Electromagnetic wave emitting device, distance measuring device, and mobile object

Abstract

To reduce the possibility of double radiation.SOLUTION: An electromagnetic radiation device 10 comprises a plurality of electromagnetic radiation circuits 15, a radiation switching element 16, and a control unit 17. The electromagnetic radiation circuits 15 include an electromagnetic radiation element 18, a capacitor 19, and an electric discharge switching element 20. The radiation switching element 16 is connected to the cathode side of a plurality of electromagnetic radiation elements 18 that are included in the plurality of electromagnetic radiation circuits 15. The radiation switching element 16 can turn on electricity to the plurality of electromagnetic radiation elements 18. After causing the electromagnetic radiation element 18 in a discretionary electromagnetic radiation circuit 15 among the plurality of electromagnetic radiation circuits 15 to be radiated by the radiation switching element, the control unit 17 discharges the capacitor 19 in the discretionary electromagnetic radiation circuit 15 before the electromagnetic radiation elements 18 in the other electromagnetic radiation circuits 15 emit light.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an electromagnetic wave emitting device, a distance measuring device, and a mobile object. [Background technology]

[0002] BACKGROUND ART A distance measuring device is known that measures the distance to an object by irradiating the object with light and dividing the time it takes for the reflected and scattered light to be received by the speed of light (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2016-053552 Summary of the Invention [Problem to be solved by the invention]

[0004] The use of multiple electromagnetic wave radiation elements in electromagnetic wave radiation devices used in distance measuring devices has been considered from the perspectives of eye safety, expanding the measurement range, etc. In a configuration in which multiple electromagnetic wave radiation elements are mounted on a semiconductor substrate, the electromagnetic wave radiation device is provided with multiple capacitors that supply power to each of the multiple electromagnetic wave radiation elements and a common switching element that energizes the multiple electromagnetic wave radiation elements. An electromagnetic wave radiation device configured in this way can cause the multiple electromagnetic wave radiation elements to emit light at different times by energizing the switching element while staggering the charging times of the multiple capacitors. However, due to charge remaining in the capacitor after emission of light by any one electromagnetic wave radiation element, there is a possibility of double emission, in which any one electromagnetic wave radiation element also emits light at the time of emission of light by another electromagnetic wave radiation element.

[0005] In view of the above, an object of the present disclosure is to provide an electromagnetic wave radiation device that reduces the possibility of double radiation in an electromagnetic wave radiation device that has a plurality of electromagnetic wave radiation elements and a common switching element for energization. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, an electromagnetic wave emission device according to a first aspect comprises: a plurality of electromagnetic wave radiation circuits each including an electromagnetic wave radiation element, a capacitor that supplies current to the electromagnetic wave radiation element, and a discharge switching element that discharges the capacitor; a radiation switching element connected to cathode sides of the plurality of electromagnetic wave radiation elements included in the plurality of electromagnetic wave radiation circuits, and capable of energizing the plurality of electromagnetic wave radiation elements; and a control unit that, after causing an electromagnetic wave radiation element in any one of the plurality of electromagnetic wave radiation circuits to emit light, discharges a capacitor in that any one of the electromagnetic wave radiation circuits before an electromagnetic wave radiation element in another electromagnetic wave radiation circuit emits light.

[0007] A distance measuring device according to a second aspect comprises: a radiation switching element connected to the cathode sides of a plurality of electromagnetic wave radiation elements included in the plurality of electromagnetic wave radiation circuits and capable of energizing the plurality of electromagnetic wave radiation elements; and a control unit that discharges the capacitor in an arbitrary electromagnetic wave radiation circuit among the plurality of electromagnetic wave radiation circuits after causing an electromagnetic wave radiation element in the arbitrary electromagnetic wave radiation circuit to emit light and before an electromagnetic wave radiation element in another electromagnetic wave radiation circuit emits light, wherein the electromagnetic wave radiation circuit includes a charge switching element that charges the capacitor, and the control unit comprises an electromagnetic wave emission device that controls the charge switching element and the discharge switching element so that the discharge time is longer than the charge time, and the distance measuring device measures the distance to an object using electromagnetic waves radiated by the electromagnetic wave emission device, and the control unit causes the discharge switching element in the arbitrary electromagnetic wave emission circuit to start discharging the capacitor after a predetermined distance measurement time has passed since the electromagnetic wave radiation element in the arbitrary electromagnetic wave radiation circuit emits light.

[0008] Furthermore, a moving body according to the third aspect is a control unit that discharges the capacitor in an arbitrary electromagnetic wave radiation circuit among the plurality of electromagnetic wave radiation circuits after causing the electromagnetic wave radiation element in the arbitrary electromagnetic wave radiation circuit to emit light and before the electromagnetic wave radiation elements in the other electromagnetic wave radiation circuits emit light, wherein the electromagnetic wave radiation circuit includes a charge switching element that charges the capacitor, and the control unit comprises an electromagnetic wave emission device that controls the charge switching element and the discharge switching element so that the discharge time is longer than the charge time, and a distance measuring device that measures the distance to an object using electromagnetic waves radiated by the electromagnetic wave emission device, wherein the control unit starts discharging the capacitor by the discharge switching element in the arbitrary electromagnetic wave radiation circuit a predetermined distance measurement time after the electromagnetic wave radiation element in the arbitrary electromagnetic wave radiation circuit emits light. [Effects of the Invention]

[0009] The present disclosure reduces the likelihood of double radiation [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a layout diagram showing the layout of a distance measuring device including an electromagnetic wave emission device according to an embodiment of the present invention on a moving object. [Figure 2] FIG. 2 is a functional block diagram showing a schematic configuration of the distance measuring device of FIG. [Figure 3] 2 is a circuit diagram showing the circuit configuration of the electromagnetic wave emission device of FIG. 1. [Figure 4] 4 is a timing chart showing the control timing of the radiation switching element, the charge switching element and the discharge switching element in each electromagnetic wave radiation circuit by the control unit in FIG. 3. [Figure 5]2 is a timing chart showing the emission and detection times of electromagnetic waves, for explaining the principle of distance measurement by the distance measuring device of FIG. 1; DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same components are denoted by the same reference numerals.

[0012] As shown in FIG. 1, a distance measuring device 11 including an electromagnetic wave emission device 10 according to the present disclosure is provided in a moving object 12, for example.

[0013] The mobile object 12 may include, for example, vehicles, ships, aircraft, etc. Vehicles may include, for example, automobiles, industrial vehicles, rail vehicles, residential vehicles, fixed-wing aircraft traveling on runways, etc. Automobiles may include, for example, passenger cars, trucks, buses, motorcycles, trolleybuses, etc. Industrial vehicles may include, for example, agricultural and construction industrial vehicles, etc. Industrial vehicles may include, for example, forklifts, golf carts, etc. Agricultural industrial vehicles may include, for example, tractors, cultivators, transplanters, binders, combines, lawn mowers, etc. Construction industrial vehicles may include, for example, bulldozers, scrapers, excavators, cranes, dump trucks, road rollers, etc. Vehicles may include human-powered vehicles. Vehicle classifications are not limited to the above examples. For example, automobiles may include industrial vehicles that can travel on roads. The same vehicle may be included in multiple classifications. Ships may include, for example, marine jets, boats, tankers, etc. Aircraft may include, for example, fixed-wing aircraft, rotary-wing aircraft, etc.

[0014] The distance measuring device 11 may be provided in the moving body 12 so that the measurement direction range includes the directional range in which distance measurement is desired. For example, the distance measuring device 11 is provided so that the measurement direction range includes a directional range centered on the front of the moving body 12. The distance measuring device 11 may be provided inside or outside the moving body 12. Inside the moving body 12, the distance measuring device 11 may be located, for example, in front of the rearview mirror near the windshield or on the dashboard. The distance measuring device 11 may be fixed to any of the front bumper, fender grille, side fender, light module, and hood of the moving body 12.

[0015] As shown in FIG. 2, the distance measuring device 11 may include an electromagnetic wave emission device 10, a detection unit 13, and a control unit 14. The distance measuring device 11 emits electromagnetic waves for measurement into space. The electromagnetic waves for measurement are, for example, measurement light. In the following explanation, electromagnetic waves will be explained using the measurement light as an example. The distance measuring device 11 detects reflected and scattered light of the measurement light irradiated onto an object ob in space. The distance measuring device 11 may generate distance information by measuring the distance to an object located in the emission direction of the measurement light based on the reflected and scattered light.

[0016] As shown in Fig. 3, the electromagnetic wave emission device 10 includes a plurality of electromagnetic wave emission circuits 15, an emission switching element 16, and a control unit 17. The plurality of electromagnetic wave emission circuits 15 may be connected in parallel. The plurality of electromagnetic wave emission circuits 15 and the emission switching element 16 may be mounted on a semiconductor circuit board. Although Fig. 3 illustrates an electromagnetic wave emission device 10 having three or more electromagnetic wave emission circuits 15, the electromagnetic wave emission device 10 may include two or more electromagnetic wave emission circuits 15.

[0017] Each electromagnetic wave radiation circuit 15 has an electromagnetic wave radiation element 18, a capacitor 19, and a discharge switching element 20. Each electromagnetic wave radiation circuit 15 may include a charge switching element 21.

[0018] The electromagnetic wave emitting element 18 emits measurement light. The electromagnetic wave emitting element 18 may emit measurement light such as infrared light, visible light, or ultraviolet light. The electromagnetic wave emitting element 18 may emit measurement light in the form of a narrow beam, for example, with a width of 0.5°. The electromagnetic wave emitting element 18 is, for example, a laser diode. The electromagnetic wave emitting element 18 emits light when powered on and emits measurement light.

[0019] The capacitor 19 may be connected in parallel to the electromagnetic wave radiating element 18. The capacitor 19 supplies current to the electromagnetic wave radiating element 18. The capacitor 19 may be connected to a power supply 22 shared by multiple electromagnetic wave radiating circuits 15 via a charging switching element 21. More specifically, the capacitor 19 may be connected to the power supply 22 at a terminal connected to the anode side of the electromagnetic wave radiating element 18.

[0020] A first resistor 23 may be provided between the capacitor 19 and the charge switching element 21. The resistance value of the first resistor 23 may be set so that the time required for charging and discharging is appropriate, for example, several μs to several hundred μs. By optimizing the charging and discharging time, the light emission interval is limited to the light emission interval specified by the laser safety standard. Note that, since light emissions at intervals of 5 μs or less are treated as the same pulse, it is desirable to set the light emission interval of the same laser element to 5 μs or more.

[0021] In order to limit the charging current, an inductor of an appropriate value may be implemented instead of the first resistor 23. In a configuration in which an inductor is implemented, the charging voltage to the capacitor 19 is boosted. Furthermore, in this configuration, the capacitor 19 is boosted to a high voltage by charging it in a discharged state.

[0022] The charging switching element 21 charges the capacitor 19 when energized. The charging switching element 21 is controlled to be energized and cut off by the control unit 17. The charging switching element 21 is, for example, a field effect transistor (FET).

[0023] The discharge switching element 20 may be connected in parallel to the capacitor 19. A second resistor 24 may be provided between the capacitor 19 and the discharge switching element 20. The resistance value of the second resistor 24 may be set so that the time required for charging and discharging is appropriate. The discharge switching element 20 discharges the capacitor 19 when energized. The control unit 17 controls the energization and cutoff of the discharge switching element 20. The discharge switching element 20 is, for example, a field effect transistor (FET). The gate charge capacity of the discharge switching element 20 may be larger than the gate charge capacity of the charge switching element 21.

[0024] The radiation switching element 16 may be connected to the cathodes of the plurality of electromagnetic wave radiation elements 18 included in the plurality of electromagnetic wave radiation circuits 15. The radiation switching element 16 may be connected to the cathode side of the plurality of electromagnetic wave radiation elements 18 included in the plurality of electromagnetic wave radiation circuits 15, for example, with a resistor provided therebetween. An inductor 25 may be provided between the plurality of electromagnetic wave radiation elements 18 and the radiation switching element 16. When energized, the radiation switching element 16 energizes the plurality of electromagnetic wave radiation elements 18, causing them to emit light. The control unit 17 controls energization and cut-off of the radiation switching element 16. The radiation switching element 16 is, for example, a field effect transistor (FET).

[0025] The control unit 17 includes one or more processors and a memory. The processor may include at least one of a general-purpose processor that loads a specific program to execute a specific function and a dedicated processor specialized for a specific process. The dedicated processor may include an application-specific integrated circuit (ASIC). The processor may include a programmable logic device (PLD). The PLD may include a field-programmable gate array (FPGA). The control unit 17 may include at least one of a system-on-a-chip (SoC) and a system in a package (SiP) in which one or more processors work together.

[0026] The control unit 17 switches between energization and cut-off of at least the emission switching element 16 and the discharge switching element 20 based on commands from the control unit 14 of the distance measuring device 11. The control unit 17 may also switch between energization and cut-off of the charge switching element 21. Control of energization and cut-off of the emission switching element 16, the discharge switching element 20, and the charge switching element 21 will be described below.

[0027] The control unit 17 may sequentially select the plurality of electromagnetic wave emission circuits 15 and, as described below, cause the electromagnetic wave emission element 18 in the selected electromagnetic wave emission circuit 15 to emit measurement light. The control unit 17 may energize the charge switching element 21 in the selected electromagnetic wave emission circuit 15 to charge the capacitor 19 in that electromagnetic wave emission circuit 15. Next, the control unit 17 may energize the emission switching element 16 to energize the charged capacitor 19 to the electromagnetic wave emission element 18 in the same electromagnetic wave emission circuit 15 to emit measurement light. The control unit 17 may energize the discharge switching element 20 in that electromagnetic wave emission circuit 15 to discharge the capacitor 19 in the same electromagnetic wave emission circuit 15.

[0028] In the present disclosure, more specifically, the control unit 17 controls the radiation switching element 16 to energize the electromagnetic wave radiation element 18 in any one of the plurality of electromagnetic wave radiation circuits 15. After the electromagnetic wave radiation element 18 is energized to emit light, the control unit 17 causes the discharge switching element 20 in that electromagnetic wave radiation circuit 15 to discharge the capacitor 19 before the electromagnetic wave radiation elements 18 in the other electromagnetic wave radiation circuits 15 of that one single electromagnetic wave radiation circuit 15 are energized to emit light. Furthermore, the control unit 17 may cause the discharge switching elements 20 in all electromagnetic wave radiation circuits 15 other than the other electromagnetic wave radiation circuit 15 to discharge the capacitors 19 before energizing the electromagnetic wave radiation elements 18 in the other electromagnetic wave radiation circuit 15.

[0029] The control unit 17 may start discharging the capacitor 19 by the discharge switching element 20 in any one of the electromagnetic wave emission circuits 15 after a predetermined distance measurement time has elapsed since the electromagnetic wave emission element 18 in any one of the electromagnetic wave emission circuits 15 is energized to emit light. The predetermined distance measurement time is the time required to measure the distance to the target by receiving the electromagnetic wave reflected by the target. More specifically, the predetermined distance measurement time is the time obtained by dividing half the maximum measurement distance designed for the distance measuring device 11 by the speed of light. The control unit 17 controls the charge switching element 21 and the discharge switching element 20 so that the capacitor 19 is not charged or discharged during distance measurement. The control unit 17 controls the charge switching element 21 and the discharge switching element 20 so that the capacitor 19 is charged and discharged before distance measurement. Because the distance measuring device 11 is controlled by the control unit 17 not to charge or discharge the capacitor 19 during distance measurement, the possibility of noise being mixed into the detection signal of the detection unit 13 can be reduced.

[0030] The control unit 17 may control the charge switching element 21 and the discharge switching element 20 so that the discharge time of the capacitor 19 is longer than the charge time. Alternatively, the control unit 17 may control the charge switching element 21 and the discharge switching element 20 so that the charge time of the capacitor 19 is equal to the discharge time. Alternatively, the control unit 17 may control the charge switching element 21 and the discharge switching element 20 so that the charge time of the capacitor 19 is longer than the discharge time.

[0031] Below, a specific example of the control by the control unit 17 of the radiation switching element 16, the discharge switching element 20, and the charge switching element 21 in the plurality of electromagnetic wave radiation circuits 15 will be described. In the following description, the plurality of electromagnetic wave radiation circuits 15 will be referred to as the first electromagnetic wave radiation circuit 151, the second electromagnetic wave radiation circuit 152, ..., the n-th electromagnetic wave radiation circuit 15n, respectively, where n is a natural number greater than or equal to 3. The electromagnetic wave radiation element 18, the capacitor 19, and the discharge switching element 20 included in the first electromagnetic wave radiation circuit 151 will be referred to as the first electromagnetic wave radiation element 181, the first capacitor 191, and the first discharge switching element 201. The electromagnetic wave radiation element 18, the capacitor 19, and the discharge switching element 20 included in the second electromagnetic wave radiation circuit 152 will be referred to as the second electromagnetic wave radiation element 182, the second capacitor 192, and the second discharge switching element 202. The electromagnetic wave radiation element 18, capacitor 19, and discharge switching element 20 included in the n-th electromagnetic wave radiation circuit 15n are referred to as the n-th electromagnetic wave radiation element 18n, the n-th capacitor 19n, and the n-th discharge switching element 20n.

[0032] 4, at timing t1, control unit 17 starts charging first capacitor 191 by starting current flow through first charging switching element 211 (see the "First charging switching element" section). At timing t2, after a predetermined charging time has elapsed since timing t1, control unit 17 turns off first charging switching element 211 (see the "First charging switching element" section), thereby ending the charging of first capacitor 191 (see the "First electromagnetic wave radiation circuit" section).

[0033] At timing t2, the control unit 17 energizes the radiation switching element 16 (see the "Radiation switching element" section), causing the first electromagnetic wave radiation element 181 to emit light and radiate measurement light (see the "First electromagnetic wave radiation circuit" section).

[0034] At timing t3, which is a predetermined distance measurement time after the first electromagnetic wave radiation element 181 has finished emitting light, the control unit 17 energizes all of the discharge switching elements 20 except the second discharge switching element 202 (see the columns "First discharge switching element" and "nth discharge switching element"), thereby discharging all of the capacitors 19 except the second capacitor 192 (see the columns "First electromagnetic wave radiation circuit" and "nth electromagnetic wave radiation circuit").

[0035] At timing t4 after all the discharge switching elements 20 except the second discharge switching element 202 have been energized, the control unit 17 starts energizing the second charge switching element 212, thereby starting charging of the second capacitor 192 (see the "Second Charge Switching Element" section). At timing t5 after a predetermined charging time has elapsed from timing t4, the control unit 17 shuts off all the discharge switching elements 20 except the second discharge switching element 202 (see the "First Discharge Switching Element" and "nth Discharge Switching Element" sections), thereby ending the discharge of all the capacitors 19 except the second capacitor 192 (see the "First Electromagnetic Wave Radiation Circuit" and "nth Electromagnetic Wave Radiation Circuit" sections). Also, at timing t5, the control unit 17 shuts off the second charge switching element 212 (see the "Second Charging Switching Element" section), thereby ending the charging of the second capacitor 192 (see the "Second Electromagnetic Wave Radiation Circuit" section). The control unit 17 controls the second charge switching element 212 and all the discharge switching elements 20 other than the second discharge switching element 202 so as to terminate charging of the second capacitor 192 and discharging of all the capacitors 19 other than the second capacitor 192 at timing t5. Since the control unit 17 controls the distance measuring device 11 not to charge or discharge the capacitors 19 during distance measurement, the possibility of noise being mixed into the detection signal of the detection unit 13 can be reduced.

[0036] At timing t5, the control unit 17 energizes the radiation switching element 16 (see the "Radiation switching element" section), causing the second electromagnetic wave radiation element 182 to emit light and radiate measurement light (see the "Second electromagnetic wave radiation circuit" section).

[0037] At timing t6, which is a predetermined distance measurement time after the end of light emission of the second electromagnetic wave emitting element 182, the control unit 17 energizes the discharge switching elements 20 of all the electromagnetic wave emitting elements 18 other than the electromagnetic wave emitting element 18 that is to emit light after the second electromagnetic wave emitting element 182 (see the columns “Second Discharge Switching Element” and “nth Discharge Switching Element”), thereby discharging all the capacitors 19 other than the electromagnetic wave emitting element 18 that is to emit light next (see the columns “First Electromagnetic Wave Radiating Circuit”, “Second Electromagnetic Wave Radiating Circuit”, and “nth Electromagnetic Wave Radiating Circuit”). The control unit 17 controls all the discharge switching elements 20 other than the second charge switching element 212 and the second discharge switching element 202 so that the second capacitor 192 is not charged and all the capacitors 19 other than the second capacitor 192 are not discharged during the period from timing t5 to timing t6, when radiation and distance measurement are performed in the second electromagnetic wave emitting circuit. The distance measuring device 11 is controlled by the control unit 17 so as not to charge or discharge the capacitor 19 during distance measurement, so that the possibility of noise being mixed into the detection signal of the detection unit 13 can be reduced.

[0038] Thereafter, the control unit 17 performs processing similar to that of the first electromagnetic wave radiation circuit 151 and the second electromagnetic wave radiation circuit 152, thereby charging the capacitor 19 in each electromagnetic wave radiation circuit 15, causing the electromagnetic wave radiation element 18 to emit light, and discharging the capacitor 19.

[0039] At timing t7 after energizing the n-th discharge switching element 20 in the n-th electromagnetic wave radiation circuit 15n that is last selected among the plurality of electromagnetic wave radiation circuits 15, the control unit 17 starts energizing the first charge switching element 211, thereby starting charging of the first capacitor 191 (see the section "First charge switching element").

[0040] At timing t8, after a predetermined charging time has elapsed since timing t7, the control unit 17 turns off all of the discharge switching elements 20 except for the first discharge switching element 201 (see the columns "Second Discharge Switching Element" and "nth Discharge Switching Element"), thereby terminating the discharging of all of the capacitors 19 except for the first capacitor 191 (see the columns "Second Electromagnetic Wave Radiation Circuit" and "nth Electromagnetic Wave Radiation Circuit"). Also, at timing t8, the control unit 17 turns off the first charge switching element 211 (see the column "First Charging Switching Element"), thereby terminating the charging of the first capacitor 191 (see the column "First Electromagnetic Wave Radiation Circuit").

[0041] At timing t8, the control unit 17 energizes the radiation switching element 16 (see the "Radiation switching element" section), causing the first electromagnetic wave radiation element 181 to emit light and radiate measurement light (see the "First electromagnetic wave radiation circuit" section). Thereafter, the control unit 17 repeats processing similar to that described above, thereby sequentially causing the first electromagnetic wave radiation circuit 151, the second electromagnetic wave radiation circuit 152, ..., the n-th electromagnetic wave radiation circuit 15n to emit light.

[0042] The measurement light emitted from the electromagnetic wave emission device 10 may be deflected so that the deflection angle is continuously changed. By irradiating the object ob with the measurement light while continuously deflecting it, the distance measuring device 11 may function as a scanning distance measuring sensor.

[0043] The detection unit 13 can detect light in a band that at least partially overlaps with the wavelength band of the measurement light. Therefore, as described above, the detection unit 13 detects reflected and scattered light of the measurement light irradiated on the object ob. The detection unit 13 may notify the control unit 14 of detection information indicating that the reflected and scattered light has been detected. The detection unit 13 may be a single element such as an APD (Avalanche PhotoDiode), a PD (PhotoDiode), or a ranging image sensor. Alternatively, the detection unit 13 may be an element array such as an APD array, a PD array, a ranging imaging array, or a ranging image sensor in a configuration in which scanning by the electromagnetic wave emission device 10 is not performed, in other words, in a configuration in which the measurement light is emitted over a wide area.

[0044] The control unit 14 includes one or more processors and memory. The processor may include at least one of a general-purpose processor that loads a specific program to execute a specific function and a dedicated processor specialized for a specific process. The dedicated processor may include an application-specific IC. The processor may include a PLD. The PLD may include an FPGA. The control unit 14 may include at least one of an SoC and a SiP in which one or more processors work together.

[0045] The control unit 14 generates distance information in the space into which the electromagnetic wave emission device 10 emits the measurement light, based on the detection of the reflected and scattered light by the detection unit 13. More specifically, the control unit 14 may generate the distance information by a ToF (Time-of-Flight) method, as described below.

[0046] As shown in FIG. 5, the control unit 14 may energize the radiation switching element 16 via the control unit 17 of the electromagnetic wave emission device 10 (see the "Radiation Switching Element" column). The electromagnetic wave emission element 18, which is included in the same electromagnetic wave emission circuit 15 as the charged capacitor 19, may emit measurement light based on the energization of the radiation switching element 16 (see the "Measurement Light Emission Amount" column). The measurement light emitted by the electromagnetic wave emission element 18 and irradiated onto an arbitrary irradiation area on the object ob is reflected from the irradiation area. When the detection unit 13 detects the reflected scattered light reflected from the irradiation area (see the "Detection Amount of Reflected Scattered Light" column), it notifies the control unit 17 of the detection information, as described above.

[0047] The control unit 17 may include a time measurement LSI (Large Scale Integrated circuit). The control unit 17 may measure the time ΔT from the time T1 when the electromagnetic wave emission element 18 is caused to emit measurement light to the time T2 when detection information is acquired (see the "Acquisition of Detection Information" section). The control unit 17 may calculate the distance to the irradiation position by multiplying the time ΔT by the speed of light and dividing by 2.

[0048] As described above, the distance measuring device 11 is configured to generate distance information by Direct ToF, which irradiates measurement light and directly measures the time it takes for the light to return, but is not limited to this configuration.

[0049] The electromagnetic wave emission device 10 of this embodiment configured as described above comprises a plurality of electromagnetic wave emission circuits 15, each including an electromagnetic wave emission element 18, a capacitor 19, and a discharge switching element 20; a emission switching element 16 connected to the cathode sides of the plurality of electromagnetic wave emission elements 18 included in the plurality of electromagnetic wave emission circuits 15 and capable of energizing the plurality of electromagnetic wave emission elements 18; and a control unit 17 that causes the electromagnetic wave emission element 18 in any single electromagnetic wave emission circuit 15 among the plurality of electromagnetic wave emission circuits 15 to emit light, and then discharges the capacitor 19 in that any single electromagnetic wave emission circuit 15 before the emission of the electromagnetic wave emission elements 18 in the other electromagnetic wave emission circuits 15. With this configuration, the electromagnetic wave emission device 10 can discharge the charge remaining in the capacitor 19 that supplied power to the electromagnetic wave emission element 18 after the electromagnetic wave emission element 18 has emitted light, while still using the emission switching element 16 connected to the cathode sides of the plurality of electromagnetic wave emission elements 18. Therefore, the electromagnetic wave emission device 10 can reduce the possibility of double light emission.

[0050] Furthermore, in the electromagnetic wave emission device 10 of this embodiment, the discharge switching element 20 in any one of the electromagnetic wave emission circuits 15 starts discharging the capacitor 19 after a predetermined distance measurement time has elapsed since the electromagnetic wave emission element 18 in that one of the electromagnetic wave emission circuits 15 is energized. Discharge of the capacitor 19 may cause noise in surrounding electronic devices. Therefore, for example, discharge of the capacitor 19 in a configuration in which the detection unit 13 is disposed near the electromagnetic wave emission device 10 may cause noise to be mixed into the detection signal of the detection unit 13. As a result, for example, the distance measurement accuracy of the distance measurement device 11 may decrease. On the other hand, in the electromagnetic wave emission device 10 configured as described above, the capacitor 19 is discharged after distance measurement is completed, thereby reducing the impact of noise generation.

[0051] Furthermore, the electromagnetic wave emission device 10 of this embodiment controls the charge switching element 21 and the discharge switching element 20 so that the discharge time is longer than the charge time. With this configuration, the electromagnetic wave emission device 10 can reduce the possibility of charge remaining in the capacitor 19, and can further reduce the possibility of double light emission.

[0052] Furthermore, in the electromagnetic wave emission device 10 of this embodiment, the gate charge capacity of the discharge switching element 20 is larger than the gate charge capacity of the charge switching element 21. With this configuration, the electromagnetic wave emission device 10 can reduce the possibility of charge remaining in the capacitor 19, and can further reduce the possibility of double emission.

[0053] The above has described an embodiment of the electromagnetic wave emission device 10, but the embodiment of the present disclosure can also be embodied as a method or program for implementing the device, as well as a storage medium on which a program is recorded (for example, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a CD-RW, a magnetic tape, a hard disk, or a memory card, etc.).

[0054] Furthermore, the implementation form of the program is not limited to application programs such as object code compiled by a compiler or program code executed by an interpreter, but may also be in the form of a program module incorporated into an operating system. Furthermore, the program may or may not be configured so that all processing is performed solely by the CPU on the control board. The program may also be configured so that part or all of it is executed by another processing unit mounted on an expansion board or expansion unit added to the board as needed.

[0055] The drawings illustrating the embodiments of the present disclosure are schematic, and the dimensional ratios and the like in the drawings do not necessarily correspond to the actual ones.

[0056] Although the embodiments of the present disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art could make various modifications or alterations based on the present disclosure. Therefore, it should be noted that these modifications or alterations are included in the scope of the present disclosure. For example, the functions included in each component can be rearranged so as not to cause logical inconsistencies, and multiple components can be combined or divided into one.

[0057] For example, in this embodiment, the control unit 17 energizes all the discharge switching elements 20 except for the arbitrary discharge switching element 20, and then starts energizing the charge switching element 21 of the electromagnetic wave emission circuit 15 that is the same as the arbitrary discharge switching element 20. However, it may simultaneously energize all the discharge switching elements 20 except for the arbitrary discharge switching element 20 and the charge switching element 21 of the electromagnetic wave emission circuit 15 that is the same as the arbitrary discharge switching element 20. Alternatively, it may energize the discharge switching elements 20 of all the electromagnetic wave emission circuits 15 other than the arbitrary charge switching element 21 after starting energization of the arbitrary charge switching element 21. The order of charging and discharging may be arbitrary, as long as charging and discharging in the same electromagnetic wave emission circuit 15 do not overlap, and as long as discharging of the capacitors 19 of all the other electromagnetic wave emission circuits 15 is completed before light emission in the arbitrary electromagnetic wave emission circuit 15.

[0058] All of the features described in this disclosure and / or all steps of all of the disclosed methods or processes may be combined in any combination except combinations in which these features are mutually exclusive. Furthermore, each feature described in this disclosure may be replaced by an alternative feature serving the same, equivalent, or similar purpose, unless expressly denied. Thus, unless expressly denied, each disclosed feature is only one example of a generic series of identical or equivalent features.

[0059] Furthermore, embodiments of the present disclosure are not limited to the specific configurations of any of the above-described embodiments, but rather extend to any novel feature or combination thereof described herein, or any novel method or process step or combination thereof described herein.

[0060] In this disclosure, descriptions such as "first" and "second" are identifiers for distinguishing the configuration. In this disclosure, the configurations distinguished by descriptions such as "first" and "second" can have their numbers interchanged. For example, the first electromagnetic wave radiating circuit and the second electromagnetic wave radiating circuit can have their identifiers "first" and "second" interchanged. The identifiers are interchanged simultaneously. The configurations remain distinguished even after the identifiers are interchanged. The identifiers may be deleted. A configuration from which an identifier has been deleted is distinguished by a symbol. The identifiers "first" and "second" in this disclosure should not be used solely to interpret the order of the configurations or to justify the existence of an identifier with a smaller number. [Explanation of symbols]

[0061] 10. Electromagnetic wave emission device 11 Ranging device 12 Mobile 13 Detector 14 Control Unit 15 Electromagnetic radiation circuit 151 First electromagnetic wave radiation circuit 152 Second electromagnetic wave radiation circuit 15n nth electromagnetic wave radiation circuit 16 Radiation switching element 17 Control Unit 18 Electromagnetic wave radiating element 181 First electromagnetic wave radiating element 182 Second electromagnetic wave radiating element 18n nth electromagnetic wave radiating element 19 Capacitors 191 First Capacitor 192 Second Capacitor 19n nth capacitor 20 Discharge switching element 201 First discharge switching element 202 Second discharge switching element 20n nth discharge switching element 21 Charging switching element 211 first charging switching element 212 second charging switching element 21n nth charging switching element 22 Power supply 23 The First Resistance 24 The Second Resistance 25 Inductor

Claims

1. a plurality of electromagnetic wave radiation circuits each including an electromagnetic wave radiation element, a capacitor that supplies current to the electromagnetic wave radiation element, and a discharge switching element that discharges the capacitor; a radiation switching element connected to cathode sides of the plurality of electromagnetic wave radiation elements included in the plurality of electromagnetic wave radiation circuits, and capable of energizing the plurality of electromagnetic wave radiation elements; a control unit that causes an electromagnetic wave radiation element in an arbitrary electromagnetic wave radiation circuit among the plurality of electromagnetic wave radiation circuits to radiate, and then discharges a capacitor in the arbitrary electromagnetic wave radiation circuit before the electromagnetic wave radiation elements in the other electromagnetic wave radiation circuits radiate. Electromagnetic wave emitting device.

2. 2. The electromagnetic wave emission device according to claim 1, the electromagnetic wave radiation circuit includes a charge switching element that causes the capacitor to be charged, The control unit controls the charge switching element and the discharge switching element so that the discharge time is longer than the charge time. Electromagnetic wave emitting device.

3. 3. A distance measuring device comprising the electromagnetic wave emission device according to claim 2, for measuring a distance to an object using electromagnetic waves emitted from the electromagnetic wave emission device, the control unit starts discharging a capacitor in the arbitrary electromagnetic wave radiation circuit after a predetermined distance measurement time has elapsed since the electromagnetic wave radiation element in the arbitrary electromagnetic wave radiation circuit emitted the electromagnetic wave, for measuring the distance to the object by detecting the reflected wave of the electromagnetic wave reflected by the object. Ranging device.

4. 4. The distance measuring device according to claim 3, The control unit controls the charge switching element and the discharge switching element so as to charge a capacitor in the arbitrary electromagnetic wave radiation circuit and discharge a capacitor other than the arbitrary electromagnetic wave radiation circuit before distance measurement. Ranging device.

5. 5. The distance measuring device according to claim 3, The control unit controls the charge switching element and the discharge switching element so as not to charge a capacitor in the arbitrary electromagnetic wave radiation circuit and not to discharge a capacitor other than the arbitrary electromagnetic wave radiation circuit while measuring the distance to the target. Ranging device.

6. The distance measuring device according to any one of claims 3 to 5 is provided. Mobile object.

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