Light projection device, distance measuring device, and method for controlling the projection of laser light

Abstract

To increase the reach distance of laser beam while enabling miniaturization and complying with laser safety standards.SOLUTION: A floodlight device includes a plurality of floodlight units that can switch the emission direction and the emission timing of the optical signal, and a plurality of first control units that control the emission direction and the emission timing of the optical signal emitted from the corresponding floodlight units among the plurality of floodlight units.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] One embodiment of the present invention relates to a light projecting device, a distance measuring device, and a method for controlling the light projection of laser light.

Background Art

[0002] In the field of autonomous driving technology, there is a need for a technology that can detect objects existing around a vehicle non-contact, at high speed, and with high precision. In general, the ToF (Time of Flight) method is adopted to detect the distance to an object based on the time from when laser light emitted from the vehicle is reflected by the object until it is received. To detect objects around the vehicle, it is necessary to irradiate laser light over a relatively wide range, and a scanning mechanism that periodically scans the laser light in two-dimensional directions is often provided. However, it is not easy to miniaturize the scanning mechanism.

[0003] In addition, since the laser light has an extremely high light intensity per unit area compared to other illumination lights, there is a risk of hurting the eyes if it directly enters the human eye. Therefore, it is necessary to make the light intensity compliant with laser safety standards. However, if the light intensity is weakened, the laser light cannot reach distant objects, and the range within which the distance can be measured is limited. Furthermore, the laser light source has a limit in its light emitting ability, and it is necessary to use a plurality of laser light sources for applications that further extend the range within which long distances can be measured. However, when using a plurality of laser light sources, an optical system that combines the plurality of laser light sources into one laser beam becomes complicated, leading to an increase in design cost and enlargement of the light projection system.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Therefore, in one embodiment of the present invention, a light projection device, a distance measuring device, and a method for controlling the projection of laser light are provided that can be miniaturized and have a longer range. In particular, the light projection device provided can also be made compliant with laser safety standards. [Means for solving the problem]

[0006] To solve the above problems, according to one embodiment of the present invention, a plurality of light-emitting units capable of switching the emission direction and emission timing of an optical signal, A light-emitting device is provided, comprising a plurality of first control units that control the emission direction and emission timing of light signals emitted from a corresponding light-emitting unit among the plurality of light-emitting units. [Brief explanation of the drawing]

[0007] [Figure 1] A block diagram showing the schematic configuration of the light projection device 1 according to the first embodiment. [Figure 2] Perspective view of multiple light-emitting units 2. [Figure 3] A block diagram showing an example of the internal configuration of each light-emitting unit 2. [Figure 4] A block diagram of the light projection device 1a, with the configuration of Figure 1 plus a second control unit 7. [Figure 5] A block diagram showing an example of the internal configuration of the second control unit 7. [Figure 6A] A diagram illustrating the first specific example of multiple types of reference command signals. [Figure 6B] A diagram illustrating a second specific example of multiple types of reference command signals. [Figure 7] A block diagram showing the schematic configuration of the light projection device 1b, with the scanning control unit 12 added to the configuration of Figure 4. [Figure 8] A perspective view of the light projection device 1b in Figure 6. [Figure 9] A schematic diagram showing the beam shape of the optical signals emitted from multiple light-emitting units 2. [Figure 10A] A diagram showing the change in beam width in the horizontal direction. [Figure 10B]A diagram showing the change in beam width in the vertical direction. [Figure 11] A diagram schematically illustrating the characteristic features of a light-emitting device according to the third embodiment. [Figure 12] A block diagram showing the schematic configuration of a rangefinder with a built-in light source. [Figure 13] A block diagram of a distance measuring device with an object detection unit and a scanning speed adjustment unit added to the configuration shown in Figure 11. [Figure 14] A diagram illustrating an example where one object is present within the light emission range. [Figure 15] A diagram illustrating an example where multiple objects exist within the light emission range. [Modes for carrying out the invention]

[0008] The following describes embodiments of the light projection device, distance measuring device, and laser light projection control method with reference to the drawings. While the main components of the light projection device and distance measuring device will be described below, there may be components and functions not shown or described in the drawings. The following description does not exclude any components or functions not shown or described.

[0009] (First Embodiment) Figure 1 is a block diagram showing the schematic configuration of the light projection device 1 according to the first embodiment. The light projection device 1 in Figure 1 has the function of emitting multiple light signals and can be built into, for example, a rangefinder, as will be described later. Note that the light projection device 1 in Figure 1 can also be used for various purposes other than rangefinders.

[0010] The light projecting device 1 in Fig. 1 includes a plurality of light projecting units 2 and a plurality of first control units 3. Each of the plurality of light projecting units 2 can switch the emission direction and emission timing of the optical signal. Each of the plurality of first control units 3 is provided corresponding to one of the light projecting units 2. Each of the plurality of first control units 3 controls the emission direction and emission timing of the optical signal emitted from the corresponding light projecting unit 2. More specifically, each of the plurality of first control units 3 supplies a control signal to the corresponding light projecting unit 2. Each light projecting unit 2 emits an optical signal with an emission direction and emission timing according to the control signal from the corresponding first control unit 3.

[0011] The optical signal emitted from each light projecting unit 2 is a so-called laser light pulse. Laser light is coherent light with a uniform wavelength and phase, and has, for example, a single wavelength of 900 nm. Note that the wavelength of the optical signal emitted from each light projecting unit 2 is arbitrary.

[0012] The light intensity of the optical signal emitted from each light projecting unit 2 generally needs to be a value compliant with the laser (eye-safe) safety standard. By emitting an optical signal compliant with the laser safety standard, such as light intensity, pulse time, and pulse repetition frequency, from each light projecting unit 2, even if the optical signal enters a human eye, there is no risk of hurting the human eye. However, in a special environment where it is not necessary to comply with the eye-safe safety standard, each light projecting unit 2 may increase the power and time of the laser pulse, etc., to extend the range of the distance measurement of the LiDAR (Light Detection And Ranging) device.

[0013] Thus, in this embodiment, the optical intensity of the optical signal emitted from each light projecting unit 2 is set to a value compliant with laser safety standards. The higher the optical intensity of the optical signal, the farther the optical signal can reach, but this is not preferable from the viewpoint of eye safety. Therefore, in this embodiment, it is kept in mind to emit an optical signal with an optical intensity compliant with laser safety standards from each light projecting unit 2. Although laser light has high straightness, as the optical path length becomes longer, the beam diameter spreads and the optical intensity per unit area becomes smaller. In this embodiment, at least a part of the beam ranges of the plurality of optical signals emitted from the plurality of light projecting units 2 overlap with each other at a distance. The optical intensity becomes high in the region where the beam ranges of the plurality of optical signals overlap. Thus, even if the optical intensity of the optical signal emitted from each light projecting unit 2 is not so high, at a distance, the beam ranges of the plurality of optical signals overlap, so that the optical intensity can be maintained high and the optical signal can reach far away.

[0014] FIG. 2 is a perspective view of the plurality of light projecting units 2. As shown in the figure, a plurality of light projecting units 2 are arranged in plural numbers in the horizontal direction X and the vertical direction Y. FIG. 2 shows an example having three light projecting units 2 in the horizontal direction X and four light projecting units 2 in the vertical direction Y, but the number of the light projecting units 2 is not limited. Also, the plurality of light projecting units 2 may be arranged in a one-dimensional direction (the horizontal direction X or the vertical direction Y).

[0015] FIG. 3 is a block diagram showing an example of the internal configuration of each light projecting unit 2. As shown in FIG. 3, each light projecting unit 2 includes a light source 4, an optical system 5, and a scanning unit 6.

[0016] The light source 4 is a laser light source 4 that emits laser light as described above. The laser light source 4 is, for example, a semiconductor laser. Alternatively, the laser light source 4 may be other than a semiconductor laser such as a HeNe laser. A pulsed optical signal is emitted from the light source 4. The light source 4 can switch the emission timing of the optical signal based on a control signal from the corresponding first control unit 3.

[0017] The optical system 5 shapes the light signal emitted from the light source 4. Here, shaping means adjusting the beam shape, direction of propagation, and beam spread angle of the light signal. An example of the optical system 5 is a collimating lens. A collimating lens can parallelize the incident diffuse light signal.

[0018] The scanning unit 6 scans the optical signal shaped by the optical system 5 within a predetermined light emission range. The scanning unit 6 can control the light emission range based on a control signal from the corresponding first control unit 3. The light emission range is a range of any size that extends in a two-dimensional or one-dimensional direction. The scanning unit 6 can also adjust the scanning speed when scanning the optical signal within the light emission range based on a control signal from the corresponding first control unit 3.

[0019] More specifically, the scanning unit 6 includes, for example, a MEMS (Micro-Electro-Mechanical Systems) mirror. The angle of the MEMS mirror can be electrically varied. By changing the angle of the MEMS mirror, the reflection direction of the light signal irradiated onto the MEMS mirror can be changed. Therefore, by changing the angle of the MEMS mirror based on the corresponding control signal from the first control unit 3, the emission direction of the light signal emitted from each light-emitting unit 2 can be gradually changed, and the light signal can be scanned within a predetermined light emission range.

[0020] MEMS mirrors come in two types: those that rotate around one axis and those that rotate around two axes. By using a MEMS mirror that rotates around two axes and gradually changing the angle of the MEMS mirror in both axes, it is possible to scan an optical signal within a light emission range that extends in two dimensions.

[0021] In this way, each light-emitting unit 2 can individually adjust the direction and timing of light signal emission based on the corresponding control signal from the first control unit 3. Therefore, multiple light signals emitted from multiple light-emitting units 2 can be emitted in substantially the same direction, or each individual light-emitting unit 2 can emit a light signal in any direction. Furthermore, all light-emitting units 2 can emit multiple light signals at substantially the same timing, or each individual light-emitting unit 2 can emit a light signal at any timing.

[0022] Multiple first control units 3 may be controlled by a second control unit 7. Figure 4 is a block diagram of a light-emitting device 1a with the second control unit 7 added to the configuration of Figure 1. The second control unit 7 supplies an angle command signal regarding the direction of emission of the light signal to each of the multiple first control units 3. The angle command signal is a signal that commands the direction of emission of the light signal emitted from each of the multiple first light-emitting units 2. In other words, in the light-emitting device 1a of Figure 4, the second control unit 7 controls the direction of emission of the light signal emitted from each light-emitting unit 2. By providing the second control unit 7, it is possible to control the direction in which the light signal is emitted from multiple light-emitting units 2 all at once, making it easier to control multiple light-emitting units 2. In addition, the second control unit 7 may control not only the direction of emission of the light signal emitted from each light-emitting unit 2, but also the emission timing.

[0023] Figure 5 is a block diagram showing an example of the internal configuration of the second control unit 7. The second control unit 7 in Figure 5 includes a reference command generation unit 8, an angle correction table 9, a plurality of adders 10, and an update control unit 11.

[0024] The reference command generation unit 8 generates a reference command signal that is given in common to all light-emitting units 2. The reference command signal does not necessarily have to be of one type. The reference command generation unit 8 may generate any of several types of reference command signals. The reference command signals generated by the reference command generation unit 8 are input to multiple adders 10.

[0025] The angle correction table 9 stores an angle correction signal for each of the multiple light-emitting units 2 to correct the reference command signal. When the reference command generation unit 8 generates one of several types of reference command signals, the angle correction table 9 stores an angle correction signal corresponding to each of the multiple light-emitting units 2 for each reference command signal. This angle correction signal includes the intended angle offset of each light-emitting unit 2, as well as the angle error of each light-emitting unit 2 due to installation, manufacturing, etc. For creating the angle error data, the angle may be measured in advance by emitting a laser from each light-emitting unit 2 using a light-receiving device or photosensitive paper (not shown in Figure 5).

[0026] Thus, the angle correction table 9 may store multiple sets of correspondences between a reference command signal and multiple angle correction signals, with each set containing different angle correction signals. In this case, the second control unit 7 selects one set from the multiple sets stored in the angle correction table 9, and based on the correspondence of the selected set, generates an angle command signal for each of the multiple light-emitting units 2 by reading the corresponding angle correction signal from the angle correction table 9 and loading the reference command signal.

[0027] Below, two specific examples of the multiple types of reference command signals and angle correction table 9 generated by the reference command generation unit 8 will be described. Figure 6A is a diagram illustrating the first specific example of the multiple types of reference command signals. In the first specific example, the reference command signal is a signal that commands the emission direction to be changed continuously or stepwise according to time at predetermined cycles, as shown in Figure 6A. The reference command signal is an analog or digital value, and may be a voltage signal or a current signal. The angle correction table 9 stores an angle correction signal for each of the multiple light-emitting units 2, for example, to make the emission directions parallel. For example, if the emission direction of one of two adjacent light-emitting units 2 is shifted by +1 degree from the other light-emitting unit in its default state, the angle correction table 9 sets the angle correction signal for the emission direction of one of the two light-emitting units 2 to 0 degrees and the angle correction signal for the emission direction of the other to -1 degree. This makes it possible to make the emission directions of the light signals emitted from the two light-emitting units 2 parallel.

[0028] Figure 6B illustrates a second specific example of multiple types of reference command signals. In this second example, the reference command signal is emitted multiple times at predetermined time intervals, resulting in a pulse train signal as shown in Figure 6B. The emission direction of each reference command signal is changed by an angle corresponding to the number of times the optical signal has been emitted. For example, if the emission direction of the optical signal changes by m degrees each time the reference command signal is emitted, the emission direction of the nth reference command signal will be changed by m × n degrees compared to the first reference command signal. The emission direction is periodically changed within the range of 0 to 360 degrees, as shown in Figure 6B.

[0029] The angle correction table 9 in the second specific example stores angle correction signals, similar to the angle correction table 9 in the first specific example, so that, for example, the emission directions of the light signals emitted from multiple light-emitting units 2 are parallel.

[0030] Furthermore, the multiple types of reference command signals and the angle correction signals stored in the angle correction table 9 are not necessarily limited to the first and second specific examples described above.

[0031] Multiple adders 10 are provided in association with multiple first control units 3. Each of the multiple adders 10 adds a reference command signal and a corresponding angle correction signal read from the angle correction table 9 to generate a corresponding angle command signal for the first control unit 3.

[0032] The angle correction signals stored in the angle correction table 9 may be made updateable as needed. The update of the angle correction signals stored in the angle correction table 9 is performed, for example, by the update control unit 11 in the second control unit 7. By updating the angle correction signals stored in the angle correction table 9 in the update control unit 11, the emission direction of the light signals emitted from the multiple light-emitting units 2 can be switched as needed, thereby realizing a reconfigurable light-emitting device 1a. The update control unit 11 and the reference command generation unit 8 may be integrated.

[0033] The second control unit 7 does not necessarily have to be configured as shown in Figure 5. For example, instead of providing a reference command signal, the second control unit 7 may directly generate angle command signals for multiple first control units 3 and supply them to the corresponding first control units 3.

[0034] In the light-emitting devices 1 and 1a shown in Figures 1 to 5, a configuration was described in which the emission direction of the light signals emitted from each of the multiple light-emitting units 2 can be individually controlled. However, the multiple light-emitting units 2 may be treated as a single unit, and the multiple light signals emitted from the multiple light-emitting units 2 may be scanned together in a one-dimensional or two-dimensional direction.

[0035] Figure 7 is a block diagram showing the schematic configuration of the light projector 1b with the addition of a scanning control unit 12 to the configuration of Figure 4, and Figure 8 is a perspective view of the light projector 1b of Figure 7. The scanning control unit 12 causes the light signals emitted from the multiple light projectors 2 to be scanned integrally in a one-dimensional or two-dimensional direction periodically. For example, as shown in Figure 8, the scanning control unit 12 may cause the light projector 1b, including its housing, to be scanned periodically in at least one of the horizontal X and vertical Y directions.

[0036] According to the light projection device 1b in Figure 7, the emission direction of multiple light signals emitted from multiple light projection units 2 can be individually controlled by the corresponding first control unit 3, and the emission direction of multiple light signals can also be controlled integrally by the scanning control unit 12.

[0037] As described above, the light-emitting devices 1, 1a, and 1b according to the first embodiment include a plurality of light-emitting units 2 and a plurality of first control units 3, and the emission direction and emission timing of the light signals emitted from each of the plurality of light-emitting units 2 are controlled by the corresponding first control unit 3. This allows the emission direction and emission timing of the light signals emitted from each of the plurality of light-emitting units 2 to be adjusted individually and arbitrarily, and the plurality of light signals emitted from the plurality of light-emitting units 2 can be used for various purposes.

[0038] Furthermore, by providing a second control unit 7 that controls multiple first control units 3, and supplying angle command signals from the second control unit 7 to the multiple first control units 3, it is possible to realize reconfigurable light-emitting devices 1, 1a, and 1b that change the emission direction and emission timing of light signals from multiple light-emitting units 2 by updating the angle command signals as needed.

[0039] (Second embodiment) The light-emitting devices 1a and 1b according to the second embodiment have a block configuration similar to that shown in Figures 4 to 7. In the light-emitting devices 1a and 1b according to the second embodiment, the second control unit 7 controls the multiple light-emitting units 2 so that light signals traveling substantially parallel to each other are emitted from the multiple light-emitting units 2.

[0040] Figure 9 schematically shows the beam shape of the light signals emitted from multiple light-emitting units 2. As shown in Figure 9, the multiple light signals emitted from the multiple light-emitting units 2 travel in a substantially parallel direction. The emission direction of the light signals emitted from each of the multiple light-emitting units 2 is controlled by the corresponding first control unit 3. As shown in Figure 4, each of the multiple first control units 3 corresponding to the multiple light-emitting units 2 is supplied with an angle command signal from the second control unit 7. Each of the multiple first control units 3 controls the emission direction of the light signal emitted from the corresponding light-emitting unit 2 based on the corresponding angle command signal. In this embodiment, the angle command signal from the second control unit 7 causes the corresponding first control unit 3 to control the emission direction of the light signal emitted from the corresponding light-emitting unit 2, so that the multiple light signals emitted from the multiple light-emitting units 2 are substantially parallel.

[0041] The beam width of the light signal emitted from each light-emitting unit 2 widens as the distance increases, but the degree of beam width widening differs between the horizontal and vertical directions. Figures 10A and 10B schematically show the beam width of the light signal emitted from each light-emitting unit 2, with Figure 10A showing the change in beam width in the horizontal direction and Figure 10B showing the change in beam width in the vertical direction.

[0042] As shown in Figure 10A, the horizontal beam width of the light signal emitted from each light-emitting unit 2 hardly changes even when the distance changes, whereas, as shown in Figure 10B, the vertical beam width changes significantly with distance. More specifically, the vertical beam width widens as the distance increases.

[0043] By arranging multiple light-emitting units 2 vertically, a region is created in which the light signals emitted from the multiple light-emitting units 2 overlap vertically at locations far from the light-emitting devices 1a and 1b. In this region, the light intensity is higher than that of a single light signal.

[0044] Thus, in the second embodiment, multiple optical signals are emitted from multiple light-emitting units 2 in substantially parallel directions, and by causing a portion of the multiple optical signals emitted from the multiple light-emitting units 2 to overlap vertically, the light intensity at long distances can be increased. As shown in Figure 10B, when the spacing between the multiple light-emitting units 2 arranged vertically changes, the range in which the multiple optical signals overlap vertically at long distances changes. If the individual laser beams do not spread very far and overlap at close range where the laser intensity is strong, the overlapping portion may not comply with eye-safe standards. Therefore, it is desirable to adjust the spacing between the multiple light-emitting units 2 arranged vertically so that the overlapping portion complies with eye-safe standards.

[0045] Furthermore, in the light-emitting devices 1a and 1b according to the second embodiment, the multiple light-emitting units 2 may emit light signals at substantially the same emission timing. For example, in a distance measuring device, which is an application example of the light-emitting devices 1a and 1b according to this embodiment, light signals are repeatedly emitted at predetermined time intervals, reflected light signals from an object are repeatedly received, and the distance to the object is measured based on the received light results. Thus, when the light-emitting devices 1a and 1b according to this embodiment are used in a distance measuring device, the operation of emitting light signals from multiple light-emitting units 2 at substantially the same timing is repeatedly performed at predetermined time intervals, reflected light signals from an object are repeatedly received, and the distance to the object is measured.

[0046] (Third embodiment) The light projecting devices 1a and 1b according to the third embodiment classify a plurality of light projecting units 2 into a plurality of light projecting groups. In the second embodiment, an example in which a plurality of optical signals are emitted from a plurality of light projecting units 2 in substantially the same emission direction was described. In the third embodiment, the plurality of light projecting units 2 are classified into two or more light projecting groups, and the emission direction of the optical signal is individually controlled for each light projecting group.

[0047] More specifically, in the third embodiment, N (N is an integer of 2 or more) light projecting units 2 are classified into M (2 < M ≤ N) light projecting groups, and the light projecting units 2 belonging to the same light projecting group emit optical signals in the same emission direction. Also, the light emission ranges of the light projecting units 2 belonging to different light projecting groups are made not to overlap or to overlap only partially.

[0048] Thereby, the light emission range of the light projecting devices 1a and 1b provided with a plurality of light projecting units 2 can be made wider than the light emission range of a single light projecting unit 2. For example, when a MEMS mirror is used for the scanning unit 6 of the light projecting unit 2, since the driving range of the MEMS mirror is narrow, the light emission range of the light projecting unit 2 becomes narrow. Therefore, by providing a plurality of MEMS mirrors, the overall light emission range can be widened.

[0049] FIG. 11 is a diagram schematically explaining a characteristic part of the light projecting devices 1a and 1b according to the third embodiment. FIG. 11 shows an example in which a plurality of (for example, four) light projecting units 2 are classified into three light projecting groups (hereinafter, the first to third light projecting groups) 2-1, 2-2, and 2-3, and the emission direction of the optical signal is individually controlled for each light projecting group.

[0050] The light-emitting unit 2 belonging to the first light-emitting group 2-1 scans the optical signal within the first light emission range OR1. The light-emitting unit 2 belonging to the second light-emitting group 2-2 scans the optical signal within the second light emission range OR2. The light-emitting unit 2 belonging to the third light-emitting group 2-3 scans the optical signal within the third light emission range OR3. Figure 11 shows an example in which the first light emission range OR1, the second light emission range OR2, and the third light emission range OR3 do not overlap, but they may overlap in part. That is, the emission direction of the optical signal emitted from the light-emitting unit 2 belonging to the first light-emitting group 2-1, the emission direction of the optical signal emitted from the light-emitting unit 2 belonging to the second light-emitting group 2-2, and the emission direction of the optical signal emitted from the light-emitting unit 2 belonging to the third light-emitting group 2-3 may be completely different, or they may overlap in part.

[0051] As can be seen from Figure 11, since each of the first to third light projection groups 2-1 to 2-3 has a different light emission range in at least part of it, the total light emission range of the light projection devices 1a and 1b can be widened compared to the light emission range of a single light projection group.

[0052] The method for classifying the multiple light-emitting units 2 into multiple light-emitting groups may be predetermined. In this case, it is sufficient for the first control unit 3 corresponding to each light-emitting unit 2 to know the direction and timing of the light signal emission.

[0053] Alternatively, the classification of the multiple light-emitting units 2 into different light-emitting groups can be arbitrarily adjusted. In this case, the second control unit 7 controls the classification of the multiple light-emitting units 2 into multiple light-emitting groups. The second control unit 7 transmits information to the multiple first control units 3 regarding which light-emitting group each corresponding light-emitting unit 2 belongs to. The information transmitted from the second control unit 7 to the multiple first control units 3 also includes information indicating the light emission range of each light-emitting group.

[0054] By allowing the second control unit 7 to change how it classifies the multiple light-emitting units 2 into different light-emitting groups as needed, reconfigurable light-emitting devices 1a and 1b can be realized. The second control unit 7 may also control the timing at which the multiple light-emitting groups emit light signals. For example, in the case of Figure 11, each light-emitting unit 2 belonging to the first to third light-emitting groups 2-1 to 2-3 may emit light signals at approximately the same timing, or they may emit light signals at different timings.

[0055] Thus, in the third embodiment, the multiple light-emitting units 2 are classified into multiple light-emitting groups, and the light emission direction is controlled for each light-emitting group. This allows for a wider light emission range compared to the case where the light emission ranges of the multiple light-emitting units 2 are aligned. Therefore, when the light-emitting devices 1a and 1b according to this embodiment are applied to a distance measuring device, the distance to objects in a wider area can be measured, increasing practicality. Furthermore, by allowing the classification of which light-emitting unit 2 is assigned to which light-emitting group to be changed as needed, reconfigurable light-emitting devices 1a and 1b can be realized.

[0056] (Fourth embodiment) As described above, the light-emitting devices 1, 1a, and 1b according to the first to third embodiments can be applied to a distance measuring device.

[0057] Figure 12 is a block diagram showing the schematic configuration of a distance measuring device 21 incorporating light projectors 1, 1a, and 1b according to any of the first to third embodiments. The distance measuring device 21 in Figure 12 comprises light projectors 1, 1a, and 1b according to any of the first to third embodiments, a light receiving device 22, and a distance measuring unit 23.

[0058] The light-receiving device 22 receives reflected light signals that are reflected by an object from multiple light signals emitted from the light-emitting devices 1, 1a, and 1b. The light-receiving device 22 may have a light-receiving module in which multiple light-receiving elements are arranged in two dimensions. The light-receiving elements may be SPADs (Single Photo Avalanche Diodes). Since SPADs can detect a single photon, they can detect weak reflected light signals from distant objects.

[0059] The distance measuring device 21 measures distance using, for example, the dToF (direct Time of Flight) method. In the dToF method, the distance to an object is measured based on the time difference between the timing when the light emitters 1, 1a, and 1b emit light signals and the timing when the light receiver 22 receives reflected light signals.

[0060] The second control unit 7 in the distance measuring device 21 in Figure 12 may supply angle command signals to multiple first control units 3 so that multiple light-emitting units 2 emit light signals in substantially the same emission direction, or it may supply angle command signals to the corresponding first control unit 3 for each light-emitting group into which the multiple light-emitting units 2 have been classified into multiple light-emitting groups.

[0061] As described above, each light-emitting unit 2 in the distance measuring device 21 repeatedly emits an optical signal while scanning the optical signal in a two-dimensional direction within a predetermined light emission range, the light-receiving device 22 continuously receives the reflected light signal, and the distance measuring unit 23 measures the distance to an object based on the received light result. The period in which each light-emitting unit 2 scans the optical signal within the light emission range does not necessarily have to be the same.

[0062] Assuming that each light-emitting unit 2 emits an optical signal at predetermined time intervals (for example, time intervals defined by the eye-safe standard), the longer the time each light-emitting unit 2 scans the optical signal within its optical emission range, the greater the number of optical signals emitted from each light-emitting unit 2 during the scan, allowing for more accurate detection of the presence and shape of objects within the optical emission range.

[0063] Figure 13 is a block diagram of the distance measuring device 21a, which has an object detection unit 24 and a scanning speed adjustment unit 25 added to the configuration of Figure 12.

[0064] The object detection unit 24 detects objects present within the light emission range while multiple light-emitting units 2 scan the light within the light emission range. The scanning speed adjustment unit 25 adjusts the length of the period in which the light signal scans the light emission range. More specifically, the scanning speed adjustment unit 25 slows down the scanning speed when scanning the light signal within the range where an object detected by the object detection unit exists compared to the scanning speed when scanning the light signal outside the range. Each light-emitting unit 2 is assumed to emit a light signal at regular time intervals.

[0065] In the distance measuring device 21a shown in Figure 13, the scanning speed adjustment unit 25 sets the length of the period in which the optical signal scans the light emission range to the first scanning period, and then starts the distance measuring operation. The object detection unit 24 detects whether the light receiving device 22 has received a reflected light signal from an object while the light emitters 1, 1a, and 1b are scanning the light emission range with the first scanning period.

[0066] The object detection unit 24 determines that a reflected light signal has been received if the signal level of the light received by the light receiving device 22 is above a predetermined threshold level. The object detection unit 24 detects all objects present throughout the entire light emission range.

[0067] For example, if one object is detected within the light emission range, the scanning speed adjustment unit 25 lowers the scanning speed of the optical signal when scanning near the detection position of the object within the light emission range. This allows more optical signals to be emitted near the detection position of the object within the light emission range, enabling more accurate detection of the object's depth shape.

[0068] Figure 14 shows an example where one object (a vehicle in the example of Figure 14) 26 is present in the lower right region within the light emission range. Each square within the light emission range in Figure 14 indicates the timing of the light signal emission. Near the detection position of object 26, the size of the squares becomes smaller, indicating that more light signals are irradiated near the detection position of object 26 to detect the depth shape of object 26 in greater detail.

[0069] The lower part of Figure 14 shows a timing diagram for scanning the light emission range twice. Hereafter, the first scanning period will be referred to as the first scanning period, and the second scanning period as the second scanning period.

[0070] In the timing diagram in the lower right of Figure 14, the horizontal axis represents time, and the vertical axis represents the scanning position within the light emission range. The vertical axis may also represent the scanning angle. In Figure 14, times t1 to t4 represent the first scanning cycle, and times t4 to t9 represent the second scanning cycle. During the first scanning cycle, each light-emitting unit 2 scans the light signal at a constant scanning speed, so the scanning position changes linearly with time. Time t2 to t3 within the first scanning period is the period during which the area where a vehicle exists within the light emission range is scanned. During this period, the signal level of the received light signal received by the light-receiving device 22 increases, causing the object detection unit 24 to detect the object 26.

[0071] In the second scanning cycle, the optical signal is initially scanned at the same scanning speed as in the first scanning cycle. When the scanning position of the optical signal approaches the position of object 26, the scanning speed adjustment unit 25 reduces the scanning speed of the optical signal. As described above, since each light-emitting unit 2 emits an optical signal at regular time intervals, when the scanning speed of the optical signal decreases, more optical signals can be emitted while scanning near the position of object 26. Therefore, the depth shape of object 26 can be detected with greater accuracy.

[0072] In Figure 14, the scanning position changes with a similar slope to that of times t1-t4 from time t4 to t5, whereas the change in scanning position per unit time becomes smaller from time t5 to t8, which is near the position of object 26. Object 26 is detected during the period from time t6 to t7. The period from t6 to t7 during which object 26 is detected in the second scanning cycle is longer than the period from t2 to t3 during which object 26 is detected in the first scanning cycle. Therefore, more optical signals can be irradiated onto object 26 during the period from time t6 to t7 than during the period from time t2 to t3.

[0073] Figure 15 shows an example where multiple objects (two in the example of Figure 15) are detected within the light emission range. In this case, the multiple light-emitting units 2 are classified into multiple light-emitting groups according to the number of detected objects 26. In the case of Figure 15, since two objects 26 were detected within the light emission range, they are classified into two light-emitting groups. The number of light-emitting units 2 belonging to each light-emitting group is arbitrary.

[0074] In Figure 15, times t1 to t6 represent the first scanning cycle, and times t6 to t15 represent the second scanning cycle. During the first scanning cycle, the entire area within the light emission range is scanned at a constant scanning speed. While scanning within the light emission range during the first scanning cycle, the object detection unit 24 detects two objects 26 within the light emission range. As described above, the object detection unit 24 detects the objects 26 when the signal level of the light received by the light receiving device 22 exceeds a predetermined threshold.

[0075] The object detection unit 24 detects two objects 26 at times t2-t3 and t4-t5 within the first scanning cycle.

[0076] The first control unit 3, having detected two objects (first object and second object) 26a and 26b by the object detection unit 24, classifies the multiple light-emitting units 2 into, for example, two light-emitting groups (first light-emitting group 2-1 and second light-emitting group 2-2). When the two light-emitting units 2 belonging to the first light-emitting group 2-1 scan near the position of the first object 26a, the scanning speed is reduced to detect the depth shape of the first object 26a with greater accuracy. Similarly, when the two light-emitting units 2 belonging to the second light-emitting group 2-2 scan near the position of the second object 26b, the scanning speed is reduced to detect the depth shape of the second object 26b with greater accuracy. In the example shown in Figure 15, the first light-emitting group 2-1 scans the optical signal at the same frequency as the first scanning cycle during the periods t6-t7 and t10-t15 within the second scanning cycle. During the period from time t7 to t10, the scanning speed of the optical signal is reduced because the location is near that of object 26. Object 26 is detected during the period from time t8 to t9. Meanwhile, the second light projection group 2-2 scans the optical signal at the same frequency as the first scanning period during the periods from time t6 to t11 and from t14 to t15 within the second scanning period. During the period from time t11 to t14, the scanning speed of the optical signal is reduced because the location is near that of object 26. Object 26 is detected during the period from time t12 to t13.

[0077] As shown in Figure 15, by using a separate light emission group to slow down the scanning speed for each object 26 detected within the light emission range and detecting the depth shape of the object 26, the depth shape of each object 26 can be detected accurately without making the second scanning period significantly longer than the first scanning period.

[0078] Thus, in the fourth embodiment, the light projection devices 1, 1a, and 1b according to the first to third embodiments are applied to the distance measuring devices 21 and 21a, enabling accurate detection of objects 26 within a wide range.

[0079] Furthermore, in the distance measuring device 21a shown in Figure 13, when an object 26 is detected within the light emission range, the scanning speed is slowed down when scanning the area around the detected object 26 with an optical signal. This allows for more accurate detection of the depth shape of the object 26.

[0080] Furthermore, if multiple objects 26 are detected within the light emission range, the multiple light-emitting units 2 are classified into multiple light-emitting groups according to the number of detected objects 26. Each light-emitting group can then detect the corresponding object 26 at a slower scanning speed, thereby enabling accurate detection of the depth shape of multiple objects 26 within the light emission range.

[0081] The aspects of this disclosure are not limited to the individual embodiments described above, but include various modifications that a person skilled in the art could conceive, and the effects of this disclosure are not limited to those described above. In other words, various additions, modifications, and partial deletions are possible, as long as they do not depart from the conceptual idea and spirit of this disclosure derived from the claims and their equivalents. [Explanation of Symbols]

[0082] 1 Light projector, 1a Light projector, 1b Light projector, 2 Light projection unit, 2-1 First light projection group, 2-2 Second light projection group, 2-3 Third light projection group, 3 First control unit, 4 Light source, 5 Optical system, 6 Scanning unit, 7 Second control unit, 8 Reference command generation unit, 9 Angle correction table, 10 Adder, 11 Update control unit, 12 Scanning control unit, 21 Distance measuring device, 21a Distance measuring device, 22 Light receiving device, 23 Distance measurement unit, 24 Object detection unit, 25 Scanning speed adjustment unit, 26 Object, 26a First object, 26b Second object

Claims

1. Floodlighting device, A light receiving device that receives a reflected light signal that is reflected by an object from the light emitting device, A distance measuring unit measures the distance to the object based on the light signal emitted from the light projector and the reflected light signal received by the light receiver. An object detection unit detects the position of the object based on the reflected light signal received by the light receiving device, The system includes a scanning speed adjustment unit that slows down the scanning speed when scanning the optical signal within the range where the object detected by the object detection unit exists, compared to the scanning speed when scanning the optical signal outside the range. The aforementioned light-emitting device is Multiple light-emitting units capable of individually controlling the direction and timing of light signal emission, Among the plurality of light-emitting units, a plurality of first control units control the emission direction and emission timing of the light signal emitted from a corresponding light-emitting unit, Each of the plurality of first control units is provided with a second control unit that supplies an angle command signal relating to the direction of emission of the optical signal, Each of the aforementioned plurality of light-emitting units is A light source that emits an optical signal according to the control of the first control unit, It has a scanning unit that scans the optical signal in a one-dimensional or two-dimensional direction, When the object detection unit detects the positions of multiple objects, the second control unit divides the multiple light-emitting units into multiple light-emitting groups according to the number of detected objects, and associates one of the objects with each light-emitting group. Each of the light-emitting units belonging to the plurality of light-emitting groups controls, based on the control by the scanning speed adjustment unit, to make the scanning speed when scanning the optical signal within the range where the corresponding object exists slower than the scanning speed when scanning the optical signal outside the range. Ranging device.

2. Each of the aforementioned plurality of light-emitting units is The optical system has an optical system for shaping the light signal emitted from the light source. The distance measuring device according to claim 1.

3. The second control unit generates the angle command signal by adding an angle correction signal corresponding to each of the multiple light-emitting units to a reference command signal that is used in common by the multiple light-emitting units. The distance measuring device according to claim 1 or 2.

4. The system further includes a storage unit that stores the correspondence between the reference command signal and the plurality of angle correction signals corresponding to each of the plurality of light-emitting units. The second control unit generates the angle command signal by reading the corresponding angle correction signal from the storage unit for each of the plurality of light-emitting units and adding it to the reference command signal. The distance measuring device according to claim 3.

5. The storage unit stores multiple sets of correspondence relationships between the reference command signal and the multiple angle correction signals, and the multiple angle correction signals differ for each set. The second control unit selects one set from the plurality of sets stored in the storage unit, and based on the correspondence of the selected set, reads the corresponding angle correction signal from the storage unit for each of the plurality of light-emitting units and adds it to the reference command signal to generate the angle command signal. The distance measuring device according to claim 4.

6. The system includes a scanning control unit that scans multiple optical signals emitted from the multiple light-emitting units in a one-dimensional or two-dimensional direction. The distance measuring device according to claim 4 or 5.

7. The second control unit supplies each of the multiple angle command signals to the corresponding light-emitting unit so that the multiple light signals emitted from the multiple light-emitting units proceed substantially in parallel. The distance measuring device according to any one of claims 1 to 6.

8. The plurality of first control units emit the optical signal at substantially the same timing. The distance measuring device according to claim 7.

9. The aforementioned light source repeatedly emits an optical signal at a constant period, The scanning unit is capable of changing the scanning speed of the optical signal within a portion of the scanning range of the optical signal. The distance measuring device according to any one of claims 1 to 8.

10. The plurality of light-emitting units emit optical signals compliant with laser safety standards, and at least a portion of the optical signals overlap within a range at a predetermined distance or more from the plurality of light-emitting units, and the optical intensity of the optical signals is set so that they comply with laser safety standards in the overlapping state. The distance measuring device according to any one of claims 1 to 9.

11. The optical signals emitted by the multiple light-emitting units exhibit a greater change in beam width relative to the optical path length in the second direction than in the first direction. Of the plurality of light-emitting units, at least two or more light-emitting units are arranged at intervals in the second direction. The distance measuring device according to any one of claims 1 to 10.

12. Floodlighting device, A distance measuring method using a light receiving device that receives a reflected light signal when a light signal emitted from the light projection device is reflected by an object, Based on the light signal emitted from the light projector and the reflected light signal received by the light receiver, the distance to the object is measured. Based on the reflected light signal received by the light receiving device, the position of the object is detected. The scanning speed when scanning the optical signal within the range where the detected object exists is made slower than the scanning speed when scanning the optical signal outside the range. The aforementioned light-emitting device is A plurality of first control processes control the emission direction and emission timing of the optical signal emitted from a corresponding optical signal, among a plurality of optical emission units capable of individually controlling the emission direction and emission timing of the optical signal. A second control process is performed to supply an angle command signal relating to the direction of emission of the optical signal to each of the plurality of first control processes. Each of the aforementioned plurality of light-emitting units is According to the corresponding first control process, an optical signal is emitted from the light source, The light signal emitted from the aforementioned light source is shaped by an optical system. The optical signal shaped by the optical system is scanned in a one-dimensional or two-dimensional direction. If the positions of multiple objects are detected, the second control process divides the multiple light-emitting units into multiple light-emitting groups according to the number of detected objects, and associates one of the objects with each light-emitting group. Each of the light-emitting units belonging to the plurality of light-emitting groups controls the scanning speed so that the scanning speed when scanning the light signal within the range where the corresponding object exists is slower than the scanning speed when scanning the light signal outside the range. Distance measurement method.

13. Floodlighting device, A distance measuring method using a light receiving device that receives a reflected light signal when a light signal emitted from the light projection device is reflected by an object, Based on the light signal emitted from the light projector and the reflected light signal received by the light receiver, the distance to the object is measured. Based on the reflected light signal received by the light receiving device, the position of the object is detected. The scanning speed when scanning the optical signal within the range where the detected object exists is made slower than the scanning speed when scanning the optical signal outside the range. The aforementioned light-emitting device is The direction and timing of light signal emission in multiple light-emitting units are individually controlled. A plurality of first control processes control the emission direction and emission timing of the light signal emitted from a corresponding light-emitting unit among the plurality of light-emitting units, A second control process is performed to supply an angle command signal relating to the direction of emission of the optical signal to each of the plurality of first control processes. Each of the aforementioned plurality of light-emitting units is According to the corresponding first control process, an optical signal is emitted from the light source, The optical signal is scanned in a one-dimensional or two-dimensional direction. If the positions of multiple objects are detected, the second control process divides the multiple light-emitting units into multiple light-emitting groups according to the number of detected objects, and associates one of the objects with each light-emitting group. Each of the light-emitting units belonging to the plurality of light-emitting groups controls the scanning speed so that the scanning speed when scanning the light signal within the range where the corresponding object exists is slower than the scanning speed when scanning the light signal outside the range. Distance measurement method.

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