Measuring device

Abstract

To improve the detection performance.SOLUTION: A measurement apparatus according to the present disclosure comprises: a light emission unit which emits measurement light toward a measurement area; a first light reception unit which receives reflection light from the measurement area; a control unit which controls the light emission unit and the first light reception unit, and calculates a distance to an object in the measurement area on the basis of the light reception result of the first light reception unit; and a second light reception unit which receives light in a wavelength different from that of the measurement light in the light from the measurement area.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a measuring device.

Background Art

[0002] There is known a measuring device that measures the distance to an object based on irradiating light and receiving the reflected light that has been reflected back by the object (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The light received by the measuring device includes not only the reflected light but also disturbing light (noise) such as sunlight and the light of an oncoming vehicle. In the above-mentioned measuring device, since these lights cannot be discriminated, there is a risk that the detection performance will deteriorate during light reception due to noise.

[0005] An object of the present invention is to improve the detection performance.

Means for Solving the Problems

[0006] One aspect of the present invention for achieving the above object includes a light emitting unit that irradiates measurement light toward a measurement area, a first light receiving unit that receives the reflected light from the measurement area, a control unit that controls the light emitting unit and the first light receiving unit and calculates the distance to an object in the measurement area based on the light reception result of the first light receiving unit, and a second light receiving unit that receives light having a wavelength different from that of the measurement light among the light from the measurement area.

Effects of the Invention

[0007] According to the present invention, detection performance can be improved. [Brief explanation of the drawing]

[0008] [Figure 1] This is an overall configuration diagram including the measuring device 1 of this embodiment. [Figure 2] This is an explanatory diagram of the configuration of the first light-receiving unit 20. [Figure 3] Figure 3A is an explanatory diagram of the signal processing unit 462. Figure 3B shows the output of the adder 462A and the comparison unit 462B. Figure 3C is an explanatory diagram of the histogram and time-of-flight (TOF). [Figure 4] This is a flowchart illustrating the processing of the control unit 40 in the first embodiment. [Figure 5] This is a flowchart illustrating a modified example of the processing of the control unit 40. [Figure 6] This is a flowchart illustrating another modified example of the processing of the control unit 40. [Figure 7] This is an explanatory diagram of the configuration of the second light receiving unit 30 of the measuring device 1 according to the second embodiment. [Figure 8] This is an explanatory diagram of the spectrum of a white LED. [Figure 9] This is a flowchart showing the processing of the control unit 40 in the second implementation configuration. [Figure 10] This is a flowchart showing a modified example of the processing of the control unit 40 in the second implementation. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the following description, identical or similar components may be denoted by the same reference numerals, and redundant descriptions may be omitted.

[0010] =====Implementation Method 1===== <<Overview of the measuring device>> Figure 1 is an overall configuration diagram including the measuring device 1 of this embodiment.

[0011] The measuring device 1 shown in FIG. 1 is a measuring device having a function as a so-called LiDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging). The measuring device 1 irradiates measurement light (infrared light in this embodiment), and measures the distance to the object 50 by measuring the time until the measurement light is reflected by the object 50 and returns. The measuring device 1 of this embodiment is mounted on a vehicle, and the object 50 is another vehicle (oncoming vehicle). The light (return light) reflected by the object 50 and returning is also referred to as "reflected light".

[0012] As shown in FIG. 1, the measuring device 1 includes a light emitting unit 10, a first light receiving unit 20, a second light receiving unit 30, and a control unit 40.

[0013] The light emitting unit 10 irradiates the measurement space (hereinafter, measurement area) of the measurement target with measurement light (here, infrared light). The light emitting unit 10 includes, for example, a surface emitting element array (VCSEL array) having a plurality of surface emitting type laser elements (VCSELs (Vertical Cavity Surface Emitting Lasers)) arranged one-dimensionally or two-dimensionally, and a light projecting optical system (both not shown) such as a lens for adjusting the light distribution of the emitted light.

[0014] The first light receiving unit 20 receives the reflected light (infrared light) from the object 50 in the measurement area. In the first light receiving unit 20 of this embodiment, a SPAD (Single Photon Avalanche Diode) is used as a sensor (light receiving element) for detecting light. Details of the first light receiving unit 20 will be described later.

[0015] The second light receiving unit 30 receives light having a wavelength different from that of the reflected light (for example, disturbing light such as sunlight or light from an oncoming vehicle) among the light from the measurement area.

[0016] The control unit 40 controls the measurement device 1. The control unit 40 is realized by a hardware configuration such as elements and circuits such as a memory and a CPU. The control unit 40 realizes a predetermined function by the CPU executing a program stored in the memory. FIG. 1 shows various functions realized by the control unit 40. The control unit 40 includes a timing control unit 42, a setting unit 44, a distance measurement unit 46, and a determination unit 48.

[0017] The timing control unit 42 controls various timings, such as the timing of irradiating light from the light emitting unit 10.

[0018] The setting unit 44 performs various settings of the measurement device 1. For example, it sets the intensity of the measurement light irradiated from the light emitting unit 10, the number of integration times and the threshold value when creating a histogram, and the like.

[0019] The distance measurement unit 46 measures the distance to the object 50. The distance measurement unit 46 includes a signal processing unit 462, a time detection unit 464, and a distance calculation unit 466. The signal processing unit 462 processes the output signal of the first light receiving unit 20. The time detection unit 464 detects the arrival time (time of flight of light: TOF) from when the light emitting unit 10 irradiates the measurement light until the reflected light reaches the first light receiving unit 20. The distance calculation unit 466 calculates the distance to the object 50 based on the time of flight (TOF) of light.

[0020] The determination unit 48 determines situations such as the presence and approach of an oncoming vehicle from the light reception result of the second light receiving unit 30. The determination by the determination unit 48 will be described later.

[0021] <<Regarding the first light receiving unit 20>> FIG. 2 is an explanatory diagram of the configuration of the first light receiving unit 20.

[0022] As shown in Figure 2, the first light-receiving unit 20 has a plurality of pixels 22 arranged in a two-dimensional manner. Each pixel (one pixel) 22 also has a plurality of light-receiving elements 24. Here, each pixel 22 has nine SPADs as light-receiving elements 24, arranged in a pattern of three in the X direction (e.g., horizontal direction) and three in the Y direction (e.g., vertical direction). When a light-receiving element 24 composed of SPADs detects a particle of light (photon), it outputs a pulse signal.

[0023] <<About histograms and TOF>> Figure 3A is an explanatory diagram of the signal processing unit 462. Figure 3B is a diagram showing an example of the output of the adder 462A and the comparison unit 462B. The signal processing unit 462 has an adder 462A, a comparison unit 462B, and a histogram generation unit 462C. Here, the signal processing unit 462 generates a histogram used in Time Correlated Single Photon Counting (TCSPC) based on the output signals of each pixel 22 of the first light receiving unit 20.

[0024] The summing unit 462A adds the output signals of multiple photodetectors 24 (SPADs) that constitute the pixel 22. The summing unit 462A may also adjust (shape) the pulse width output by the photodetectors 24 before adding the output signals of the multiple photodetectors 24. The comparison unit 462B compares the output signal of the summing unit 462A with a threshold value and outputs a signal if the output signal of the summing unit 462A is greater than or equal to the threshold value. The timing at which the comparison unit 462B outputs a signal is thought to be the timing at which the photodetectors 24 of the first photodetector 20 detect light.

[0025] Incidentally, ambient light photons are incident on each photodetector 24 randomly in time. In contrast, reflected light photons are incident on each photodetector 24 after a predetermined delay time (time of flight corresponding to the distance to the object 50) from the time of irradiation. For this reason, when ambient light photons are incident on the photodetector 24 randomly in time, the probability that the output signal of the summer 462A will be above the threshold is low. On the other hand, when reflected light photons are incident on the photodetector 24, multiple photodetectors 24 constituting the pixel 22 detect the photons simultaneously, so the probability that the output signal of the summer 462A will be above the threshold is high. For this reason, the output signals of multiple photodetectors 24 are added by the summer 462A, and the output signal of the summer 462A is compared with the threshold by the comparison unit 462B to measure the time at which the photodetector 24 is thought to have detected the reflected light.

[0026] Note that once the photodetector 24 detects a photon, a hold-off time (dead time) occurs. By adding the output signals of multiple photodetectors 24 (SPAD) in the adder 462A, the effects of the hold-off time can be suppressed.

[0027] Figure 3C is an explanatory diagram of a histogram and time-of-flight (TOF). In the figure, the horizontal axis represents time, and the vertical axis represents frequency (number of occurrences). The histogram generation unit 462C generates a histogram by repeatedly measuring the time at which the light-receiving elements 24 of each pixel 22 of the first light-receiving unit 20 detect light, based on the output of the comparison unit 462B, and by incrementing the frequency (number of occurrences) associated with that time. When the histogram generation unit 462C increments the frequency (number of occurrences), it may increase the number corresponding to the output signal (added value) of the adder unit 462A instead of increasing the number by one.

[0028] As mentioned above, the setting unit 44 (see Figure 1) pre-sets the number of integrations required to generate the histogram. The timing control unit 42 causes the light-emitting unit 10 to emit measurement light multiple times according to the set number of integrations. For each emission of measurement light from the light-emitting unit 10, the adder unit 462A outputs a signal once or multiple times. The histogram generation unit 462C generates a histogram by incrementing the frequency (number of times) according to the output signal of the comparison unit 462B until the set number of integrations is reached.

[0029] After generating the histogram, the distance measuring unit 46 (time detection unit 464) detects the time of flight (TOF) from the time of light irradiation until the reflected light arrives, based on the histogram. As shown in Figure 3C, the distance measuring unit 46 (time detection unit 464) detects the time corresponding to the peak frequency of the histogram (the time of flight of light, TOF). Then, the distance measuring unit 46 (distance calculation unit 466) calculates the distance to the object 50 based on that time. Since light travels twice the distance to the object during the time of flight (TOF), if the speed of light is Co and the time of flight (TOF) is Tf, the distance L to the object is: L = (Tf × Co) / 2 ·····(1) The distance calculation unit 466 calculates the distance to the object 50 according to equation (1).

[0030] <<Regarding the second light-receiving unit 30>> As described above, the second light-receiving unit 30 receives light of a different wavelength than reflected light (infrared light). For this reason, the second light-receiving unit 30 is equipped with a sensor (for example, a photodiode) capable of detecting light of a different wavelength than reflected light (infrared light) (for example, sunlight). The sensor (not shown) of the second light-receiving unit 30 is installed in the same orientation as the light-receiving surface of the first light-receiving unit 20 and receives light from the measurement area according to instructions from the control unit 40.

[0031] <<Regarding the processing of the control unit 40>> Figure 4 is a flowchart illustrating the processing of the control unit 40 in the first embodiment.

[0032] First, the control unit 40 (timing control unit 42) causes the second light receiving unit 30 to receive light from the measurement area that has a different wavelength from the measurement light (ambient light, hereinafter referred to as sunlight) (S101). Then, the setting unit 44 of the control unit 40 sets the intensity of the measurement light (infrared light) emitted by the light emitting unit 10 based on the light reception result (S102). For example, it is set so that the intensity of the measurement light increases as the sunlight is stronger.

[0033] Next, the timing control unit 42 controls the light-emitting unit 10 to emit measurement light (infrared light) of the intensity set in step S102 toward the measurement area (S103). The timing control unit 42 also causes the first light-receiving unit 20 to receive light from the measurement area (including reflected light and sunlight) (S104). The timing control unit 42 causes the first light-receiving unit 20 to repeatedly receive light for each emission.

[0034] The histogram generation unit 462C of the distance measuring unit 46 (signal processing unit 462) generates a histogram showing the frequency over time based on the output of the comparison unit 462B (comparison result), which compares the output of the adder unit 462A (addition result) with a predetermined threshold (S105).

[0035] If the cumulative count is not n (i.e., less than n) (No in step S106), the process returns to step S103, and the control unit 40 causes the light-emitting unit 10 to be irradiated with measurement light again.

[0036] On the other hand, if the number of integrations in step S106 is n (Yes in step S106), the time detection unit 464 of the distance measuring unit 46 finds the peak of the generated histogram and calculates the time from the timing of light emission to the peak (time of flight time) (S107).

[0037] Next, the distance calculation unit 466 of the distance measuring unit 46 calculates the distance to the object according to equation (1) using the time of flight (TOF) (S108).

[0038] As described above, the control unit 40 (setting unit 44) of the measuring device 1 in this embodiment sets the intensity of the measuring light emitted by the light-emitting unit 10 based on the light-receiving result of the second light-receiving unit 30. This allows detection accuracy to be maintained by increasing the intensity of the measuring light when there is a lot of ambient light. Conversely, power consumption can be reduced by decreasing the intensity of the measuring light when there is little ambient light.

[0039] <Example 1> Figure 5 is a flowchart illustrating a modified version (modification 1) of the processing of the control unit 40. The configuration of the measuring device 1 is the same as in the embodiment described above. In this modified version, the setting unit 44 determines the number of integrations n based on the light reception result of the second light receiving unit 30.

[0040] First, the timing control unit 42 of the control unit 40 causes the second light receiving unit 30 to receive light from the measurement area that has a different wavelength from the measurement light (ambient light, for example, sunlight) (S201). Then, the setting unit 44 of the control unit 40 sets (determines) the number of integration steps n based on the light reception result (S202). For example, it is set so that the stronger the ambient light, the more the number of integration steps n increases.

[0041] Next, the timing control unit 42 controls the light-emitting unit 10 to irradiate the measurement area with measurement light (infrared light) of a predetermined intensity (S203). Furthermore, the timing control unit 42 causes the first light-receiving unit 20 to receive light (infrared light, including sunlight) from the measurement area (S204). The timing control unit 42 causes the first light-receiving unit 20 to repeatedly receive light for each light emission.

[0042] The histogram generation unit 462C of the distance measuring unit 46 (signal processing unit 462) generates a histogram based on the output of the comparison unit 462B (comparison result), which compares the output of the adder unit 462A (addition result) with a predetermined threshold (S205).

[0043] If the cumulative count is not n (i.e., less than n) (No in step S206), the process returns to step S203, and the control unit 40 causes the light-emitting unit 10 to be irradiated with measurement light again.

[0044] On the other hand, if the number of cumulative measurements is n (Yes in step S206), the time detection unit 464 of the distance measuring unit 46 finds the peak of the generated histogram and calculates the time from the timing of light emission to that peak (time of flight time) (S207).

[0045] Next, the distance calculation unit 45 of the rangefinder unit 46 calculates the distance to the object using the time of flight (TOF) according to equation (1) (S208).

[0046] As explained above, the setting unit 44 in this modified example sets the number of integration steps n based on the light reception result of the second light receiving unit 30. This allows the number of integration steps to be optimized according to the ambient light conditions. For example, if there is a lot of ambient light, the detection accuracy can be maintained by setting a large number of integration steps n. Conversely, if there is little ambient light, the measurement speed can be improved by setting a small number of integration steps n.

[0047] <Modification 2> Figure 6 is a flowchart illustrating another modified example (modification 2) of the processing of the control unit 40. The configuration of the measuring device 1 is the same as in the embodiment described above. In this modified example, the comparison unit 462B sets a threshold value (see Figures 3A and 3B) that is compared with the output of the adder 462A based on the light reception result of the second light receiving unit 30.

[0048] First, the timing control unit 42 of the control unit 40 causes the second light receiving unit 30 to receive light of a different wavelength from the measurement light (disturbing light, such as sunlight) from the measurement area (S301). Then, the setting unit 44 of the control unit 40 determines a threshold value based on the received light result (S302).

[0049] Furthermore, if the threshold value is small, the histogram will be greatly affected by ambient light when there is a lot of ambient light, which may reduce the detection accuracy of the light arrival time. On the other hand, if the threshold value is large, it may take a long time to generate a histogram for a predetermined number of integrations. Therefore, in this embodiment, based on the light reception result of the second light receiving unit 30, the threshold value is set to a large value when there is a lot of ambient light, thereby maintaining detection accuracy. Also, based on the light reception result of the second light receiving unit 30, the threshold value is set to a small value when there is little ambient light. This makes it possible to increase the histogram generation speed.

[0050] Next, the timing control unit 42 controls the light-emitting unit 10 to irradiate the measurement area with measurement light (infrared light) of a predetermined intensity (S303). Furthermore, the timing control unit 42 causes the first light-receiving unit 20 to receive light (infrared light, including sunlight) from the measurement area (S304). The timing control unit 42 causes the first light-receiving unit 20 to repeatedly receive light for each light emission.

[0051] The histogram generation unit 462C of the distance measuring unit 46 (signal processing unit 462) generates a histogram (S305) based on the output (comparison result) of the comparison unit 462B, which compares the summation result of the summation unit 462A with the threshold value set in step S302.

[0052] If the cumulative count is not n (i.e., less than n) (No in step S306), the process returns to step S303, and the control unit 40 causes the light-emitting unit 10 to be irradiated with measurement light again.

[0053] On the other hand, if the number of cumulative measurements is n (Yes in step S306), the time detection unit 464 of the distance measuring unit 46 finds the peak of the generated histogram and calculates the time from the timing of light emission to that peak (time of flight time) (S307).

[0054] Next, the distance calculation unit 466 of the distance measuring unit 46 calculates the distance to the object 50 using the time of flight (TOF) according to equation (1) (S308).

[0055] As explained above, in this modified example, the setting unit 44 sets a threshold for generating the histogram based on the light reception result of the second light receiving unit 30. This allows detection accuracy to be maintained by setting a large threshold value when there is a lot of ambient light. Conversely, when there is little ambient light, the histogram generation speed can be increased by setting a small threshold value.

[0056] =====Second Embodiment===== Figure 7 is an explanatory diagram of the configuration of the second light receiving unit 30 of the measuring device 1 according to the second embodiment. The second light-receiving unit 30 of the second embodiment has two sensors (first sensor 32 and second sensor 34) with different detection ranges, which receive light of a different wavelength than the measurement light (infrared light) emitted by the light-emitting unit 10. As will be described later, the first sensor 32 is a sensor capable of detecting blue light, and the second sensor 34 is a sensor capable of detecting yellow light.

[0057] Furthermore, the object 50 of the second embodiment (hereinafter referred to as the oncoming vehicle) is equipped with a white LED as the light source for the vehicle's lamps (for example, low beams, DRL (Daytime Running Lamp), etc.). The white LED is composed of a combination of a blue LED and a yellow phosphor. In other words, the light generated by the blue LED is irradiated through the yellow phosphor. This results in the irradiation of white light. The second light receiving unit 30 of the measuring device 1 then detects the light irradiated from the white LED of the oncoming vehicle.

[0058] Figure 8 is an explanatory diagram of the spectrum of a white LED. The horizontal axis of the figure represents wavelength, and the vertical axis represents the energy of the light. As shown in the figure, the spectrum of a white LED contains two peaks: one around 465 nm and another around 560 nm. The peak at approximately 465 nm is the central wavelength of light emitted by a blue LED, and the peak at approximately 560 nm is the central wavelength of light emitted by a yellow phosphor.

[0059] Furthermore, region R1 shown in Figure 8 is the detectable region of the first sensor 32 (a sensor capable of detecting blue light). Region R2 is the detectable region of the second sensor 34 (a sensor capable of detecting yellow light). As shown in the figure, the first sensor 32 can detect light with a wavelength of 465 nm, and the second sensor 34 can detect light with a wavelength of 560 nm. Note that the wavelength of region R1 detectable by the first sensor 32 corresponds to the "first wavelength," and the wavelength of region R2 detectable by the second sensor 34 corresponds to the "second wavelength."

[0060] By providing a first sensor 32 and a second sensor 34 with different detection ranges, the presence of an object 50 (oncoming vehicle) can be determined from the respective detection results (light intensity ratio).

[0061] Figure 9 is a flowchart showing the processing of the control unit 40 in the second implementation configuration.

[0062] The control unit 40 (timing control unit 42) causes the second light receiving unit 30 to receive light from the measurement area (S401). The control unit 40 also detects the intensity of blue light (light with a central wavelength of 465 nm) based on the light reception result of the first sensor 32 of the second light receiving unit 30 (S402).

[0063] The control unit 40 also detects the intensity of yellow light (light with a central wavelength of 560 nm) based on the light reception result of the second sensor 34 of the second light receiving unit 30 (S403).

[0064] Next, the discrimination unit 48 of the control unit 40 determines the presence or absence of an oncoming vehicle based on the ratio of the intensity of the blue light to the intensity of the yellow light (S404). For example, if the intensity of the blue light is higher than the intensity of the yellow light, the discrimination unit 48 determines that the light is emitted from an oncoming vehicle (white LED) (i.e., an oncoming vehicle is present). Also, if the intensity of the yellow light is higher than the intensity of the blue light (for example, sunlight), the discrimination unit 48 determines that the light is not emitted from an oncoming vehicle (i.e., no oncoming vehicle is present).

[0065] As described above, the second light receiving unit 30 of the measuring device 1 of the second embodiment has a first sensor 32 capable of detecting blue light and a second sensor 34 capable of detecting yellow light. As a result, the discrimination unit 48 can determine the presence or absence of an oncoming vehicle (object 50) based on the ratio of the intensity of blue light detected by the first sensor 32 and the intensity of yellow light detected by the second sensor 34.

[0066] <Variation> Figure 10 is a flowchart showing a modified version of the processing of the control unit 40 in the second embodiment. In this modified version, the measuring device 1 (control unit 40) detects the approach of an oncoming vehicle based on the detection result of the second light receiving unit 30.

[0067] First, the control unit 40 causes the first sensor 32 and the second sensor 34 of the second light receiving unit 30 to receive light from the measurement area (S501). Here, as in the embodiment described above, the first sensor 32 receives blue light and the second sensor 34 receives yellow light. Based on this light reception result, the presence or absence of an oncoming vehicle (object 50) can be detected.

[0068] Furthermore, the control unit 40 detects the approach of an oncoming vehicle based on the change in the light reception result (amount of light received) of the second light receiving unit 30 over time (S502). For example, when an oncoming vehicle is approaching, the amount of light received by the first sensor 32 and the amount of light received by the second sensor 34 both increase over time. As a result, the discrimination unit 48 of the control unit 40 determines that an oncoming vehicle is approaching based on the change in the light reception result of the second light receiving unit 30.

[0069] Furthermore, the control unit 40 (distance measuring unit 46), similar to the first embodiment, calculates the distance to the oncoming vehicle (object 50) based on the light reception result of the first light receiving unit 20 (S503).

[0070] The control unit 40 then compares the change in the distance to the oncoming vehicle (see first embodiment), calculated based on the detection result of the first light receiving unit 20, with the change in the light reception result of the second light receiving unit 30 (S504). This improves the reliability of measuring the distance to the oncoming vehicle (object 50).

[0071] =====Summary===== The measuring device 1 of this embodiment has been described above. The measuring device 1 comprises a light-emitting unit 10, a first light-receiving unit 20, a second light-receiving unit 30, and a control unit 40. The light-emitting unit 10 irradiates measurement light (infrared light) toward the measurement area. The first light-receiving unit 20 receives reflected light from the measurement area (measurement light reflected by the object 50). The control unit 40 controls the light-emitting unit 10 and the first light-receiving unit 20, and calculates the distance to the object 50 in the measurement area based on the light-receiving result of the first light-receiving unit 20. The second light-receiving unit 30 receives light from the measurement area that has a different wavelength than the measurement light. This improves the detection performance.

[0072] Furthermore, the control unit 40 calculates the distance to the object 50 based on the light reception result of the second light receiving unit 30. This suppresses the influence of ambient light (such as sunlight) and improves the accuracy of the measurement.

[0073] Specifically, in the first embodiment, the setting unit 44 sets the intensity of the measurement light emitted from the light-emitting unit 10 based on the light-receiving result of the second light-receiving unit 30. Then, the control unit 40 calculates the distance based on the light-receiving result of the first light-receiving unit 20 when the measurement light of that intensity is emitted from the light-emitting unit 10. This allows detection accuracy to be maintained by increasing the intensity of the measurement light when there is a lot of ambient light. Conversely, power consumption can be reduced by decreasing the intensity of the measurement light when there is little ambient light.

[0074] Furthermore, the setting unit 44 of the modified example 1 of the first embodiment determines the number of integrations n based on the light reception result of the second light receiving unit 30. The control unit 40 then causes the first light receiving unit 20 to receive reflected light at the determined number of integrations n, and calculates the distance based on the light reception result of the first light receiving unit 20 corresponding to the number of integrations n. This allows detection accuracy to be maintained by setting a large number of integrations n when there is a lot of ambient light. Conversely, the measurement speed can be improved by setting a small number of integrations n when there is little ambient light.

[0075] The control unit 40 (distance measuring unit 46) includes an adder 462A, a comparison unit 462B, and a histogram generation unit 462C. The adder 462A adds the outputs of multiple light-receiving elements 24, and the comparison unit 462B compares the output of the adder 462A with a threshold value. The histogram generation unit 462C generates a histogram based on the comparison result of the comparison unit 462B. The time detection unit 464 detects the time of arrival of light (time of flight) based on the peak of the histogram. In this configuration, the setting unit 44 of the modified example 2 of the first embodiment sets a threshold value based on the light-receiving result of the second light-receiving unit 30. This allows detection accuracy to be maintained by setting a large threshold value when there is a lot of ambient light. Also, when there is little ambient light, the histogram generation speed can be increased by setting a small threshold value.

[0076] Furthermore, the control unit 40 of the second embodiment determines the presence or absence of an oncoming vehicle (object 50) based on the light reception result of the second light receiving unit 30. Specifically, the second light receiving unit 30 of the second embodiment has a first sensor 32 and a second sensor 34 that can detect light of different wavelengths, respectively. The discrimination unit 48 of the control unit 40 then determines the presence or absence of an oncoming vehicle based on the ratio of the light intensity based on the detection result of the first sensor 32 and the light intensity based on the detection result of the second sensor 34. This improves the oncoming vehicle detection performance.

[0077] Furthermore, the first sensor 32 can detect blue light (light with a wavelength of 465 nm), and the second sensor 34 can detect yellow light (light with a wavelength of 560 nm). This allows for the detection of the white LED lights of oncoming vehicles.

[0078] Furthermore, the control unit 40 of the modified second embodiment detects the approach of an oncoming vehicle based on the change in the light reception result of the second light receiving unit 30. This makes it possible to detect the approach of an oncoming vehicle from the light reception result of the second light receiving unit 30.

[0079] Furthermore, in the modified version of the second embodiment, the control unit 40 compares the change in distance calculated based on the light reception result of the first light receiving unit 20 with the change in the light reception result of the second light receiving unit 30. This improves the reliability of distance measurement.

[0080] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. Furthermore, the present invention may be modified or improved without departing from its spirit, and it goes without saying that equivalents thereof are included. [Explanation of Symbols]

[0081] 10 Light-emitting part 20 1st light receiving section 22 pixels 24 light-receiving elements 30 2nd light receiving section 32 First Sensor 34. Second Sensor 40 Control Unit 42 Timing Control Unit 44 Setting section 46 Ranging section 462 Signal Processing Unit 462A Addition section 462B Comparison section 462C Histogram Generation Unit 464 Time detection unit 466 Distance Calculation Unit 48 Discrimination part 50 Object (oncoming vehicle)

Claims

1. A light-emitting unit that illuminates the measurement area with measurement light, A first light receiving unit that receives reflected light from the measurement area, A control unit controls the light-emitting unit and the first light-receiving unit, and calculates the distance to the object in the measurement area based on the light-receiving result of the first light-receiving unit, A second light receiving unit that receives light of a different wavelength from the measurement light from the measurement area, Equipped with, The second light receiving unit includes a first sensor capable of detecting light of a first wavelength and a second sensor capable of detecting light of a second wavelength different from the first wavelength. The control unit determines the presence or absence of an oncoming vehicle based on the ratio of the intensity of light of the first wavelength based on the detection result of the first sensor and the intensity of light of the second wavelength based on the detection result of the second sensor. The first light-receiving unit has a plurality of light-receiving elements, The control unit, An adder that adds up the outputs of multiple light-receiving elements, A comparison unit compares the addition result of the addition unit with a threshold value, A histogram generation unit generates a histogram based on the comparison results of the comparison unit, A time detection unit that detects the arrival time of light based on the peak of the histogram. Having, Based on the light reception result of the second light receiving unit, the threshold is set. Measuring device.

2. The measuring device according to Claim 1, The control unit, Based on the light reception result of the second light receiving unit, the intensity of the measurement light irradiated from the light emitting unit is set. The distance is calculated based on the light reception result of the first light receiving unit when the measurement light of the intensity corresponding to the light reception result of the second light receiving unit is irradiated. Measuring device.

3. A measuring device according to claim 1, The control unit, Based on the light reception result of the second light receiving unit, the number of integrations is determined. The first light receiving unit receives the reflected light at the determined number of cumulative counts. Based on the light reception result of the first light receiving unit corresponding to the number of cumulative counts, the distance is calculated. Measuring device.

4. A measuring device according to claim 1, The first sensor is capable of detecting light with a wavelength of 465 nm, The second sensor is capable of detecting light with a wavelength of 560 nm. Measuring device.

5. A measuring device according to claim 1 or 4, The first sensor is capable of detecting blue light, The second sensor is capable of detecting yellow light. Measuring device.

6. A measuring device according to any one of claims 1 to 4, The control unit detects the approach of the oncoming vehicle based on the change in the light reception result of the second light receiving unit. Measuring device.

7. The measuring device according to claim 6, The control unit compares the change in distance calculated based on the light reception result of the first light receiving unit with the change in the light reception result of the second light receiving unit. Measuring device.

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