Method for determining the scanning method

Abstract

To improve the efficiency of measurements in measuring devices. [Solution] The measuring device 200 has a measuring unit 202 and a control unit 204. The measuring unit 202 performs scanning by irradiating electromagnetic waves while changing the irradiation direction. The control unit 204 irradiates electromagnetic waves a total of M times in N consecutive main scans, and controls the measuring unit 202 such that the irradiation timing of the electromagnetic waves differs from one another in the N main scans, and that electromagnetic waves are irradiated at least once in each main scan.

Description

Technical Field

[0001] The present invention relates to a technique for performing measurement by irradiating electromagnetic waves.

Background Art

[0002] Techniques for detecting obstacles and the like by irradiating electromagnetic waves to scan an object have been developed. Patent Document 1 discloses a technique for detecting obstacles and the like by irradiating laser light and performing scanning within a target area in a device installed in an automobile or the like. Further, Patent Document 1 discloses a technique for changing the central axis in the lateral direction of the scanning area according to the steering angle of the automobile.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a measuring device as shown in Patent Document 1, measurement may be performed with a granularity greater than the required resolution (measurement granularity), and there are problems such as wasteful consumption of power.

[0005] The present invention has been made in view of the above problems, and one object thereof is to provide a technique for improving the efficiency of measurement by a measuring device.

Means for Solving the Problems

[0006] A first invention is a method for determining a scanning method of a measuring device installed in a moving body, where the measuring device is a device that performs scanning by irradiating electromagnetic waves while changing the irradiation direction, A frequency higher than the frequency of vibrations generated when the moving body is in motion is determined as the scanning frequency of the main scan of the measuring device. This method for determining a scanning method involves determining the timing of electromagnetic wave irradiation so that, at the determined scanning frequency of the main scan, each pixel arranged in a line in the main scanning direction is irradiated with electromagnetic waves once in total over the course of multiple consecutive main scans.

[0007] The second invention is, This is a measurement method in which the measuring device scans using the scanning method determined by the above determination method. [Brief explanation of the drawing]

[0008] [Figure 1] This figure illustrates a measuring device according to Embodiment 1. [Figure 2] This diagram conceptually illustrates oscillation scanning using a typical measuring device. [Figure 3] This diagram shows the scanning range of a typical oscillating scan using a measurement device, viewed in plan view with respect to the xy plane. [Figure 4] This diagram conceptually illustrates rotational scanning using a typical measuring device. [Figure 5] This diagram shows the scanning range of a rotational scan performed by a typical measuring device, unfolded onto the xy-plane and viewed from a plan perspective. [Figure 6] This is Figure 3 with the trajectory removed. [Figure 7] This diagram illustrates the overlapping of electromagnetic wave spots. [Figure 8] This figure illustrates the scanning range of the oscillation scan performed by the measuring device of this embodiment, viewed from a planar perspective in the xy plane. [Figure 9] This is Figure 8 with the trajectory removed. [Figure 10] This figure illustrates the spots of each electromagnetic wave in Figure 9. [Figure 11] This figure illustrates the scanning range of the rotational scan performed by the measuring device of this embodiment, as seen in plan view when unfolded in the xy plane. [Figure 12]It is a diagram showing a part of the rocking scan by the measuring device shown in FIG. 8. [Figure 13] It is a diagram showing a part of the rotational scan by the measuring device. [Figure 14] It is a diagram showing an example in which the scanning frequency in the main scanning direction is lowered. [Figure 15] It is a diagram exemplifying a case where electromagnetic waves are irradiated at equal intervals by the measuring device. [Figure 16] It is a diagram for explaining the pixel where electromagnetic waves are first irradiated in each main scan. [Figure 17] It is a diagram exemplifying a case where the difference in the number of times electromagnetic waves are irradiated in each main scan is 1 or less. [Figure 18] It is a diagram exemplifying the hardware configuration of the control unit. [Figure 19] It is a diagram exemplifying the hardware configuration of the measurement unit. [Figure 20] It is a diagram exemplifying the hardware configuration of the measurement unit that irradiates light. [Figure 21] It is a diagram exemplifying the hardware configuration of the measuring device that receives the reflected wave without going through the scanner. [Figure 22] It is a diagram exemplifying the light source drive signal. [Figure 23] It is a diagram exemplifying the measuring device installed in the moving body.

Embodiments of the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same components are denoted by the same reference numerals, and the description will be omitted as appropriate. Also, unless otherwise specified, each block represents a configuration in terms of functional units, not hardware units.

[0010] Figure 1 is a diagram illustrating a measuring device 200 according to Embodiment 1. The measuring device 200 has a measuring unit 202 and a control unit 204. The measuring unit 202 scans an object by irradiating it with electromagnetic waves while changing the irradiation direction and receiving the reflected waves of the irradiated electromagnetic waves. The control unit 204 controls the scanning by the measuring unit 202. Furthermore, the control unit 204 measures the time from when the electromagnetic waves are irradiated by the measuring unit 202 until the reflected waves of those electromagnetic waves are received. This measurement result is used, for example, to determine the distance between the object that reflected the electromagnetic waves and the measuring device 200 (so-called distance measurement). The measuring device 200 is, for example, a Lidar (Light Detection and Ranging) sensor or a millimeter-wave radar.

[0011] The measurement unit 202 scans an object by changing the direction of electromagnetic wave irradiation in two directions, the main scanning direction and the sub-scanning direction, over time. The sub-scanning direction is a direction that intersects the main scanning direction (for example, a direction that is approximately perpendicular to the main scanning direction).

[0012] Scanning objects using electromagnetic waves includes methods such as oscillation scanning and rotational scanning. Hereafter, oscillation scanning will be referred to as oscillation scanning, and rotational scanning as rotational scanning. These two types of scanning will be briefly explained below.

[0013] Figure 2 is a conceptual illustration of oscillation scanning using a typical measuring device 60. In Figure 2, the measuring device 60 is depicted as a cylindrical device. The scanning range 300 represents the range through which electromagnetic waves emitted from the measuring device can pass.

[0014] Figure 2(a) is a plan view of the oscillation scanning process in the xz plane. Figure 2(b) is a plan view of the oscillation scanning process in the yz plane. For example, when the measuring device 60 is installed on a vehicle such as an autonomous vehicle, the z direction is the direction of travel of the vehicle, the y direction is the vertical direction, and the x direction is perpendicular to both the y and z directions.

[0015] In oscillating scanning, the direction of electromagnetic wave irradiation is oscillated in both the primary and secondary scanning directions. However, while the direction of electromagnetic wave irradiation is oscillated once in the secondary scanning direction, the direction of electromagnetic wave irradiation is oscillated multiple times in the primary scanning direction. In other words, the frequency of the oscillation in the primary scanning direction is higher than the frequency of the oscillation in the secondary scanning direction.

[0016] Figure 3 is a plan view of the scanning range 300 of a typical oscillating scan using a measuring device 60, with respect to the xy plane. The trajectory 302 represents the change in the direction of the electromagnetic waves emitted from the measuring device.

[0017] Generally, measuring devices intermittently emit electromagnetic waves. The cross marks in Figure 3 indicate the positions through which the electromagnetic waves emitted from the measuring device pass. In other words, the cross marks in Figure 3 indicate the timing of electromagnetic wave emission from the measuring device. Note that electromagnetic wave emission by the measuring device is performed during scanning in the main scanning direction (solid line portion of trajectory 302). Hereafter, for oscillating scanning, the scan performed during one oscillation of the electromagnetic wave irradiation direction in the main scanning direction will be referred to as "one main scan" or "one line main scan".

[0018] Figure 4 is a conceptual illustration of rotational scanning using a typical measuring device 60. Figure 4(a) is a plan view of the rotational scanning process in the xz plane. Figure 4(b) is a plan view of the rotational scanning process in the yz plane.

[0019] In rotational scanning, the direction of electromagnetic wave irradiation is changed (rotated) in one direction relative to the main scanning direction, and simultaneously oscillated in the sub-scanning direction. However, while the direction of electromagnetic wave irradiation is oscillated once in the sub-scanning direction, the direction of electromagnetic wave irradiation is rotated multiple times relative to the main scanning direction. In other words, the frequency of rotation in the main scanning direction is higher than the frequency of oscillation in the sub-scanning direction.

[0020] Figure 5 is a plan view of the scanning range 300 of a rotational scan performed by a typical measuring device 60, unfolded on the xy plane. As mentioned above, the direction of electromagnetic wave irradiation in rotational scanning changes in one direction with respect to the main scanning direction. Here, for rotational scanning, the scan performed while the direction of electromagnetic wave irradiation changes 360 degrees with respect to the main scanning direction is called "one main scan" or "one line main scan".

[0021] In both oscillating and rotational scanning, the measuring device 60 repeatedly performs the scan represented by the trajectory 302. That is, when the direction of electromagnetic wave irradiation reaches the end point of the trajectory 302, the direction of electromagnetic wave irradiation is reset to the starting point of the trajectory 302.

[0022] In the scanning range 300 shown in Figures 3 and 5, the pixels 304, which are grid-like divided regions, represent the resolution (grain size of measurement) required of the measuring device 60. In other words, the measuring device 60 is required to irradiate each pixel 304 in the scanning range 300 with electromagnetic waves at least once.

[0023] As shown in Figures 3 and 5, in a typical measuring device 60, electromagnetic waves are irradiated at the same timing (the timing of passing through each pixel 304) in each of the multiple main scans. Furthermore, there are multiple main scans in which electromagnetic waves can be irradiated to a single pixel 304. As a result, electromagnetic waves are irradiated to a single pixel 304 multiple times. Figure 6 is a view of Figure 3 with the trajectory 302 removed. Looking at Figure 6, it can be seen that electromagnetic waves are irradiated to each pixel 304 four times.

[0024] The size of the electromagnetic wave spot emitted from the measuring device is set to match, for example, the size of a pixel 304. Therefore, if an electromagnetic wave is emitted from a single pixel 304 multiple times, it means that parts of the multiple electromagnetic wave spots overlap. In other words, it means that the same location is scanned multiple times by the measuring device.

[0025] Figure 7 illustrates the overlapping of electromagnetic wave spots. In Figure 7, an electromagnetic wave spot 306 irradiated onto pixel 304 at the upper left corner is shown. As can be seen from this figure, parts of multiple electromagnetic wave spots 306 overlap each other.

[0026] Thus, in typical measuring devices, scanning is performed at a resolution higher than the required resolution. In other words, more electromagnetic waves than necessary are emitted during scanning by the measuring device. As a result, the measuring device consumes more power than necessary. In addition, various mechanisms of the measuring device (such as the light source) are worn out more than necessary, shortening the lifespan of the measuring device.

[0027] Therefore, the measuring device 200 of this embodiment irradiates electromagnetic waves a necessary and sufficient number of times to satisfy the resolution required for the measuring device 200. In other words, the control unit 204 of this embodiment controls the irradiation of electromagnetic waves by the measuring unit 202 so that electromagnetic waves are irradiated once to each pixel representing the resolution required for the measuring device 200.

[0028] In this way, the measuring device 200 of this embodiment is irradiated with electromagnetic waves a sufficient number of times to satisfy the required resolution of the measuring device 200. Therefore, the power consumption of the measuring device 200 is reduced compared to a general measuring device. In addition, wear and tear on various mechanisms of the measuring device 200 (e.g., light source) can be reduced, thus extending the lifespan of the measuring device 200.

[0029] Figure 8 illustrates a plan view of the scanning range of the oscillation scan performed by the measuring device 200 of this embodiment in the xy plane. The meanings of the scanning range 220, trajectory 222, and pixel 224 are the same as those of the scanning range 300, trajectory 302, and pixel 304 in Figure 3, respectively.

[0030] In Figure 8, similar to the case in Figure 3, there are four main scans that can irradiate a single pixel (pixel 224) with electromagnetic waves. However, the measurement unit 202 irradiates a single pixel 224 with electromagnetic waves during only one of the four main scans that can irradiate it.

[0031] Figure 9 is a view of Figure 8 with the trajectory 222 removed. As can be seen in Figure 9, in the measuring device 200 of this embodiment, each pixel 224 is irradiated with electromagnetic waves only once.

[0032] Figure 10 illustrates the electromagnetic wave spots in Figure 9. In this example, the electromagnetic wave spots are set to match the size of the pixels 224. As can be seen in Figure 10, in the measuring device 200 of this embodiment, the spots pass through all pixels 224 without overlapping. Therefore, the same location is not scanned multiple times by the measuring device 200.

[0033] Figures 9 and 10 show that, as shown in Figure 8, electromagnetic waves are irradiated a sufficient number of times to meet the required resolution for the measuring device 200.

[0034] The scanning performed by the measuring device 200 in this embodiment may be rotational scanning. Figure 11 is a diagram illustrating a plan view of the scanning range of rotational scanning by the measuring device 200 in this embodiment, unfolded in the xy plane. Similar to the case in Figure 8, the measuring unit 202 irradiates electromagnetic waves to one pixel 224 with electromagnetic waves in only one of the four main scans that can irradiate a single pixel 224 with electromagnetic waves.

[0035] The specific control by the control unit 204 in this embodiment satisfies the following first and second requirements. The first requirement is that "the measurement unit 202 irradiates electromagnetic waves a total of M times during N consecutive main scans." The second requirement is that "the timing of the irradiation of electromagnetic waves from the measurement unit 202 is different for each of the N consecutive main scans." M is the number of pixels of the resolution required for the measurement device 200 during N consecutive main scans. For example, in Figure 8, the number of pixels 224 is 8 during 4 consecutive main scans. Therefore, in Figure 8, N=4 and M=8.

[0036] Here, the specific definitions of N and M are as follows, for example. Figure 12 is a diagram showing a part of the oscillation scan by the measuring device 200 shown in Figure 8. A represents the width of one pixel in the sub-scanning direction (height of pixel 224). B represents the width of one pixel in the main scanning direction (width of pixel 224). X represents the width of the scanning range 220. dy represents the scanning interval in the sub-scanning direction.

[0037] N is the number of main scans that can irradiate one pixel (224 pixels) with electromagnetic waves. For example, in Figure 8, the value of N is 4. Specifically, N is the largest integer less than or equal to A / dy, or the smallest integer greater than or equal to A / dy. Below, we will assume that N is the largest integer less than or equal to A / dy.

[0038] M is the number of pixels 224 included in the main scanning direction within the scanning range 220 (the number of pixels that give the resolution required by the measuring device 200 in N consecutive main scans). For example, in Figure 8, the value of M is 8. Specifically, M is the smallest integer greater than or equal to X / B, or the largest integer less than or equal to X / B. Hereafter, we will assume that M is the smallest integer greater than or equal to X / B.

[0039] The meanings of the symbols described above are the same even when the measuring device 200 performs rotational scanning. Figure 13 shows a part of the rotational scanning performed by the measuring device 200. The meanings of the symbols in Figure 13 are the same as those of the symbols in Figure 12.

[0040] When electromagnetic waves are irradiated in a manner that satisfies the first requirement described above, the electromagnetic waves are irradiated M times in multiple scans (N consecutive scans) in which electromagnetic waves can be irradiated to M pixels 224 contained in one row of the scanning range 220. Then, when electromagnetic waves are irradiated in a manner that satisfies both the first and second requirements, each of the M pixels 224 contained in one row of the scanning range 220 is irradiated once with electromagnetic waves.

[0041] Thus, according to the measuring device 200 of this embodiment, electromagnetic waves are irradiated a sufficient number of times to satisfy the resolution required for the measuring device 200. Therefore, the power consumption of the measuring device 200 is reduced compared to a general measuring device. In addition, wear and tear on various mechanisms of the measuring device 200 (e.g., light source) can be reduced, thus extending the lifespan of the measuring device 200.

[0042] Here, one possible control to ensure that each pixel is irradiated with electromagnetic waves only once is to reduce the frequency of scanning in the main scanning direction (lower the scanning frequency in the main scanning direction). Figure 14 shows an example where the scanning frequency in the main scanning direction is lowered. In this example, compared to the cases in Figures 3 and 8, the scanning frequency in the main scanning direction is 1 / 4, and each pixel 304 is irradiated with electromagnetic waves only once. Therefore, even if the measuring device irradiates electromagnetic waves at every timing as it passes through each pixel 304, each pixel 304 is irradiated with electromagnetic waves only once.

[0043] However, this method has the problem that the measuring device is susceptible to ambient vibrations. Measuring devices such as lidar sensors and millimeter-wave radar are installed on moving objects such as autonomous vehicles. Therefore, various vibrations generated when the moving object is in motion are transmitted to the measuring device.

[0044] To minimize the effects of such ambient vibrations, it is preferable to increase the scanning frequency in the main scanning direction of the measuring device to a certain extent, thereby increasing the discrepancy between the scanning frequency in the main scanning direction and the frequencies of other vibrations. In this regard, the measuring device 200 of this embodiment has a scanning frequency in the main scanning direction that is relatively high (the aforementioned N is 2 or more), and the number of times electromagnetic waves are irradiated to one pixel 224 is 1. Therefore, (1) the number of times electromagnetic waves are irradiated is sufficient to satisfy the resolution required of the measuring device 200, and (2) the scanning by the measuring device 200 is less susceptible to vibrations generated around the measuring device 200.

[0045] Here, the timing of electromagnetic wave irradiation in each main scan may or may not be equal intervals. Figure 15 illustrates a case where electromagnetic waves are irradiated at equal intervals in each main scan. In Figure 15, in each of the main scans from the first to the fourth row, electromagnetic waves are irradiated at intervals of "one wave every four pixels (224)".

[0046] Furthermore, in order to ensure that the pixel 224 irradiated with electromagnetic waves differs in each of the N consecutive main scans, the control unit 204 makes the pixel 224 that is first irradiated with electromagnetic waves different in each of the N consecutive main scans. For example, in Figures 8 and 15, each time the direction of electromagnetic wave irradiation moves down the scan range 220, the position of the pixel 224 that is first irradiated with electromagnetic waves is shifted to the pixel 224 to the right. Specifically, in Figure 15, the pixel 224 that is first irradiated with electromagnetic waves in the first main scan is the first pixel 224 from the left. On the other hand, the pixel 224 that is first irradiated with electromagnetic waves in the second main scan is the second pixel 224 from the left.

[0047] However, the method for making the first pixel 224 irradiated with electromagnetic waves different in each main scan is not limited to the method of "shifting one position to the right each time you move down one row" described above. Figure 16 is a diagram illustrating the first pixel 224 irradiated with electromagnetic waves in each main scan. In Figure 16, the first pixels 224 irradiated with electromagnetic waves in the main scans of rows 1 through 4 are the 1st, 3rd, 2nd from the left, and 4th from the right pixels, respectively.

[0048] The number of times electromagnetic waves are emitted during each main scan may be the same or different. In the former case, the number of times electromagnetic waves are emitted during each main scan is M / N. In the case of Figure 8 mentioned above, the number of times electromagnetic waves are emitted during each main scan is the same (2 times).

[0049] Note that M / N may not be an integer. In this case, instead of making the number of times electromagnetic waves are irradiated the same in each main scan, the control unit 204 makes the difference in the number of times electromagnetic waves are irradiated in each main scan 1 or less. In other words, the control unit 204 makes the number of times electromagnetic waves are irradiated in each main scan either the smallest integer greater than or equal to M / N or the largest integer less than or equal to M / N.

[0050] Figure 17 illustrates a case where the difference in the number of times electromagnetic waves are irradiated in each main scan is 1 or less. In this example, the number of main scans that can irradiate one pixel 224 with electromagnetic waves is 4 (N=4). Also, the number of pixels 304 included in one row of the scan range 220 is 7 (M=7). Therefore, the measurement unit 202 irradiates electromagnetic waves twice in the main scans of the first to third rows, and irradiates electromagnetic waves once in the main scan of the fourth row.

[0051] <Example of hardware configuration of measuring device 200> Each functional component of the measuring device 200 may be implemented by hardware (e.g., hardwired electronic circuits) or by a combination of hardware and software (e.g., a combination of an electronic circuit and a program to control it). The case in which each functional component of the measuring device 200 is implemented by a combination of hardware and software will be further explained below.

[0052] <<Example of hardware configuration of control unit 204>> Figure 18 is a diagram illustrating the hardware configuration of the control unit 204. The integrated circuit 100 is an integrated circuit that implements the control unit 204. For example, the integrated circuit 100 is a SoC (System On Chip).

[0053] The integrated circuit 100 includes a bus 102, a processor 104, a memory 106, a storage device 108, an input / output interface 110, and a network interface 112. The bus 102 is a data transmission path for the processor 104, memory 106, storage device 108, input / output interface 110, and network interface 112 to send and receive data to and from each other. However, the method of connecting the processor 104 and the other components is not limited to bus connection. The processor 104 is an arithmetic processing unit implemented using a microprocessor or the like. The memory 106 is a main memory device implemented using RAM (Random Access Memory) or the like. The storage device 108 is an auxiliary memory device implemented using ROM (Read Only Memory) or flash memory or the like.

[0054] The input / output interface 110 is an interface for connecting the integrated circuit 100 to peripheral devices. In Figure 18, the irradiator drive circuit 30 and the scanner drive circuit 32 are connected to the input / output interface 110. The irradiator drive circuit 30 and the scanner drive circuit 32 will be described later.

[0055] The network interface 112 is an interface for connecting the integrated circuit 100 to a communication network. This communication network is, for example, a CAN (Controller Area Network) communication network. The method by which the network interface 112 connects to the communication network may be wireless or wired.

[0056] The storage device 108 stores program modules for realizing the functions of the control unit 204. The processor 104 reads these program modules into memory 106 and executes them to realize the functions of the control unit 204.

[0057] The hardware configuration of the integrated circuit 100 is not limited to the configuration shown in Figure 18. For example, the program module may be stored in the memory 106. In this case, the integrated circuit 100 does not need to include the storage device 108.

[0058] <<Example Hardware Configuration of Measurement Unit 202>> Figure 19 illustrates the hardware configuration of the measurement unit 202. The measurement unit 202 includes an irradiator 10, a scanner 12, an irradiator drive circuit 30, a scanner drive circuit 32, and a receiver 50. The irradiator 10 emits electromagnetic waves used for scanning an object. The scanner 12 changes the direction of propagation of the electromagnetic waves emitted from the irradiator 10 to a desired direction. In this way, the irradiator 10 and the scanner 12 allow the measurement unit 202 to irradiate electromagnetic waves to various locations outside the measurement unit 202. The electromagnetic waves whose direction of propagation has been changed by the scanner 12 are irradiated to the outside of the measurement device 200.

[0059] Electromagnetic waves reflected by an object outside the measuring device 200 (hereinafter referred to as reflected waves) enter the inside of the measuring device 200 and then have their direction of travel changed by the scanner 12. The receiver 50 receives the reflected waves whose direction of travel has been changed by the scanner 12.

[0060] The irradiator drive circuit 30 is a circuit that drives the irradiator 10. More specifically, the irradiator drive circuit 30 has a circuit that drives a mechanism (e.g., a light source) that irradiates electromagnetic waves. The scanner drive circuit 32 is a circuit that drives the scanner 12. More specifically, the scanner drive circuit 32 has a circuit that drives a mechanism (e.g., a mirror) that changes the direction of electromagnetic wave irradiation.

[0061] The control unit 204 detects that the receiver 50 has received a reflected wave. For example, the receiver 50 is configured to transmit a predetermined signal to the control unit 204 in response to the reception of a reflected wave. The control unit 204 detects that the receiver 50 has received a reflected wave by receiving this predetermined signal.

[0062] The control unit 204 measures the elapsed time from when electromagnetic waves are emitted from the irradiator 10 until the reflected waves are received by the receiver 50, and stores this measured time in a memory device (e.g., storage device 108) in association with the direction of electromagnetic wave irradiation (irradiation timing of electromagnetic waves). This elapsed time is expressed, for example, by multiplying the number of clock signals counted between the time when electromagnetic waves are emitted from the irradiator 10 until the reflected waves are received by the clock period. Alternatively, for example, this elapsed time may be expressed as the number of clock signals counted. Based on this elapsed time, for example, the distance between the scanned object and the measuring device 200 can be calculated.

[0063] The electromagnetic waves emitted by the irradiator 10 may be light such as laser light, or radio waves such as millimeter waves. Below, an example of the hardware configuration of the measurement unit 202 when the irradiator 10 emits light will be given. A similar configuration can be adopted for the measurement unit 202 when the irradiator 10 emits electromagnetic waves.

[0064] Figure 20 illustrates the hardware configuration of the measurement unit 202 that irradiates light. The light source 14, movable reflector 16, light source drive circuit 36, and movable reflector drive circuit 34 in Figure 20 are examples of the irradiator 10, scanner 12, irradiator drive circuit 30, and scanner drive circuit 32 in Figure 19, respectively.

[0065] The light source 14 is any light source that emits light. The light source drive circuit 34 is a circuit that drives the light source 14 by controlling the supply of power to the light source 14. The light emitted by the light source 14 is, for example, laser light. In this case, for example, the light source 14 is a semiconductor laser that emits laser light.

[0066] The movable reflector 16 changes the direction of light emitted from the light source 14 by reflecting the light emitted from the light source 14. The light reflected by the movable reflector 16 is emitted to the outside of the measuring device 200. The movable reflector 16 also changes the direction of light reflected by an object outside the measuring device 200 (hereinafter referred to as reflected light).

[0067] The drive circuit 36 ​​for the movable reflector is a circuit that drives the movable reflector 16. The movable reflector 16 has a single mirror that is configured to rotate in each of two axes, for example. The two axes described above are, respectively, the first axis for changing the direction of light irradiation in the main scanning direction and the second axis for changing the direction of light irradiation in the sub-scanning direction. The mirror described above is, for example, a MEMS (Micro Electro Mechanical System) mirror.

[0068] The configuration of the movable reflective section 16 is not limited to the configuration shown in Figure 20. For example, the movable reflective section 16 may consist of two mirrors whose rotation axes intersect with each other. The rotation axes of these two mirrors are the first axis and the second axis, respectively.

[0069] The operation of the light source drive circuit 34 and the movable reflector drive circuit 36 ​​is controlled by the control unit 204. Specifically, the control unit 204 transmits a drive signal to the light source drive circuit 34 instructing it to drive the light source 14. This drive signal is read from, for example, the storage device 108. The light source drive circuit 34 drives the light source 14 based on the received drive signal. For example, if the drive signal is a pulse signal consisting of two values, high and low, the light source drive circuit 34 drives the light source 14 (irradiates light from the light source 14) at the timing when the pulse signal changes from low to high.

[0070] Similarly, the control unit 204 transmits a drive signal to the drive circuit 36 ​​of the movable reflector unit, instructing it to drive the movable reflector unit 16. This drive signal is also read from, for example, the storage device 108. Based on this drive signal, the drive circuit 36 ​​of the movable reflector unit controls the orientation of the movable reflector unit 16. This control controls the direction of light irradiation. For example, the direction of light irradiation is controlled as shown in the trajectory 222 in Figure 8.

[0071] Furthermore, the measuring unit 202 has a light receiver 52. The light receiver 52 is an example of the receiver 50 in Figure 19. For example, the light receiver 52 is constructed using an APD (Avalanche Photodiode). The light receiver 52 receives reflected light whose direction of travel has been changed by the movable reflector 16.

[0072] Note that the configuration of the measurement unit 202 is not limited to the configurations shown in Figures 19 and 20. For example, in Figure 19, the measurement unit 202 is configured so that reflected waves reflected by an object are received by the receiver 50 via the scanner 12. However, reflected waves reflected by an object may be received by the receiver 50 without going through the scanner 12. Figure 21 is a diagram illustrating a hardware configuration of a measurement device 200 in which reflected waves are received without going through the scanner 12.

[0073] In addition, as shown in Figure 19, the measurement unit 202 is configured to irradiate electromagnetic waves in various directions by changing the direction of propagation of the electromagnetic waves irradiated from the irradiator 10 using the scanner 12. However, the configuration for irradiating electromagnetic waves in various directions is not limited to the configuration shown in Figure 19. For example, the irradiator 10 itself may have a mechanism that rotates on each of the two axes mentioned above. In this case, the measurement unit 202 can irradiate light in various directions by controlling the orientation of the irradiator 10. Also in this case, the measurement unit 202 does not need to have the scanner 12 and the scanner drive circuit 32. Furthermore, in this case, the irradiator drive circuit 30 includes a drive circuit that irradiates electromagnetic waves onto the irradiator 10 and a drive circuit that changes the orientation of the irradiator 10.

[0074] The hardware that implements the control unit 204 (see Figure 18) and the hardware that implements the measurement unit 202 (see Figures 19 and 20) may be packaged in the same housing or in separate housings.

[0075] <Method for controlling the timing of electromagnetic wave irradiation by the measurement unit 202> The timing of electromagnetic wave irradiation from the measuring device 200 can be controlled by a drive signal (hereinafter referred to as the light source drive signal) transmitted to the light source drive circuit 34. Therefore, a light source drive signal is generated in advance to control the measuring unit 202 in a manner that satisfies the first and second requirements described above. This light source drive signal is stored, for example, in a storage device 108. The control unit 204 reads this light source drive signal from the storage device 108 and transmits it to the light source drive circuit 34. In this way, the measuring unit 202 is controlled in a manner that satisfies the first and second requirements described above. The generation of the light source drive signal is performed, for example, before the start of operation of the measuring device 200 (for example, before the measuring device 200 is shipped).

[0076] Figure 22 illustrates a light source drive signal. In both Figure 22(a) and Figure 22(b), the graph represents the light source drive signal. The arrows on the graph indicate points (pulses) where the value of the light source drive signal changes from 0 to 1. The light source emits electromagnetic waves at the timing indicated by these arrows. Above the graph, the scanning trajectory of a measuring device controlled by the light source drive signal is shown.

[0077] Figure 22(a) shows the light source drive signal that enables scanning using the general measuring device shown in Figure 2. In contrast, Figure 22(b) shows the light source drive signal that enables scanning using the measuring device 200 of this embodiment shown in Figure 8.

[0078] <Example of installation of measuring device 200> The measuring device 200 is installed on a moving object, such as an automobile or a train. Figure 23 illustrates the measuring device 200 installed on a moving object. In Figure 23, the measuring device 200 is fixed to the top of the moving object 240. The measuring device 200 is also connected to the control device 244. The control device 244 is a control device that controls the moving object 240. For example, the control device 244 is an ECU (Electronic Control Unit).

[0079] Here, the control unit 204 may be implemented as part of a control device 244 that controls the mobile body 240. In this case, a program module that implements the aforementioned control unit 204 is stored in the storage device of the control device 244.

[0080] Furthermore, the location where the measuring device 200 is installed is not limited to the top of the mobile body 240. For example, the measuring device 200 may be installed inside the mobile body 240 (e.g., indoors). Alternatively, the measuring device 200 may be installed on a stationary object.

[0081] The embodiments of the present invention have been described above with reference to the drawings, but these are merely examples of the present invention, and combinations of the above embodiments or various other configurations can also be adopted. The embodiments of the present invention have been described above with reference to the drawings, but these are merely examples of the present invention, and combinations of the above embodiments or various other configurations can also be adopted. Examples of reference formats are provided below. 1. A measurement unit that performs scanning by irradiating electromagnetic waves while changing the irradiation direction, A measuring device comprising: a control unit that controls the measuring unit so that electromagnetic waves are irradiated a total of M times in N consecutive main scans, and the irradiation timing of the electromagnetic waves differs from one another in the N main scans, and electromagnetic waves are irradiated at least once in each main scan. 2. The measuring apparatus according to 1, wherein M is the number of pixels of the resolution obtained in the N consecutive main scans. 3. If the scanning interval in the sub-scanning direction is dy, and the width of one pixel in the sub-scanning direction is A, then N is either the largest integer less than or equal to A / dy, or the smallest integer greater than or equal to A / dy. The measuring device according to 1. or 2., wherein X is the width of the scan range in the main scanning direction, and B is the width of one pixel in the main scanning direction, and M is either the smallest integer greater than or equal to X / B or the largest integer less than or equal to X / B. 4. The control unit irradiates electromagnetic waves at equal intervals during each main scan, as described in any one of 1 to 3. 5. The control device according to any one of 1 to 4, wherein the control unit sets the number of electromagnetic wave irradiations in each of the N main scans to either the smallest integer greater than or equal to M / N and the largest integer less than or equal to M / N. 6. A control method in which a computer controls a measuring device that performs scanning by irradiating electromagnetic waves while changing the direction of irradiation, A control method for controlling the measuring device such that it irradiates an electromagnetic wave a total of M times in N consecutive main scans, and the irradiation timing of the electromagnetic wave differs from one another in the N main scans, and that an electromagnetic wave is irradiated at least once in each main scan. [Explanation of Symbols]

[0082] 10 Irradiator 12 Scanner 14 Light source 16 Movable reflector 30. Driving circuit of the irradiator 32 Scanner drive circuit 34 Light source driving circuit 36. Drive circuit for the movable reflector 50 Receiver 52 Receiver 100 Integrated Circuits Bus 102 104 Processors 106 memory 108 Storage Devices 110 Input / Output Interfaces 112 Network Interfaces 200 measuring devices 202 Measurement Unit 204 Control Unit 220 scanning range 222 Trajectory 224 pixels 240 Mobile Units 244 Control device 300 scanning range 302 Trajectory 304 pixels 306 spots

Claims

[Claim 1] A method for determining the scanning method of a measuring device installed on a mobile body, The aforementioned measuring device is a device that performs scanning by irradiating electromagnetic waves while changing the irradiation direction. A frequency higher than the frequency of vibrations generated when the moving body is in motion is determined as the scanning frequency of the main scan of the measuring device. A method for determining a scanning method, which involves determining the timing of electromagnetic wave irradiation so that, at the determined scanning frequency of the main scan, each pixel arranged in a line in the main scanning direction is irradiated with electromagnetic waves once in total over the sum of multiple consecutive main scans.

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