Object detection device and object detection method

Abstract

This object detection device comprises: a light-emitting element that projects projection light; a light-receiving element; and a controller. The controller is capable of setting: a first light projection mode for generating a plurality of light projection reference timings and projecting each light projection reference timing as a light projection timing; and a second light projection mode for projecting light according to each light projection timing obtained by temporally shifting each light projection reference timing. In the second light projection mode, each light projection reference timing is determined by shifting each light projection timing such that a shift time at which each light projection reference timing shifts is changed by a fixed time.

Description

Object detection device and object detection method

[0001] The present disclosure relates to an object detection device and an object detection method for optically detecting an object.

[0002] A pulse-echo distance measurement device is known that adjusts a slot number indicating the light emission timing to prevent erroneous measurements due to interference light (see Patent Document 1). In this distance measurement device, a slot generation circuit generates a light emission signal indicating the light emission timing based on a slot number set by a CPU, and a pulsed laser beam is emitted by a light emission circuit in response to this light emission signal. The emitted pulsed laser beam is projected by a scanner that performs scanning based on a scanner control signal provided by a timing generation circuit. A counter counts the time from the light emission timing to the light reception timing at which the projected pulsed laser beam is received by a preceding vehicle, and the CPU calculates the inter-vehicle distance from the preceding vehicle based on the count. A light reception monitoring circuit detects the presence or absence of interference light based on the light reception signal from the light reception circuit. If interference light is detected, the CPU changes the slot number.

[0003] Japanese Patent Application Publication No. 7-35863

[0004] When the distance measurement device of Patent Document 1 is placed opposite another distance measurement device with the same light emission timing, if the two distance measurement devices emit light at the same timing, the projected light from one distance measurement device may be received by the other distance measurement device, resulting in the detection of the projected light. In this case, the distance measurement device of Patent Document 1 changes the slot number and projects the projected light at a different timing. However, if the two distance measurement devices have the same specifications and change their slot numbers in the same way, one distance measurement device may still receive the next projected light from the other distance measurement device. In this case, one distance measurement (measurement) device may erroneously detect the presence of an object due to interference with the projected light from the other distance measurement (measurement) device.

[0005] The present disclosure provides an object detection device and an object detection method that can suppress erroneous detection of the presence of an object due to interference with projected light from another object detection device, even when another object detection device is placed opposite.

[0006] One aspect of the present disclosure is an object detection device that includes a light-emitting element that emits projection light in accordance with a light-projection timing, a light-receiving element that receives light reflected from an object by the light-projection light and generates a light-receiving signal, and a controller, wherein the controller generates a plurality of light-projection reference timings to emit light a plurality of times at a constant period, and is capable of setting a first light-projection mode in which light is projected using each light-projection reference timing as the light-projection timing, and a second light-projection mode in which light is projected in accordance with each light-projection timing that is a temporally shifted version of each light-projection reference timing, and in the second light-projection mode, the controller determines each light-projection timing by shifting each light-projection reference timing so that the shift time for shifting each light-projection reference timing changes by a constant time.

[0007] One aspect of the present disclosure is an object detection method including: projecting projection light in accordance with light-projection timings; receiving light that is reflected by an object and generating a light-receiving signal; generating a plurality of light-projection reference timings to project light a plurality of times at a constant period; and setting a light-projection mode, wherein the light-projection mode can be set to a first light-projection mode in which light is projected using each light-projection reference timing as the light-projection timing; and a second light-projection mode in which light is projected in accordance with each light-projection timing obtained by temporally shifting the each light-projection reference timing, and setting the light-projection mode includes, when the second light-projection mode is set as the light-projection mode, determining each light-projection timing by shifting each light-projection reference timing so that a shift time by which each light-projection reference timing is shifted changes by a constant time.

[0008] According to the present disclosure, even when another object detection device is placed opposite, it is possible to prevent erroneous detection of the presence of an object due to interference of projected light from the other object detection device.

[0009] FIG. 1 is a perspective view of the appearance of an object detection device according to a first embodiment of the present disclosure; FIG. 2 is a longitudinal sectional view of the object detection device according to the first embodiment; FIG. 3 is a top view of the object detection device shown in FIG. 1, as viewed from above; FIG. 4 is a block diagram showing an example of the functional configuration of the object detection device according to the first embodiment; FIG. 5 is a diagram for explaining details of object detection; FIG. 6 is a diagram showing an example of the position of an object present within the detection area; FIG. 7 is a diagram showing an example of the timing of projecting the projected light and the timing of receiving the detection light when an object is present within the detection area; FIG. 3 shows a third example of the timing of light projection and light reception when shift light projection mode SM1 is specified. FIG. 4 shows an example of the timing of light projection and light reception when shift light projection mode SM2 is specified. FIG. 5 shows an example of the timing of light projection and light reception when shift light projection mode SM3 is specified. FIG. 6 shows an example of the timing of light projection and light reception when shift light projection mode SM4 is specified. FIG. 7 shows an example of the timing of light projection and light reception when shift light projection mode SM5 is specified. FIG. 8 shows an example of the timing of light projection when another shift light projection mode SM6 is specified. FIG. 9 shows the layout relationship of a plurality of distance measurement devices in a comparative example. FIG. 10 shows the timing of each light projection and each light reception when an object is erroneously detected in the comparative example. FIG. 11 shows the timing of each light projection and each light reception when an object is erroneously detected in the comparative example.

[0010] Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed descriptions of well-known matters or descriptions of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0011] Furthermore, the term "unit" or "device" in the embodiments is not limited to a physical configuration that is mechanically realized by hardware, but also includes a configuration whose functions are realized by software such as a program. Furthermore, the functions of one configuration may be realized by two or more physical configurations, or the functions of two or more configurations may be realized by, for example, one physical configuration.

[0012] (How the Embodiments of the Present Disclosure Were Achieved) Assume that multiple distance measurement devices (object detection devices) of a comparative example are installed facing each other, as shown in FIG. 18 . The distance measurement device of the comparative example is, for example, the distance measurement device disclosed in Patent Document 1. Assume that distance measurement device 1XA and distance measurement device 1XB operate asynchronously. In this case, at the timing when distance measurement device 1XA emits projected light A to measure distance, projected light B emitted by distance measurement device 1XB to measure distance may be received by the light receiving element of distance measurement device 1XA. In this case, as shown in FIG. 19 , if a two-dimensional scanning distance measurement device detects projected light B, for example, N consecutive times and M consecutive rotations (N and M are integers greater than or equal to 2) within the longest detectable time corresponding to the maximum detectable distance (i.e., within the detection area), distance measurement device 1XA will erroneously detect that an object is present within the detection area. In other words, as shown in FIG. 20 , interference can cause a false detection in which an object is recognized as being present in space (specifically, within the detection area) even though there is no object present.

[0013] In the following embodiments, an object detection device and an object detection method are described that can suppress false detection of the presence of an object due to interference with projected light from another object detection device, even when another object detection device is placed opposite.

[0014] (Embodiments) <Physical configuration of object detection device> Fig. 1 is an external perspective view of an object detection device 1 according to embodiment 1. Fig. 2A is a longitudinal cross-sectional view of the object detection device according to embodiment 1. Fig. 2A corresponds to the A-A cross-sectional view of the object detection device 1 shown in Fig. 1. Fig. 2B is a top view of the object detection device 1 shown in Fig. 1, as seen from above. Some components such as a housing are omitted in Fig. 2B.

[0015] The object detection device 1 is, for example, a LiDAR (Light Detection and Ranging) device. The object detection device 1 optically detects a target object using light such as laser light and measures the distance to the target object (ranging). The object detection device 1 uses light in a scanner system to perform two-dimensional scanning to detect and range to the object.

[0016] As shown in FIGS. 1 and 2A, the object detection device 1 includes a fixed part 100, a rotating part 300, and an outer cover part 10.

[0017] The fixed unit 100 has a substantially rectangular parallelepiped shape. The rotating unit 300 is connected to the upper surface of the fixed unit 100 and has a cylindrical shape that rotates around a rotation axis C that is perpendicular to the upper surface. The outer cover unit 10 has a substantially cylindrical shape and covers the rotating unit 300 from above. The outer cover unit 10 has a wavelength window 11 formed using a wavelength selection member on at least a portion of its side surface. The wavelength selection member is a material that transmits light of a predetermined wavelength (frequency) component used for object detection and distance measurement and blocks light of a wavelength (frequency) component in the visible range. The wavelength selection member has the role of blocking ambient light, such as natural light and electric light.

[0018] For ease of explanation, as shown in FIG. 1, the axis perpendicular to the top surface (or bottom surface) of the fixed part 100 is referred to as the Z axis. The axis perpendicular to the Z axis is referred to as the X axis. The axis perpendicular to the Z axis and the X axis is referred to as the Y axis. For ease of explanation, the positive direction of the Z axis may be referred to as "up," the negative direction of the Z axis as "down," and the direction away from the Z axis in the X axis direction or the Y axis direction as "sideways." Note that these directional expressions are used for ease of explanation and are not intended to limit the orientation of the structure during actual use. For example, the object detection device 1 shown in FIG. 1 may be used upside down. The A-A cross-sectional view shown in FIG. 2A corresponds to a cross-sectional view in the YZ plane.

[0019] The bottom surface of the fixed part 100 may be fixedly installed on a predetermined plane (for example, a floor surface or the surface of a housing of a predetermined device).

[0020] The rotating unit 300 rotates around a rotation axis C, which is the central axis in the height direction (Z axis) of the cylinder. As the rotating unit 300 rotates, the optical axis of projected light (hereinafter referred to as projected light 3A) projected laterally from a portion of the side surface of the rotating unit 300 rotates around the rotation axis C. Accordingly, the projected light 3A and an area in which object detection and distance measurement are possible using the projected light 3A (hereinafter referred to as the detection area) also rotate. As will be described later, the object detection device 1 detects whether an object is present in the detection area and measures the distance to the object present in the detection area based on the time difference (Time of Flight (TOF)) between the timing at which the projected light 3A is projected and the timing at which light reflected from the projected light 3A by an object in the detection area (hereinafter referred to as reflected light 3B) is received. As the rotating part 300 rotates around the rotation axis C, the object detection device 1 can measure the distance to an object present in a detection area of ​​360 degrees around in the horizontal direction.

[0021] The fixed unit 100 includes a substrate 101, a light-emitting element 102, a light-receiving element 103, a condenser lens 104, a collimator lens 105, a coil 106, and a photointerrupter 107. The rotating unit 300 includes a rotating member 301, a magnet 302, and a reflecting mirror 303.

[0022] A hollow motor 402 (see FIG. 3 ) is formed by the coil 106 of the fixed part 100 and the magnet 302 of the rotating part 300, and when driven by this motor 402, the rotating part 300 rotates around a rotation axis C. As shown in FIG. 2B , a plurality of coils 106 are arranged in a ring shape along the XY plane, radially outward from the rotating part 300, with the rotation axis C as the center.

[0023] 2A, the substrate 101 is, for example, a printed circuit board (PCB). A comparator 401, a TDC 500, and a controller 600 (see FIG. 3), which will be described later, are mounted on the substrate 101. Note that TDC is an abbreviation for Time to Digital Converter.

[0024] The light emitting element 102 is arranged along the rotation axis C and projects the projection light 3A upward.

[0025] The collimator lens 105 corrects the projection light 3A emitted from the light emitting element 102 to be approximately parallel light and outputs it upward.

[0026] The reflecting mirror 303 is provided on the rotating member 301 so as to reflect the parallel light projected upward from the light emitting element 102 and corrected by the collimator lens 105 in the horizontal direction (direction along the XY plane). Because the reflecting mirror 303 rotates together with the rotating member 301, the projected light is projected (scanned) 360 degrees around the rotation axis C in a direction (horizontal direction) perpendicular to the rotation axis C over time. The projected light 3A reflected by the reflecting mirror 303 passes through the wavelength window 11 of the outer cover unit 10 and is projected onto the detection area.

[0027] The reflected light 3B, which is the projected light 3A reflected by the object, passes through the wavelength window 11 of the outer cover part 10 and is reflected downward by the reflecting mirror 303.

[0028] The condenser lens 104 condenses the reflected light 3B reflected downward by the reflecting mirror 303 and outputs the condensed light downward.

[0029] The light receiving element 103 receives the reflected light 3 B condensed by the condenser lens 104 .

[0030] The rotating member 301 has a plurality of ribs 311 (slits) at regular intervals. For example, the rotating member is annular, with the ribs spaced at regular intervals around the circumference. The photointerrupter 107 (photocoupler) is positioned so as to detect the passage of each rib 311. By using the photointerrupter 107 to detect and count the passage of each rib 311, the controller 600 (described later) can detect the rotation angle (rotation position) of the rotating member 301 (i.e., the rotating unit 300). Therefore, the photointerrupter 107 and the ribs 311 can form a rotation angle detector 403 (see FIG. 3 ) (described later).

[0031] <Functional Configuration of Object Detection Device> FIG. 3 is a block diagram showing an example of the functional configuration of the object detection device 1 according to the first embodiment.

[0032] The object detection device 1 includes a light-emitting element 102, a light-receiving element 103, an amplifier circuit 108, a laser driver circuit 109, a comparator 401, and a TDC 500. The object detection device 1 also includes a motor 402, a rotation angle detector 403, and a motor driver circuit 404. The object detection device 1 also includes a controller 600, a memory 710, a switch 720, and an external input / output circuit 730. The controller 600 functions as a distance measurement control unit 610, a distance calculation unit 620, a rotation control unit 630, a light-projection timing generation unit 640, and a light-projection timing correction unit 650. Note that each unit in the controller 600 may be configured as a dedicated circuit in hardware, or may be configured functionally in software.

[0033] The light emitting element 102 is configured by, for example, a laser diode. A drive signal for driving the light emitting element 102 is input from a laser drive circuit 109 to the light emitting element 102, and the light emitting element 102 projects (emits) projection light 3A (illumination light) in accordance with the drive signal. The light emitting element 102 periodically projects light, and projects projection light 3A in accordance with the light projection timing.

[0034] The light receiving element 103 is configured by, for example, a photodiode. The light receiving element 103 receives the reflected light 3B and outputs a light receiving signal (electrical signal) according to the light receiving level. The reflected light 3B may be detection light from a detected object, or may include scattered light scattered by the object.

[0035] The amplifier circuit 108 receives the light-receiving signal from the light-receiving element 103 and amplifies it to increase the signal level of the light-receiving signal.

[0036] The laser drive circuit 109 receives a pulse signal from the light projection timing correction unit 650 of the controller 600, which instructs the light emitting element 102 to project light. The laser drive circuit 109 outputs a pulsed drive signal corresponding to the input pulse signal (also referred to as an input pulse signal) to the light emitting element 102. As a result, the light emitting element 102 projects pulsed projection light 3A. In FIG. 3 , the input of the input pulse signal is expressed as TDC START (START signal).

[0037] The comparator 401 receives the amplified light-receiving signal from the light-receiving element 103. The comparator 401 binarizes the light-receiving signal according to its signal level and outputs a pulse signal (also referred to as a light-receiving pulse signal). The light-receiving pulse signal is at a predetermined high level while the level of the light-receiving signal is equal to or greater than a predetermined comparator threshold (comparator slice level), and is at a predetermined ground level while the level of the light-receiving signal is less than the comparator threshold. The high level is greater than the ground level. In FIG. 3, the output of the light-receiving pulse signal is expressed as a TDC stop (stop signal).

[0038] The TDC 500 receives a START signal from the light projection timing correction unit 650. The input timing of this START signal corresponds to the timing of projection of the light 3A by the light emitting element 102. The TDC 500 receives a STOP signal from the comparator 401. The input timing of the STOP signal corresponds to the timing of reception of the reflected light 3B by the light receiving element 103, and more specifically, corresponds to the timing of generation of a light reception pulse signal. The TDC 500 outputs TOF (time of flight) information based on the START signal and STOP signal. Therefore, the TDC 500 can be said to measure the time from when the laser drive circuit 109 is driven to when the signal from the comparator 401 changes. The TDC 500 may also output information on the pulse width of the light reception signal.

[0039] The motor 402 provides the rotating unit 300 with a driving force that rotates the rotating unit 300 based on a motor driving signal from the motor driving circuit 404. By rotating the rotating unit 300 with this driving force, the motor 402 can change the projection direction of the projected light 3A to any direction and can change the reception direction of the reflected light 3B to any direction. The rotation angle detector 403 detects the rotation angle of the rotating unit 300. This rotation angle indicates an angle relative to a predetermined reference angle. The rotation angle detector 403 may also detect the rotation speed of the motor 402. The motor driving circuit 404 generates a drive signal that drives the motor 402 based on a rotation control signal from the rotation control unit 630 of the controller 600 and sends the drive signal to the motor 402.

[0040] The controller 600 may be configured to include an MPU (Micro Processing Unit), a CPU (Central Processing Unit), a DSP (Digital Signal Processor), etc. The controller 600 may be configured with various integrated circuits (e.g., an LSI (Large Scale Integration), an FPGA (Field Programmable Gate Array)). The controller 600 realizes various functions by executing programs stored in a memory located inside or outside the controller 600. The controller 600 has various functional units such as a distance measurement control unit 610, a distance calculation unit 620, a rotation control unit 630, a light projection timing generation unit 640, and a light projection timing correction unit 650.

[0041] The ranging control unit 610 controls ranging by the object detection device 1 and comprehensively controls each unit in the controller 600. The ranging control unit 610 also inputs information obtained from the memory 710 and the switch 720 as parameters for the controller 600 to perform various processes and controls. The ranging control unit 610 also outputs information on the results of the various processes and controls performed by the controller 600 to the external input / output circuit 730.

[0042] The distance calculation unit 620 acquires information about the TOF and pulse width from the TDC 500. The distance calculation unit 620 calculates the distance from the object detection device 1 to the object by converting the TOF (a digital value over time) into a distance based on the acquired TOF and the speed of light, for example. This distance is a distance value measured according to the TOF, and is also referred to as a measured distance value.

[0043] Furthermore, the distance calculation unit 620 may obtain information on the rotation angle corresponding to the light projection timing corresponding to the START signal that is the basis of the TOF corresponding to the measured distance value from the rotation angle detector 403 or the like, or may derive the information by calculation. The distance calculation unit 620 may identify the two-dimensional position of the object based on the measured distance value and the obtained rotation angle.

[0044] The rotation control unit 630 controls the rotation of the motor 402, that is, the rotation of the rotating unit 300. Specifically, the rotation control unit 630 sends a rotation control signal that controls the rotation of the motor 402 to the motor drive circuit 404. The rotation control unit 630 generates a rotation control signal that causes the motor 402 to rotate at a constant speed, based on the rotation angle information and rotation speed information from the rotation angle detector 403. In other words, the rotation control unit 630 causes the motor 402 and the rotating unit 300 to rotate at a constant speed.

[0045] The light-projection timing generation unit 640 acquires information on the rotation angle and rotation speed detected by the rotation angle detector 403. The light-projection timing generation unit 640 generates a light-projection reference timing (light-emission reference timing) based on the acquired rotation angle or the rotation angle and rotation speed. The light-projection reference timing is a light-projection timing (light-emission timing) that serves as a reference for the light-emitting element 102.

[0046] For example, the light-projection timing generation unit 640 may generate a light-projection reference timing so that the light-emitting element 102 projects light at a timing when the detected rotation angle is a predetermined angle (for example, 0.5 degrees, 1.0 degrees, 1.5 degrees, ... with respect to a reference angle). In other words, the light-projection timing generation unit 640 may acquire the rotation angle detected by the rotation angle detector 403 and determine a fixed cycle for generating the light-projection reference timing based on the rotation angle.

[0047] For example, the light-projection timing generation unit 640 may generate the light-projection reference timing so that the light-emitting element 102 projects light at a constant cycle of a clock generated by a clock generator (not shown), that is, at predetermined time intervals (for example, time intervals of 0.5 degrees, 1.0 degrees, 1.5 degrees, ... with respect to a reference angle). In other words, the light-projection timing generation unit 640 may obtain the clock generated by the clock generator and determine the constant cycle at which the light-projection reference timing is generated based on the clock.

[0048] By generating the light-projection reference timing based on a clock, even if the rotation speed of the rotating part 300 is not constant, the light-emitting element 102 can project light at a constant cycle. Furthermore, by generating the light-projection reference timing based on the rotation angle, even if the clock generation is not constant, the light-emitting element 102 can project light at a constant cycle.

[0049] The light-projection timing correction unit 650 corrects the light-projection reference timing generated by the light-projection timing generation unit 640 by shifting it in time to determine the light-projection timing. The amount of time by which the light-projection reference timing is shifted by the correction (also referred to as the shift amount or shift time) varies depending on each light-projection reference timing. For example, the shift time may vary depending on the angle at which the rotation unit 300 is rotated relative to the reference angle (e.g., 0.5 degrees, 1.0 degrees, etc.). The correction of multiple light-projection reference timings may include multiple light-projection reference timings with different shift times by which the light-projection timing is shifted in time, or multiple light-projection reference timings with the same shift time. When the shift times are different, for example, consecutive light-projection timings are set so that the shift times differ by a certain time α. Furthermore, among the multiple generated light-projection reference timings, there may be some light-projection reference timings whose light-projection reference timings are determined as the light-projection timings without being corrected.

[0050] The memory 710 may be, for example, a non-volatile memory, or may include other memories or storage devices. The memory 710 stores various types of data, information, programs, etc. The memory 710 may store, for example, area information related to the detection area DR. The detection area DR is formed in a circular or sector shape around the object detection device 1 and is an area in which the object detection device 1 can detect and distance to an object. The area information may include information such as the position and size of the detection area DR. The size of the detection area DR is determined by the length of the radius of the detection area DR. This radius is the maximum distance at which the object detection device 1 can detect an object, and is also referred to as the area detection setting distance DL.

[0051] The memory 710 may include light projection mode information related to the light projection modes described below. The light projection mode information may include at least one of information on each light projection reference timing at which the light emitting element 102 projects light, a shift amount (shift time) by which each light projection reference timing is shifted in time, and each light projection timing after each light projection reference timing is corrected. The light projection mode information may be stored in the memory 710 for each light projection mode.

[0052] The switch 720 is, for example, a DIP switch or other switch, and is used to input various types of information. Note that, instead of the switch 720, an input device (for example, a button, a key, or a touch panel) that can input various types of information may be provided in the object detection device 1. The switch 720, for example, specifies a detection area.

[0053] The external input / output circuit 730 communicates with an external device (for example, a programmable logic controller (PLC)) via wired or wireless communication. The external input / output circuit 730 receives instructions from the external device and sends notifications to the external device.

[0054] <Outline of Light Projection Mode> Next, an outline of the light projection mode will be described.

[0055] The distance measurement control section 610 of the controller 600 sets a light projection mode that determines how light is projected by the light emitting element 102. The light projection modes include a normal light projection mode and a shift light projection mode.

[0056] In the normal light-projection mode, the generated light-projection reference timings are used as the light-projection timings without being shifted, and light is projected in accordance with the light-projection timings. Thus, in the normal light-projection mode, the projection light 3A is projected at a constant cycle.

[0057] The shift light-projection mode is a light-projection mode in which each generated light-projection reference timing is corrected and light is projected according to each corrected light-projection timing. In the shift light-projection mode, the light-projection reference timing is corrected so that the shift time from the light-projection reference timing changes by a fixed time α, that is, by an integer multiple of α. The shift light-projection mode may include multiple shift light-projection modes based on the method of correcting the light-projection reference timing, for example, based on the way the shift amount changes at each successive light-projection timing. The distance measurement control unit 610 may select and set one light-projection mode from multiple light-projection modes, or may switch between multiple light-projection modes.

[0058] The ranging control unit 610 may set the detection area by acquiring area information from, for example, the memory 710. The ranging control unit 610 may set, for example, a projection mode designated by the switch 720 from among the projection modes related to the projection mode information stored in the memory 710. The ranging control unit 610 may switch between a plurality of projection modes according to the designation by the switch 720.

[0059] The distance measurement control unit 610 may be capable of setting, for example, multiple light projection modes or of switching between light projection modes. Furthermore, assume that multiple object detection devices 1 are arranged within each detection area and are asynchronous. Even in such a case, the distance measurement control unit 610 can prevent erroneous recognition of the presence of an object when no object actually exists in the space within the detection area due to interference from the projected light 3A projected by another object detection device 1. For example, if two object detection devices 1 are mounted on two AGVs (Automated Guided Vehicles), one object detection device 1 may receive the projected light 3A projected by the other object detection device 1 when the two AGVs pass each other. Even in this case, erroneous detection can be prevented. For example, if one object detection device 1 is set to the normal light projection mode and the other object detection device 1 is set to the shift light projection mode, there is a possibility that the projected light 3A will be received once, but the likelihood of receiving the light multiple times consecutively can be reduced, thereby preventing erroneous object detection.

[0060] Furthermore, although the normal light-projection mode is a general light-projection mode, if there are other object detection devices that perform similar periodic light projection, once interference occurs, it is likely to occur continuously. In contrast, by setting the object detection device 1 to the shift light-projection mode, interference with other object detection devices is less likely to occur, and even if interference does occur once, it is possible to continuously suppress the occurrence of interference.

[0061] <Details of Object Detection> Next, details of object detection will be described.

[0062] FIG. 4 is a diagram for explaining details of object detection.

[0063] In the object detection device 1, for example, the light-emitting element 102 periodically emits light, and the light-emission period is, for example, 69.444 μs (microseconds), which corresponds to 0.5 degrees. Also, for example, the rotation frequency of the motor 402 is, for example, 20 Hz. Also, for example, the distance conversion coefficient in TOF is 150 mm / ns.

[0064] For example, assume that the rotating unit 300 rotates at a constant speed, and when the rotation angle of the rotating unit 300 reaches a predetermined rotation angle, the light-emitting element 102 emits light by a predetermined rotation angle. In this case, when each light-projection reference timing is arranged on the time axis, the light-projection reference timings are arranged side by side at a constant time interval (e.g., 69.444 μs). On the time axis, with respect to the light-projection reference timing, the ranging interval (detection interval) is a time interval of, for example, 0.030 μs (microseconds), and the non-ranging interval (non-detection interval) is a time interval of, for example, 69.414 μs. In other words, if the light-emitting element 102 emits projected light 3A at the light-projection reference timing, and reflected light 3B is not detected within the temporal response range of the TDC 500, the TDC 500 times out. The time until the TDC 500 times out is the maximum ranging interval (maximum detectable interval).

[0065] For example, if the reflected light 3B is received consecutively within the time response range of the TDC 500 based on light projection at consecutive light projection timings (e.g., light projection reference timings), the ranging control unit 610 determines that an object is present in the detection area. For example, if the reflected light 3B is not received consecutively within the time response range of the TDC 500 based on light projection at consecutive light projection timings (e.g., light projection reference timings), the ranging control unit 610 determines that an object is not present in the detection area. Also, for example, if the reflected light 3B other than the reflected light 3B (e.g., projected light projected by another object detection device) is received consecutively within the time response range of the TDC 500 based on light projection at consecutive light projection timings (e.g., light projection reference timings), the ranging control unit 610 detects that an object is present in the detection area. This detection is a false detection.

[0066] Fig. 5 is a diagram showing an example of the position of an object present within the detection area DR. Fig. 6 is a diagram showing an example of the timing of projecting the projected light 3A and the timing of receiving the detection light (here, reflected light 3B) when an object is present within the detection area DR. Fig. 7 is a diagram showing an example of the position of an object present outside the detection area DR. Fig. 8 is a diagram showing an example of the timing of projecting the projected light 3A and the timing of receiving the detection light (here, reflected light 3B) when an object is present outside the detection area DR.

[0067] As an example, when motor 402, i.e., rotating unit 300, rotates at a constant speed of, for example, 50 ms (milliseconds) per rotation, and is detected with a detection resolution of 0.5 degrees, light emitting element 102 emits light 3A at a constant time interval of 69.444 μs. In other words, the time interval between successive light projection reference timings emitted by light emitting element 102 is a constant time interval of 69.444 μs.

[0068] For example, if the time from when the projection light 3A is projected to when the detection light is received is T (s), T (s) is the time it takes for the light to travel back and forth, and the one-way time is half of that. Therefore, the speed of light is 3.0 × 10 ８ (m / s), the distance OL to the object is T(s) × 3.0 × 10 ８ It is calculated as (m / s) / 2.

[0069] The ranging control unit 610 calculates the distance OL to the object. The ranging control unit 610 also compares the distance OL to the object with the area detection setting distance DL. If the distance OL to the object is equal to or shorter than the area detection setting distance DL, the ranging control unit 610 determines that the object is present within the detection area DR (see FIGS. 5 and 6). If the distance OL to the object is longer than the area detection setting distance DL, the ranging control unit 610 determines that the object is present outside the detection area DR (see FIGS. 7 and 8).

[0070] 6 and 8 show the temporal positional relationship, indicating that an object is present within the detection area DR when the time difference between the projected light 3A and the detection light is within the area detection set time DT corresponding to the area detection set distance DL. Also, indicating that an object is present outside the detection area DR when the time difference between the projected light 3A and the detection light is outside the area detection set time DT. The area detection set time DT is a time based on the longest distance possible with the projected light 3A (i.e., the area detection set distance DL) and the speed of light. Since it is the time required for light to travel the area detection set distance DL and back, it is calculated by dividing twice the area detection set distance DL by the speed of light (i.e., the area detection set distance DL × 2 / speed of light). Note that the area detection set time DT starts timing immediately after the projection of the projected light 3A.

[0071] <Details of Normal Light Projection Mode> Next, the details of the normal light projection mode will be described.

[0072] In the normal light-projection mode, the light-projection timing generation unit 640 generates each light-projection reference timing for each predetermined rotation angle, that is, at regular time intervals, and the light-projection timing correction unit 650 determines each light-projection reference timing as the respective light-projection timing without shifting the respective light-projection reference timing in time.

[0073] Fig. 9 is a diagram showing a first example of the light projection timing and the light reception timing in the normal light projection mode, Fig. 10 is a diagram showing a second example of the light projection timing and the light reception timing in the normal light projection mode, and Fig. 11 is a diagram showing a third example of the light projection timing and the light reception timing in the normal light projection mode.

[0074] 9 to 11, as an example, the light projection timing generation unit 640 generates the light projection reference timing so as to project the projection light 3A every time there is a rotation of 0.5 degrees relative to the reference angle X degrees, that is, at X+0.5 degrees, X+1.0 degrees, and so on.

[0075] 9 and 10, the detection condition for detecting an object is that the width of the object must be detected. Therefore, it is necessary to detect the detection light at multiple consecutive points, and it is determined that an object is present in the detection area DR when the detection light is received N times consecutively for each projected light 3A within the area detection setting time DT. Here, N=2 is used as an example.

[0076] More specifically, the detection conditions may include a condition for determining that an object is (possibly) present, and this condition may include a condition for detecting multiple points consecutively, since it is necessary to detect the width of the object. The detection conditions may also include a condition for determining that an object is present, and this condition may include detecting the width of the object over multiple revolutions (M revolutions). In this case, detecting over multiple revolutions may include detecting at different angles over multiple revolutions (e.g., the first revolution and the other revolutions). Note that as long as multiple points are detected consecutively over each of the M revolutions, the number of consecutive points may differ. Note that the multiple revolutions here may be consecutive or discontinuous revolutions.

[0077] 9 , at X+0.5 degrees, X+1.0 degrees, X+1.5 degrees, and X+2.0 degrees, reflected light 3B is received at a time point after the area detection setting time DT has elapsed (also referred to as the time point at which the area detection setting time DT has elapsed). Therefore, the ranging control unit 610 determines that no object is present in the detection area DR because the reflected light 3B (detection light) is not received within the area detection setting time DT for the projected light 3A projected at successive light projection reference timings. Therefore, the detection conditions may include a condition for determining that no object is present. These conditions may include, for example, not detecting the width of the object (i.e., not detecting multiple points consecutively) and not detecting the width of the object multiple times consecutively.

[0078] 10 , at X+0.5 degrees and X+2.0 degrees, reflected light 3B is received after the area detection setting time DT has elapsed. Also, at X+1.0 degrees and X+1.5 degrees, reflected light 3B is received before the area detection setting time DT has elapsed. Therefore, the ranging control unit 610 determines that an object is present in the detection area DR because reflected light 3B (detection light) is received consecutively within the area detection setting time DT in response to projected light 3A projected at consecutive light projection reference timings.

[0079] 11, the detection condition for detecting an object is that an object is determined to be present in the detection area DR when the detection light is received N times consecutively for each projected light 3A and M times consecutively for the rotation of the rotating part 300 within the area detection setting time DT. For example, let N=2 and M=2 here. Also, since the object may be moving, the position at which the object is detected may be at a different angle or in a different range.

[0080] 11, whether the rotation of the rotating unit 300 is the Yth rotation or the Y+1th rotation, the reflected light 3B is received at X+1.0 degrees and X+1.5 degrees before the area detection setting time DT has elapsed, as in FIG. 10. In other words, in FIG. 11, the reflected light 3B is received twice in a row, over two consecutive rotations, before the area detection setting time DT has elapsed. Therefore, the distance measurement control unit 610 determines that an object is present in the detection area DR.

[0081] In this way, by tightening the object detection conditions, the object detection device 1 can prevent erroneous detection of objects that do not actually exist, such as floating dust. For example, the object detection device 1 detects the presence or absence of an object within the detection area DR for each detection resolution, and if detection light is received N consecutive times and M consecutive times (N and M are 2 or more) before the area detection setting time DT has elapsed, the ranging control unit 610 determines that an object is present within the detection area DR. The ranging control unit 610 then outputs the determination result to the external input / output circuit 730. The external input / output circuit 730 notifies an external device of the determination result.

[0082] <Details of Shift Light-Projection Mode> Next, details of the shift light-projection mode SM will be described. The shift light-projection mode SM may include one or more shift light-projection modes SM that differ in the method of correcting each light-projection reference timing. The shift light-projection mode SM may include, for example, at least one of shift light-projection modes SM1 to SM5, which will be described later.

[0083] In the shift light-projection mode, similarly to the normal light-projection mode, the light-projection timing generation unit 640 generates a plurality of light-projection reference timings so that light is projected a plurality of times at a constant cycle. In addition, the light-projection timing correction unit 650 determines each light-projection timing by shifting each light-projection reference timing so that the shift time for shifting each light-projection reference timing changes by a constant time α that is longer than the area detection setting time DT.

[0084] Furthermore, in the shift light-projection mode, the light-projection timing generation unit 640 may generate a plurality of light-projection reference timings so that light is projected at regular angles (for example, every 0.5 degrees) during rotation by the rotation unit 300. The light-projection timing correction unit 650 may determine each light-projection timing by shifting each light-projection reference timing so that the shift time for shifting each light-projection reference timing changes by a fixed time α for each regular angle.

[0085] Fig. 12 is a diagram showing an example of the light projection timing and light reception timing when shift light projection mode SM1 is specified. Fig. 13 is a diagram showing an example of the light projection timing and light reception timing when shift light projection mode SM2 is specified. Fig. 14 is a diagram showing an example of the light projection timing and light reception timing when shift light projection mode SM3 is specified. Fig. 15 is a diagram showing an example of the light projection timing and light reception timing when shift light projection mode SM4 is specified. Fig. 16 is a diagram showing an example of the light projection timing and light reception timing when shift light projection mode SM5 is specified.

[0086] 12 to 16, as an example, the light-projection timing generation unit 640 generates the light-projection reference timing so that the projection light 3A is projected every 0.5 degree rotation relative to the reference angle X degree, that is, at X+0.5 degrees, X+1.0 degrees, etc. The projection angle for the kth light shot is X+k×0.5 (degrees), and for example, to project light at an angle between 160 degrees and 200 degrees, X=159.5 degrees and k=1 to 81, and if the maximum number of emissions is Kmax, then the number of emissions is 81.

[0087] 12 to 16, the detection condition for detecting an object is that when the detection light is received N times consecutively for each projected light 3A within a set area detection time DT corresponding to a set area detection distance DL, it is determined that an object is present in the detection area DR. Here, N=2 is used as an example.

[0088] As an example, when motor 402, i.e., rotating unit 300, rotates at a constant speed of, for example, 50 ms (milliseconds) per rotation, and detection is performed with a detection resolution of 0.5 degrees, light emitting element 102 emits light 3A at a constant time interval of 69.444 μs. In other words, the time interval between successive light projection reference timings projected by light emitting element 102 is a constant time interval of 69.444 μs.

[0089] 12 to 16, it is assumed that multiple object detection devices 1 (1A, 1B) are arranged facing each other. Therefore, the projected light 3A projected by the object detection device 1B may be received by one of the object detection devices 1A. It is assumed that the object detection device 1A is set to one of the shift projection modes, and projects the projected light 3A with the projection timing shifted at a fixed interval. It is assumed that the object detection device 1B is set to the normal projection mode, and projects the projected light 3A at a fixed interval. In FIGS. 12 to 16, the projected light 3A projected by the object detection device 1A is indicated as "LA," and the projected light 3A projected by the object detection device 1B is indicated as "LB."

[0090] In FIG. 12, the light-projection timing correction unit 650 determines each light-projection timing by shifting each light-projection reference timing so that the shift time increases by a fixed time α.

[0091] 12 , if the correction amount of the light projection timing as the shift time is α (ns), then the shift time is 0×α when the first light 3A is projected at X+0.5 degrees. The shift time is 1×α when the second light 3A is projected at X+1.0 degrees. The shift time is (k−1)×α when the kth light 3A is projected at X+k×0.5 degrees. In other words, the light projection timing correction unit 650 lengthens the shift time by a fixed time α and adds this gradually increasing shift time to each light projection reference timing, thereby gradually shifting the light projection timing to a later time.

[0092] This allows the object detection device 1 to correct the light-projection timing while minimizing the time shift from the light-projection reference timing, and shift the light-projection timing to a timing close to the originally scheduled light-projection timing. Also, in FIG. 12 , detection light (here, projected light 3A of object detection device 1B) is received within the area detection setting time DT for the first projected light 3A. However, for the second and subsequent projects, detection light is not received within the area detection setting time DT. Therefore, the object detection device 1 can prevent erroneous detection of the presence of an object.

[0093] In FIG. 13, the light-projection timing correction unit 650 determines each light-projection timing by shifting each light-projection reference timing so that the shift time decreases by a fixed time α.

[0094] In FIG. 13 , if the correction amount of the light projection timing as the shift time is α (ns), the shift time is (Kmax-1)×α when the first light 3A is projected at X+0.5 degrees. The shift time is (Kmax-2)×α when the second light 3A is projected at X+1.0 degrees. The shift time is (Kmax-k)×α when the kth light 3A is projected at X+k×0.5 degrees. The shift time is 0×α when the Kmaxth light 3A is projected at X+Kmax×0.5 degrees. In other words, the light projection timing correction unit 650 shortens the shift time by a fixed time α and adds this gradually shortening shift time to each light projection reference timing, thereby gradually shifting the light projection timing back.

[0095] As a result, the object detection device 1 is more likely to be able to avoid receiving projected light 3A from another object detection device 1 (here, object detection device 1B) within the area detection setting time DT at early light projection timings such as the first and second shots, thereby reducing the possibility of false recognition of the presence of an object.

[0096] 14, the light-projection timing correction unit 650 may shift each light-projection reference timing over a predetermined number of shifts (e.g., n shifts) so that the shift time is increased by a fixed time α. The light-projection timing correction unit 650 may then return the light-projection timing to the light-projection reference timing after the predetermined number of shifts have been completed, and may determine each light-projection timing by repeating the same shift of each light-projection reference timing over the predetermined number of shifts. In FIG. 14, n=3 is illustrated as an example.

[0097] Specifically, to repeat the shift count (n times), the shift time can be repeated by shifting the kth light projection by the remainder when (k-1) is divided by n times. Assume that a function outputting the remainder of (k-1) / n is MOD((k-1), n), and the correction amount of the light projection timing as the shift time is α (ns). Also, in FIG. 14 , n=3. In this case, when the first light 3A is projected at X+0.5 degrees, the shift time is MOD(0, 3)×α (= 0×α). When the second light 3A is projected at X+1.0 degrees, the shift time is MOD(1, 3)×α (= 1×α). When the third light 3A is projected at X+1.5 degrees, the shift time is MOD(2, 3)×α (= 2×α). When the third shot of light 3A is projected at X+1.0 degrees, the shift time is MOD(2,3)×α (=2×α). When the fourth shot of light 3A is projected at X+2.0 degrees, the shift time is MOD(3,3)×α (=0×α). Therefore, when n=3, it can be repeated three times. Therefore, when the kth shot of light 3A is projected at X+k×0.5 degrees, the shift time is MOD((k-1),n)×α.

[0098] In other words, the light-projection timing correction unit 650 lengthens the shift time by a fixed time α for a predetermined number of shifts, and gradually shifts the light-projection timing later by adding this gradually longer shift time to each light-projection reference timing. The light-projection timing correction unit 650 then resets the temporal shift of the light-projection reference timing, and gradually shifts the light-projection timing later again by the fixed time α. Thus, the object detection device 1 can prevent the shift time from accumulating and becoming too long, and can prevent a decrease in the frequency of projecting the projected light 3A.

[0099] 15, the light-projection timing correction unit 650 may shift each light-projection reference timing over a predetermined number of shifts (e.g., n shifts) so that the shift time is shortened by a fixed time α. The light-projection timing correction unit 650 may then return the light-projection timing to the light-projection reference timing after the predetermined number of shifts have been completed, and may determine each light-projection timing by repeating the same shift of each light-projection reference timing over the predetermined number of shifts. In FIG. 15, n=3 is illustrated as an example.

[0100] Specifically, to repeat the shift count (n times), the shift time can be changed by subtracting the remainder obtained by dividing (k-1) by n times from n when projecting the kth light. Assume that the function outputting the remainder of (k-1) / n is MOD(k-1,n), and the correction amount of the light projection timing as the shift time is α (ns). Also, assume n=3 in FIG. 15 . In this case, when the first light 3A is projected at X+0.5 degrees, the shift time is (3-(MOD(0,3)))×α (=3×α). When the second light 3A is projected at X+1.0 degrees, the shift time is 3-(MOD(1,3))×α (=2×α). When the third shot of light 3A is projected at X+1.5 degrees, the shift time is 3-(MOD(2,3))×α (=1×α). When the fourth shot of light 3A is projected at X+2.0 degrees, the shift time is 3-(MOD(3,3))×α (=3×α). Therefore, when n=3, it can be repeated three times. Therefore, when the kth shot of light 3A is projected at X+k×0.5 degrees, the shift time is (n-(MOD((k-1),n)))×α.

[0101] In other words, the light-projection timing correction unit 650 shortens the shift time by a fixed time α for a predetermined number of shifts and adds this gradually shortening shift time to each light-projection reference timing, thereby gradually shifting the light-projection timing back. The light-projection timing correction unit 650 then resets the temporal shift of the light-projection reference timing and gradually shifts the light-projection timing back again by the fixed time α. This prevents the shift time from becoming shorter, making it easier for the object detection device 1 to ensure a proper time interval between the light-projection reference timing and the corrected light-projection timing. This effectively prevents the object detection device 1 from receiving projected light 3A from another object detection device 1 (here, object detection device 1B) within the area detection set time DT, reducing the likelihood of erroneous recognition of the presence of an object.

[0102] 16 , the light-projection timing correction unit 650 may determine each light-projection timing by first shifting each light-projection reference timing so that the shift time increases (lengthens) by a fixed time α, and then shifting each light-projection reference timing so that the shift time decreases (shortens) by a fixed time α. Alternatively, the light-projection timing correction unit 650 may determine each light-projection timing by shifting each light-projection reference timing so that the shift time decreases by a fixed time α, and then shifting each light-projection reference timing so that the shift time increases by a fixed time α. FIG. 16 illustrates an example where n=4.

[0103] Specifically, to repeat the shift count (n times), the light projection timing correction unit 650 can handle the shift time by repeatedly switching processing depending on whether the remainder when (k-1) is divided by n times is less than n / 2 or greater than n / 2 when the kth light is projected. Assume that the function outputting the remainder when (k-1) is divided by n is MOD(k-1, n), and the correction amount of the light projection timing as the shift time is α (ns). Also, assume n=4 in FIG. 16 . In this case, for the projection timing of the first light 3A projected at X+0.5 degrees, MOD(0, 4)=0, which is smaller than n / 2 (=2), and therefore the shift time is MOD(0, 4)×α (=0×α). At the projection timing of the second light 3A at X+1.0 degrees, MOD(1,4)=1, which is smaller than n÷2 (=2), so the shift time is (MOD(1,4))×α (=1×α). At the projection timing of the third light 3A at X+1.5 degrees, MOD(2,4)=2, which is greater than or equal to n÷2 (=2), so the shift time is (4-(MOD(2,4)))×α (=2×α). At the projection timing of the fourth light 3A at X+2.0 degrees, MOD(3,4)=3, which is greater than or equal to n÷2 (=2), so the shift time is (4-(MOD(3,4)))×α (=1×α). At the projection timing of the fifth light beam 3A at X+2.5 degrees, MOD(4,4)=0, which is smaller than n÷2 (=2), so the shift time is (MOD(4,4))×α (=0×α). Therefore, at the projection timing of the kth light beam 3A at X+k×0.5 degrees, the shift time is (MOD((k-1),n))×α when MOD((k-1),n) is smaller than n÷2, and is (n-(MOD((k-1),n)))×α when MOD((k-1),n) is n÷2 or greater. The light projection timing correction unit 650 may correct the light projection reference timing so as to repeat such changes in the shift time.

[0104] Even with such a peak-shaped or valley-shaped light projection reference timing, the object detection device 1 can prevent the object detection device 1 from receiving projected light 3A from another object detection device 1 within the area detection setting time DT, thereby preventing the object from being mistakenly recognized as being present within the detection area DR.

[0105] The fixed time α is set to be greater than the maximum measurable interval (maximum detectable interval) until the TDC 500 times out. Specifically, if the maximum measurable interval (maximum detectable interval) is L = 4500 mm, the speed of light is 3.0 × 10^8 m / s, so the time it takes light to travel back and forth through L = 4500 mm is T = L × 2 ÷ speed of light = 30 (nsec). Therefore, the light projection timing correction unit 650 sets the value of α (ns), which is the basis of the shift time as the timing correction amount, to be greater than the above T.

[0106] FIG. 17 is a diagram showing an example of the light projection timing when another shift light projection mode SM6 is specified.

[0107] The light-projection timing correction unit 650 determines each light-projection timing by incrementally shifting the light-projection reference timing in the ± direction for each scan rotation, i.e., for each rotation of the rotating unit 300, in accordance with the shift light-projection mode SM6. The scan rotation here may be a rotation of a predetermined angle within one rotation of the rotating unit 300 as described above, or may be a rotation of one rotation of the rotating unit 300. The shift time for incremental shifting is increased or decreased by the fixed time α as described above. The light-projection timing correction unit 650 determines each light-projection timing so that light is projected by a time shift of the fixed time α for each scan rotation relative to the light-projection reference timing. After determining each light-projection timing by shifting it by the set number of shifts, the light-projection timing correction unit 650 projects light at the light-projection reference timing in the next scan rotation. Thereafter, the light-projection timing correction unit 650 similarly determines each light-projection timing while shifting the light-projection reference timing by the fixed time α.

[0108] The fixed time α on which the shift time is based must be greater than the time it takes for light to go back and forth, T = L × 2 ÷ speed of light = 30 (nsec), calculated from the maximum measurable section (maximum detectable section) L = 4500 mm, so for example, with a margin of twice this, it is 60 ns. In this case, the light is projected at intervals of 69.444 μs, so the maximum number of shifts is 1157, calculated by dividing the light projection interval by the fixed time α.

[0109] In this way, when one object detection device 1A is set to normal light projection mode and the other object detection device 1B is set to shift light projection mode, the object detection device 1A can suppress interference caused by the projected light 3A of the other object detection device 1B, as shown in Figures 12 to 16, and can suppress erroneous detection of objects.

[0110] Furthermore, by setting the shift time between two successive light-projection timings to differ by a fixed time α that is longer than the area detection set time DT, even if interference occurs at the earlier light-projection timing, the interference can be suppressed at the later light-projection timing. This is because the fixed time α is longer than the area detection set time DT, and therefore it is possible to prevent the periodically projected light from being received within the area detection set time DT at the later light-projection timing.

[0111] When one object detection device 1A is set to normal light projection mode and the other object detection device 1B is set to shift light projection mode, the object detection device 1A can suppress interference caused by the projected light 3A of the other object detection device 1B, as shown in Figures 12 to 16, and can suppress erroneous detection of objects.

[0112] Furthermore, as in the normal light projection mode, the object detection device 1 tightens the object detection conditions in the shift light projection mode, thereby preventing false detection of non-existent objects, such as floating dust particles. For example, the object detection device 1 detects the presence or absence of an object within the detection area DR for each detection resolution. If the object detection device 1 receives detection light N consecutive times and M consecutive times (N and M are 2 or greater) before the area detection setting time DT has elapsed, the ranging control unit 610 determines that an object is present within the detection area DR. The ranging control unit 610 then outputs the determination result to the external input / output circuit 730. The external input / output circuit 730 notifies an external device of the determination result.

[0113] In this way, the object detection device 1 of this embodiment can switch between multiple light projection modes, thereby preventing continuous interference caused by the projected light 3A projected by other object detection devices when multiple object detection devices 1 are installed. This prevents the object detection device 1 from erroneously detecting the presence of an object in space when no object actually exists due to interference.

[0114] Furthermore, by setting the shift light projection mode, the object detection device 1 can flexibly speed up or slow down the light projection timing to prevent interference. For example, even if the light projection reference timing is generated at the same fixed cycle, the probability of interference can be increased by setting different light projection modes. When a different light projection mode is set, it is possible to prevent the continuation of interference caused by the projected light 3A projected by another object detection device.

[0115] Furthermore, the object detection device 1 may have a high light receiving sensitivity of the light receiving element 103 to detect as much of the projected light as possible. In this case, if multiple object detection devices 1 are arranged opposite each other, there is a high probability of interference. Furthermore, if stray light from production equipment and factory automation equipment in the factory where the object detection device 1 is installed is also included, the possibility of interference becomes even higher. In response to this, the object detection device 1 can project light at each light projection timing with the light projection reference timing regularly corrected, thereby suppressing the occurrence of interference.

[0116] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0117] <Outline of the Present Embodiment> As described above, the present disclosure describes at least the following matters. Note that, in parentheses, examples of components corresponding to the above-described embodiment are shown, but the present disclosure is not limited to these.

[0118] (Item 1) An object detection device (object detection device 1) comprising: a light-emitting element (light-emitting element 102) that emits projection light (projection light 3A) in accordance with a light-projection timing; a light-receiving element (light-receiving element 103) that receives light reflected from an object when the projection light is emitted and generates a light-receiving signal; and a controller (controller 600), wherein the controller generates a plurality of light-projection reference timings so as to emit light a plurality of times at a constant cycle, and is capable of setting a first light-projection mode (normal light-projection mode) in which light is projected using each light-projection reference timing as the light-projection timing, and a second light-projection mode (shifted light-projection mode) in which light is projected in accordance with each light-projection timing obtained by shifting each light-projection reference timing in time, and in the second light-projection mode, the object detection device (object detection device 1) determines each light-projection timing by shifting each light-projection reference timing so that the shift time for shifting each light-projection reference timing changes by a constant time (constant time α).

[0119] This allows the object detection device to prevent continuous interference caused by the light projected by other object detection devices, even if multiple object detection devices are placed nearby, thereby reducing the risk of falsely detecting the presence of an object.

[0120] (Item 2) The object detection device according to Item 1, wherein the controller, in the second light-projection mode, shifts the light-projection reference timings so that the shift times change by the fixed time intervals over a predetermined number of shifts, returns the light-projection timings to the light-projection reference timings after the predetermined number of shifts have been completed, and determines the light-projection timings so that the shifting of the light-projection reference timings over the predetermined number of shifts is repeated.

[0121] This prevents the time difference between the light-projection reference timing and the corrected light-projection timing from becoming too long due to accumulated changes in the shift time, thereby preventing the object detection device from reducing the frequency of projecting light or detecting an object in a detection direction different from the originally intended detection direction.

[0122] (Item 3) The object detection device according to Item 1 or 2, wherein in the second light-projection mode, the controller determines the light-projection timings by shifting the light-projection reference timings so that the shift times increase by the fixed time.

[0123] This allows the object detection device to correct the light-projection timing while minimizing the time shift from the light-projection reference timing, for example by gradually increasing the light-projection reference timing. Thus, the object detection device can shift the light-projection timing so that it is closer to the originally scheduled light-projection timing.

[0124] (Item 4) The object detection device according to item 1 or 2, wherein in the second light-projection mode, the controller determines the light-projection timings by shifting the light-projection reference timings so that the shift times are reduced by the fixed time.

[0125] As a result, the object detection device can be expected to be able to confirm whether or not it has received projected light 3A from another object detection device at an early stage of light projection timing by gradually shortening the shift time by a fixed amount, for example, starting from a timing that is as far away from the light projection reference timing after the light projection reference timing. Therefore, the object detection device is likely to be able to avoid receiving interfering light within the longest time corresponding to the longest distance that can be measured using projected light, and the possibility of erroneous object detection can be reduced.

[0126] (Item 5) The object detection device according to item 1 or 2, wherein in the second light-projection mode, the controller determines each of the light-projection timings by shifting the light-projection reference timings so that the shift time increases by the fixed time increments, and then shifting the light-projection reference timings so that the shift time decreases by the fixed time increments, or by shifting the light-projection reference timings so that the shift time decreases by the fixed time increments, and then shifting the light-projection reference timings so that the shift time increases by the fixed time increments, thereby determining each of the light-projection timings.

[0127] This allows the object detection device to prevent continuous interference from light projected by other object detection devices, even when the shift time is increased or decreased by a fixed amount multiple times in succession, thereby reducing false detection of the presence of an object.

[0128] (Item 6) The object detection device according to any one of items 1 to 5, further comprising a rotation unit (rotation unit 300) that projects the projected light along a first plane (top or bottom surface of fixed unit 100, floor surface, or housing surface of a specified device) and rotates the projection direction of the projected light along the first plane, wherein the controller controls the rotation unit to rotate at a constant speed, generates the plurality of light-projection reference timings so that light is projected at each constant angle in the rotation by the rotation unit, and in the second light-projection mode, determines each light-projection timing by shifting each light-projection reference timing so that the shift time for shifting each light-projection reference timing changes by the constant time for each constant angle.

[0129] This means that when the object detection device is able to detect objects by projecting light in various directions through rotation by the rotating part, it is possible to prevent interference from occurring continuously due to projected light projected by other object detection devices, thereby suppressing erroneous detection of objects.

[0130] (Item 7) The object detection device according to any one of Items 1 to 6, wherein the certain time is longer than a time (area detection set time DT) based on the longest distance measurable by the projected light (area detection set distance DL) and the speed of light.

[0131] As a result, even if interference occurs at a previous light-projection timing, the object detection device can suppress the interference at a later light-projection timing because the periodically projected light can be prevented from being received within the above-mentioned time (area detection set time DT) at the later light-projection timing.

[0132] (Item 8) The object detection device according to any one of items 1 to 7, wherein the controller acquires a clock generated by a clock generator, and determines the constant period based on the clock.

[0133] This allows the object detection device to determine the constant period even if the operation of the rotation angle detector is inaccurate.

[0134] (Item 9) The object detection device according to any one of items 1 to 7, further comprising: acquiring the rotation angle detected by a rotation angle detector (rotation angle detector 403) that detects the rotation angle of the rotating part; and determining the constant period based on the rotation angle.

[0135] This allows the object detection device to determine a constant period even if the clock generator operates inaccurately.

[0136] (Item 10) An object detection method comprising: projecting projection light in accordance with a light-projection timing; receiving light reflected from an object and generating a light-receiving signal; generating a plurality of light-projection reference timings so as to project light a plurality of times at a constant period; and setting a light-projection mode, wherein the light-projection mode can be set to a first light-projection mode in which light is projected using each light-projection reference timing as the light-projection timing, and a second light-projection mode in which light is projected in accordance with each light-projection timing obtained by shifting each light-projection reference timing in time, and setting the light-projection mode includes, when the second light-projection mode is set as the light-projection mode, determining each light-projection timing by shifting each light-projection reference timing so that a shift time by which each light-projection reference timing is shifted changes by a constant time.

[0137] This provides the same effect as item 1.

[0138] This application is based on a Japanese patent application (Patent Application No. 2023-221086) filed on December 27, 2023, the contents of which are incorporated herein by reference.

[0139] The present disclosure is useful for an object detection device and an object detection method that can suppress false detection of the presence of an object due to interference from projected light from another object detection device, even when another object detection device is placed opposite.

[0140] REFERENCE SIGNS LIST 1 object detection device 3A projected light 3B reflected light 10 outer cover part 11 wavelength window 100 fixed part 101 substrate 102 light emitting element 103 light receiving element 104 condenser lens 105 collimator lens 106 coil 107 photointerrupter 108 amplifier circuit 109 laser drive circuit 300 rotating part 301 rotating member 302 magnet 303 reflecting mirror 311 rib 401 comparator 402 motor 403 rotation angle detector 404 motor drive circuit 500 TDC 600 controller 610 distance measurement control part 620 distance calculation part 630 rotation control part 640 light projection timing generation part 650 light projection timing correction part

Claims

1. An object detection device, comprising: a light-emitting element that projects projection light according to projection timing; a light-receiving element that receives reflected light reflected by an object from the projection light and generates a light-receiving signal; and a controller, wherein the controller generates a plurality of light projection reference timings to perform light projection a plurality of times at a constant period, and can set a first light projection mode in which each light projection reference timing is used as each light projection timing to perform light projection, and a second light projection mode in which light projection is performed according to each light projection timing obtained by temporally shifting each light projection reference timing. In the second light projection mode, each light projection reference timing is shifted to determine each light projection timing such that a shift time for shifting each light projection reference timing changes by a constant time each time.

2. The object detection device according to claim 1, wherein in the second light projection mode, the controller shifts each light projection reference timing such that the shift time changes by the constant time each time over a predetermined number of shift times, returns the light projection timing to the light projection reference timing after the end of the predetermined number of shift times, and determines each light projection timing so as to repeat the shift of each light projection reference timing over the predetermined number of shift times.

3. The object detection device according to claim 1 or 2, wherein in the second light projection mode, the controller shifts each light projection reference timing such that the shift time increases by the constant time each time to determine each light projection timing.

4. The object detection device according to claim 1 or 2, wherein in the second light projection mode, the controller shifts each light projection reference timing such that the shift time decreases by the constant time each time to determine each light projection timing.

5. The object detection device according to claim 1 or 2, wherein in the second light projection mode, the controller shifts each light projection reference timing such that the shift time increases by the constant time each time, and then shifts each light projection reference timing such that the shift time decreases by the constant time each time to determine each light projection timing, or shifts each light projection reference timing such that the shift time decreases by the constant time each time, and then shifts each light projection reference timing such that the shift time increases by the constant time each time to determine each light projection timing.

6. The apparatus further comprises a rotating unit configured to project the projection light along a first plane and rotate the projection direction of the projection light along the first plane. The controller controls the rotating unit to rotate at a constant speed, generates the plurality of light projection reference timings to project light at each fixed angle during the rotation by the rotating unit, and in the second light projection mode, shifts each light projection reference timing to determine each light projection timing such that the shift time for shifting each light projection reference timing by each fixed angle changes by the fixed time. The object detection apparatus according to claim 1 or 2.

7. The fixed time is longer than a time based on the longest distance measurable by the projection light and the speed of light. The object detection apparatus according to claim 1 or 2.

8. The controller acquires a clock generated by a clock generator and determines the fixed period based on the clock. The object detection apparatus according to claim 1 or 2.

9. The rotation angle is acquired from a rotation angle detector that detects the rotation angle of the rotating unit, and the fixed period is determined based on the rotation angle. The object detection apparatus according to claim 6.

10. A method for object detection, comprising: projecting projection light according to a light projection timing; receiving reflected light reflected by an object from the projection light to generate a received light signal; generating a plurality of light projection reference timings to project light a plurality of times at a fixed period; setting a light projection mode; wherein the light projection mode can be set to a first light projection mode in which each light projection reference timing is used as each light projection timing, and a second light projection mode in which light is projected according to each light projection timing obtained by temporally shifting each light projection reference timing; and setting the light projection mode includes, when the second light projection mode is set as the light projection mode, shifting each light projection reference timing to determine each light projection timing such that the shift time for shifting each light projection reference timing changes by a fixed time.

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