Distance measuring apparatus and distance measuring method

Abstract

To improve measurement accuracy by reducing noise derived from weather in a distance measuring device using reflection of light.SOLUTION: The output unit 110 outputs a plurality of light beams having different peak wavelengths. The acquisition unit 120 acquires a reflection pattern, which is an intensity waveform of reflected light, for each of the plurality of lights. The processing unit 130 specifies a component derived from the weather included in at least one reflection pattern among the plurality of reflection patterns based on the plurality of reflection patterns. The distance calculation unit 150 calculates a distance between the distance measuring device 10 and a target object irradiated with light.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a distance measurement device and a distance measurement method. [Background technology]

[0002] In recent years, there has been progress in the development of non-contact distance measurement devices that can be used in autonomous driving, etc. Non-contact distance measurement devices measure the distance to surrounding objects by measuring the time it takes for emitted light to be reflected by an object and return. However, noise can occur in the reflected light depending on the weather.

[0003] For example, Patent Document 1 describes a device that irradiates a laser beam onto an object at a known distance and determines the weather based on received waveform data of the reflected light.

[0004] Furthermore, for example, Patent Document 2 describes a technology that projects near-infrared light in a wavelength range that is highly absorbed by water and near-infrared light in a wavelength range that is less absorbed by water, and distinguishes between snow, sleet, and rain based on the fluctuation value of the intensity of each near-infrared light. Specifically, the technology in Patent Document 2 defines a fluctuation value equal to or greater than a threshold as an effective value, compares the effective values ​​of each wavelength to determine a discrimination value, and compares the discrimination value with a reference value to make a discrimination. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-52465 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-122413 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the techniques of Patent Documents 1 and 2 were unable to reduce noise in the reflection intensity waveform that is caused by weather.

[0007] One example of a problem to be solved by the present invention is to reduce noise caused by weather and improve measurement accuracy in a distance measurement device that uses light reflection. [Means for solving the problem]

[0008] The first invention is an output unit that outputs a plurality of light beams each having a different peak wavelength; an acquisition unit that acquires a reflection pattern, which is an intensity waveform of reflected light, for each of the plurality of light beams; a processing unit that identifies a weather-related component included in at least one of the plurality of reflection patterns based on the plurality of reflection patterns; A distance measuring device comprising:

[0009] The second invention is: It outputs multiple lights with different peak wavelengths, acquiring a reflection pattern, which is an intensity waveform of reflected light, for each of the plurality of light beams; The distance measurement method is for identifying a weather-related component contained in at least one of the plurality of reflection patterns based on the plurality of reflection patterns. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram illustrating a functional configuration of a distance measurement device according to a first embodiment. [Figure 2] 1 is a diagram illustrating the configuration and usage environment of a distance measurement device according to a first embodiment. [Figure 3] FIG. 10 is a diagram illustrating an example of a reflection pattern. [Figure 4] FIG. 2 is a block diagram illustrating the functional configuration of a processing unit according to the first embodiment. [Figure 5] 3 is a flowchart of a distance measurement method according to the first embodiment. [Figure 6] 4 is a flowchart illustrating processing content performed by a processing unit in the first embodiment. [Figure 7] FIG. 10 is a diagram showing a first example of a plurality of reflection patterns. [Figure 8] FIG. 10 is a diagram showing a second example of a plurality of reflection patterns. [Figure 9] 10 is a flowchart showing a modified example of the processing content performed by the processing unit in the first embodiment. [Figure 10] FIG. 10 is a block diagram illustrating the functional configuration of a distance measurement device according to a second embodiment. [Figure 11] FIG. 10 is a block diagram illustrating the functional configuration of a processing unit according to a second embodiment. [Figure 12] 10 is a flowchart of a distance measurement method according to a second embodiment. [Figure 13] FIG. 10 is a block diagram illustrating the functional configuration of a processing unit according to a third embodiment. [Figure 14] 10 is a flowchart showing the steps of identifying components derived from weather according to the third embodiment. [Figure 15] FIG. 10 is a block diagram illustrating the configuration of a distance measurement device according to a fourth embodiment. [Figure 16] FIG. 10 is a diagram showing an environment in which a distance measuring device according to a fourth embodiment is used. [Figure 17] FIG. 2 is a block diagram illustrating a functional configuration of a server. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, like components are designated by like reference numerals, and the description thereof will be omitted as appropriate.

[0012] In the following description, the output unit 110, acquisition unit 120, processing unit 130, distance calculation unit 150, memory unit 140, matching peak extraction unit 132, matching peak number determination unit 134, identification unit 136, weather information acquisition unit 160, weather determination unit 138, communication unit 170, communication unit 610, selection unit 620, and memory unit 630 of the distance measurement device 10 represent functional blocks rather than hardware-based configurations. The acquisition unit 120, processing unit 130, distance calculation unit 150, memory unit 140, coincident peak extraction unit 132, coincident peak number determination unit 134, identification unit 136, weather information acquisition unit 160, weather determination unit 138, communication unit 170, communication unit 610, selection unit 620, and memory unit 630 of the distance measurement device 10 are realized by any combination of hardware and software, centered on the CPU, memory, program loaded into memory, storage media such as a hard disk for storing the program, and a network connection interface of any computer. There are many variations in the realization methods and devices.

[0013] (First embodiment) FIG. 1 is a block diagram illustrating the functional configuration of a distance measurement device 10 according to the first embodiment. The distance measurement device 10 according to this embodiment includes an output unit 110, an acquisition unit 120, and a processing unit 130. The output unit 110 outputs a plurality of light beams each having a different peak wavelength. The acquisition unit 120 acquires a reflection pattern, which is an intensity waveform of the reflected light, for each of the plurality of light beams. The processing unit 130 identifies a weather-related component included in at least one of the plurality of reflection patterns based on the plurality of reflection patterns.

[0014] The distance measurement device 10 according to this embodiment further includes a distance calculation unit 150 that calculates the distance between the distance measurement device 10 and the target object onto which light is irradiated. The distance calculation unit 150 generates a corrected reflection pattern by subtracting a component due to weather from at least one reflection pattern, and calculates the distance based on the corrected reflection pattern. Furthermore, in the example shown in the figure, the distance measurement device 10 includes a memory unit 140.

[0015] Fig. 2 is a diagram illustrating the configuration and usage environment of the distance measurement device 10 according to this embodiment. Each component of the distance measurement device 10 will be described in detail below using Fig. 1 and Fig. 2. In Fig. 2, multiple light beams are indicated by solid arrows and dashed arrows. Hereinafter, the light beams indicated by the solid arrows will be referred to as first light beams, and the light beams indicated by the dashed arrows will be referred to as second light beams.

[0016] The distance measurement device 10 is a device that measures the distance from the distance measurement device 10 to a target object 20. A plurality of light beams emitted from the output unit 110 (e.g., laser light source 810) of the distance measurement device 10 are reflected by the target object 20 and return toward the distance measurement device 10. The reflected light beams are incident on the first light receiving element 850a and the second light receiving element 850b, and the intensity of the reflected light is detected. The distance measurement device 10 measures the time from when the light beam is emitted from the output unit 110 to when the reflected light is detected. The acquisition unit 120 acquires information indicating the relationship between this time and the intensity of the reflected light as information indicating a reflection pattern. Peaks resulting from the light beam reflected by the target object 20 appear in the reflection pattern. The round-trip distance from the distance measurement device 10 to the target object 20 is calculated by multiplying the time from when the light beam is emitted from the output unit 110 to when the reflected light beam is incident on the first light receiving element 850a and the second light receiving element 850b by the speed of light. The position of the peak in the reflection pattern corresponds to the time from when light is emitted from the laser light source 810 until the reflected light is incident on the first light receiving element 850a and the second light receiving element 850b, i.e., corresponds to the distance from the distance measurement device 10 to the object that reflected the light. The distance measurement device 10 is, for example, a LIDAR (Laser Imaging Detection and Ranging) device.

[0017] The output unit 110 is, for example, a laser light source 810. The light output by the output unit 110 is pulsed light. The output unit 110 outputs multiple light beams each having a different peak wavelength. The peak wavelength of the first light is a first wavelength, and the peak wavelength of the second light is a second wavelength. Here, the peak wavelength is the wavelength showing the maximum intensity peak in the spectrum of each light beam. The first wavelength and the second wavelength are different from each other. The light of the first wavelength is, for example, visible light, and the first wavelength is, for example, 380 nm or more and 800 nm or less. The light of the second wavelength is, for example, near-infrared light, and the second wavelength is, for example, 800 nm or more and 2500 nm or less. However, the light of the first wavelength may also be near-infrared light. Specifically, a light source for the first light may be a semiconductor laser emitting light with a wavelength of 780 nm. A light source for the second light may be a semiconductor laser emitting light with a wavelength of 820 nm. The peak wavelengths of the multiple light beams are, for example, 50 nm or more apart from each other.

[0018] Alternatively, a semiconductor laser emitting light with a wavelength of 780 nm or 820 nm may be used as the light source of the first light, and a semiconductor laser with a wavelength of 980 nm may be used as the light source of the second light. Considering the spectral reflectance characteristics of snow shown in "The Effect of Snow Surface Reflection on the Amount of Power Generated by Solar Cells" (The Bulletin of Laboratory for Energy, Environment and Systems, Hachinohe Institute of Technology, 10, 29-34, March 30, 2012), noise reduction can be achieved with even greater precision by using such wavelengths as the first and second wavelengths. Meanwhile, because the magnitude of light scattering varies depending on the particle size and wavelength, if the size of the particles causing the noise to be removed is known, it is preferable to use wavelengths that straddle that particle size as the first and second wavelengths.

[0019] The optical axes of the first light and the second light are substantially aligned. However, for convenience in this diagram, the optical axes of the solid and dashed arrows are shown shifted from each other. As the output unit 110, a packaged light source capable of outputting multiple light beams with different peak wavelengths, such as a dual-wavelength output laser diode, can be used, as in the example of FIG. 2. However, without being limited to the example shown in this diagram, the output unit 110 may be configured using multiple light sources that output a single light beam. In this case, the optical axes of the multiple light beams can be aligned using a dichroic mirror, a polarizing prism, a half mirror, or the like, and the beams can be output to the outside of the distance measurement device 10.

[0020] A plurality of pulsed beams with different peak wavelengths are simultaneously output from the laser light source 810. The output timing of the laser light source 810 is controlled by a controller 812. The controller 812 controls the laser light source 810 based on an input signal from an information processing device 870. The information processing device 870 is, for example, a computer including a CPU, a memory, a program loaded into the memory, a storage medium such as a hard disk for storing the program, an interface for network connection, etc.

[0021] The light output from the laser light source 810 is output to the outside of the distance measurement device 10 via the collimator lens 814 and the half mirror 830. It is then reflected by the target object 20 and returns to the distance measurement device 10. The timing, direction, and position of the output of multiple light beams from the distance measurement device 10 are approximately the same. At least a portion of the light returned to the distance measurement device 10 is guided to the first light receiving element 850a and the second light receiving element 850b via the half mirror 830 and the detection-side lens 852. The first light receiving element 850a and the second light receiving element 850b are, for example, photodiodes. The first light receiving element 850a and the second light receiving element 850b may be the same element, or may have different detectable wavelength bands so that the first light and the second light can be effectively detected, respectively.

[0022] Note that a polarizing beam splitter may be used instead of the half mirror 830. In the example of FIG. 2, the acquisition unit 120 is realized by at least a first light receiving element 850a, a second light receiving element 850b, a detection circuit 853, and an information processing device 870. A first filter 851a is provided between the first light receiving element 850a and the detection-side lens 852, and a second filter 851b is provided between the second light receiving element 850b and the detection-side lens 852. The first filter 851a is an optical filter that transmits light of a first wavelength and suppresses transmission of light of other wavelengths, and the second filter 851b is an optical filter that transmits light of a second wavelength and suppresses transmission of light of other wavelengths. For example, the transmittance of the first filter 851a for light of the first wavelength is 90% or more and the transmittance of the second wavelength is 50% or less. Furthermore, the transmittance of the second filter 851b for light of the second wavelength is 90% or more and the transmittance of the first wavelength is 50% or less.

[0023] The first light and the second light may be incident on both the first filter 851a and the second filter 851b. However, the first light is preferentially incident on the first light receiving element 850a by passing through the first filter 851a, and the second light is preferentially incident on the second light receiving element 850b by passing through the second filter 851b. Therefore, the first light receiving element 850a and the second light receiving element 850b can individually detect the reflected light of the first light and the reflected light of the second light.

[0024] The configuration of the distance measurement device 10 is not limited to the example shown in FIG. 2 as long as it can detect the reflected light of the first light and the reflected light of the second light individually. For example, instead of using the first filter 851a and the second filter 851b, a dichroic mirror may be used to separate multiple light beams with different peak wavelengths, and each may be detected by a light receiving element. Also, while FIG. 2 shows an example in which the first filter 851a and the second filter 851b are provided adjacent to each other, the configuration is not limited to this example. For example, a mixture of the first light beam and the second light beam may be separated into multiple optical paths by a half mirror, and then the multiple optical paths may be incident on optical filters and light receiving elements with different transmission wavelengths.

[0025] The optical system of the distance measurement device 10 may also be configured similarly to an optical disk pickup. That is, p-polarized light that passes through a polarizing prism is emitted to the outside of the distance measurement device 10 via a 1 / 4λ plate. Light reflected from the target object 20 or the like is converted to s-polarized light by passing it through a 1 / 4λ plate, and then reflected by a polarizing prism, so that theoretically 100% of the light amount can be detected. For two wavelengths, appropriate wave plates can be calculated and designed accordingly.

[0026] Whichever optical system is used, it is important to design the distances from the light source to the target object and from the target object to the light receiving element to be equal for the two wavelengths.

[0027] When light is incident on the first light receiving element 850a and the second light receiving element 850b, an electrical signal corresponding to the intensity of the incident light is generated by the detection circuit 853 and input to the information processing device 870. Then, the information processing device 870 associates the received light intensity with time. In this way, the acquisition unit 120 acquires a reflection pattern for each of the multiple light beams. Here, the reflection pattern indicates the intensity waveform of the reflected light. Note that the intensity waveform indicates the relationship between the time from when light is emitted from the output unit 110 to when the reflected light is detected and the intensity of the reflected light.

[0028] Furthermore, for example, a gate means may be provided between the first light receiving element 850a and the second light receiving element 850b and the detection-side lens 852 so that detection is performed only during the time when light reflected from the target object 20 is expected to be incident. By doing so, noise resulting from external light and reflected light from objects other than the target object 20 can be reduced.

[0029] Here, when measuring distances outdoors using the distance measurement device 10, particles 22 floating between the distance measurement device 10 and the target object 20 due to rain, fog, snow, or the like cause noise. That is, the light output from the output unit 110 hits the particles 22 before reaching the target object 20, and is reflected or scattered. The light reflected by the particles 22 also enters the first light receiving element 850a and the second light receiving element 850b, and is reflected in the reflection pattern. In this case, noise peaks other than the target peaks originating from the target object 20 appear in the reflection pattern, making it difficult to distinguish between them.

[0030] 3 is a diagram showing an example of a reflection pattern. In this example, the reflection pattern includes a noise peak 41 resulting from noise and a target peak 42 resulting from the target object 20. However, in reality, it is unclear which peaks in the reflection pattern are noise peaks 41 and which are target peaks 42. Furthermore, the effect of weather on the reflection pattern varies depending on the weather, and the shapes of the noise peak 41 and the target peak 42 may each vary depending on the weather.

[0031] As will be described later, in the distance measurement device 10 according to this embodiment, the processing unit 130 compares peaks that appear in multiple reflection patterns obtained using multiple lights with different peak wavelengths, and identifies components that are attributable to weather. This reduces noise peaks 41 from the reflection patterns, thereby improving the accuracy of distance measurement.

[0032] The processing unit 130 is realized by the information processing device 870. Based on the plurality of reflection patterns acquired by the acquisition unit 120, the processing unit 130 identifies a component derived from weather that is included in at least one of the plurality of reflection patterns.

[0033] 4 is a block diagram illustrating the functional configuration of the processing unit 130 according to the first embodiment. In this embodiment, the processing unit 130 includes a coincident peak extraction unit 132, a coincident peak number determination unit 134, and an identification unit 136. The coincident peak extraction unit 132 extracts coincident peaks whose positions match in a plurality of reflection patterns. The coincident peak number determination unit 134 determines the number of coincident peaks extracted by the coincident peak extraction unit 132. The identification unit 136 identifies components derived from weather based on the determination result of the coincident peak number determination unit 134.

[0034] 1 and 2, distance calculation unit 150 is realized by information processing device 870. Distance calculation unit 150 generates a corrected reflection pattern by subtracting the weather-related component identified by processing unit 130 from at least one reflection pattern. Then, distance is calculated based on the corrected reflection pattern. The processing details of processing unit 130 and distance calculation unit 150 will be described in detail later.

[0035] 5 is a flowchart of a distance measurement method according to the first embodiment. This distance measurement method can be realized by a distance measurement device 10. In this distance measurement method, a plurality of light beams, each with a different peak wavelength, are output (step S10), a reflection pattern, which is an intensity waveform of the reflected light, is acquired for each of the plurality of light beams (step S20), and a component attributable to weather contained in at least one of the plurality of reflection patterns is identified based on the plurality of reflection patterns (step S30).

[0036] In the distance measurement method according to this embodiment, a corrected reflection pattern in which components derived from weather are reduced is generated (step S40), and the corrected reflection pattern is used to calculate the distance between the distance measurement device 10 and the target object 20 (step S50). This will be explained in detail below.

[0037] First, in step S10, output unit 110 outputs a plurality of light beams as described above. Then, in step S20, acquisition unit 120 acquires a reflection pattern for each of the plurality of light beams as described above.

[0038] Next, in step S30, the processing unit 130 identifies components of the reflection pattern that are attributable to weather, for example, as described below.

[0039] 6 is a flowchart illustrating the processing performed by the processing unit 130 in this embodiment. The coincident peak extraction unit 132 of the processing unit 130 extracts coincident peaks whose positions coincide in multiple reflection patterns (step S310). Specifically, first, for each reflection pattern, the time point at which the differential value of the reflected light intensity with respect to time turns from positive to negative is extracted as the peak position. The peak positions extracted here may be one or more for each reflection pattern. Then, the peak positions of the multiple reflection peaks are compared to extract coincident peaks whose positions coincide. Note that "peak positions coincide" does not only mean a perfect match, but also includes cases where the positions differ within the range of measurement error.

[0040] If no matching peak is found, for example, the output unit 110 outputs light again, and multiple reflection patterns are obtained.

[0041] Next, the coincident peak number determination unit 134 determines the number of coincident peaks extracted by the coincident peak extraction unit 132 (step S320). For example, the coincident peak number determination unit 134 determines whether the number of coincident peaks is one, or two or more.

[0042] The identifying unit 136 then identifies the components that are derived from the weather based on the determination result of the matched peak number determining unit 134. Specifically, the identifying unit 136 can identify the components that are derived from the weather, for example, as follows.

[0043] When the number of matching peaks is 1 (Y in step S320), the identification unit 136 of the processing unit 130 identifies, in at least one reflection pattern, peaks other than the matching peak among the peaks extracted by the matching peak extraction unit 132, as components derived from weather (step S330). Here, when the number of matching peaks is 1, this can be said to mean that the positions of peaks appearing in the reflection patterns match each other at only one position among multiple reflection patterns, in other words, when there is only one position where the peaks match.

[0044] FIG. 7 is a diagram showing a first example of multiple reflection patterns. The upper diagram in this diagram shows the reflection pattern of the first light, and the lower diagram shows the reflection pattern of the second light. The origin of both reflection patterns is the time of light output. In this example, the number of coincident peaks is one. In this case, peaks whose positions do not coincide among the reflection peaks in the upper and lower diagrams can be considered to be noise peaks 41 due to weather. For example, differences in the wavelength of light can affect the probability of light being scattered by particles 22, or a slight mismatch in the optical path can result in only one of the multiple light beams being reflected by particles 22. As a result, the peak positions of light reflected by particles 22 may not coincide among the multiple reflection patterns. On the other hand, peaks from sufficiently large target objects 20 are considered to coincide. Therefore, the identification unit 136 can identify peaks other than the peaks whose positions coincide as components due to weather. The number of peaks identified as components due to weather may be one or more in each reflection pattern.

[0045] In the reflection pattern, each peak is identified, for example, by the time period in which the peak appears. Alternatively, each peak may be identified by peak data, which will be described below. When each peak is identified by peak data, the information indicating the reflection pattern includes multiple peak data. Each peak data is data indicating one peak of light intensity with respect to time, and may be, for example, a graph, a table, or a mathematical formula. Alternatively, each peak data may be a combination of the peak position, peak intensity, and half-width. The reflection pattern is represented by a superposition of peaks indicated by multiple peak data. By fitting the acquired reflection pattern (intensity waveform) with a predetermined function, the peaks can be separated and multiple peak data can be generated.

[0046] On the other hand, when the number of matching peaks is not 1 (N in step S320), that is, when the positions of peaks appearing in the reflection patterns match each other at two or more positions among the multiple reflection patterns, the identification unit 136 of the processing unit 130 identifies the peak among the matching peaks whose level increases as the peak wavelength of the light becomes longer as a component resulting from weather (step S340).

[0047] FIG. 8 is a diagram showing a second example of multiple reflection patterns. The upper diagram in this diagram is the reflection pattern of the first light, and the lower diagram is the reflection pattern of the second light. The origin of both reflection patterns is the time of light output. In this example, the peak wavelength of the first light is shorter than the peak wavelength of the second light. In this example, the number of coincident peaks is two. In this case, the coincident peaks whose peak intensity (level) increases as the wavelength of light increases can be considered to be noise peaks 41 caused by weather.

[0048] For example, the longer the wavelength of light, the smaller the intensity of backscattering by particles 22. As a result, it is believed that the peak intensity of light reflected by particles 22 increases as the wavelength of light increases. On the other hand, it is believed that the reflectance of light from target object 20 is less affected by the wavelength of light. In particular, if the reflective surface of target object 20 is white, the difference in reflectance due to differences in wavelength becomes small. An example of such a case is when distance measurement device 10 is mounted on a moving object such as a vehicle and detects reflected light from a white license plate of another moving object, i.e., a vehicle ahead.

[0049] Here, the comparison of peak intensities between multiple reflection patterns is performed using the normalized peak intensity for each reflection pattern. For example, the sum of the peak intensities of all coincident peaks in a reflection pattern is expressed as I t , the peak intensity of the target peak is I o When I o / I t The value obtained by the above formula is used as the normalized peak intensity. Furthermore, the comparison of peak intensities of coincident peaks is performed between peaks whose peak positions coincide with each other.

[0050] Note that, when the particle size of the particles 22 is smaller than the wavelength of the first light and the second light, the longer the wavelength of the light, the smaller the intensity of scattering by the particles 22 may be. When such weather or environment is predicted in advance, the user may perform a switching operation or the like to identify, in step S340, a peak whose level decreases as the wavelength of the light becomes longer, as a component resulting from the weather.

[0051] If the number of coincident peaks is not 1 (N in step S320), the identifying unit 136 may further identify peaks other than the coincident peaks as components derived from weather, as in step S330.

[0052] 9 is a flowchart showing a modified example of the processing performed by the processing unit 130 in this embodiment. As shown in this figure, after the matching peaks are extracted, the identification unit 136 may identify peaks other than the matching peaks as components attributable to weather before determining the number of matching peaks (step S330). In this case, the matching peak number determination unit 134 determines the number of matching peaks after step S330 (step S320). If the number of matching peaks is one (Y in step S320), the identification unit 136 identifies only the peak identified in step S330 as components attributable to weather. If the number of matching peaks is not one (N in step S320), the identification unit 136 further identifies peaks whose levels increase as the wavelength of light becomes longer as components attributable to weather (step S340).

[0053] In this way, the processing unit 130 identifies the component due to weather. The processing unit 130 outputs the time period of the peak due to weather in the reflection pattern or the above-mentioned peak data as information indicating the component due to weather in at least one reflection pattern (for example, the reflection pattern of the first light).

[0054] Returning to FIG. 5, the distance calculation unit 150 then generates a corrected reflection pattern by subtracting the weather-related component identified by the processing unit 130 from at least one reflection pattern (step S40). Specifically, the distance calculation unit 150 acquires information indicating the weather-related component from the processing unit 130. Then, the distance calculation unit 150 subtracts the peak indicated by the information indicating the weather-related component from the reflection pattern in which the weather-related component has been identified (for example, the reflection pattern of the first light). For example, the distance calculation unit 150 may generate a corrected reflection pattern by setting the intensity of the reflection pattern to zero during a time period in which the weather-related peak is located. Furthermore, if the information indicating the weather-related component is peak data, the distance calculation unit 150 may generate a corrected reflection pattern by subtracting the peak from the reflection pattern.

[0055] Furthermore, when a matching peak is identified as a peak attributable to weather, such as the peak identified in step S340, the distance calculation unit 150 can generate a corrected reflection pattern as follows. Below, we will explain the case where a noise peak 41 (a component attributable to weather) in the reflection pattern of the first light is smaller than the peak at the same position in the reflection pattern of the second light, as shown in FIG. 8. In this case, the overall intensity of the reflection pattern of the second light is multiplied by a predetermined magnification factor α. Then, the second reflection pattern multiplied by α is subtracted from the reflection pattern of the first light. In this way, a corrected reflection pattern can be generated in which the noise peak 41 is reduced from the reflection pattern of the first light.

[0056] Here, information indicating the magnification α can be derived, for example, by a preliminary test or the like using the intensity ratio of the noise peaks 41 in the first light and the second light, and stored in the storage unit 140, from which the distance calculation unit 150 can read and use it. Alternatively, the distance calculation unit 150 may derive the magnification α each time from the relationship α=I1 / I2 using the peak intensity I1 of the noise peak 41 in the first light and the peak intensity I2 of the noise peak 41 in the second light, which are positioned to coincide with each other. Here, if there are multiple noise peaks 41 positioned to coincide in each reflection pattern, I1 / I2 can be calculated for each noise peak 41, and the average value thereof can be used as α.

[0057] In the above, when subtracting the second reflection pattern multiplied by α from the reflection pattern of the first light, the subtraction may be performed only for the time period in which the noise peak 41 occurs in the first reflection pattern.

[0058] Next, distance calculation unit 150 calculates the distance between distance measurement device 10 and target object 20 using the corrected reflection pattern (step S50). That is, the maximum peak in the corrected reflection pattern is considered to be the reflection peak from target object 20, and the time from when light is emitted to when the reflection peak is detected is calculated based on the position of that peak. Then, the round-trip distance from distance measurement device 10 to target object 20 is calculated by multiplying the calculated time by the speed of light.

[0059] Alternatively, the output unit 110 may output a plurality of light beams multiple times, the acquisition unit 120 may acquire a reflection pattern each time, and the distance calculation unit 150 may generate a plurality of corrected reflection patterns. The distance may then be calculated by accumulating the plurality of corrected reflection patterns. This allows for even more accurate distance measurement.

[0060] As described above, according to this embodiment, the output unit 110 outputs multiple light beams each with a different peak wavelength, the acquisition unit 120 acquires a reflection pattern, which is an intensity waveform of the reflected light, for each of the multiple light beams, and the processing unit 130 identifies a weather-related component contained in at least one of the multiple reflection patterns based on the multiple reflection patterns. Therefore, it is possible to reduce noise caused by weather and improve measurement accuracy.

[0061] (Second embodiment) Fig. 10 is a block diagram illustrating the functional configuration of a distance measurement device 10 according to the second embodiment, and Fig. 11 is a block diagram illustrating the functional configuration of a processing unit 130 according to the second embodiment. The distance measurement device 10 according to this embodiment is similar to the distance measurement device 10 according to the first embodiment, except that the processing unit 130 identifies components derived from weather using weather information indicating the weather at the time when multiple reflection patterns are acquired.

[0062] The distance measurement device 10 according to this embodiment further includes a weather information acquisition unit 160. The weather information acquisition unit 160 acquires weather information indicating the weather at the location where the distance measurement device 10 measures the target object 20 at the time the acquisition unit 120 acquires the reflection pattern. The weather information includes information indicating weather such as sunny, rainy, foggy, snowy, and cloudy. The weather information may also include information indicating photochemical smog and the concentration of fine particles suspended in the air. The weather information acquisition unit 160 can acquire the information indicating the weather, for example, via a communication network. Specifically, the weather information can be acquired by accessing a server of a weather information providing service. The weather information acquisition unit 160 may also determine the weather and acquire the weather information based on information indicating temperature acquired from a temperature sensor disposed near the distance measurement device 10 or information indicating illuminance acquired from an illuminance sensor.

[0063] The processing unit 130 according to this embodiment also includes a weather determination unit 138. For example, when the weather is sunny or cloudy, it is considered that noise peaks caused by the weather are unlikely to occur. Therefore, in such weather, it is possible to omit identifying components caused by the weather and generating a corrected reflection pattern, thereby reducing the processing load on the information processing device 870.

[0064] 12 is a flowchart of the distance measurement method according to this embodiment. In this distance measurement method, the contents of steps S10 and S20 are the same as those of the method according to the first embodiment. In the distance measurement method according to this embodiment, after step S20, the weather information acquisition unit 160 acquires weather information (step S22).

[0065] Next, the weather determination unit 138 of the processing unit 130 determines whether the weather indicated by the acquired weather information satisfies a predetermined criterion. Note that information indicating the criterion is pre-stored in the storage unit 140, and the weather determination unit 138 can read it and use it for the determination. The criterion may be a specific weather condition such as sunny or cloudy, or may be a standard value for the level of photochemical smog or the concentration of fine particles suspended in the air, or a combination thereof.

[0066] In the example shown in the figure, weather determination unit 138 determines whether the weather is sunny or cloudy (step S24). If the weather information indicates sunny or cloudy (Y in step S24), processing unit 130 does not identify components derived from the weather. Distance calculation unit 150 then calculates the distance using at least one of the acquired reflection patterns, similar to step S50 in the first embodiment, without generating a corrected reflection pattern.

[0067] If the weather information does not indicate sunny or cloudy (N in step S24), the processing unit 130 then identifies components resulting from the weather (step S30). The distance calculation unit 150 then generates a corrected reflection pattern (step S40) and calculates the distance (step S50). Steps S30 to S50 in this embodiment can be performed in the same way as in the first embodiment.

[0068] The weather determination unit 138 may further determine whether or not the concentration of photochemical smog or airborne fine particles exceeds a reference value, and even if the weather information indicates sunny or cloudy, if the photochemical smog or airborne fine particle concentration indicated by the weather information exceeds a reference value, perform the same processing as when the weather information does not indicate sunny or cloudy (N in step S24). This is because there is a possibility that a noise peak will appear, just as in the case of rain or fog.

[0069] As described above, in this embodiment as well, the output unit 110 outputs multiple light beams each with a different peak wavelength, the acquisition unit 120 acquires a reflection pattern, which is an intensity waveform of the reflected light, for each of the multiple light beams, and the processing unit 130 identifies a weather-related component contained in at least one of the multiple reflection patterns based on the multiple reflection patterns. Therefore, it is possible to reduce noise caused by weather and improve measurement accuracy.

[0070] Additionally, according to this embodiment, the processing unit 130 identifies components originating from weather using weather information indicating the weather at the time when the multiple reflection patterns are acquired. Therefore, it is possible to identify components originating from weather only when an increase in noise originating from weather is expected, thereby reducing the load on information processing.

[0071] (Third embodiment) Fig. 13 is a block diagram illustrating the functional configuration of the processing unit 130 according to the third embodiment. Fig. 14 is a flowchart illustrating the contents of the step (step S30) of identifying components derived from weather according to the third embodiment. The distance measurement device 10 according to this embodiment is similar to the distance measurement device 10 according to the second embodiment except for the configuration of the processing unit 130 and the processing contents of the step (step S30) of identifying components derived from weather.

[0072] For example, when the weather is foggy or rainy, it is highly likely that noise peaks will appear as coincident peaks. Furthermore, when the weather is snowy, the particle diameter is large and the spacing between floating particles is also large, so it is highly likely that the positions of noise peaks will be shifted for multiple lights. Therefore, by using weather information, it is possible to perform processing appropriate for that weather and identify components originating from the weather, without determining the number of coincident peaks.

[0073] The distance measurement method according to this embodiment can be explained using a flowchart similar to that of Fig. 12. In the distance measurement method according to this embodiment, steps other than step S30 are performed in the same manner as in the second embodiment.

[0074] In the distance measurement device 10 according to this embodiment, step S30 is performed as follows. First, the coincident peak extraction unit 132 extracts coincident peaks similar to those in the first embodiment (step S310). Next, the weather determination unit 138 determines whether the weather indicated by the weather information satisfies a predetermined criterion. Information indicating the criterion is pre-stored in the storage unit 140, and the weather determination unit 138 can read it and use it for the determination. The criterion may be a specific weather condition such as rain or fog, or a reference value for the level of photochemical smog or the concentration of fine particles suspended in the air, or a combination thereof. In the example shown in the figure, the weather determination unit 138 determines whether the weather indicated by the weather information is fog or rain (step S350).

[0075] If the weather is foggy or rainy (Y in step S350), the identifying unit 136 identifies the coincident peak, the longer the wavelength, the higher the level, as a component derived from the weather, in the same manner as in the first embodiment (step S340).

[0076] On the other hand, if the weather is not foggy or rainy (N in step S350), the identification unit 136 identifies peaks other than the coincident peaks as components derived from the weather, as in the first embodiment (step S330). Furthermore, the weather determination unit 138 may further determine whether or not the concentrations of photochemical smog or airborne fine particles exceed a reference value, and may perform the same processing as when the weather information indicates fog or rain (Y in step S350) if the photochemical smog or airborne fine particle concentrations indicated by the weather information exceed a reference value even when the weather is not foggy or rainy.

[0077] If the weather is foggy or rainy (Y in step S350), the identifying unit 136 may identify peaks other than the coincident peaks as components derived from the weather, similar to step S330.

[0078] As a modification of step S30, after extracting the matching peaks, the identifying unit 136 may first identify peaks other than the matching peaks as components attributable to the weather, and then the weather determination unit 138 may determine the weather. If the weather is not foggy or rainy, the identifying unit 136 may identify only the peaks already identified above as components attributable to the weather. If the weather is foggy or rainy, the identifying unit 136 may further identify peaks whose levels increase as the wavelength of light becomes longer as components attributable to the weather.

[0079] In this embodiment, in step S350, the weather determination unit 138 may determine whether the weather is snowy or not, instead of determining whether the weather is foggy or rainy. In this case, if the weather is snowy, the same processing as in the case where the weather is not foggy or rainy (N in step S350) is performed, and if the weather is not snowy, the same processing as in the case where the weather is foggy or rainy (Y in step S350) is performed.

[0080] As described above, in this embodiment as well, the output unit 110 outputs multiple light beams each with a different peak wavelength, the acquisition unit 120 acquires a reflection pattern, which is an intensity waveform of the reflected light, for each of the multiple light beams, and the processing unit 130 identifies a weather-related component contained in at least one of the multiple reflection patterns based on the multiple reflection patterns. Therefore, it is possible to reduce noise caused by weather and improve measurement accuracy.

[0081] Additionally, according to this embodiment, when the weather is neither foggy nor rainy, the processing unit 130 identifies, in at least one reflection pattern, peaks other than the coincident peaks extracted by the coincident peak extraction unit 132 as components attributable to the weather. On the other hand, when the weather is foggy or rainy, the processing unit 130 identifies, among the coincident peaks, peaks whose levels increase as the wavelength of light becomes longer as components attributable to the weather. Therefore, it is possible to perform processing appropriate for the weather and identify components attributable to the weather without determining the number of coincident peaks.

[0082] (Fourth embodiment) Fig. 15 is a block diagram illustrating the configuration of a distance measurement device 10 according to the fourth embodiment, and Fig. 16 is a diagram showing the environment in which the distance measurement device 10 according to this embodiment is used. The distance measurement device 10 according to this embodiment is similar to at least one of the second and third embodiments except that a weather information acquisition unit 160 acquires weather information from other distance measurement devices 10 via a communication unit 170.

[0083] The distance measuring device 10 according to this embodiment is connected to a server 60 via a communication network 70, and further includes a communication unit 170. When the weather information acquiring unit 160 determines the weather based on information indicating temperature and information indicating illuminance and acquires weather information, the communication unit 170 transmits the acquired weather information to the server 60 together with information indicating the position of the distance measuring device 10 and the time.

[0084] In this embodiment, the communication unit 170 transmits to the server 60 a signal requesting weather information and information indicating the position of the distance measurement device 10. When the communication unit 170 receives weather information from the server 60 based on the request, the weather information acquisition unit 160 acquires the received weather information. When the communication unit 170 is unable to receive weather information from the server 60, the weather information acquisition unit 160 determines the weather based on information indicating temperature or illuminance obtained by a sensor installed near the distance measurement device 10, and acquires the weather information. When the communication unit 170 is unable to receive weather information from the server 60, the weather information acquisition unit 160 may access a server of a weather information providing service to acquire weather information.

[0085] The communication unit 170 is an interface for wirelessly transmitting and receiving information via the communication network 70. The server 60 can transmit and receive information to and from a plurality of distance measurement devices 10 via the communication network 70. The distance measurement device 10 according to this embodiment is attached to a mobile object, for example. The mobile object is also provided with a position recognition means, such as a GPS (Global Positioning System) device, that can recognize the position (latitude, longitude) of the mobile object. The position recognition means generates information indicating the position of the mobile object.

[0086] In this embodiment, the server 60 receives and stores weather information, location information, and time information transmitted from the distance measurement device 10, and provides weather information that is valid in light of the location information, etc., to the other distance measurement devices 10. By sharing information in this way, each distance measurement device 10 can efficiently improve the accuracy of distance measurement.

[0087] 17 is a block diagram illustrating the functional configuration of the server 60. Specifically, the server 60 includes a communication unit 610, a selection unit 620, and a storage unit 630. The communication unit 610 is an interface for transmitting and receiving information via the communication network 70. The communication unit 610 receives weather information transmitted from the communication unit 170 of the distance measurement device 10. This weather information is information acquired by determining the weather in each distance measurement device 10. The weather information is accompanied by information indicating the location and time at which the weather information was acquired. The received weather information is then stored in the storage unit 630 together with the information indicating the location and time.

[0088] On the other hand, when the communication unit 610 receives a request for weather information accompanied by location information from another distance measurement device 10, the selection unit 620 selects valid weather information from the storage unit 630 based on the location information and the time the request was received. In selecting valid weather information, the selection unit 620 compares the location information accompanying the weather information with the location information accompanying the request to determine whether the locations indicated by the information are sufficiently close. For example, if the distance between the two locations is equal to or less than a predetermined reference distance, the locations are determined to be sufficiently close. The selection unit 620 also compares the time information accompanying the weather information with the time the request was received to determine whether the times are sufficiently close. For example, if the difference between the two times is equal to or less than a predetermined reference time, the locations are determined to be sufficiently close. Here, the information indicating the reference distance and reference time is stored in advance in the storage unit 630, and the selection unit 620 can read and use it.

[0089] The selection unit 620 performs the above determination for each of the multiple pieces of weather information stored in the storage unit 630, and selects the weather information that is determined to be sufficiently close in both location and time. Note that if multiple pieces of weather information are determined to be sufficiently close in both location and time, the weather information with the closest location is selected. Alternatively, the weather information with the closest time may be selected.

[0090] The server 60 transmits the weather information selected by the selection unit 620 to the distance measurement device 10 that sent the request. The distance measurement device 10 that sent the request receives the weather information from the server 60 and can use it to reduce noise.

[0091] On the other hand, if the selection unit 620 determines that there is no weather information that is sufficiently close in both location and time, the server 60 transmits information to the distance measurement device 10 that sent the request indicating that weather information cannot be provided. A distance measurement device 10 that is unable to receive weather information will determine the weather itself and acquire weather information based on information indicating temperature and information indicating illuminance obtained by a sensor installed in the mobile object. Furthermore, when the communication unit 170 is unable to receive weather information from the server 60, the weather information acquisition unit 160 may access a server of a weather information providing service to acquire weather information.

[0092] As described above, in this embodiment as well, the output unit 110 outputs multiple light beams each with a different peak wavelength, the acquisition unit 120 acquires a reflection pattern, which is an intensity waveform of the reflected light, for each of the multiple light beams, and the processing unit 130 identifies a weather-related component contained in at least one of the multiple reflection patterns based on the multiple reflection patterns. Therefore, it is possible to reduce noise caused by weather and improve measurement accuracy.

[0093] Additionally, in this embodiment, when the communication unit 170 receives weather information from the server 60, the processing unit 130 uses the weather information to reduce noise in the reflection pattern. By sharing information in this way, each distance measuring device 10 can obtain the latest weather information with pinpoint accuracy, i.e., with higher positional accuracy, and the accuracy of distance measurement can be improved efficiently.

[0094] Although the embodiments and examples have been described above with reference to the drawings, these are merely examples of the present invention, and various configurations other than those described above can also be adopted.

[0095] For example, in the sequence diagrams and flowcharts used in the above description, multiple steps (processes) are described in order, but the execution order of the steps performed in each embodiment is not limited to the order described. In each embodiment, the order of the steps shown in the drawings can be changed to the extent that the content is not affected. Furthermore, the above-described embodiments can be combined to the extent that the content is not contradictory. [Explanation of symbols]

[0096] 10 Distance measuring device 20 Target Object 22 particles 41 Noise Peak 42 target peaks 60 servers 70 Communication Network 110 Output section 120 Acquisition Department 130 Processing section 132 Match Peak Extraction Unit 134 Matching Peak Number Judgment Unit 136 Specific part 138 Weather Judgment Department 140,630 storage section 150 Distance calculation unit 160 Weather information acquisition department 170,610 Communications Department 620 Selection Section 810 Laser Light Source 812 Controller 814 Collimator Lens 830 Half Mirror 850a First light receiving element 850b Second light receiving element 851a 1st filter 851b 2nd filter 852 Detection side lens 853 Detection circuit 870 Information processing equipment

Claims

1. A distance measuring device for measuring a distance from itself to a target object, an output unit that outputs a plurality of light beams each having a different peak wavelength; an acquisition unit that acquires, for each of the plurality of light beams, a reflection pattern that is an intensity waveform that indicates the relationship between the time from when the light is emitted from the output unit until when the reflected light reflected by the target object and particles floating between the distance measurement device and the target object is detected, and the intensity of the reflected light; a processing unit that identifies a weather-related component included in at least one of the plurality of reflection patterns based on the plurality of reflection patterns; a distance calculation unit that generates a corrected reflection pattern by subtracting the weather-related component identified by the processing unit from the at least one reflection pattern, and calculates the distance based on the corrected reflection pattern; Equipped with The processing unit a coincidence peak extracting unit that extracts coincidence peaks that coincide in time with peaks in the intensity of reflected light from the plurality of reflection patterns; a coincidence peak number determination unit that determines the number of coincidence peaks; A distance measurement device comprising an identifying unit that identifies a peak that is a component derived from the weather based on a determination result of the coincident peak number determining unit.

2. 2. The distance measuring device according to claim 1, The coincidence peak extraction unit extracts the coincidence peak by comparing the time points of the peak intensities of the reflected light in the plurality of reflection patterns.

3. 3. The distance measuring device according to claim 1, The identification unit identifies peaks other than the peak whose time point coincides with the peak as a component derived from the weather when the number of coincident peaks is 1 as a result of the determination by the coincident peak number determination unit.

4. The distance measuring device according to any one of claims 1 to 3, The identification unit is a distance measurement device that, when the number of matching peaks is two or more in the judgment result of the matching peak number judgment unit, identifies, among the peaks whose peak times coincide, the peak intensity increases as the peak wavelength of the light becomes longer, as a component derived from the weather.

5. The distance measuring device according to any one of claims 1 to 4, The processing unit is a distance measurement device that identifies components derived from the weather using weather information indicating the weather at the time the multiple reflection patterns are acquired.

6. The distance measuring device according to any one of claims 1 to 5, The distance measurement device, wherein the coincident peak number determination unit determines whether the number of coincident peaks is one, or two or more.

7. A distance measurement method for measuring a distance from a distance measurement device to a target object, comprising: It outputs multiple lights with different peak wavelengths, For each of the plurality of light beams, a reflection pattern is acquired, which is an intensity waveform showing the relationship between the time from when the light is emitted until when the reflected light reflected by the target object and particles floating between the distance measurement device and the target object is detected, and the intensity of the reflected light; Identifying a weather-related component included in at least one of the plurality of reflection patterns based on the plurality of reflection patterns; generating a corrected reflection pattern by subtracting the identified weather-related component from the at least one reflection pattern, and calculating the distance based on the corrected reflection pattern; In identifying the components derived from the weather, extracting coincident peaks at the same time points of peak intensity of reflected light from the plurality of reflection patterns; determining the number of coincident peaks; A distance measurement method for identifying a peak that is a component derived from weather based on the determination result of the number of matching peaks.

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