transfer temperature Tt outside the reference heat transfer range τt according to the correlation relationship of Equations 5 and 6, the light emission output Pl of each light source element 24 is individually controlled so as to fall within the allowable output range ρl in response to a decrease in the applied voltage Vl corresponding to an increase in the heat transfer temperature Tt.

[0075] (Effect)

[0076] The following describes the effects of the first embodiment described so far.

[0077] In the light projecting unit 21 of the first embodiment, the control unit 51 monitors the heat transfer temperature Tt of the light source element 24. Therefore, the control unit 51 also monitors the temperature change ΔTj of the junction temperature Tj of the light source element 24, which is correlated with the efficiency change Δη of the luminous efficiency η and the heat transfer change ΔTt of the heat transfer temperature Tt, which decreases in the light source element 24 as the heat transfer temperature Tt increases. Thus, the control unit 51 controls the light emission output Pl of the light source element 24 to absorb the temperature change ΔTj of the junction temperature Tj. This prevents a reduction in the life of the light source element 24 due to temperature increases, thereby ensuring durability.

[0078] In the first embodiment, the control unit 51 accurately adjusts the voltage Vl applied to the light source element 24 to absorb the temperature change ΔTj of the junction temperature Tj, thereby enabling appropriate control of the light emission output Pl. This improves the reliability of ensuring durability.

[0079] According to the first embodiment, the temperature range set for the heat transfer temperature Tt, corresponding to the allowable temperature range τj of the junction temperature Tj, is considered as the reference heat transfer range τt. Therefore, when the heat transfer temperature Tt rises outside the reference heat transfer range τt, the control unit 51 controls the light emission output Pl to absorb the temperature change ΔTj of the junction temperature Tj. This accurately absorbs the temperature change ΔTj of the junction temperature Tj, which is expected to occur outside the allowable temperature range τj. This improves the reliability of ensuring durability.

[0080] According to the first embodiment, the permissible output range of the light output Pl is designated as the permissible output range ρl. Therefore, when the heat transfer temperature Tt rises outside the reference heat transfer range τt, the control unit 51 controls the light output Pl within the permissible output range ρl to absorb the temperature change ΔTj of the junction temperature Tj. This not only improves the reliability of ensuring durability, but also ensures the safety of the projected light beam Bp and the accuracy of the detection signal by ensuring the intensity of the reflected light beam Br by maintaining the light output Pl within the permissible output range ρl.

[0081] In the first embodiment, the control unit 51 maintains the applied voltage Vl to the light source element 24 while the heat transfer temperature Tt is within the reference heat transfer range τt, thereby controlling the light output Pl to be within the allowable output range ρl. This allows the light output Pl to be maximized within the allowable output range ρl, ensuring the safety of the projected light beam Bp, at a heat transfer temperature Tt within the reference heat transfer range τt, assuming a junction temperature Tj within the allowable temperature range τj. This voltage hold function reduces the control load required to ensure the accuracy of the detection signal.

[0082] In the light projecting unit 21 of the first embodiment, a light projecting light source unit 22, which includes a plurality of light source elements 24, generates a projected light beam Bp. Therefore, the control unit 51 monitors the heat transfer temperature Tt from each light source element 24 to a common surrounding area. Therefore, the control unit 51 also individually controls the light emission output Pl of each light source element 24 so that the light output Pl is adjusted according to the temperature change ΔTj of the junction temperature Tj absorbed by each light source element 24. This prevents the lifetime of each light source element 24 from being shortened due to temperature increases, ensuring the durability of each light source element 24.

[0083] (Second embodiment)

[0084] The second embodiment is a modified example of the first embodiment. Figure 10 As shown, the reference heat transfer range τt of the second embodiment is divided into a high temperature range τth where the heat transfer temperature Tt is on the boundary temperature Ttb side and a low temperature range τtl where the heat transfer temperature Tt is lower than the high temperature range τth.

[0085] Therefore, when the heat transfer temperature Tt is within the high temperature range τth, the control unit 51 of the second embodiment maintains the applied voltage Vl to each light source element 24 at a separate applied voltage Vlb, similar to the reference heat transfer range τt in the first embodiment, so that the light emission output Pl of each light source element 24 is individually controlled within the allowable output range ρl. On the other hand, when the heat transfer temperature Tt is within the low temperature range τtl, the control unit 51 of the second embodiment individually adjusts the applied voltage Vl to each light source element 24, based on the correlation between equations 7 and 8, so that the light emission output Pl of each light source element 24 is collectively controlled to the maximum output Plu within the allowable output range ρl. Consequently, in both the high temperature range τth and the low temperature range τtl, the junction temperature Tj of each light source element 24 remains within the allowable temperature range τj, and the light emission output Pl of each light source element 24 is variably controlled or maintained within the allowable output range ρl.

[0086] [Number 7]

[0087]

[0088] [Number 8]

[0089]

[0090] Thus, in the control unit 51 of the second embodiment, when the heat transfer temperature Tt within the reference heat transfer range τt is within a low temperature range τtl, which is lower than the high temperature range τth within which the applied voltage Vl to the light source element 24 is maintained, the light emission output Pl is controlled to the maximum output Plu of the allowable output range ρl. Thus, within the high temperature range τth within the reference heat transfer range τt, the light emission output Pl is maximized within the allowable output range ρl that ensures the safety of the projected light beam Bp, thereby reducing the control load required to ensure the accuracy of the detection signal through the voltage hold function. On the other hand, within the low temperature range τtl within the reference heat transfer range τt, the light emission output Pl is increased to the maximum output Plu within the allowable output range ρl that ensures the safety of the projected light beam Bp, thereby improving the accuracy of the detection signal.

[0091] (Third embodiment)

[0092] The third embodiment is a modified example of the first embodiment. Figure 6 ) in which the power supply voltage Vs output from the DC-DC regulator 220 is relative to the set voltage Vd output from the digital-to-analog converter 221. Figure 11 Therefore, the control unit 51 of the third embodiment controls the set voltage Vd output from the digital-to-analog converter 221 to absorb the fluctuation of the power supply voltage Vs corresponding to the rise and fall of the heat transfer temperature Tt.

[0093] In the light projecting unit 21 of the third embodiment, as in the first embodiment, the voltage Vl applied to the light source element 24 is adjusted by the adjustment circuit 4 based on the power supply voltage Vs supplied by the power supply circuit 2. Therefore, the control unit 51 of the third embodiment controls the power supply circuit 2 to absorb fluctuations in the power supply voltage Vs corresponding to increases and decreases in the heat transfer temperature Tt. This allows the voltage Vl applied to the light source element 24 to be accurately adjusted based on the stable power supply voltage Vs to absorb the temperature variation ΔTj of the junction temperature Tj. Consequently, control can be achieved with respect to the light emission output Pl to appropriately absorb this temperature variation ΔTj, thereby improving reliability in ensuring durability.

[0094] (Other embodiments)

[0095] Although a plurality of embodiments have been described above, the present disclosure is not limited to these embodiments and can be applied to various embodiments and combinations within a scope not departing from the gist of the present disclosure.

[0096] In the modified examples of the first to third embodiments, Figure 12As shown, by connecting a common third switching element 1245 to each light source element 24, each light source element 24 emits light simultaneously when the third switching element 1245 is turned on, thereby collectively forming a linear projection beam Bp. In this case, by collectively adjusting the applied voltage V1 for each light source element 24, the light output P1 of each light source element 24 can be collectively controlled.

[0097] In the variations of the first to third embodiments, only one set of light source elements 24 and third switching elements 245 may be provided. In the variations of the first to third embodiments, at least the adjustment circuit 4 of the circuits 2, 4, and 6 may be configured as a circuit having only one set of light source elements 24 and third switching elements 245, with each light source element 24 being provided separately. The third embodiment may also be applied to the variations of the second embodiment.

[0098] In the modified examples of the first to third embodiments, the Y-axis direction along the horizontal direction and the X-axis direction along the vertical direction may also be specified. In the modified examples of the first to third embodiments, the mobile object to which the optical sensor 10 is applied may be, for example, a remotely controlled traveling robot. In the modified examples of the first to third embodiments, the optical sensor 10 may be applied to objects other than mobile objects, such as stationary structures.

[0099] (Supplementary explanation)

[0100] This specification discloses the following technical concepts and their combinations.

[0101] (Technical Thought 1)

[0102] An optical sensor (10) projects a light beam (Bp) and receives a reflected light beam (Br) reflected from the light beam, comprising:

[0103] A light projection unit (21) generates the light projection beam by a light source element (24);

[0104] a light receiving unit (41) that outputs a detection signal by receiving the reflected light beam; and

[0105] A control unit (51) controls the light projecting unit and the light receiving unit,

[0106] The control unit is configured to perform the following control:

[0107] monitoring a heat transfer temperature (Tt) transferred from the light projecting portion to the periphery of the light source element; and

[0108] The luminous output (Pl) in the light source element is controlled in a manner that absorbs the temperature change of the junction temperature (Tj) in the light source element, which is related to the efficiency change of the luminous efficiency that decreases in the light source element according to the increase of the heat transfer temperature and the heat transfer change of the heat transfer temperature.

[0109] (Technical Thought 2)

[0110] The optical sensor according to technical idea 1, wherein:

[0111] The control unit controls the light emission output by adjusting the applied voltage (V1) applied to the light source element so as to absorb the temperature change.

[0112] (Technical Thought 3)

[0113] The optical sensor according to technical idea 1 or 2, wherein:

[0114] The control unit sets the temperature range set for the heat transfer temperature corresponding to the allowable temperature range (τj) allowed by the junction temperature as a reference heat transfer range (τt), and controls the light-emitting output in a manner that absorbs the temperature change when the heat transfer temperature rises outside the reference heat transfer range.

[0115] (Technical Thought 4)

[0116] The optical sensor according to technical idea 3, wherein:

[0117] The control unit sets the output range allowed for the luminous output as an allowed output range (ρl), and controls the luminous output within the allowed output range by absorbing the temperature change when the heat transfer temperature rises outside the reference heat transfer range.

[0118] (Technical Thought 5)

[0119] The optical sensor according to technical idea 4, wherein:

[0120] When the heat transfer temperature is within the reference heat transfer range, the control unit controls the light emission output within the allowable output range by maintaining the applied voltage (V1) applied to the light source element.

[0121] (Technical Thought 6)

[0122] The optical sensor according to technical idea 5, wherein:

[0123] The control unit maintains the luminous output at the maximum output (Plu) of the allowable output range when the heat transfer temperature within the reference heat transfer range is within a low temperature range (τtl) lower than a high temperature range (τth) for maintaining the applied voltage (Vl) applied to the light source element.

[0124] (Technical Thought 7)

[0125] The optical sensor according to any one of technical concepts 1 to 6, wherein:

[0126] The light projection part has a light projection light source unit (22), and the light projection light source unit (22) is provided with a plurality of light source elements for generating the light projection beam.

[0127] The control unit monitors the heat transfer temperature transferred from each of the light source elements to a common surrounding portion.

[0128] The control unit individually controls the light emission output of each of the light source elements so that each of the light source elements absorbs the temperature change.

[0129] (Technical Thought 8)

[0130] The optical sensor according to any one of technical ideas 2, 5, and 6, wherein:

[0131] The light projecting unit has:

[0132] a power supply circuit (2) for supplying a power supply voltage (Vs); and

[0133] an adjustment circuit (4) for adjusting an applied voltage (V1) applied to the light source element according to the power supply voltage,

[0134] The control unit controls the power supply circuit so as to absorb fluctuations in the power supply voltage corresponding to increases and decreases in the heat transfer temperature.

Claims

1. An optical sensor (10) for projecting a light beam (Bp) and receiving a reflected light beam (Br) formed by reflecting the light beam, characterized in that: have: A light projection unit (21) generates the light projection beam by a light source element (24); a light receiving unit (41) that outputs a detection signal by receiving the reflected light beam; and A control unit (51) controls the light projecting unit and the light receiving unit, The control unit is configured to perform the following control: monitoring a heat transfer temperature (Tt) transferred from the light projecting portion to the periphery of the light source element; and The luminous output (Pl) in the light source element is controlled in a manner that absorbs the temperature change of the junction temperature (Tj) in the light source element, which is related to the efficiency change of the luminous efficiency that decreases in the light source element according to the increase of the heat transfer temperature and the heat transfer change of the heat transfer temperature.

2. The optical sensor according to claim 1, wherein The control unit controls the light emission output by adjusting the applied voltage (V1) applied to the light source element so as to absorb the temperature change.

3. The optical sensor according to claim 1, wherein The control unit sets the temperature range set for the heat transfer temperature corresponding to the allowable temperature range (τj) allowed by the junction temperature as a reference heat transfer range (τt), and controls the light-emitting output in a manner that absorbs the temperature change when the heat transfer temperature rises outside the reference heat transfer range.

4. The optical sensor according to claim 3, wherein The control unit sets the output range allowed by the light emitting output as the allowed output range (ρl), When the heat transfer temperature rises outside the reference heat transfer range, the control unit controls the light emission output to fall within the allowable output range so as to absorb the temperature change.

5. The optical sensor according to claim 4, wherein: When the heat transfer temperature is within the reference heat transfer range, the control unit controls the light emission output within the allowable output range by maintaining the applied voltage (V1) applied to the light source element.

6. The optical sensor according to claim 5, characterized in that The control unit maintains the luminous output at the maximum output (Plu) of the allowable output range when the heat transfer temperature within the reference heat transfer range is within a low temperature range (τtl) lower than the high temperature range (τth) for maintaining the applied voltage (Vl) applied to the light source element.

7. The optical sensor according to any one of claims 1 to 6, characterized in that The light projection part has a light projection light source unit (22), and the light projection light source unit (22) is provided with a plurality of light source elements for generating the light projection beam. The control unit monitors the heat transfer temperature transferred from each of the light source elements to a common surrounding portion. The control unit individually controls the light emission output of each of the light source elements so that each of the light source elements absorbs the temperature change.

8. The optical sensor according to any one of claims 2, 5 and 6, characterized in that: The light projecting unit has: a power supply circuit (2) for supplying a power supply voltage (Vs); and an adjustment circuit (4) for adjusting an applied voltage (V1) applied to the light source element according to the power supply voltage, The control unit controls the power supply circuit so as to absorb fluctuations in the power supply voltage corresponding to increases and decreases in the heat transfer temperature.

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