DISTANCE MEASURING DEVICE

Abstract

Distance measuring device which features: a light-emitting unit (10, 20) designed to emit light; a light detection unit (30) designed to detect reflected light; a background light calculation unit (S90) designed to calculate, for each of several position areas formed by subdividing a light irradiation area illuminated by the light, a background light level parameter relating to a level of background light arriving from the position area, based on a result of a detection by the light detection unit; a target position selection unit (S218, S220, S224, S240, S250, S300 to S330) designed to successively select one of the position areas as a target position area; a coefficient calculation unit (S260) designed to calculate a multiplication coefficient for the target position area selected by the target position selection unit and several ambient position areas in the vicinity of the target position area such that the respective multiplication coefficients for the respective ambient position areas each exhibit a negative correlation to a difference between the background light level parameter for the target position area and the background light level parameter for the respective ambient position area; a distance measurement waveform generation unit (S20, S110 to S140) designed to generate distance measurement waveform data for each of the position ranges, indicating temporal changes of a light detection parameter up to the expiration of a preset distance measurement period since the emission of the light, wherein the light detection parameter indicates the result of the detection by the light detection unit; a coefficient multiplication waveform generation unit (S270) designed to generate coefficient multiplication waveform data for the target position range and the surrounding position ranges, which are obtained by multiplying the corresponding distance measurement waveform data by the corresponding multiplication coefficient; an integration waveform generation unit (S280) designed to generate integration waveform data by integrating or summing the coefficient multiplication waveform data from the target positional region and from the surrounding positional regions; and a measuring unit (S290) designed to measure a distance to an object reflecting light using the integration waveform data generated by the integration waveform generation unit.

Description

Technical field

[0001] The present invention relates to a distance measuring device that emits light and measures a distance to an object that reflects the light. State of the art

[0002] JP 2018-109 560 A describes a distance measuring device comprising a scanning unit that performs scanning using laser light projected by a light projection unit, a light receiving unit that receives reflected light corresponding to the laser light projected at predetermined intervals, an integration unit that integrates or sums a time sequence of received light intensity signals output by the light receiving unit, and a distance calculation unit that calculates a distance to an object based on a result of the integration or summation performed by the integration unit.

[0003] US 2017 / 0363740A1 discloses a distance measuring device comprising: a light emitting unit designed to emit light; and a light detection unit designed to detect reflected light.

[0004] US 6,522,396 B1 discloses a distance measuring device comprising: a light emitting unit designed to emit light; a light sensing unit designed to sensing reflected light; a background light calculation unit designed to calculate, for each of several position ranges formed by subdividing a light irradiation area illuminated by the light, a background light level parameter relating to a level of background light arriving from the position range, based on a result of a sensing by the light sensing unit; and a target position selection unit designed to successively select one of the position ranges as a target position range, with thresholds for the position ranges being determined based on a background light level parameter.

[0005] US 2013 / 0 176 386 A1 discloses a distance measuring device comprising: a light detection unit designed to detect reflected light; and a background light calculation unit designed to calculate, for each of several position areas formed by subdividing a light irradiation area illuminated with light, a background light level parameter relating to a level of background light arriving from the position area, based on a result of a detection by the light detection unit.

[0006] US 2012 / 0 134 598 A1 discloses a distance measuring device comprising: a light emitting unit designed to emit light; a light detection unit designed to detect reflected light; and a background light calculation unit designed to calculate, for each of several position areas formed by subdividing a light irradiation area illuminated with light, a background light level parameter relating to a level of background light arriving from the position area, based on a result of a detection by the light detection unit.

[0007] US 2021 / 0 166 354 A1 and DE 10 2017 002 235 A1 disclose further distance measuring devices. Summary of the invention

[0008] However, as a result of a detailed investigation carried out by the inventors, it was found that the detection sensitivity of the reflected light in the technology described in JP 2018-109 560 A is low due to the effect of noise detected in the light receiving unit.

[0009] The present invention improves the detection sensitivity with respect to reflected light.

[0010] One aspect of the present invention provides a distance measuring device comprising a light emission unit, a light detection unit, a background light calculation unit, a target position selection unit or target azimuth selection unit or target orientation selection unit, a coefficient calculation unit, a distance measurement waveform generation unit, a coefficient multiplication waveform generation unit, an integration waveform generation unit and a measuring unit.

[0011] The light-emitting unit is designed to emit light. The light-sensing unit is designed to detect reflected light.

[0012] The background light calculation unit is designed to calculate, for each of several position areas or orientation areas formed by subdividing a light irradiation area illuminated by the light, a background light level parameter relating to a level of background light arriving from the position area, based on a result of a detection by the light detection unit.

[0013] The target location selection unit is designed to successively select one of the location areas as a target location area or subject location area.

[0014] The coefficient calculation unit is designed to calculate a respective multiplication coefficient for the target position area selected by the target position selection unit and several ambient position areas in the vicinity of the target position area such that for each of the ambient position areas, the respective multiplication coefficient has a negative correlation to a difference between the background light level parameter of the target position area and the background light level parameter of the ambient position area.

[0015] The distance measurement waveform generation unit is designed to generate distance measurement waveform data for each of the position ranges, specifying temporal changes of a light detection parameter up to the expiration of a preset distance measurement period since the emission of the light, where the light detection parameter specifies the result of a detection by the light detection unit.

[0016] The coefficient multiplication waveform generation unit is designed to generate coefficient multiplication waveform data of the target position range and the respective surrounding position ranges, which are obtained by multiplying the corresponding distance measurement waveform data with the corresponding multiplication coefficient.

[0017] The integration waveform generation unit is designed to generate integration waveform data by integrating or summing the respective coefficient multiplication waveform data of the target position area and the surrounding position areas.

[0018] The measuring unit is designed to measure a distance to an object that reflects light, using the integration waveform data generated by the integration waveform generation unit.

[0019] The distance measuring device, designed as described above, can reduce randomly generated noise in the integration waveform data. This noise arises because the distance measuring device integrates or sums the coefficient multiplication waveform data of the target position area and the adjacent position areas to measure the distance to the object that is present in the position direction or orientation corresponding to the target position area.

[0020] Furthermore, the distance measuring device calculates the multiplication coefficients of the target position area and the surrounding position areas in the vicinity of the target position area such that for each of the surrounding position areas the respective multiplication coefficient has a negative correlation to the difference between the background light level parameter of the target position area and the background light level parameter of the surrounding position area, and generates the coefficient multiplication waveform data of the target position area and the surrounding position areas by multiplying the corresponding distance measurement waveform data with the corresponding multiplication coefficient.In cases where the background light levels of the respective ambient position areas are higher than the background light level of the target position area, the distance measuring device of the present invention is able to reduce the contribution of the distance measurement waveform data of the ambient position areas to the integration waveform data. Therefore, in cases where the background light levels of the respective ambient position areas are higher than the background light level of the target position area, the distance measuring device can avoid a situation in which the integration waveform data becomes noisier than the distance measurement waveform data of the target position area, and can also reduce the noise in the integration waveform data.

[0021] As described above, the distance measuring device of the present invention can improve the detection sensitivity of the light detection unit that detects the reflected light. Brief description of the drawings Fig. Figure 1 is a block diagram of a LIDAR device; Fig. Figure 2 is a perspective view of the LIDAR device; Fig. Figure 3 is a perspective view of a photo capture module; Fig. Figure 4 is a front view of the photo capture module, with part of its frame removed; Fig. Figure 5 is a top view of the LIDAR device with its housing removed; Fig. 6 represents a structure of a mirror module; Fig. 7 represents a structure of a light source; Fig. Figure 8 represents a structure of a light-receiving element; Fig. 9 represents a path of emitted light; Fig. 10 represents a path of received light; Fig. Figure 11 represents a position setting of light sources and the light receiving element; Fig. 12 represents an illumination area of ​​light rays emitted by a deflecting mirror; Fig. 13 represents a correspondence between the light emission areas of the light sources and a light reception area of ​​the light receiving element; Fig. Figure 14 is a flowchart of a data acquisition process; Fig. 15 represents several positional areas in a two-dimensional matrix and background light waveform data; Fig. 16 represents several position ranges in a two-dimensional matrix and distance measurement waveform data; Fig. Figure 17 is a flowchart of an integration distance measurement process of the first embodiment; Fig. 18 represents a target location area and adjacent location areas; Fig. 19 presents a method for calculating noise values; Fig. 20 presents a special example of multiplication coefficients and an equation (1); Fig. 21 presents a method for calculating integration waveform data; Fig. Figure 22 is a flowchart of an integration distance measurement process according to a second embodiment; Fig. Figure 23 is a flowchart of an integration distance measurement process according to a third embodiment; Fig. Figure 24 is a flowchart of an integration distance measurement process according to a fourth embodiment; Fig. Figure 25 is a flowchart of an integration distance measurement process according to a fifth embodiment; and Fig. Figure 26 represents a normal distribution with a low luminous level standard deviation and a normal distribution with a high luminous level standard deviation. Description of the embodiments: First embodiment

[0022] A first embodiment of the present invention is described below with reference to the accompanying drawings.

[0023] A LIDAR device 1 according to the present embodiment is installed in a vehicle and is used to detect various objects around the vehicle. LIDAR is an abbreviation for Light Detection and Ranging.

[0024] As it is in Fig. As shown in Figure 1, the LIDAR device 1 includes a photo acquisition module 2, which will be described later, and a controller 3. The controller 3 is an electronic control unit containing a microcomputer with a CPU 61, a ROM 62, and a RAM 63. Various functions of the microcomputer are implemented by the CPU 61 executing a program stored in a non-volatile physical storage medium. In this example, the ROM 62 corresponds to the non-volatile physical storage medium in which the program is stored. A procedure corresponding to this program is carried out by executing the program. Some or all of the functions implemented by the CPU 61 can be implemented in hardware by one or more integrated circuits (ICs) or similar devices. Furthermore, one or more microcomputers can implement the controller 3.

[0025] A vehicle speed sensor 71, a front camera 72, and a navigation device 73 are connected to the controller 3. The vehicle speed sensor 71 detects the speed (hereinafter referred to as vehicle speed) of the vehicle carrying the LIDAR device 1 (hereinafter referred to as own vehicle) and outputs a vehicle speed detection signal, indicating a result of the detection, to the controller 3. The front camera 72 is installed on the front of the own vehicle and repeatedly records the ground surface in front of the own vehicle.

[0026] The navigation device 73 obtains road map data from a map storage medium containing road map data and various other information, determines the vehicle's current location based on GPS signals received via GPS antennas and similar devices, and performs route guidance or similar functions from the current location to a destination. The aforementioned road map data includes various data such as road locations, road types, road shapes, road widths, road names, number of lanes, and road gradients.

[0027] The LIDAR device 1 contains, as in Fig. Figure 2 shows a housing 100 and an optical window 200.

[0028] The housing 100 is a rectangular resin box with an opening in one of its six faces and contains the photo acquisition module 2 described later.

[0029] The optical window 200 is designed as a resin cover that is fixed to the housing 100 to cover the opening of the housing 100. The photo-detection module 2, which is installed in the housing 100, emits laser light that passes through the optical window 200.

[0030] In the following, the direction along the length of the essentially rectangular opening is referred to as the X-axis direction, the direction along the width of the opening is referred to as the Y-axis direction, and the direction orthogonal to both the X-axis and Y-axis directions is referred to as the Z-axis direction. Right and left in the X-axis direction and up and down in the Y-axis direction are defined from the perspective of the opening in the housing 100. In the Z-axis direction, forward is defined as a direction from the depth of the housing 100 toward the opening, and backward is defined as a direction toward the depth.

[0031] The photo capture module 2 contains, as in the Fig. 3, Fig. 4 and Fig. Figure 5 shows a light projection unit 10, a scanning unit 20, a light reception unit 30 and a frame 40. The photo capture module 2 is installed in the housing 100 via the frame 40.

[0032] The scanning unit 20 contains a mirror module 21, a partition or separator 22 and a motor 23.

[0033] The mirror module 21 contains, as in Fig. Figure 6 shows a pair of deflecting mirrors 211 and 212 and a mirror frame 213.

[0034] The pair of deflecting mirrors 211 and 212 consists of flat elements, each having a reflective surface that reflects light. The mirror frame 213 includes a circular plate 213a and a support 213b. The circular plate 213a is a disk-shaped section and is fixed at the center of the circle to a rotating shaft of the motor 23. The support 213b is a plate element, with the deflecting mirrors 211 and 212 fixed to its two sides. The support 213b projects from the circular surface of the circular plate 213a in a direction perpendicular to the circular surface of the circular plate 213a.

[0035] The deflecting mirrors 211 and 212 and the support 213b each have a shape in which two rectangles of different widths are integrated in the longitudinal direction. More precisely, the deflecting mirrors 211 and 212 and the support 213b have a shape consisting of two integrated rectangles arranged along their central axes, which extend in the lateral direction and are aligned with each other. In the following, in the integrated section of the deflecting mirrors 211 and 212 and the support 213b of the mirror module 21, the rectangular part whose length in the longitudinal direction is shorter is referred to as the narrower section, and the rectangular part whose length in the longitudinal direction is longer is referred to as the wider section.

[0036] The two deflecting mirrors 211 and 212, integrated via the mirror frame 213, are arranged such that the wider section is below the narrower section and their central axis is aligned with the center of the circular plate 213a, and such that they project from the circular surface of the plate 213a in a direction perpendicular to the circular surface of the plate 213a. This arrangement allows the deflecting mirrors 211 and 212 to rotate about the rotating shaft of the motor 23 in accordance with the motor's drive. The reflective surfaces of the deflecting mirrors 211 and 212 are parallel to the rotating shaft of the motor 23, regardless of the motor's rotational position.

[0037] The partition 22 is a disk-shaped element whose diameter is equal to the length of the wider section of the mirror module 21. The partition 22 is divided into two semicircular sections. The two semicircular sections hold the narrower section of the mirror module 21 from both sides and are fixed in contact with a step formed by the wider and narrower sections of the mirror module 21.

[0038] In the following, the part in the deflection mirrors 211 and 212 above the separation 22 (i.e. the part of the narrower section) is referred to as a transmitting light deflector 20a, and the part below the separation 22 (i.e. the part of the wider section) is referred to as a receiving light deflector 20b.

[0039] The light projection unit 10 contains, as in the Fig. 3, Fig. 4 to Fig. Figure 5 shows a pair of light sources 11 and 12, a pair of light projection lenses 13 and 14 and a rotating transmitting mirror 15.

[0040] Light sources 11 and 12 have the same configuration. Therefore, only the configuration of light source 11 is described here. Light source 11 is as shown in Fig. Figure 7 shows a so-called multistrip semiconductor laser containing several light-emitting regions A1 and A2. The light-emitting regions A1 and A2 are designed as rectangles that are aligned or arranged relative to each other in their longitudinal directions. The light-emitting regions A1 and A2 have a region length L in the arrangement direction that is equal to or greater than the region spacing S between the light-emitting region A1 and the light-emitting region A2. The light-emitting regions A1 and A2 emit light beams whose optical axes are parallel to each other.

[0041] In the following, the point on which light rays from light sources 11 and 12 fall within the transmitting light deflector 20a is referred to as a reflection point. Furthermore, the plane orthogonal to the axis of rotation containing the reflection point is referred to as a reference plane.

[0042] As it is in the Fig. 3, Fig. 4 to Fig. As shown in Figure 5, the light source 11 is located on the left side along the X-axis away from the reflection point, with its light-emitting surface facing the emitting light deflector 20a. The light source 12 is located on the rear side along the Z-axis away from the pivot point, at or near the midpoint of the path from the reflection point to the light source 11, with its light-emitting surface facing forward along the Z-axis. With respect to the positions of the light sources 11 and 12 in the Y-axis direction, the light source 11 is located below the reference plane, and the light source 12 is located above the reference plane. The light sources 11 and 12 are arranged such that their light-emitting areas A1 and A2 are aligned with each other in the Y-axis direction.

[0043] The light projection lens 13 is arranged facing the light-emitting surface of the light source 11. Similarly, the light projection lens 14 is arranged facing the light-emitting surface of the light source 12. The light sources 11 and 12 are arranged near the respective focal points of the light projection lenses 13 and 14.

[0044] The rotating reflector 15, which is arranged at the pivot point described above, reflects and directs light emitted by the light source 12 to the reflection point described above. The rotating reflector 15 is, for example, as shown in Fig. Figure 9 shows the optical path of the light emitted by the light source 11 to the reflection point, arranged such that the path is not obstructed. The optical path from the light source 11 to the reflection point has the same length as the optical path from the light source 12 to the reflection point via the rotating reflector 15. The light source 11 has an optical axis inclined upwards by 1 to 2 degrees from the reference plane, and the light source 12 has an optical axis inclined downwards by 1 to 2 degrees from the reference plane. In other words, the optical axes of the light sources 11 and 12 are symmetrically aligned about the reference plane. The angles are not limited to 1 to 2 degrees but can be suitably determined depending on the intended beam emission angle in the sub-scanning direction or the secondary scanning direction.

[0045] The light receiving unit 30 contains, as in the Fig. 3, Fig. 4 to Fig. Figure 5 shows a light receiving element 31, a light receiving lens 32 and a receiving light rotating mirror 33.

[0046] The light receiving element 31 contains, as in Fig. Figure 8 shows an avalanche photodiode array 311 (hereinafter referred to as APD array 311) and a lens array 312. APD is an abbreviation for avalanche photodiode. The APD array 311 contains 12 avalanche photodiodes (hereinafter referred to as APDs) arranged in a row. The lens array 312 contains 12 lenses, each facing the respective 12 APDs of the APD array 311 in a one-to-one correspondence, and constricts and directs light incident on the light-receiving element 31 to the APDs.

[0047] The light receiving element 31 is as in the Fig. 4 and Fig. 10 is shown below the receiving light rotating mirror 33, with the light receiving surface pointing upwards along the Y-axis and the APDs of the APD array 311 being aligned with the X-axis direction. Fig. 4 is part of frame 40, which is not shown to increase the visibility of a given arranged component.

[0048] The receiving light rotating mirror 33 is arranged along the X-axis on the left side of the receiving light deflector 20b. The receiving light rotating mirror 33 deflects the optical path essentially 90 degrees downwards in the Y-axis direction, so that light incident from the receiving light deflector 20b via the light receiving lens 32 reaches the light receiving element 31.

[0049] The light-receiving lens 32 is arranged between the receiving light deflector 20b and the receiving light rotating mirror 33. The light-receiving lens 32 narrows or focuses the light beam incident on the light-receiving element 31, so that its width in the Z-axis direction becomes essentially equal to the APD element width.

[0050] The frame 40 is an element that integrates each component contained in the light projection unit 10, the scanning unit 20, and the light reception unit 30. That is, the components contained in the light projection unit 10, the scanning unit 20, and the light reception unit 30 are installed in the housing 100 with a specific positional relationship to one another.

[0051] Frame 40 contains, as in the Fig. 3, Fig. 4 to Fig. Figure 5 shows a frame base 41, a frame side 42, a frame back 43 and a partition or divider 44.

[0052] The frame base 41 is supported by a photoreceiver substrate (carrier) 51, to which the light receiving element 31 is fixed, and a motor substrate (carrier) 52, to which the scanning unit 20 is fixed. Thus, the frame base 41 has holes at a location through which light passes from the receiving light rotating mirror 33 to the light receiving element 31, and at a location where the motor 23 of the scanning unit 20 is arranged.

[0053] The frame side 42 has a front surface, which is the surface facing the scanning unit 20, and a cylindrical mount 421 is installed on the front surface. The light projection lens 13 is mounted in the opening at the front end of the mount 421 (i.e., the right end in the X-axis direction). A photoemitter substrate 53, on which the light source 11 is mounted, is attached to the rear surface of the frame side 42. When the photoemitter substrate 53 is attached to the frame side 42, the light source 11 is located at the rear end of the mount 421 (i.e., at the left end in the X-axis direction).

[0054] In the same way as on frame side 42, a bracket 431 is installed on the frame back 43. The light projection lens 14 is attached to the front end (i.e., the forward end in the Z-axis direction) of the bracket 431. A photoemitter substrate 54, on which the light source 12 is installed, is attached to the rear surface of the frame back 43. With the photoemitter substrate 54 attached to the frame back 43, the light source 12 is located at the rear end of the bracket 431 (i.e., the back end in the Z-axis direction).

[0055] The partition 44 is arranged such that it defines a space in which the components of the light projection unit 10 are arranged, and a space in which the components of the light receiving unit 30 are arranged. The transmitting light rotating mirror 15, the receiving light rotating mirror 33, and the light receiving lens 32 are attached to the partition 44.

[0056] The photoreceiver substrate 51 and the photoemitter substrates 53 and 54 are each screwed to the frame 40. The LIDAR device 1 enables three-dimensional fine adjustment of the installation position and angle of the light-receiving element 31 and the light sources 11 and 12 by modifying the installation positions and angles of the photoreceiver substrate 51 and the photoemitter substrates 53 and 54. In the present embodiment, the brackets 421 and 431 are integrated with or formed integrally with the frame side 42 and the frame back 43, respectively. However, the brackets 421 and 431 can also be integrated with or formed integrally with the photoemitter substrate 53 and the photoemitter substrate 54.

[0057] The control unit 3 is, for example, attached to the housing 100. The control unit 3 controls the timing of the light emission from the light sources 11 and 12 synchronously with a rotation of the mirror module 21 of the scanning unit 20. More precisely, the control unit 3 controls the light beam from the light source 11 so that it strikes the deflecting mirror 211, and the light beam from the light source 12 so that it strikes the deflecting mirror 212.

[0058] As it is in Fig. As shown in Figure 9, the light emitted by light source 11 strikes the reflection point P on the transmitting light deflector 20a through the light projection lens 13. The light emitted by light source 12 passes through the light projection lens 14. Its direction of propagation is then deflected by approximately 90 degrees by the transmitting light rotating mirror 15. The light then strikes the reflection point P on the transmitting light deflector 20a. Note that light source 11 and light source 12 use different surfaces of the transmitting light deflector 20a. The light striking the reflection point P is aligned according to the rotational position of the mirror module 21.

[0059] As it is in Fig. As shown in Figure 10, the light reflected from an object positioned in a predetermined direction is reflected by the receiving light deflector 20b according to the rotational position of the mirror module 21 (i.e., the direction in which light is emitted by the transmitting light deflector 20a) and detected in the light receiving element 31 by the light receiving lens 32 and the receiving light rotating mirror 33. Note that objects are different targets to be detected by the LIDAR device 1.

[0060] More precisely, in the LIDAR device 1, horizontal scanning in the X-axis direction (hereinafter referred to as primary scanning) is achieved mechanically by rotating the mirror module 21. In addition, vertical scanning in the Y-axis direction (hereinafter referred to as sub-scanning or secondary scanning) is achieved electronically by the light sources 11 and 12, which emit four beams that are adjacent to each other in the vertical direction, and the APD array 311, which receives the four beams.

[0061] As it is in the Fig. 9, Fig. 10 to Fig. As shown in Figure 11, the light sources 11 and 12 are arranged such that their optical paths to the reflection point P on the transmitting light deflector 20a have the same length, and their optical axes intersect at the reflection point P. The light receiving element 31 is arranged near the focal point of the light receiving lens 32.

[0062] Light rays from the light emission areas A1 and A2 of the light source 11 are hereinafter referred to as B11 and B12, and light rays from the light emission areas A1 and A2 of the light source 12 are hereinafter referred to as B21 and B22. As is stated in Fig. As shown in Figure 12, the light rays emitted from the reflection point P on the transmitting light deflector 20a are light ray B11, light ray B21, light ray B12, and light ray B22, in order from top to bottom along the Y-axis. Furthermore, the positions of the light sources 11 and 12 are adjusted so precisely that no gap is formed between light rays B11, B21, B12, and B22. As shown in Fig. As shown in Figure 13, the positions of the light sources 11 and 12 are adjusted so finely that the APD array 311 of the light receiving element 31 receives reflected light (hereinafter referred to as return light rays) from the object illuminated by the light rays B11, B21, B12 and B22, and the return light rays are directed towards the center in the Z-axis direction of each APD, with each ray hitting three different elements.

[0063] The reflective surface of the transmitting light deflector 20a is parallel to the rotation axis of the mirror module 21, and thus the inclination angle of the reflective surface in a vertical plane containing the path of the light striking the transmitting light deflector 20a is not affected by the rotation position of the mirror module 21. Vertical planes here refer to planes along the Y-axis. As shown in the graph of the Fig. As specified in Figure 12, the emission angle or transmission angle in the Y-axis direction (i.e., the vertical angle), which is the secondary scanning direction, is constant, independent of the transmission angle in the X-axis direction (i.e., the horizontal angle), which is the primary scanning direction of the light emitted by the transmitting light deflector 20a. Therefore, the light rays strike the entire two-dimensionally defined scanning area. Hereinafter, the emission angle in the X-axis direction is also referred to as the primary scanning angle, and the emission angle in the Y-axis direction is referred to as the secondary scanning angle.

[0064] The following describes the process steps of a data acquisition process performed by CPU 61 of controller 3. This data acquisition process is performed repeatedly during the operation of controller 3.

[0065] When this data acquisition process is started, CPU 61 determines how in Fig. Figure 14 shows that in step S10, the CPU 61 first checks whether the backlight acquisition time, which occurs after a preset distance measurement cycle, has been reached. If the backlight acquisition time has not yet been reached, the CPU 61 repeats process step S10 and waits until the backlight acquisition time is reached. When the backlight acquisition time is reached, in step S20, the CPU 61 acquires the rotational position (i.e., the principal scanning angle) of the mirror module 21 by acquiring the scanning angle detection signal from the mirror module 21.

[0066] Then, in step S30, the CPU 61 obtains the light detection signals from the light receiving element 31. In step S40, the CPU 61 stores background light detection data in the RAM 63, which indicates the signal intensities of the light detection signals that were obtained in step S30.

[0067] As it is in Fig. As shown in Figure 15, the CPU 61 stores the background light detection data in a two-dimensional matrix, configured as an array of principal scanning angles in rows and an array of secondary scanning angles in columns, in association with one of several positional areas defined by subdividing the light irradiation area Ri illuminated by the laser light. The light irradiation area Ri of the present embodiment is an area extending over a principal scanning angle range of -60 to +60 degrees and a secondary scanning angle range of -4 to +4 degrees.

[0068] The position regions are equal subregions with Nm main scanning direction regions Rm along the main scanning direction and twelve secondary scanning direction regions Rs along the secondary scanning direction. The Nm main scanning direction regions Rm are designated Rm_1, Rm_2, ..., Rm_Nm - 1, Rm_Nm in ascending order of the main scanning angles. The twelve secondary scanning direction regions Rs are designated Rs_1, Rs_2, Rs_3, Rs_4, ..., Rm_11, Rm_12 in descending order of the secondary scanning angles. The position region specified by the main scanning direction region Rmi and the secondary scanning direction region Rsj is called the position region OR(i, j), where i is an integer from 1 to Nm and j is an integer from 1 to 12.

[0069] More precisely, in step S40, the CPU 61 first sets one of the Nm main scanning direction ranges Rm based on the scanning angle detected in S20.

[0070] The CPU 61 stores the respective signal intensities of the light reception signals from the twelve APDs in the RAM 63 as background light detection data, corresponding to the time at which the light detection signal was acquired, the main scanning direction range Rm set above, and the secondary scanning direction range Rs preset for each APD (i.e., in relation to the time and position range). The signal intensities acquired by the three APDs corresponding to light beam B11 are each assigned to the secondary scanning direction ranges Rs_1, Rs_2, and Rs_3, respectively. Similarly, the signal intensities acquired by the three APDs corresponding to light beam B21 are each assigned to the secondary scanning direction ranges Rs_4, Rs_5, and Rs_6, respectively. The signal intensities obtained from the three APDs corresponding to the light beam B12 are each assigned to the secondary scanning direction areas Rs_7, Rs_8 and Rs_9.The signal intensities obtained from the three APDs corresponding to the light beam B22 are each assigned to the secondary scanning direction areas Rs_10, Rs_11 and Rs_12.

[0071] As it is in Fig. As shown in Figure 14, in step S50, CPU 61 determines whether the transmission time, at which a preset background light acquisition period has elapsed since the background light acquisition time, has been reached. If the transmission time has not been reached, CPU 61 proceeds to step S30. If the transmission time has been reached, in step S60, CPU 61 causes light sources 11 and 12 to emit a light beam.

[0072] Then, in step S70, the CPU 61 generates twelve background light waveform data segments corresponding to the respective secondary scanning direction regions Rs_1, Rs_2, Rs_3, ..., Rs_11 and Rs_12, based on the background light acquisition data obtained in steps S30 and S40, and stores these in the RAM 63. The background light waveform data indicates temporal changes in signal intensity from the time of background light acquisition until the time of transmission.

[0073] In each background light waveform data section, the main scanning direction range Rm set above and one of the secondary scanning direction ranges Rs_1, Rs_2, Rs_3, ..., Rs_11 and Rs_12 are set. As indicated by the arrow L1 in Fig. As specified in 15, each background light waveform data part D1 is therefore stored in RAM 63 in association with the position area.

[0074] As it is in Fig. As shown in Figure 14, the CPU 61 performs a filtering process on the background light waveform data generated in step S70 in step S80. In the present embodiment, the CPU 61 performs the filtering process using a bilateral filter. The bilateral filter is a filter that preserves and smooths edges.

[0075] In step S90, the CPU 61 calculates a noise value for the background light waveform data for which the filtering process was performed in step S80 and stores the noise value in RAM 63. The noise value is the standard deviation of the signal intensities in the background light waveform data, as defined in Fig. Figure 15 is shown. As described above, each background light waveform data segment has the main sampling direction range Rm set above and one of the secondary sampling direction ranges Rs_1, Rs_2, Rs_3, ..., Rs_11 and Rs_12. Therefore, the noise value is stored in RAM 63 in association with the position range, as indicated by arrow L2 in Fig. 15 is indicated.

[0076] The CPU 61 then calculates the total positional standard deviation Var in step S100, as described in Fig. Figure 14 shows that the overall positional standard deviation Var is the standard deviation of the noise values ​​in all positional regions OR(i, j). However, the CPU 61 does not calculate the overall positional standard deviation Var in cases where the noise value in at least one of the positional regions OR(i, j) is not stored in the RAM 63.

[0077] Subsequently, in step S110, the CPU 61 obtains the light detection signals from the light receiving element 31. In addition, in step S120, the CPU 61 stores distance measurement data in the RAM 63, which specify the signal intensities of the light detection signals obtained in step S110.

[0078] More precisely, in step S120, the CPU 61 first sets one of the Nm main scanning direction ranges Rm based on the scanning angle detected in step S20.

[0079] Then, in the same way as in step S40, the CPU 61 stores the respective signal intensities of the light detection signals from the twelve APDs in the RAM 63 as distance measurement data in relation to the time at which the light detection signal was obtained, the main scanning direction range Rm set above, and the secondary scanning direction range Rs set in advance for each APD (i.e., in relation to the time and position range).

[0080] In step S130, the CPU 61 then determines whether the distance measurement termination time, at which a preset distance measurement period has elapsed since the transmission time, has been reached. If the distance measurement termination time has not been reached, the CPU 61 proceeds to step S110. If the distance measurement termination time has been reached, in step S140 the CPU 61 generates twelve distance measurement waveform data segments corresponding to the respective secondary scanning direction regions Rs_1, Rs_2, Rs_3, ..., Rs_11 and Rs_12, based on the distance measurement data acquired in steps S110 and S120, and stores them in RAM 63. The distance measurement waveform data indicates temporal changes in signal intensity from the transmission time to the distance measurement termination time.

[0081] Then, in the distance measurement waveform data, the main scanning direction range Rm set above and one of the secondary scanning direction ranges Rs_1, Rs_2, Rs_3, ..., Rs_11, Rs_12 are set. As indicated by arrow L3 in Fig. As specified in 16, the distance measurement waveform data D2 are therefore stored in RAM 63 in association with the position range.

[0082] After the process in step S140 is completed, CPU 61 terminates the data acquisition process.

[0083] The following describes an integration distance measurement process performed by CPU 61 of controller 3. This integration distance measurement process is performed repeatedly during the operation of controller 3.

[0084] If the integration distance measurement process, which is in Fig. As shown in Figure 17, and initiated, CPU 61 determines in step S210 whether the last total positional standard deviation Var, calculated in step S100, is greater than a preset distance measurement value J1. If the total positional standard deviation Var is equal to or less than the distance measurement value J1, CPU 61 terminates the integration distance measurement process.

[0085] If the total positional standard deviation Var is greater than the distance measurement value J1, the CPU 61 sets a column index value n in RAM 63 to 1 and an end column index value Nend in RAM 63 to Nm in step 220. Hereinafter, the positional range OR(n, 1), the positional range OR(n, 2), the positional range OR(n, 3), and the positional range OR(n, 4) are also referred to as the positional range in the nth column.

[0086] Then, in step S230, CPU 61 determines whether the background light waveform data associated with the position ranges in the (n + 1)th column has been updated since the previous cycle of the integration distance measurement process. If the background light waveform data associated with the position ranges in the (n + 1)th column has not been updated, CPU 61 waits by repeating process step S230 until the background light waveform data has been updated. If the background light waveform data has been updated, in step S240, CPU 61 sets a row index value m in RAM 63 to 1. Hereafter, the position range OR(n, m) is also referred to as the position range in the nth column and the mth row.

[0087] Subsequently, in step S250, CPU 61 sets the target position range in the nth column and the mth row. In step S260, CPU 61 calculates the multiplication coefficient using the noise value calculated in step S90 for the target position range and adjacent position ranges. The target position range is position range OR(n, m). The adjacent position ranges are position range OR(n - 1, m - 1), position range OR(n - 1, m), position range OR(n - 1, m + 1), position range OR(n, m - 1), position range OR(n, m + 1), position range OR(n + 1, m - 1), position range OR(n + 1, m + 1). As is the case, for example, in Fig. As shown in Figure 18, the target location area is the location area OR0 if the target location area is in the nth column and the second row, and the adjacent location areas are the location areas OR1, OR2, OR3, OR4, OR5, OR6, OR7 and OR8.

[0088] In the following, the positional region OR(n - 1, m - 1) is referred to as the first adjacent positional region. The positional region OR(n - 1, m) is referred to as the second adjacent positional region. The positional region OR(n - 1, m + 1) is referred to as the third adjacent positional region. The positional region OR(n, m - 1) is referred to as the fourth adjacent positional region. The positional region OR(n, m + 1) is referred to as the fifth adjacent positional region. The positional region OR(n + 1, m - 1) is referred to as the sixth adjacent positional region. The positional region OR(n + 1, m) is referred to as the seventh adjacent positional region. The positional region OR(n + 1, m + 1) is referred to as the eighth adjacent positional region.

[0089] More precisely, in step S260, the CPU 61 calculates the multiplication coefficient W(0) for the target position region and the multiplication coefficient W(k) for the k-th neighboring position region according to the following equation (1), where the noise value for the target position region is equal to Vn(0) and the noise value for the k-th neighboring position region is equal to Vn(k), as shown in Fig. Figure 19 shows that σ in equation (1) is the standard deviation of the normal distribution. σ has a preset value. W(k)=exp{(Vn(0)−Vn(k))2 / 2σ2}

[0090] The graph G1 in Fig. 20 is a special example of equation (1). (Vn(0) - Vn(k)) in equation (1) corresponds to a noise value difference on the horizontal axis of graph G1.

[0091] The matrix M1 in Fig. Figure 20 is a specific example of the multiplication coefficients of the target location area and the first through eighth adjacent location areas. Matrix M1 shows that the multiplication coefficient for the target location area is 1, the multiplication coefficient for the first through third adjacent location areas is 0.1 each, the multiplication coefficient for the fourth, fifth, and seventh adjacent location areas is 0.6 each, and the multiplication coefficient for the sixth and eighth adjacent location areas is 0.9 each.

[0092] As it is in Fig. As shown in Figure 17, in step S270, CPU 61 also multiplies the signal intensity of the distance measurement waveform data of the target position area and the first to eighth adjacent position areas by the respective multiplication coefficients calculated in step S260. That is, CPU 61 multiplies the signal intensity of the distance measurement waveform data of the k-th adjacent position area by the multiplication coefficient W(k). The data obtained by multiplying the signal intensity of the distance measurement waveform data by the multiplication coefficient are referred to below as coefficient multiplication waveform data.

[0093] In step S280, the CPU 61 integrates or sums the coefficient multiplication waveform data of the subject position region and the first through eighth adjacent position regions. The data obtained by integrating or summing the coefficient multiplication waveform data of the target position region and the first through eighth adjacent position regions are subsequently referred to as integration waveform data. Fig. Figure 21 shows that the integration waveform data are obtained by integrating or adding the distance measurement waveform data of the target position area and the first to eighth adjacent position areas, which are multiplied by their respective multiplication coefficients.

[0094] Then the CPU 61 executes in step S290 as in Fig. Figure 17 shows a distance measurement process for measuring a distance to the object reflecting the light beam, using the integration waveform data obtained in step S280, to calculate a time from the emission of the light beam to the detection of the light beam by the light receiving element 31.

[0095] The CPU 61 then increments (i.e., adds one) the row index value m in step S300. Next, in step S310, the CPU 61 determines whether the row index value m is greater than twelve. If the row index value m is equal to or less than twelve, the CPU 61 proceeds to step S250. If the row index value m is greater than twelve, the CPU 61 increments the column index value n in step S320. Then, in step S330, the CPU 61 determines whether the column index value n is greater than the end column index value Nend. If the column index value n is equal to or less than the end column index value Nend, the CPU 61 proceeds to step S230. If the column index value n is greater than the end column index value Nend, the CPU 61 terminates the integration distance measurement process.

[0096] The LIDAR device 1, which is designed in this way, contains the light projection unit 10, the scanning unit 20, the light receiving unit 30 and the control unit 3.

[0097] The light projection unit 10 and the scanning unit 20 emit the laser light. The light receiving unit 30 detects the reflected laser light.

[0098] For each of the position areas OR(i, j) formed by dividing the light irradiation area Ri, the controller 3 calculates a noise value that is assigned to the level of the background light assigned to the position area OR(i, j) based on the result of the detection by the light receiving unit 30.

[0099] The controller 3 sequentially selects one of the position ranges OR(i, j) as the target position range.

[0100] Controller 3 calculates the multiplication coefficient of the target position area and the adjacent position areas such that the multiplication coefficient of each of the adjacent position areas exhibits a negative correlation with the noise value difference between the target position area and the corresponding adjacent position area. The expression "negative correlation with the noise value difference" implies not only that the multiplication coefficient decreases continuously with an increase in the noise value difference, but can also imply that the multiplication coefficient decreases stepwise with an increase in the noise value difference.

[0101] The controller 3 generates distance measurement waveform data for each of the position ranges OR(i, j), which indicate temporal changes in signal intensity from the time at which the laser light was emitted until the time at which a preset distance measurement period has elapsed.

[0102] For the distance measurement waveform data of the target position area and the adjacent position areas, the controller 3 generates the coefficient multiplication waveform data by multiplying the distance measurement waveform data by the corresponding multiplication coefficient.

[0103] The controller 3 generates the integration waveform data by integrating or summing the coefficient multiplication waveform data of the target position area and the adjacent position areas.

[0104] Controller 3 uses the integration waveform data to measure the distance to the object that reflected the laser light.

[0105] In this way, the LIDAR device 1 can reduce randomly generated noise in the integration waveform data. This noise arises because the LIDAR device 1 integrates or sums the coefficient multiplication waveform data of the target position area and the adjacent position areas to measure the distance to the object that is present in the position direction corresponding to the target position area.

[0106] Furthermore, the LIDAR device 1 calculates the multiplication coefficients of the target position area and the adjacent position areas such that the multiplication coefficient of the respective adjacent position areas exhibits a negative correlation to the noise difference between the target position area and the respective adjacent position areas, and generates the coefficient multiplication waveform data of the target position area and the adjacent position areas by multiplying the distance measurement waveform data by the corresponding multiplication coefficients. In cases where the background light levels of the adjacent position areas are greater than the background light level of the target position area, the LIDAR device 1 can reduce the contribution of the distance measurement waveform data of the adjacent position areas to the integration waveform data.Therefore, in cases where the background light levels of the adjacent position areas are greater than the background light level of the target position area, the LIDAR device 1 can prevent the occurrence of a situation in which the integration waveform data become noisier than the distance measurement waveform data of the target position area, and can also reduce the noise in the integration waveform data.

[0107] As described above, the LIDAR device 1 can improve the detection sensitivity when detecting the reflected laser light at the light receiving unit 30.

[0108] The controller 3 also calculates the total positional standard deviation Var with respect to the standard deviation of the background light levels across the entire irradiation area Ri. The controller 3 prevents the execution of process steps S220 to S350 in cases where the total positional standard deviation Var is equal to or less than the predefined distance measurement value J1. This means that the LIDAR device 1 can prevent the generation of integration waveform data in situations with low background light, such as at night or in a tunnel, where the multiplication coefficients for adjacent positional areas cannot be calculated correctly. This allows the controller 3 to prevent a reduction in the accuracy of the distance measurement to the object reflecting the laser light.

[0109] For each of the position ranges OR(i, j), the controller 3 generates the background light waveform data based on the result of the acquisition by the light receiver unit 30. This data specifies temporal changes in signal intensity within a background light acquisition period or time interval, which is defined such that it does not overlap with the distance measurement period or time interval. Furthermore, the controller 3 performs the filtering process on the background light waveform data for each of the position ranges OR(i, j). The controller 3 then calculates the noise value using the filtered background light waveform data for each of the position ranges OR(i, j).

[0110] This enables the LIDAR device 1 to reduce the background light noise in the background light waveform data, thereby improving the detection sensitivity with respect to the reflected laser light at the light receiving unit 30.

[0111] The controller 3 calculates the noise values ​​based on the result of the acquisition by the light receiver 30 immediately before the start of the distance measurement period. This simplifies the configuration of the LIDAR device 1, as the background light can be acquired by the light receiver 30 without the need for a separate sensor to detect the background light.

[0112] In the embodiment described above, the LIDAR device 1 corresponds to a distance measuring device, the light projection unit 10 and the scanning unit 20 correspond to a light emission unit, and the light receiving unit 30 corresponds to a light detection unit. Process step S90 corresponds to a process performed by a background light calculation unit.

[0113] Process steps S220, S240, S250, and S300 to S330 correspond to a process performed by a target position selection unit. Process step S260 corresponds to a process performed by a coefficient calculation unit. Process steps S20 and S110 to S140 correspond to processes performed by a distance measurement waveform generation unit. Process step S270 corresponds to a process performed by a coefficient multiplication waveform generation unit.

[0114] Process step S280 corresponds to a process performed by an integration waveform generation unit. Process step S290 corresponds to a process performed by a measurement unit.

[0115] The noise value corresponds to a background light level parameter, the adjacent position areas correspond to ambient position areas, and the signal intensity corresponds to a light detection parameter.

[0116] Process step S100 corresponds to a process performed by a standard deviation calculation unit. Process step S210 corresponds to a process performed by a deviation prevention unit. The total positional standard deviation Var corresponds to a standard deviation parameter, and the distance measurement determination value J1 corresponds to a deviation determination value.

[0117] Process steps S10 to S50 and S70 correspond to processes performed by a background light waveform generation unit, and process step S80 corresponds to a process performed by a filter unit. Second embodiment

[0118] A second embodiment of the present invention is described below with reference to the accompanying drawings. In the second embodiment, only the part that differs from the first embodiment is described. The same reference numerals are used for the same components.

[0119] The second embodiment of the LIDAR device 1 differs from the first embodiment in that the integration distance measurement process is modified.

[0120] The integration distance measurement process of the second embodiment differs from that of the first embodiment in that process step S210 is not present and process step S212 is added instead.

[0121] That is, if the integration distance measurement process is as in Fig. As shown in Figure 22, the CPU 61 determines in step S212 whether the vehicle speed Vv, indicated by the last vehicle speed detection signal obtained from the vehicle speed sensor 71, is greater than a preset distance measurement value J2 (for example, 60 km / h in the present embodiment). If the vehicle speed Vv is equal to or less than the distance measurement value J2, the CPU 61 terminates the integration distance measurement process. If the vehicle speed Vv is greater than the distance measurement value J2, the CPU 61 proceeds to step S220.

[0122] In the LIDAR device 1 thus configured, the controller 3 determines whether the vehicle speed Vv of the vehicle itself is equal to or less than the distance measurement value J2. If the controller 3 determines that the vehicle speed Vv is equal to or less than the distance measurement value J2, it prevents the execution of process steps S220 to S350. That is, the LIDAR device 1 only generates the integration waveform data during high-speed travel.

[0123] This enables the LIDAR device 1 to prevent distance measurements based on integration waveform data in situations where it is necessary to measure distances to complex and detailed structures or objects (for example, roadside objects such as guardrails or pedestrians) located near the vehicle. For complex and detailed objects located near the vehicle, it may not be possible to correctly calculate the multiplication coefficients for adjacent areas. Therefore, the LIDAR device 1 can prevent a reduction in measurement accuracy when measuring distances to objects located near the vehicle.

[0124] In the embodiment described above, process step S212 corresponds to a process performed by a vehicle speed determination unit and a vehicle speed prevention unit. The vehicle speed Vv corresponds to a driving speed, and the distance measurement determination value J2 corresponds to a vehicle speed determination value. Third embodiment

[0125] A third embodiment of the present invention is described below with reference to the accompanying drawings. In the third embodiment, only the part that differs from the first embodiment is described. The same reference numerals are used for the same components.

[0126] The third embodiment of the LIDAR device 1 differs from the first embodiment in that the integration distance measurement process is modified.

[0127] The integration distance measurement process of the third embodiment differs from that of the first embodiment in that process step S210 is not present, and process steps S214, S216 and S218 are added instead.

[0128] That is, if the integration distance measurement process of the third embodiment is as described in Fig. As shown in Figure 23, the CPU 61 acquires image data from the front camera 72 in step S214. Subsequently, in step S216, the CPU 61 detects the left and right boundary positions of the lane in which the vehicle is traveling (hereinafter also referred to as the vehicle's own lane) by performing an image recognition process using the image data acquired in step S214. The boundary positions of the vehicle's own lane can be detected by identifying white lines of the lane via the image recognition process.

[0129] Then, in step S216, CPU 61 sets the column indication value n based on the left boundary position of the vehicle's lane, sets the end column indication value Nend based on the right boundary position of the vehicle's lane, and then proceeds to step S230. More precisely, CPU 61 sets the column indication value n, for example, by referencing a left-side adjustment characteristic curve field in which a relationship between the left boundary position and the column indication value n is predefined. CPU 61 sets the end column indication value Nend, for example, by referencing a right-side adjustment characteristic curve field in which a relationship between the right boundary position and the end column indication value Nend is predefined.

[0130] In the LIDAR device 1 thus configured, the controller 3 detects the position of the lane on which the vehicle is traveling. The controller 3 then selects the positional region OR(i, j) in which the lane is located as the target positional region among the positional regions OR(i, j). This allows the LIDAR device 1 to reduce the number of target positional regions required to generate the integration waveform data, thereby reducing the processing load on the controller 3.

[0131] In the embodiment described above, process steps S214 and S216 correspond to a process performed by a lane detection unit, and process steps S218, S240, S250, and S300 to S330 correspond to a process performed by a target position selection unit. Fourth embodiment

[0132] A fourth embodiment of the present invention is described below with reference to the accompanying drawings. In the fourth embodiment, only the part that differs from the first embodiment is described. The same reference numerals are used for the same components.

[0133] The fourth embodiment of the LIDAR device 1 differs from the first embodiment in that the integration distance measurement process is modified.

[0134] The integration distance measurement process of the fourth embodiment differs from that of the first embodiment in that process steps S210 and S220 are not present and process steps S222 and S224 are added instead.

[0135] That is, if the integration distance measurement process of the fourth embodiment is as described in Fig. As shown in step 24, the CPU 61 in step S222 obtains road map data, which specifies a road shape in front of the vehicle, from the navigation device 73.

[0136] Then, in step S224, CPU 61 sets the column indication value n and the end column indication value Nend based on the road shape specified by the road map data acquired in step S222. More precisely, CPU 61 sets the column indication value n and the end column indication value Nend such that, in cases where the road in front of the vehicle is straight, the average of the column indication value n and the end column indication value Nend corresponds to a scanning angle of 0°. In cases where the road in front of the vehicle curves to the left, CPU 61 decreases the column indication value n and the end column indication value Nend as the leftward curvature of the curve increases. In cases where the road in front of the vehicle curves to the right, CPU 61 increases the column indication value n and the end column indication value Nend as the rightward curvature of the curve increases.

[0137] In the LIDAR device 1 thus configured, the controller 3 acquires road map data that specifies the shape of the road in front of the vehicle. Then, based on this acquired road map data, the controller 3 selects the positional region OR(i, j) from the available positions OR(i, j) in which the road in front of the vehicle is located as the target positional region. This allows the LIDAR device 1 to reduce the number of target positional regions required to generate the integration waveform data, thereby reducing the processing load on the controller 3.

[0138] In the embodiment described above, process step S222 corresponds to a process carried out by a road shape procurement unit, and process steps S224, S240, S250 and S300 to S330 correspond to a process carried out by a target location selection unit. Fifth embodiment

[0139] A fifth embodiment of the present invention is described below with reference to the accompanying drawings. In the fifth embodiment, only the part that differs from the first embodiment is described. The same reference numerals are used for the same components.

[0140] The fifth embodiment of the LIDAR device 1 differs from the first embodiment in that the integration distance measurement process is modified.

[0141] The integration distance measurement process of the fifth embodiment differs from that of the first embodiment in that the process S252 is added.

[0142] That is, when process step S250 is completed, CPU 61 in step S252 sets the standard deviation σ of the normal distribution, represented by equation (1) above, based on the noise value of the target location area calculated in step S90, and then proceeds to step S260, as described in Fig. Figure 25 illustrates this. In the present embodiment, more precisely, the CPU 61 sets the standard deviation σ to a preset low-light standard deviation σ1 when the noise value of the target location range is equal to or less than a predefined standard deviation determination value. When the noise value of the target location range is greater than the predefined standard deviation determination value, the CPU 61 sets the standard deviation σ to a preset high-light standard deviation σ2. The low-light standard deviation σ1 is smaller than the high-light standard deviation σ2. In the present embodiment, the low-light standard deviation σ1 is the standard deviation of the normal distribution ND1, as shown in Figure 25. Fig. Figure 26 shows the high-light level standard deviation σ2, which is the standard deviation of the normal distribution ND2, as shown in Fig. 26 is shown.

[0143] In the LIDAR device 1 thus configured, the controller 3 calculates the multiplication coefficient for each of the position ranges OR(i, j) such that the multiplication coefficient exhibits a positive correlation with the level of the background light of the target position range. The expression "positive correlation with the level of the background light" means not only that the multiplication coefficient increases continuously with an increase in the level of the background light, but can also mean that the multiplication coefficient increases stepwise with an increase in the level of the background light.

[0144] That is, in cases where there is a vehicle located in the target position area, the multiplication coefficient decreases for a vehicle color with a low background light level (e.g., black) and increases for a vehicle color with a high background light level (e.g., white).

[0145] With this configuration, the LIDAR device 1 can prevent the integration or summation of unsuitable coefficient multiplication waveform data in the case of a vehicle color with a low background light level and can increase the effectiveness of improving the detection sensitivity of the light receiving unit 30 by integrating or summing the coefficient multiplication waveform data in the case of a vehicle color with a high background light level.

[0146] In the embodiment described above, process steps S252 and S260 correspond to a process carried out by a coefficient calculation unit.

[0147] While specific embodiments of the present invention have been described above, the present invention is not limited to the embodiments described above, and various modifications are possible. First modification

[0148] In each of the above embodiments, the coefficient multiplication waveform data of the target position area and the position areas immediately adjacent to the target position area (i.e., the position areas that are one column and / or one row away from the target position area) are integrated or summed. According to one modification, the coefficient multiplication waveform data of the target position area and the position areas that are one or more columns and / or one or more rows away from the target position area can be integrated or summed. Second modification

[0149] In each of the above embodiments, the filtering process is carried out using a bilateral filter. According to one modification, instead of the bilateral filter, any other filter that preserves and smooths the edges of the waveform can be used in the filtering process. Third modification

[0150] In the second embodiment described above, the integration or summation of the coefficient multiplication waveform data is prevented if the vehicle speed Vv is less than the distance measurement value J2. According to a modification, the controller 3 can determine, based on information from the navigation device 73, whether the vehicle is traveling on a highway and can prevent the integration or summation of the coefficient multiplication waveform data if the vehicle is traveling on a highway. That is, if the controller 3 determines that the vehicle is traveling on a highway, the controller 3 can determine that the vehicle speed Vv exceeds 80 km / h. Fourth modification

[0151] In the embodiment above, the total positional standard deviation Var is calculated using the result of the acquisition by the light receiving unit 30. According to a modification, the total positional standard deviation Var can be calculated based on image data acquired by a camera designed to image the vehicle's surroundings. Fifth modification

[0152] In the fifth embodiment above, the standard deviation σ of the normal distribution, represented by equation (1) above, is adjusted stepwise depending on the noise level of the target position domain. According to a modification, the standard deviation σ can be changed continuously depending on the noise level of the target position domain.

[0153] The control system 3 and its methods described herein can be implemented by an associated computer containing a processor and memory, programmed to execute one or more functions performed by computer programs. Alternatively, the control system 3 and its methods described herein can be implemented by an associated computer containing a processor comprised of one or more associated hardware logic circuits, or by one or more associated computers comprising a combination of a processor and memory programmed to perform one or more functions, and a processor comprised of one or more associated hardware logic circuits. The computer programs can be defined as instructions to be executed by a computer.Commands must be stored in a non-volatile, physical, computer-readable storage medium.

[0154] In the embodiments described above, multiple functions of a single component can be implemented by multiple components, or a single function of a single component can be implemented by multiple components. Furthermore, multiple functions of multiple components can be implemented by a single component, or a function that is implemented by multiple components can be implemented by a single component.

[0155] Apart from the LIDAR device 1 described above, the present invention can be implemented in various modes, for example as a system that includes the LIDAR device 1 as a component, a program for causing a computer to serve as the LIDAR device 1, a non-volatile physical storage medium such as a semiconductor memory that stores this program, a distance measurement method, and other things.

Claims

[1] Distance measuring device comprising: a light-emitting unit (10, 20) designed to emit light; a light detection unit (30) designed to detect reflected light; a background light calculation unit (S90) designed to calculate, for each of several position areas formed by subdividing a light irradiation area illuminated by the light, a background light level parameter relating to a level of background light arriving from the position area, based on a result of a detection by the light detection unit; a target position selection unit (S218, S220, S224, S240, S250, S300 to S330) designed to successively select one of the position areas as a target position area; a coefficient calculation unit (S260) designed to calculate a multiplication coefficient for the target position area selected by the target position selection unit and several ambient position areas in the vicinity of the target position area such that the respective multiplication coefficients for the respective ambient position areas each exhibit a negative correlation to a difference between the background light level parameter for the target position area and the background light level parameter for the respective ambient position area; a distance measurement waveform generation unit (S20, S110 to S140) designed to generate distance measurement waveform data for each of the position ranges, indicating temporal changes of a light detection parameter up to the expiration of a preset distance measurement period since the emission of the light, wherein the light detection parameter indicates the result of the detection by the light detection unit; a coefficient multiplication waveform generation unit (S270) designed to generate coefficient multiplication waveform data for the target position range and the surrounding position ranges, which are obtained by multiplying the corresponding distance measurement waveform data by the corresponding multiplication coefficient; an integration waveform generation unit (S280) designed to generate integration waveform data by integrating or summing the coefficient multiplication waveform data from the target positional region and from the surrounding positional regions; and a measuring unit (S290) designed to measure a distance to an object reflecting light using the integration waveform data generated by the integration waveform generation unit. [2] Distance measuring device according to claim 1, which further comprises: a standard deviation calculation unit (S100) designed to calculate a standard deviation parameter relating to the standard deviation of the background light levels over the entire illuminance range; and a deviation prevention unit (S210) designed to prevent the execution of processing by at least the background light calculation unit, the target position selection unit and the coefficient calculation unit in cases where the standard deviation parameter is equal to or less than a preset deviation determination value. [3] Distance measuring device according to claim 1 or 2, wherein the coefficient calculation unit is designed to calculate the respective multiplication coefficient for the respective ambient position range such that the multiplication coefficient has a positive correlation to the level of the background light of the target position range. [4] Distance measuring device according to one of claims 1 to 3, which further comprises: a background light waveform generation unit (S10-S50, S70) designed to generate, for each of the position ranges, background light waveform data based on the result of the acquisition by the light sensing unit, indicating temporal changes of the light sensing parameter within a background light acquisition period set such that it does not overlap with the distance measurement period; and a filter unit (S80) designed to perform a filtering process with respect to the background light waveform data for each of the position ranges, wherein the background light calculation unit is designed to calculate the background light level parameter for each of the position ranges using the background light waveform data with respect to which the filtering process was carried out by the filter unit. [5] Distance measuring device according to any one of claims 1 to 4, wherein the background light calculation unit is designed to calculate the background light level parameter on the basis of the result of the detection by the light detection unit immediately before a start of the distance measurement period. [6] Distance measuring device according to any one of claims 1 to 5, wherein the distance measuring device is designed to be mounted on a vehicle and furthermore comprises: a vehicle speed determination unit (S212) designed to determine whether a vehicle's speed is equal to or less than a preset vehicle speed determination value; and a vehicle speed prevention unit (S212) designed to prevent, in response to the vehicle speed determination unit determining that the vehicle's speed is equal to or less than the preset vehicle speed determination value, the execution of processing by at least the background light calculation unit, the target position selection unit and the coefficient calculation unit. [7] Distance measuring device according to any one of claims 1 to 6, wherein the distance measuring device is designed to be mounted on a vehicle and also includes a lane detection unit (S214, S216) designed to detect the position of a lane on which the vehicle is traveling, The target position selection unit (S218, S240, S250, S300 to S330) is designed to select, based on a result of a detection by the lane detection unit, the position area in which the lane is located among the position areas, as the target position area. [8] Distance measuring device according to any one of claims 1 to 7, wherein the distance measuring device is designed to be mounted on a vehicle and also includes a road shape acquisition unit (S222) designed to acquire road map data that specifies a shape of a road around the vehicle, and The target position selection unit (S224, S240, S250, S300 to S330) is designed to select, based on the procured road map data from the position areas, the position area in which the road is arranged around the vehicle as the target position area.

Images