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EP-4194891-B1 - ELECTROMAGNETIC WAVE DETECTOR

EP4194891B1EP 4194891 B1EP4194891 B1EP 4194891B1EP-4194891-B1

Inventors

  • KASHIWASE SUSUMU
  • INUKAI TSUNEYASU

Dates

Publication Date
20260513
Application Date
20210804

Claims (11)

  1. An electromagnetic-wave detection apparatus (10) comprising: a radiation system (111) configured to radiate an electromagnetic wave toward a space in which a target is present; a first detection unit (20) configured to detect a reflected wave that is the electromagnetic wave radiated by the radiation system (111) and reflected by the target; a calculation unit (145) configured to calculate a distance to the target based on detection information that is obtained by the first detection unit (20) and that relates to the reflected wave; and a radiation control unit (143) configured to cause the radiation system (111) to radiate the electromagnetic wave, wherein the radiation control unit (143) is configured to cause a first electromagnetic wave (L1) to be radiated and then cause a second electromagnetic wave (L2) with a greater output than the first electromagnetic wave (L1) to be radiated, and wherein the calculation unit (145) is configured to calculate the distance to the target based on the reflected wave of the first electromagnetic wave (L1) when the first detection unit (20) becomes saturated with the reflected wave of the second electromagnetic wave (L2), characterized in that (i) the radiation control unit (143) is configured to adjust a time interval (td) between radiation of the first electromagnetic wave (L1) and radiation of the second electromagnetic wave (L2) based on a detection result relating to the reflected wave of the first electromagnetic wave (L1) and a detection result relating to the reflected wave of the second electromagnetic wave (L2), the detection results being obtained by the first detection unit (20), and/or (ii) the electromagnetic-wave detection apparatus (10) further comprises: a second detection unit (17) configured to detect light from the space and to output image information of the space, wherein the radiation control unit (143) is configured to adjust a time interval (td) between radiation of the first electromagnetic wave (L1) and radiation of the second electromagnetic wave (L2) based on the image information, and/or (iii) the electromagnetic-wave detection apparatus (10) is configured to be mounted on a vehicle, wherein, when the space includes a first region and a second region located below the first region, and the electromagnetic wave is radiated toward the second region, the radiation control unit (143) is configured to increase a time interval (td) between radiation of the first electromagnetic wave (L1) and radiation of the second electromagnetic wave (L2) to be larger than the time interval (td) between radiation of the first electromagnetic wave (L1) and radiation of the second electromagnetic wave (L2) when the electromagnetic wave is radiated toward the first region.
  2. The electromagnetic-wave detection apparatus (10) according to claim 1, wherein the radiation control unit (143) is configured to cause the second electromagnetic wave (L2) to be radiated before the reflected wave of the first electromagnetic wave (L1) is incident on the first detection unit (20).
  3. The electromagnetic-wave detection apparatus (10) according to claim 1, wherein the radiation control unit (143) is configured to cause the first electromagnetic wave (L1) to be radiated and then to cause the second electromagnetic wave (L2) to be radiated before the first detection unit (20) becomes able to detect the reflected wave of the first electromagnetic wave (L1).
  4. The electromagnetic-wave detection apparatus (10) according to any one of claims 1 to 3 in combination with item (i) of claim 1, wherein the radiation control unit (143) is configured to increase the time interval (td) between radiation of the first electromagnetic wave (L1) and radiation of the second electromagnetic wave (L2) when one of the reflected wave that is the first electromagnetic wave (L1) reflected by the target and the reflected wave that is the second electromagnetic wave (L2) reflected by the target is detected by the first detection unit (20).
  5. The electromagnetic-wave detection apparatus (10) according to any one of claims 1 to 3 in combination with item (i) of claim 1, wherein, if the radiation control unit (143) causes the radiation system (111) to perform radiation of the electromagnetic wave multiple times including radiation of the first electromagnetic wave (L1) and radiation of the second electromagnetic wave (L2), and a number of times the first detection unit (20) detects the reflected wave is smaller than a number of times the radiation system (111) performs radiation of the electromagnetic wave, the radiation control unit (143) is configured to increase the time interval (td) between the radiations of the electromagnetic waves performed by the radiation system (111).
  6. The electromagnetic-wave detection apparatus (10) according to any one of claims 1 to 5 in combination with item (ii) of claim 1, wherein, when an object (ob) among one or more targets that is inclined with respect to an optical axis is irradiated with the electromagnetic wave, the radiation control unit (143) is configured to increase the time interval (td) between radiation of the first electromagnetic wave (L1) and radiation of the second electromagnetic wave (L2) based on the image information.
  7. The electromagnetic-wave detection apparatus (10) according to any one of claims 1 to 6 in combination with item (ii) of claim 1, wherein the radiation control unit (143) is configured to increase a difference of magnitude of output between the first electromagnetic wave (L1) and the second electromagnetic wave (L2) based on a luminance of the target included in the image information.
  8. The electromagnetic-wave detection apparatus (10) according to any one of claims 1 to 7, wherein, when a ratio between a distance to a position of a farthest object (ob) among multiple objects (ob) present in the space and a distance to a position of a closest object (ob) among the multiple objects (ob) is equal to or greater than a predetermined ratio, the radiation control unit (143) is configured to increase a ratio of magnitude of output between the first electromagnetic wave (L1) for one frame and the second electromagnetic wave (L2) for one frame.
  9. The electromagnetic-wave detection apparatus (10) according to any one of claims 1 to 8, wherein, when a number of the reflected waves detected by the first detection unit (20) is one, and the single reflected wave has a pulse width smaller than a predetermined width, the calculation unit (145) is configured to calculate the distance to the target while considering the reflected wave as the reflected wave of the second electromagnetic wave (L2).
  10. The electromagnetic-wave detection apparatus (10) according to any one of claims 1 to 9, wherein the radiation system (111) includes a light-source driving device configured such that a first control signal for causing the radiation system (111) to radiate the first electromagnetic wave (L1) and a second control signal for causing the radiation system (111) to radiate the second electromagnetic wave (L2) can be input from the radiation control unit (143), and wherein the light-source driving device includes a laser diode (DDD) configured to emit pulsed light, a capacitor (C1) connected to the laser diode (DDD) in such a manner as to be capable of supplying a current to the laser diode (DDD), a first transistor (Q2) configured to cause, upon receiving the first control signal, part of electric charge accumulated in the capacitor (C1) to be discharged and cause the laser diode (DDD) to emit light such that the first electromagnetic wave (L1) is radiated, and a second transistor (Q3) configured to cause, upon receiving the second control signal, a remaining part of the electric charge of the capacitor (C1) to be discharged and cause the laser diode to emit light such that the second electromagnetic wave (L2) with an intensity greater than an intensity of the first electromagnetic wave (L1) is radiated.
  11. The electromagnetic-wave detection apparatus (10) according to claim 10, configured such that the second control signal is input to the light-source driving device 3 ns to 10 ns after the first control signal has been input to the light-source driving device.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims the priority of JP 2020-133326 A filed on August 5, 2020. TECHNICAL FIELD The present disclosure relates to an electromagnetic-wave detection apparatus. BACKGROUND OF INVENTION In recent years, an apparatus that acquires information relating to surroundings from detection results obtained by a plurality of detectors configured to detect electromagnetic waves has been developed. Such an apparatus may sometimes detect, for example, a distance to a subject by acquiring an image including the subject captured by an imaging device and detecting electromagnetic waves including a reflected wave reflected by the subject. Here, a reflected wave came from a distant place is weak, and consequently, a highly sensitive detector is required. In contrast, a reflected wave came from a nearby place is extremely strong, and consequently, it saturates a detector and becomes a cause of measurement errors. Accordingly, for example, the apparatus disclosed in Patent Literature 1 radiates two types of laser beams, which are strong and weak laser beams, and when a detector included in the apparatus becomes saturated, the apparatus performs distance measurement using reflection of light emitted from a low-power laser oscillator included in the apparatus. CITATION LIST PATENT LITERATURE Patent Literature 1: Japanese Unexamined Patent Application Publication No. JP H05-066263 Moreover, JP 2019 120515 A discloses a radar device and an object detection method; US 2014/071428 A1 discloses a distance measurement apparatus that measures distance to a target by irradiating the target with laser beams and detecting light reflected by the target; JP 2011 027451 A discloses a ranging device and a ranging method; US 2019/018107 A1 discloses an optical transmitting device for a distance measurement system; and JP 2019 507340 A discloses methods and systems for performing multiple pulse LIDAR measurements. SUMMARY The present invention provides an electromagnetic-wave detection apparatus according to claim 1. Preferred embodiments are described in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating a schematic configuration of an electromagnetic-wave detection apparatus according to an embodiment.FIG. 2 is a diagram illustrating a travelling direction of an electromagnetic wave in a first state and a travelling direction of an electromagnetic wave in a second state in the electromagnetic-wave detection apparatus illustrated in FIG. 1.FIG. 3 is a diagram for describing detection of electromagnetic waves including a reflected wave.FIG. 4 is a diagram illustrating an example of a radiation wave and an example of a reflected wave.FIG. 5 is a diagram illustrating the case of saturation.FIG. 6 is a diagram illustrating the case in which a single reflected wave is detected.FIG. 7 is a diagram illustrating the case in which reflected waves overlap each other.FIG. 8 is a diagram illustrating the case in which overlapping of reflected waves occurs.FIG. 9 is a diagram illustrating a circuit configuration of a light-source driving device. DESCRIPTION OF EMBODIMENTS FIG. 1 is a diagram illustrating a schematic configuration of an electromagnetic-wave detection apparatus 10 according to an embodiment. The electromagnetic-wave detection apparatus 10 includes a radiation system 111, a light reception system 110, and a control unit 14. In the present embodiment, the distance-measurement apparatus 10 functions as a distance-measurement apparatus. In the present embodiment, although the electromagnetic-wave detection apparatus 10 includes the single radiation system 111 and the single light reception system 110, the electromagnetic-wave detection apparatus 10 may include multiple light reception systems 110 and multiple radiation systems 111, and the multiple light reception systems 110 may correspond to their respective radiation systems 111. The radiation system 111 includes a radiation unit 12 and a deflection unit 13. The light reception system 110 includes an incident unit 15, a separation unit 16, a first detection unit 20, a second detection unit 17, a switching unit 18, and a first subsequent-stage optical system 19. The control unit 14 includes an image-information acquisition unit 141, a radiation control unit 143, and a calculation unit 145. Details of each functional block of the electromagnetic-wave detection apparatus 10 will be described later. In the drawings, dashed lines connecting the functional blocks each indicate a flow of a control signal or a flow of information that is transmitted and received. Each of the communications indicated by the dashed lines may be wired communication or may be wireless communication. In the drawings, solid arrows each indicate an electromagnetic wave in the form of a beam, and an object ob is a subject of the electromagnetic-wave detection apparatus 10. The subject may include, for example, objects such as