Distance measuring device and distance measuring method

Abstract

This distance measuring device comprises a light emitting element that projects pulse wave projected light, a light receiving element that receives reflected light, and a controller that measures the distance to an object on the basis of the time between a light emission timing of the light emitting element and a light reception timing of the light receiving element, wherein, among a measured first distance, at least one second distance measured after the first distance, and a third distance measured after the second distance, if the first distance and the third distance are estimated not to be abnormal and the second distance is estimated to be abnormal, the controller uses the first distance or the third distance to complement the second distance.

Description

Distance measuring device and distance measuring method

[0001] The present disclosure relates to a distance measurement device and a distance measurement method.

[0002] Distance measuring devices that transmit pulse waves, measure the time required for the reflected waves to return, and calculate the distance to an object are known. Patent Document 1 discloses a distance measuring device that includes: a transmitting means for transmitting pulse waves, a receiving means for receiving the waves reflected from an object, a time measuring means for measuring the time required from the transmission of the pulse waves to the detection of the reflected waves, a pulse width measuring means for capturing the waveform of the reflected waves received by the receiving means and measuring the pulse width of the received waveform, a correction value calculating means for calculating a correction value for the required time corresponding to the pulse width of the received waveform based on the input / output characteristics of the active region and the saturated region of the receiving means, and a distance calculating means for correcting the required time measured by the time measuring means using the correction value and multiplying it by the propagation speed of the pulse waves to calculate the distance to the object.

[0003] Japanese Patent Application Publication No. 8-179032

[0004] Because the received waveform of the actual reflected wave varies in level, the comparator may not be able to perform normal binarization for the received waveform with a level near the threshold, and may output an abnormal signal. The distance to the object calculated using such an abnormal signal may be unreliable and erroneous. In other words, an incorrect distance may be output.

[0005] An object of the present disclosure is to provide a technology that prevents a distance measurement device from outputting an erroneous distance.

[0006] A distance measuring device according to one embodiment comprises a light-emitting element that projects pulse wave projection light, a light-receiving element that receives light reflected from an object when the projection light is reflected, and a controller that measures the distance to the object based on the time between the light-emitting element's light-emitting timing and the light-receiving element's light-receiving timing, wherein the controller complements the second distance using the first distance or the third distance when, among a measured first distance, at least one second distance measured after the first distance, and a third distance measured after the second distance, the first distance and the third distance are estimated to be normal and the second distance is estimated to be abnormal.

[0007] A distance measurement method according to one embodiment measures the distance to an object based on the time between the light-emitting timing when a light-emitting element projects pulse wave projection light and the light-receiving timing when a light-receiving element receives the reflected light of the projection light reflected by the object, and if, among a measured first distance, at least one second distance measured after the first distance, and a third distance measured after the second distance, the first distance and the third distance are estimated to be normal and the second distance is estimated to be abnormal, the first distance or the third distance is used to complement the second distance.

[0008] According to the present disclosure, it is possible to prevent a distance measurement device from outputting an erroneous distance.

[0009] FIG. 1 is a perspective view of an external appearance of a distance measuring device according to the first embodiment; FIG. 2 is a longitudinal sectional view of a distance measuring device according to the first embodiment; FIG. 3 is a block diagram showing an example of a functional configuration of a distance measuring device according to the first embodiment; FIG. 4 is a diagram for explaining a signal input to a comparator according to the first embodiment and a signal output from the comparator; FIG. 5 is a block diagram showing an example of a functional configuration of a TDC according to the first embodiment; FIG. 6 is a diagram for explaining a method of measuring TOF and a received light pulse width by a TDC according to the first embodiment; FIG. 7 is a diagram for explaining an operating condition under which a TDC according to the first embodiment can normally measure TOF and a received light pulse width;

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with appropriate reference to the drawings. However, more detailed description than necessary may be omitted. For example, detailed descriptions of well-known matters and redundant 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] (Embodiment 1) <Physical configuration of distance measurement device> Fig. 1 is an external perspective view of a distance measurement device 1 according to embodiment 1. Fig. 2 is a longitudinal sectional view of the distance measurement device according to embodiment 1. Fig. 2 corresponds to the AA sectional view of the distance measurement device 1 shown in Fig. 1.

[0012] As shown in FIGS. 1 and 2, the distance measurement device 1 includes a fixed part 100, a rotating part 300, and an outer cover part 10.

[0013] 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 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.

[0014] For ease of explanation, as shown in FIG. 1, the axis perpendicular to the top surface (or bottom surface) of the fixed unit 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 distance measurement device 1 shown in FIG. 1 may be used upside down. The A-A cross-sectional view shown in FIG. 2 corresponds to a cross-sectional view in the YZ plane.

[0015] 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).

[0016] 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 the projection light (hereinafter referred to as projection light 3A) projected laterally from a portion of the side surface of the rotating unit 300 rotates around the rotation axis C. Accordingly, the projection light 3A and the area where distance measurement can be performed using the projection light 3A (hereinafter referred to as the distance measurement area) also rotate. As described below, the distance measurement device 1 measures the distance to an object in the distance measurement area based on the time difference (Time of Flight (TOF)) between the timing when the projection light 3A is projected and the timing when the light reflected from the projection light 3A by an object in the distance measurement area (hereinafter referred to as reflected light 3B) is received. As the rotating unit 300 rotates around the rotation axis C, the distance measurement device 1 can measure the distance to an object in the distance measurement area 360 degrees around it in the horizontal direction.

[0017] The fixed part 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 part 300 includes a rotating member 301, a magnet 302, and a reflecting mirror 303.

[0018] The coil 106 of the fixed part 100 and the magnet 302 of the rotating part 300 form a hollow motor 402 (see FIG. 3). When the motor 402 is driven, the rotating part 300 rotates around the rotation axis C.

[0019] The substrate 101 is, for example, a printed circuit board (PCB), and includes a comparator 401, a TDC 500, and a controller 600 (see FIG. 3), which will be described later. Note that TDC is an abbreviation for Time to Digital Converter.

[0020] The light emitting element 102 is arranged along the rotation axis C and projects the projection light 3A upward.

[0021] The collimator lens 105 corrects the projection light 3A projected from the light emitting element 102 to be approximately parallel light and outputs it upward.

[0022] The reflecting mirror 303 is provided on the rotating member 301 so as to reflect, in the horizontal direction (direction along the XY plane), the parallel light that is projected upward from the light-emitting element 102 and corrected by the collimator lens 105. 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 distance measurement area.

[0023] 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.

[0024] The condenser lens 104 condenses the reflected light 3B reflected downward by the reflecting mirror 303 and outputs the condensed light downward.

[0025] The light receiving element 103 receives the reflected light 3 B condensed by the condenser lens 104 .

[0026] The rotating member 301 has a plurality of ribs 311 spaced at regular intervals. The photointerrupter 107 is positioned so as to detect the passage of one rib 311. By using the photointerrupter 107 to detect and count the passage of one rib 311, a controller 600 (described later) can detect the rotational position (rotation angle) of the rotating member 301 (i.e., the rotating unit 300). Therefore, the photointerrupter 107 and the ribs 311 can form a rotational position detector 403 (see FIG. 3 ) (described later).

[0027] <Functional Configuration of Distance Measuring Device> FIG. 3 is a block diagram showing an example of the functional configuration of the distance measuring device 1 according to the first embodiment.

[0028] The distance measurement device 1 includes a light emitting element 102, a light receiving element 103, a comparator 401, a TDC 500, a motor 402, a rotational position detector 403, and a controller 600. The configuration shown in Fig. 3 is an example, and at least one of the comparator 401 and the TDC 500 may be included in the controller 600.

[0029] The light-emitting element 102 projects pulsed projection light 3A in response to an input pulse signal (hereinafter referred to as an input pulse signal). Note that in FIG. 3, the input of the input pulse signal is expressed as START. The projection light 3A may be interpreted as a laser beam or a beam. The light-receiving element 103 receives the reflected light 3B as described above, and outputs a light-receiving signal in response to the light-receiving level.

[0030] 4 is a diagram for explaining signals input to and output from the comparator 401 according to the first embodiment. Next, the comparator 401 will be described with reference to FIG.

[0031] As shown in Fig. 4(a), the comparator 401 receives a light-receiving signal from the light-receiving element 103, and outputs a pulse signal (hereinafter referred to as a light-receiving pulse signal) that has a predetermined High level during the period when the level of the light-receiving signal is equal to or higher than a predetermined comparator threshold, and a predetermined GND level during the period when the level of the light-receiving signal is below the comparator threshold. Note that the High level is higher than the GND level. In Fig. 3, the output of the light-receiving pulse signal is expressed as STOP.

[0032] When the level of the input light reception signal is less than the comparator threshold value over the entire period, the comparator 401 outputs a light reception pulse signal at the GND level, as shown in FIG. 4(c).

[0033] However, when the maximum level of the input light receiving signal is near the comparator threshold, the comparator 401 may output a light receiving pulse signal with an abnormal waveform that is not sure whether it is a high level or a ground level, as shown in Fig. 4(b) In this embodiment, a method will be described that can output a highly reliable distance measurement result even when the comparator 401 outputs a light receiving pulse signal with such an abnormal waveform.

[0034] Fig. 5 is a block diagram showing an example of the functional configuration of the TDC 500 according to the first embodiment. Fig. 6 is a diagram for explaining a method for measuring the TOF and the received light pulse width by the TDC 500 according to the first embodiment. Fig. 7 is a diagram for explaining operating conditions under which the TDC 500 according to the first embodiment can normally measure the TOF and the received light pulse width. Next, the TDC 500 will be described with reference to Figs. 5, 6, and 7.

[0035] The TDC 500 includes a measurement unit 501, a data register 502, a status register 503, and an input / output I / F 504. Note that "I / F" is an abbreviation for Interface.

[0036] The measurement unit 501 receives an input pulse signal as shown in FIG. 6( a) at the same timing as the input pulse signal is input to the light-emitting element 102 (START). The comparator 401 receives a light-receiving signal as shown in FIG. 6( b) from the light-receiving element 103 and outputs a light-receiving pulse signal as shown in FIG. 6( c). The measurement unit 501 receives a light-receiving pulse signal as shown in FIG. 6( c) at the same timing as the comparator 401 outputs the light-receiving pulse signal (STOP). The measurement unit 501 measures the time from the input pulse signal to the input light-receiving pulse signal (i.e., TOF) and the pulse width of the light-receiving pulse signal (hereinafter referred to as the light-receiving pulse width). The measurement unit 501 writes the measured TOF and light-receiving pulse width to the data register 502. The measurement unit 501 also writes operating information indicating the operating state at the time of measurement to the status register 503. The operation information may include the number of rising edges and the number of falling edges of the input pulse signal and the number of rising edges and the number of falling edges of the received light pulse signal. The operation information may also include information indicating whether the received light pulse signal was input within a predetermined time from the timing of input of the input pulse signal (i.e., whether a timeout has occurred).

[0037] The input / output I / F 504 outputs the measurement results of the TOF and the received light pulse width written in the data register 502. The input / output I / F 504 outputs operation information written in the status register 503 in response to an external request or together with the output of the measurement results of the TOF and the received light pulse width.

[0038] 7, there are operating conditions under which TOF can be measured normally in the measurement unit 501. In FIG. 7, the horizontal axis indicates time, and the vertical axis indicates the level of the received light pulse signal.

[0039] As shown in area A in FIG. 7, when the level of the received light pulse signal is less than a predetermined threshold, the measuring unit 501 does not detect the received light pulse signal.

[0040] As shown in area B of Figure 7, even if the level of the received light pulse signal is equal to or greater than a predetermined threshold, if the time from when the input pulse signal is input to when the received light pulse signal is input or the pulse width of the received light pulse signal is shorter than a predetermined minimum value (min), the measurement unit 501 will result in an abnormal measurement.

[0041] As shown in area C of Figure 7, even if the level of the received light pulse signal is equal to or greater than a predetermined threshold, the measurement unit 501 times out if the time from when the input pulse signal is input to when the received light pulse signal is input or the pulse width of the received light pulse signal is longer than a predetermined maximum value (max).

[0042] As shown in region D of Figure 7, the measurement unit 501 can measure the TOF normally when the level of the received light pulse signal is equal to or higher than a predetermined threshold value, and the time from when the input pulse signal is input to when the received light pulse signal is input or the pulse width of the received light pulse signal is between a predetermined minimum value (min) and a maximum value (max).

[0043] As shown in region E in Fig. 7, when the level of the received light pulse signal is near a predetermined threshold (see Fig. 4(b)), the measurement unit 501 performs an abnormal measurement. In this embodiment, the output of an unreliable distance measurement result due to such an abnormal measurement is prevented.

[0044] Returning to the description of FIG.

[0045] As described above, the motor 402 is configured by the coil 106 and the magnet 302, and rotates the rotating member 301 around the central axis C.

[0046] As described above, the rotation position detector 403 is composed of the rib 311 of the rotating member 301 and the photointerrupter 107, and outputs a start signal at a predetermined rotation angle resolution of the rotating part 300. This start signal is used as a signal indicating the timing of light emission.

[0047] The controller 600 performs processes such as calculating the distance to an object present in the ranging area (hereinafter referred to as the object distance) and controlling the motor 402. The controller 600 includes a ranging control unit 601, a distance calculation unit 602, a storage unit 603, an interpolation unit 604, and a motor control unit 605.

[0048] The distance measurement control unit 601 receives a start signal from the rotation position detector 403. The distance measurement control unit 601 outputs a light emission pulse signal (START) to the light emitting element 102 and the TDC 500 at the timing when the start signal is input.

[0049] The ranging control unit 601 receives the measurement results of the TOF and the received light pulse width from the TDC 500. The ranging control unit 601 acquires, from the TDC 500, operation information corresponding to the input measurement results of the TOF and the received light pulse width.

[0050] The distance measurement control unit 601 includes a TDC abnormality determination unit 611. The TDC abnormality determination unit 611 determines (estimates) whether the TOF or received light pulse width measurement results are abnormal based on the measurement results themselves or operation information corresponding to the measurement results. For example, if the TOF measurement results or the received light pulse width measurement results are outside a predetermined range, the TDC abnormality determination unit 611 determines (estimates) that the TOF and received light pulse width measurement results are abnormal. For example, if the operation information indicates that the number of rising edges and the number of falling edges of the received light pulse signal do not match, the TDC abnormality determination unit 611 determines (estimates) that the TOF and received light pulse width measurement results are abnormal. If the TDC abnormality determination unit 611 determines (estimates) that the TOF or received light pulse width measurement results are abnormal, it outputs an abnormality flag indicating that the TOF and received light pulse width measurement results are abnormal to the distance calculation unit 602.

[0051] The distance calculation unit 602 receives the measurement results of the TOF and the received light pulse width from the TDC 500. If the measurement results of the TOF and the received light pulse width are abnormal, the distance calculation unit 602 receives an abnormality flag from the distance measurement control unit 601.

[0052] The distance calculation unit 602 calculates the object distance based on the measurement results of the TOF and the received light pulse width. The time indicated by TOF is the time (round trip time) from when the projected light 3A is projected to when the reflected light 3B is received, and is approximately twice the time it takes for the projected light 3A to reach the object. Therefore, the distance calculation unit 602 first calculates a basic distance (called the edge distance) using (the propagation speed of the projected light 3A x TOF / 2). Next, the distance calculation unit 602 corrects this edge distance according to the measurement results of the received light pulse width at that time to calculate the object distance.

[0053] The distance calculation unit 602 stores the calculated object distance in the storage unit 603. At this time, if an abnormality flag is associated with the measurement results of the TOF and the light-receiving pulse width used to calculate the object distance, the distance calculation unit 602 stores the object distance in the storage unit 603 in association with the abnormality flag.

[0054] The storage unit 603 stores three consecutive object distances (i.e., three consecutive rotation angles). The storage unit 603 also stores information indicating whether an abnormality flag is associated with the object distance. The storage unit 603 may be configured with a volatile storage medium and / or a non-volatile storage medium.

[0055] The complementing unit 604 outputs the second object distance of the three object distances stored in the storage unit 603. However, if an abnormality flag is associated with the second object distance of the three object distances stored in the storage unit 603, the complementing unit 604 complements the second object distance using the first and / or third object distance, and outputs the complemented second object distance. Note that, although details of this process will be described later, this results in a highly reliable object distance being output.

[0056] The motor control unit 605 controls the rotation speed of the motor 402. For example, the motor control unit 605 controls the motor 402 so that the rotation speed is constant.

[0057] <Smallest Object to Which Distance Can Be Measured> FIG. 8 is a diagram for explaining the smallest object to which distance can be measured according to the first embodiment.

[0058] If the difference between the distances of two adjacent objects is less than a predetermined threshold, the distance calculation unit 602 uses the object distance. That is, as shown in FIG. 8 , the smallest measurable object size is one that can reflect two adjacent projected beams of light 3A. In other words, an object that is small enough to reflect only one projected beam of light 3A is not detected as a measurement target. This prevents the distance measurement device 1 from accidentally detecting minute particles of dust or dirt in the air as a measurement target.

[0059] <Flowchart> Fig. 9 is a flowchart showing an example of processing by the controller 600 according to embodiment 1. Next, processing performed by the controller 600 will be described with reference to Fig. 9 .

[0060] The distance measurement control unit 601 waits until a start signal is input from the rotational position detector 403 (S101: NO), and when the input of the start signal is detected (S101: YES), the process proceeds to the next step S102.

[0061] The distance measurement control unit 601 performs predetermined start settings (for example, initialization) on the TDC 500 (S102).

[0062] The distance measurement control unit 601 outputs a light emission pulse signal to the light emitting element 102 and the TDC 500 (S103).

[0063] The TDC 500 waits until a light receiving pulse signal is input from the comparator 401 (S104: NO), and if a light receiving pulse signal is input (S104: YES), it outputs the measurement results of the TOF and light receiving pulse width, and proceeds to step S105.

[0064] The distance calculation unit 602 acquires the edge distance and / or pulse width from the measurement results of the TOF and the received light pulse width input from the TDC 500 (S105). Then, the ranging control unit 601 acquires operation information from the TDC 500 and determines whether to associate an abnormality flag with the object distance to be calculated later based on the operation information (S106). For example, if the operation information indicates that the number of rising edges and the number of falling edges of the received light pulse signal do not match, or if the edge distance or the received light pulse width is outside a predetermined range, the TDC abnormality determination unit 611 of the ranging control unit 601 determines that an abnormality flag should be associated with the calculated object distance.

[0065] If the distance measurement control unit 601 determines that an abnormality flag is not associated (S106: YES), the process proceeds to step S108.

[0066] If it is determined that an abnormality flag should be associated (S106: NO), the distance measurement control unit 601 sets the abnormality flag to be associated with the object distance to be calculated later (S107), and the process proceeds to step S108.

[0067] The distance calculation unit 602 calculates the object distance based on the edge distance and the light-receiving pulse width (S108).

[0068] The distance calculation unit 602 stores the calculated object distance in the storage unit 603. At this time, if an abnormality flag is associated with the object distance when the object distance is calculated, the distance calculation unit stores the object distance in the storage unit 603 in association with the abnormality flag (S109).

[0069] The memory unit 603 stores at least the object distance calculated this time (hereinafter referred to as the third object distance), as well as the object distance calculated last time (hereinafter referred to as the second object distance) and the object distance calculated two times before last (hereinafter referred to as the first object distance).

[0070] The complementing unit 604 determines whether or not an abnormality flag is associated with the second object distance stored in the storage unit 603 (S110).

[0071] If an abnormality flag is associated with the second object distance (S110: YES), the complementing unit 604 complements the second object distance using the first object distance or the third object distance (S111). In this case, the second object distance becomes the object distance after complementation. Details of the complementing method will be described later. Then, the process proceeds to step S112.

[0072] If the complementing unit 604 determines that the second object distance is not associated with an abnormality flag (S110: NO), the process proceeds to step S112.

[0073] The complementing unit 604 outputs the second object distance (S112), and the process returns to step S101.

[0074] By the above processing, if an abnormality flag is associated with the second object distance, i.e., if the reliability of the second object distance is low, the second object distance is complemented with an object distance with high reliability and output.

[0075] <Method of Complementing Second Object Distance> Fig. 10 is a diagram for explaining a method of complementing when an abnormality flag is associated with the second object distance according to embodiment 1. Fig. 11 is a diagram showing an example of storage of the first object distance, the second object distance, and the third object distance in storage unit 603 according to embodiment 1. Next, with reference to Figs. 10 and 11 , the method of complementing the second object distance performed in step S113 of Fig. 9 will be described in detail.

[0076] 10 and 11 , suppose that an object distance d1 for a rotation angle θ1 is measured at time t=1, an object distance d2 for a rotation angle θ2 is measured at time t=2, an object distance d3 for a rotation angle θ3 is measured at time t=3, an object distance d4 for a rotation angle θ4 is measured at time t=4, and an object distance d5 for a rotation angle θ5 is measured at time t=5. Furthermore, suppose that an abnormality flag is associated with the object distance d3 and the object distance d5. The rotation angle θ indicates an angle from a predetermined reference angle (0 degrees).

[0077] First, when t = 3, the storage unit 603 stores the object distance d1 when t = 1, the object distance d2 when t = 2, and the object distance d3 when t = 3. In this case, the complement unit 604 outputs the object distance d2 as is, since no abnormality flag is associated with the second object distance d2.

[0078] Next, when t = 4, the storage unit 603 stores the object distance d2 at t = 2, the object distance d3 at t = 3, and the object distance d4 at t = 4. In this case, since the second object distance d3 is associated with an abnormality flag, the complement unit 604 complements the second object distance d3 using the adjacent first object distance d2 or third object distance d4, which are not associated with an abnormality flag. For example, if d2 < d4, the complement unit 604 replaces the second object distance d3 with the smaller object distance d2. That is, the complement unit 604 outputs d2 as the object distance at t = 4. This prevents the unreliable object distance d3 from being output as is. Note that the reason for replacing the second object distance with the smaller of the adjacent object distances is to prioritize safety when using the distance measurement device 1 in a surveillance area, etc. Therefore, depending on the usage mode of the distance measurement device 1, the second object distance may be replaced with the larger of the adjacent object distances.

[0079] Next, when t = 5, the storage unit 603 stores the object distance d3 when t = 3, the object distance d4 when t = 4, and the object distance d5 when t = 5. In this case, the complementing unit 604 outputs the object distance d4 as is, because no abnormality flag is associated with the second object distance d4.

[0080] Next, at t=6, the storage unit 603 stores the object distance d4 at t=4, the object distance d5 at t=5, and the object distance d6 at t=6. In this case, since an abnormality flag is associated with the second object distance d5, the complement unit 604 complements the second object distance d5 using the adjacent first object distance d4 or third object distance d6 that is not associated with an abnormality flag. For example, if d4<d6, the complement unit 604 replaces the second object distance d5 with the smaller object distance d4. In other words, d4 is output as the object distance at t=4. This prevents the distance measurement device 1 from outputting an unreliable object distance d4 as is.

[0081] <When abnormality flags are associated with two or more consecutive points> FIG. 12 is a diagram for explaining an example of operation when abnormality flags are associated with two or more consecutive points according to the first embodiment.

[0082] For example, as shown in FIG. 12, it is assumed that an abnormality flag is associated with object distance d2 when t=2, and an abnormality flag is also associated with object distance d3 when t=3, which follows.

[0083] In this case, the complementing unit 604 may output the object distance d3 as is without performing the object distance complementation described above. As shown in Figure 12, the object distance d3 may not be the distance to the object, but may be the distance to dust or other particles that are in front of the object. However, since the object to be detected in the monitoring area may not be visible due to the dust or other particles, the object is treated as having been detected, prioritizing safety. However, the processing described with reference to Figure 12 is not an essential function of the distance measurement device 1.

[0084] In the above-described embodiment, the second object distance associated with the abnormality flag is complemented by replacing it with the first object distance or the third object distance, but the complementation method is not limited to this. For example, the average value of the first object distance and the third object distance may be calculated as the second object distance.

[0085] In the above-described embodiment, the storage unit 603 stores three consecutive object distances (e.g., t=1 to 3) (i.e., at three consecutive rotation angles), but it may store four or more object distances (e.g., t=1 to 4).

[0086] In the above-described embodiment, three temporally consecutive object distances (e.g., t=1 to 3) (i.e., at three consecutive rotation angles) are stored in storage unit 603, and the second object distance associated with an abnormality flag is interpolated. However, multiple object distances associated with abnormality flags may be interpolated at once. That is, if, among a measured first object distance, multiple second object distances measured after the first distance, and a third object distance measured after the second object distance, the first object distance and the third object distance are estimated to be normal and multiple second object distances are estimated to be abnormal, the multiple second object distances may be interpolated using the first object distance or the third object distance. For example, among four temporally consecutive object distances (e.g., t=1 to 4), the object distance at t=2 and the object distance at t=3 associated with abnormality flags may be interpolated at once with the object distance at t=1 or the object distance at t=4.

[0087] (Summary of First Embodiment) The above description of the first embodiment discloses the following techniques.

[0088] <Technology 1> A distance measurement device (1) includes a light-emitting element (102) that projects pulsed wave projection light (3A), a light-receiving element (103) that receives reflected light (3B) of the projection light reflected by an object, and a controller (600) that measures the distance to the object based on the time between the light-emitting element's emission timing and the light-receiving element's reception timing, wherein the controller, when it estimates that the first distance and the third distance are not abnormal and the second distance is abnormal, among a measured first distance, at least one second distance measured after the first distance, and a third distance measured after the second distance, uses the first distance or the third distance to complement the second distance. As a result, the second distance estimated to be abnormal is complemented by the first distance or the third distance estimated to be normal, thereby preventing the distance measurement device from outputting an erroneous distance.

[0089] <Technology 2> In the distance measurement device described in Technology 1, the projected light used to measure the first distance, the projected light used to measure the second distance, and the projected light used to measure the third distance have different projection directions. As a result, the distance to the object estimated to be abnormal is complemented with the distance to the object estimated to be normal, which is measured using projected light that is adjacent in time and space, so that the distance estimated to be abnormal can be complemented with high accuracy.

[0090] <Technology 3> In the distance measurement device according to Technology 1 or 2, the controller detects the object when it has been able to measure at least two distances that are adjacent in time, thereby preventing the distance measurement device from accidentally detecting even minute objects such as dust or dirt.

[0091] <Technology 4> In the distance measurement device according to any one of technologies 1 to 3, the time between the light emission timing and the light reception timing is measured by a time-to-digital converter (TDC), and the controller estimates whether the measured distance is abnormal based on the measurement result of the TDC. This allows the controller to estimate whether the measured distance is abnormal based on the measurement result of the TDC.

[0092] <Technology 5> In the distance measurement device according to any one of technologies 1 to 4, when the controller complements the second distance, it complements the second distance using the smaller of the first distance and the third distance. This allows the object distance measurement device to perform highly secure complementation when complementing a distance estimated to be abnormal.

[0093] <Technology 6> In the distance measurement device according to any one of Technologies 1 to 5, the projection light is projected in a direction perpendicular to a predetermined axis (C) as a rotation axis, and the different projection directions mean that the rotation angles at which the projection light is projected are different from each other. This allows the distance measurement device to scan a 360-degree space in a direction perpendicular to the rotation axis.

[0094] <Technology 7> In a distance measurement method for measuring a distance to an object based on the time between a light-emitting element (102) projecting a pulsed wave projection light (3A) and a light-receiving element (103) receiving reflected light (3B) of the projection light reflected by the object, the method includes: a first distance measured, at least one second distance measured after the first distance, and a third distance measured after the second distance; if the first distance and the third distance are estimated to be normal and the second distance is estimated to be abnormal, the first distance or the third distance is used to complement the second distance. This prevents the distance measurement device from outputting an erroneous distance because the second distance estimated to be abnormal is complemented by the first distance or the third distance estimated to be normal.

[0095] Although the embodiments have been described above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications, alterations, substitutions, additions, deletions, and equivalents within the scope of the claims, and it is understood that these also fall within the technical scope of the present disclosure. Furthermore, the components in the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0096] This application is based on a Japanese patent application (Patent Application No. 2023-202864) filed on November 30, 2023, the contents of which are incorporated herein by reference.

[0097] The techniques of the present disclosure are useful in devices that measure the distance to an object.

[0098] REFERENCE SIGNS LIST 1 Distance measuring 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 300 Rotating part 301 Rotating member 302 Magnet 303 Reflector 311 Rib 401 Comparator 402 Motor 403 Rotation position detector 500 TDC 501 Measuring part 502 Data register 503 Status register 504 Input / output I / F 600 Controller 601 Distance measurement control part 602 Distance calculation part 603 Storage part 604 Complement part 605 Motor control part 611 TDC abnormality determination part

Claims

1. A distance measuring device comprising: a light-emitting element that projects a pulse wave projection light; a light-receiving element that receives light reflected by an object from the projected light; and a controller that measures a distance to the object based on the time between the light-emitting element's light-emitting timing and the light-receiving element's light-receiving timing, wherein the controller complements the second distance using the first distance or the third distance when, among a measured first distance, at least one second distance measured after the first distance, and a third distance measured after the second distance, the first distance and the third distance are estimated to be normal and the second distance is estimated to be abnormal.

2. The distance measuring device according to claim 1, wherein the projected light used to measure the first distance, the projected light used to measure the second distance, and the projected light used to measure the third distance have different projection directions.

3. The distance measuring device according to claim 1, wherein the controller detects the object when at least two distances that are adjacent in time are measured.

4. The distance measuring device according to claim 1, wherein the time between the light emission timing and the light reception timing is measured by a Time to Digital Converter (TDC), and the controller estimates whether the measured distance is abnormal based on the measurement result of the TDC.

5. The distance measuring device according to claim 1, wherein when the controller complements the second distance, the controller complements the second distance using the smaller of the first distance and the third distance.

6. A distance measuring device according to any one of claims 1 to 5, wherein the projection light is projected in a direction perpendicular to a predetermined axis, the axis being a rotation axis, and the projection directions being different from one another means that the rotation angles at which the projection light is projected are different from one another.

7. A distance measurement method for measuring a distance to an object based on the time between an emission timing when a light-emitting element projects a pulse wave projection light and a light-receiving element receives the reflected light of the projection light reflected by the object, the distance measurement method comprising: when, among a measured first distance, at least one second distance measured after the first distance, and a third distance measured after the second distance, the first distance and the third distance are estimated to be normal and the second distance is estimated to be abnormal, the first distance or the third distance is used to complement the second distance.

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