Floodlight device, range finder, and method of controlling laser beam projection

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 light projection of laser light.

Background Art

[0002] In the field of autonomous driving technology, there is a need for a technology to detect non-contact, at high speed, and with high precision, objects existing around a vehicle. 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 for periodically scanning 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 emission 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 for combining 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, there is provided a light projecting device, a distance measuring device, and a method for controlling the projection of laser light, which can be miniaturized and can increase the distance that the laser light reaches. In particular, the provided light projecting device can also comply with laser safety standards.

Means for Solving the Problems

[0006] In order to solve the above problems, according to one embodiment of the present invention, there are provided a plurality of light projecting units capable of switching the emission direction and emission timing of an optical signal, and a plurality of first control units that control the emission direction and emission timing of the optical signal emitted from the corresponding light projecting unit among the plurality of light projecting units. A light projecting device is provided.

Brief Description of the Drawings

[0007]

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Embodiments for Carrying Out the Invention

[0008] Hereinafter, with reference to the drawings, embodiments of the light projecting device, the distance measuring device, and the light projection control method of the laser light will be described. Hereinafter, the main components of the light projecting device and the distance measuring device will be mainly described, but the light projecting device and the distance measuring device may have components and functions not shown or described in the drawings. The following description does not exclude components and functions not shown or described in the drawings.

[0009] (First Embodiment) FIG. 1 is a block diagram showing the schematic configuration of the light projecting device 1 according to the first embodiment. The light projecting device 1 in FIG. 1 has a function of emitting a plurality of optical signals and can be incorporated, for example, in a distance measuring device as will be described later. Note that the light projecting device 1 in FIG. 1 can also be used for various purposes other than the distance measuring device.

[0010] The light projection device 1 in Fig. 1 includes a plurality of light projection units 2 and a plurality of first control units 3. Each of the plurality of light projection 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 in association with one of the light projection 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 projection unit 2. More specifically, each of the plurality of first control units 3 supplies a control signal to the corresponding light projection unit 2. Each light projection 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 projection 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 projection unit 2 is arbitrary.

[0012] The light intensity of the optical signal emitted from each light projection 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 projection 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 projection unit 2 may increase the power and time of the laser pulse to extend the ranging distance range of the LiDAR (Light Detection And Ranging) device.

[0013] Thus, in the present 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 the present embodiment, it is contemplated that an optical signal having an optical intensity compliant with laser safety standards is emitted from each light projecting unit 2. Although laser light has high directivity, as the optical path length becomes longer, the beam diameter spreads and the optical intensity per unit area becomes smaller. In the present 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 with each other. 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 with each other, so that the optical intensity can be maintained high and the optical signal can reach a distance.

[0014] FIG. 2 is a perspective view of a 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 light projecting units 2 is not limited. Further, the plurality of light projecting units 2 may be arranged in a one-dimensional direction (horizontal direction X or 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 optical signal emitted from the light source 4. Here, shaping means adjusting the beam shape, propagation direction, beam divergence angle, etc. of the optical signal. An example of the optical system 5 is a collimating lens. The collimating lens can parallelize the incident divergent optical 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 the control signal from the corresponding first control unit 3. The light emission range is a range of any size that spreads in two-dimensional or one-dimensional directions. Also, the scanning unit 6 can adjust the scanning speed when scanning the optical signal within the light emission range based on the control signal from the corresponding first control unit 3.

[0019] More specifically, the scanning unit 6 has, 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 optical signal irradiated on the MEMS mirror can be changed. Therefore, by changing the angle of the MEMS mirror based on the control signal from the corresponding first control unit 3, the emission direction of the optical signal emitted from each light projection unit 2 can be changed little by little, and the optical signal can be scanned within a predetermined light emission range.

[0020] There are MEMS mirrors that rotate around one axis and those that rotate around two axes. By using a MEMS mirror that rotates around two axes and changing the angle of the MEMS mirror little by little in two-axis directions, the optical signal can be scanned within a light emission range that spreads in two-dimensional directions.

[0021] In this way, each light projecting unit 2 can individually adjust the emission direction and emission timing of the optical signal based on the control signal from the corresponding first control unit 3. Therefore, it is possible to emit a plurality of optical signals emitted from the plurality of light projecting units 2 in substantially the same direction, or to emit an optical signal in an arbitrary direction for each individual light projecting unit 2. Also, it is possible for all the light projecting units 2 to emit a plurality of optical signals at substantially the same timing, or for each individual light projecting unit 2 to emit an optical signal at an arbitrary timing.

[0022] The plurality of first control units 3 may be controlled by the second control unit 7. FIG. 4 is a block diagram of a light projecting device 1a in which the second control unit 7 is added to the configuration of FIG. 1. The second control unit 7 supplies an angle command signal regarding the emission direction of the optical signal to each of the plurality of first control units 3. The angle command signal is a signal for commanding the emission direction of the optical signal emitted from each of the plurality of first light projecting units 2. That is, in the light projecting device 1a of FIG. 4, the second control unit 7 controls the emission direction of the optical signal emitted from each light projecting unit 2. By providing the second control unit 7, it is possible to collectively control in which direction the optical signal is emitted from the plurality of light projecting units 2, and the control of the plurality of light projecting units 2 becomes easier. Also, the second control unit 7 may control not only the emission direction of the optical signal emitted from each light projecting unit 2 but also the emission timing.

[0023] FIG. 5 is a block diagram showing an example of the internal configuration of the second control unit 7. The second control unit 7 in FIG. 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 commonly given to all the light projecting units 2. The reference command signal does not necessarily have to be of one type. The reference command generation unit 8 may generate any one of a plurality of types of reference command signals. The reference command signal generated by the reference command generation unit 8 is input to the plurality of adders 10.

[0025] The angle correction table 9 stores, for each of the plurality of light projecting units 2, an angle correction signal for correcting a reference command signal. When the reference command generation unit 8 generates any one of a plurality of types of reference command signals, the angle correction table 9 stores, for each reference command signal, an angle correction signal corresponding to each of the plurality of light projecting units 2. This angle correction signal includes the offset of the intended angle for each light projecting unit 2 and the angle error of each light projecting unit 2 due to installation, manufacturing, etc. Regarding the creation of angle error data, a laser may be emitted from each light projecting unit 2 in advance, and the angle may be measured with a light receiving device or light-sensitive paper (not shown in FIG. 5).

[0026] In this way, the angle correction table 9 may store a plurality of sets of the correspondence relationships between the reference command signal and the plurality of angle correction signals, and the plurality of angle correction signals may be different for each set. In this case, the second control unit 7 selects one set from the plurality of sets stored in the angle correction table 9, and based on the correspondence relationship of the selected set, for each of the plurality of light projecting units 2, reads out the corresponding angle correction signal from the angle correction table 9 and loads the reference command signal, thereby generating an angle command signal.

[0027] Hereinafter, two specific examples of the plurality of types of reference command signals generated by the reference command generation unit 8 and the angle correction table 9 will be described. FIG. 6A is a diagram for explaining a first specific example of the plurality of types of reference command signals. The reference command signal in the first specific example is, as shown in FIG. 6A, a signal that commands to continuously or stepwise change the emission direction according to time at a predetermined period. The reference command signal is an analog value or a digital value, and may be a voltage signal or a current signal. The angle correction table 9 stores, for each of the plurality of light projecting units 2, an angle correction signal for making the emission directions parallel, for example. For example, when the emission direction of one of two adjacent light projecting units 2 is offset by +1 degree from the other light projecting unit in the default state, the angle correction table 9 sets the angle correction signal of the emission direction of one of the two light projecting units 2 to 0 degree, and the angle correction signal of the emission direction of the other to -1 degree. Thereby, the emission directions of the optical signals emitted from the two light projecting units 2 can be made parallel.

[0028] FIG. 6B is a diagram for explaining a second specific example of a plurality of types of reference command signals. The reference command signals in the second specific example are emitted a plurality of times at predetermined time intervals and become a pulse train signal as shown in FIG. 6B. The emission direction of each reference command signal is changed by an angle corresponding to the number of times the optical signal is 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 is 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 FIG. 6B.

[0029] Similar to the angle correction table 9 in the first specific example, the angle correction table 9 in the second specific example stores an angle correction signal so that the emission directions of the optical signals emitted from the plurality of light projecting units 2 are parallel, for example.

[0030] Note that the plurality of 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] The plurality of adders 10 are provided in association with the plurality of first control units 3. Each of the plurality of adders 10 adds a reference command signal and a corresponding angle correction signal read from the angle correction table 9 to generate an angle command signal for the corresponding first control unit 3.

[0032] The angle correction signals stored in the angle correction table 9 may be updated as necessary. The update of the angle correction signals stored in the angle correction table 9 is performed, for example, by an update control unit 11 in the second control unit 7. By updating the angle correction signals stored in the angle correction table 9 by the update control unit 11, the emission directions of the optical signals emitted from the plurality of light projecting units 2 can be switched as necessary, and a reconfigurable light projecting device 1a can be realized. Note that 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 FIG. 5. For example, without providing a reference command signal, the angle command signals for the plurality of first control units 3 may be directly generated by the second control unit 7 and supplied to the corresponding first control units 3.

[0034] In the light projection devices 1 and 1a of FIGS. 1 to 5, the configuration in which the emission directions of the optical signals emitted from each of the plurality of light projection units 2 can be individually controlled has been described. However, the plurality of light projection units 2 may be integrated, and the plurality of optical signals emitted from the plurality of light projection units 2 may be collectively scanned in a one-dimensional direction or a two-dimensional direction.

[0035] FIG. 7 is a block diagram showing a schematic configuration of a light projection device 1b in which a scanning control unit 12 is added to the configuration of FIG. 4, and FIG. 8 is a perspective view of the light projection device 1b of FIG. 7. The scanning control unit 12 periodically scans the optical signals emitted from the plurality of light projection units 2 integrally in a one-dimensional direction or a two-dimensional direction. For example, as shown in FIG. 8, the scanning control unit 12 may periodically scan the light projection device 1b as a whole in at least one of the horizontal direction X and the vertical direction Y.

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

[0037] As described above, the light projection devices 1, 1a, and 1b according to the first embodiment include a plurality of light projection units 2 and a plurality of first control units 3, and control the emission direction and emission timing of the optical signals emitted from each of the plurality of light projection units 2 by the corresponding first control units 3. Thereby, the emission direction and emission timing of the optical signals emitted from each of the plurality of light projection units 2 can be individually and arbitrarily adjusted, and the plurality of optical signals emitted from the plurality of light projection units 2 can be used for various applications.

[0038] In addition, a second control unit 7 for controlling a plurality of first control units 3 is provided, and an angle command signal is supplied from the second control unit 7 to the plurality of first control units 3. Therefore, by updating the angle command signal as needed, a reconfigurable light projecting device 1, 1a, 1b capable of changing the emission direction and emission timing of the optical signals from the plurality of light projecting units 2 can be realized.

[0039] (Second Embodiment) The light projecting devices 1a, 1b according to the second embodiment have the same block configuration as that shown in FIGS. 4 to 7. In the light projecting devices 1a, 1b according to the second embodiment, the second control unit 7 controls the plurality of light projecting units 2 so that optical signals traveling substantially in parallel are emitted from the plurality of light projecting units 2.

[0040] FIG. 9 is a diagram schematically showing the beam shape of the optical signals emitted from the plurality of light projecting units 2. As shown in FIG. 9, the plurality of optical signals emitted from the plurality of light projecting units 2 travel in substantially parallel directions. The emission direction of the optical signal emitted from each of the plurality of light projecting units 2 is controlled by the corresponding first control unit 3. As shown in FIG. 4, an angle command signal is supplied from the second control unit 7 to each of the plurality of first control units 3 corresponding to the plurality of light projecting units 2. Each of the plurality of first control units 3 controls the emission direction of the optical signal emitted from the corresponding light projecting unit 2 based on the corresponding angle command signal. In the case of this embodiment, the corresponding first control unit 3 controls the emission direction of the optical signal emitted from the corresponding light projecting unit 2 with the angle command signal from the second control unit 7, so that the plurality of optical signals emitted from the plurality of light projecting units 2 become substantially parallel.

[0041] The optical signal emitted from each light projecting unit 2 has a beam width that widens as it goes farther away, but the degree of widening of the beam width is different in the horizontal direction and the vertical direction. FIGS. 10A and 10B are diagrams schematically showing the beam width of the optical signal emitted from each light projecting unit 2. FIG. 10A shows the change in the beam width in the horizontal direction, and FIG. 10B shows the change in the beam width in the vertical direction.

[0042] As shown in FIG. 10A, the optical signals emitted from each light projecting unit 2 hardly change in the horizontal beam width even when the distance changes. On the other hand, as shown in FIG. 10B, the vertical beam width changes greatly according to the distance. More specifically, the vertical beam width becomes wider as the distance increases.

[0043] By arranging the plurality of light projecting units 2 in the vertical direction, in a distant location from the light projecting devices 1a and 1b, a region where the optical signals emitted from the plurality of light projecting units 2 overlap in the vertical direction is generated. In this region, the light intensity becomes higher than that of a single optical signal.

[0044] Thus, in the second embodiment, by emitting a plurality of optical signals in a substantially parallel direction from the plurality of light projecting units 2 and causing a part of the plurality of optical signals emitted from the plurality of light projecting units 2 to overlap in the vertical direction, the light intensity at a distance can be increased. As shown in FIG. 10B, when the interval between the plurality of light projecting units 2 arranged in the vertical direction changes, the range in which the plurality of optical signals overlap in the vertical direction at a distance changes. If each laser beam does not spread much and overlaps at a short distance where the laser intensity is strong, the overlapping portion may not comply with eye safety. Therefore, it is desirable to adjust the interval between the plurality of light projecting units 2 arranged in the vertical direction so that the overlapping range complies with the eye safety standard.

[0045] Also, in the light projecting devices 1a and 1b according to the second embodiment, the plurality of light projecting units 2 may emit optical signals at substantially the same emission timing. For example, in a distance measuring device which is an application example of the light projecting devices 1a and 1b according to the present embodiment, an optical signal is repeatedly emitted at a predetermined time interval, the reflected optical signal from an object is repeatedly received, and the distance to the object is measured based on the reception result. Thus, when the light projecting devices 1a and 1b according to the present embodiment are used in a distance measuring device, the operation of emitting optical signals from the plurality of light projecting units 2 at substantially the same timing is repeatedly performed at a predetermined time interval, the reflected optical signal from the object is repeatedly received, and the distance to the object is measured.

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

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

[0048] Thereby, the light emission range of the light projection devices 1a and 1b provided with a plurality of light projection units 2 can be made wider than the light emission range of a single light projection unit 2. For example, when a MEMS mirror is used for the scanning unit 6 of the light projection unit 2, since the driving range of the MEMS mirror is narrow, the light emission range of the light projection 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 projection devices 1a and 1b according to the third embodiment. FIG. 11 shows an example in which a plurality of (for example, four) light projection units 2 are classified into three light projection groups (hereinafter, the first to third light projection groups) 2-1, 2-2, and 2-3, and the emission direction of the optical signal is individually controlled for each light projection group.

[0050] The light projecting unit 2 belonging to the first light projecting group 2-1 scans the optical signal within the first light emission range OR1. The light projecting unit 2 belonging to the second light projecting group 2-2 scans the optical signal within the second light emission range OR2. The light projecting unit 2 belonging to the third light projecting group 2-3 scans the optical signal within the third light emission range OR3. FIG. 11 shows an example where 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 partially overlap. That is, the emission direction of the optical signal emitted from the light projecting unit 2 belonging to the first light projecting group 2-1, the emission direction of the optical signal emitted from the light projecting unit 2 belonging to the second light projecting group 2-2, and the emission direction of the optical signal emitted from the light projecting unit 2 belonging to the third light projecting group 2-3 may be completely different or may partially overlap.

[0051] As can be seen from FIG. 11, since at least a part of the light emission ranges of the first to third light projecting groups 2-1 to 2-3 are different, the light emission range of the entire light projecting devices 1a and 1b can be made wider than the light emission range of a single light projecting group.

[0052] The method of classifying the plurality of light projecting units 2 into a plurality of light projecting groups may be determined in advance. In this case, it is only necessary for the first control unit 3 corresponding to each light projecting unit 2 to grasp the emission direction and emission timing of the optical signal.

[0053] Alternatively, it may be possible to arbitrarily adjust how the plurality of light projecting units 2 are classified into which light projecting groups. In this case, the second control unit 7 performs control to classify the plurality of light projecting units 2 into a plurality of light projecting groups. The second control unit 7 transmits information regarding to which light projecting group the corresponding light projecting unit 2 belongs to the plurality of first control units 3. The information transmitted from the second control unit 7 to the plurality of first control units 3 also includes information indicating the light emission range of each light projecting group.

[0054] By enabling the second control unit 7 to change as needed how the plurality of light projecting units 2 are classified into light projecting groups, reconfigurable light projecting devices 1a and 1b can be realized. Further, the second control unit 7 may control the timing at which the plurality of light projecting groups emit optical signals. For example, in the case of FIG. 11, each light projecting unit 2 belonging to the first to third light projecting groups 2-1 to 2-3 may emit an optical signal at substantially the same timing, or may emit an optical signal at different timings.

[0055] Thus, in the third embodiment, since the plurality of light projecting units 2 are classified into a plurality of light projecting groups and the light emission direction is controlled for each light projecting group, the light emission range can be expanded compared to the case where the light emission ranges of the plurality of light projecting units 2 are made uniform. Therefore, when the light projecting devices 1a and 1b according to the present embodiment are applied to a distance measuring device, the distances of objects existing in a wider range can be measured, and the practicality is enhanced. Also, by enabling the classification of each light projecting unit 2 into a light projecting group to be changed as needed, reconfigurable light projecting devices 1a and 1b can be realized.

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

[0057] FIG. 12 is a block diagram showing a schematic configuration of a distance measuring device 21 incorporating the light projecting device 1, 1a, or 1b according to any of the first to third embodiments. The distance measuring device 21 in FIG. 12 includes the light projecting device 1, 1a, or 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 optical signals obtained by reflecting a plurality of optical signals emitted from the light projecting device 1, 1a, or 1b by an object. The light receiving device 22 may have a light receiving module in which a plurality of light receiving elements are two-dimensionally arranged. The light receiving element may be a SPAD (Single Photo Avalanche Diode). Since a SPAD can detect one photon, it can detect a weak reflected optical signal from a distant object.

[0059] The distance measurement device 21 measures distance, for example, by the dToF (direct Time of Flight) method. In the dToF method, the distance of an object is measured based on the time difference between the timing when the light emitting devices 1, 1a, and 1b emit an optical signal and the timing when the light receiving device 22 receives the reflected optical signal.

[0060] The second control unit 7 in the distance measurement device 21 in FIG. 12 may supply an angle command signal to the plurality of first control units 3 so that the plurality of light emitting units 2 emit optical signals in substantially the same emission direction, or may supply an angle command signal to the corresponding first control unit 3 for each light emitting group obtained by classifying the plurality of light emitting units 2 into a plurality of light emitting groups.

[0061] As described above, each light emitting unit 2 in the distance measurement 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 optical signal, and the distance measurement unit 23 measures the distance of the object based on the light reception result. The periods during which each light emitting unit 2 scans the optical signal within the light emission range do not necessarily have to be the same.

[0062] If each light emitting unit 2 emits an optical signal at a predetermined time interval (for example, the time interval defined by the eye safety standard), the longer the time during which each light emitting unit 2 scans the optical signal within the light emission range, the more the number of optical signals emitted from each light emitting unit 2 during the scan of the light emission range increases, and the presence or absence of an object and the shape of the object within the light emission range can be detected with higher accuracy.

[0063] FIG. 13 is a block diagram of a distance measurement device 21a obtained by adding an object detection unit 24 and a scan speed adjustment unit 25 to the configuration of FIG. 12.

[0064] While the plurality of light projecting units 2 scan the optical signal within the light emission range, the object detection unit 24 detects an object existing within the light emission range. The scanning speed adjustment unit 25 adjusts the length of the period during which the optical signal scans the light emission range. More specifically, the scanning speed adjustment unit 25 makes the scanning speed of the optical signal when scanning within the range where the object detected by the object detection unit exists slower than the scanning speed when scanning the optical signal outside the range. Note that each light projecting unit 2 emits the optical signal at regular time intervals.

[0065] In the distance measuring device 21a of FIG. 13, after the scanning speed adjustment unit 25 sets the length of the period during which the optical signal scans the light emission range to the first scanning period, the distance measuring operation is started. The object detection unit 24 detects whether the light receiving device 22 has received the reflected optical signal while the light projecting devices 1, 1a, and 1b scan the optical signal in the light emission range in the first scanning period.

[0066] If the signal level of the light receiving signal of the light receiving device 22 is equal to or higher than a predetermined threshold level, the object detection unit 24 determines that the reflected optical signal has been received. The object detection unit 24 detects all the objects existing in the entire area within the light emission range.

[0067] For example, when one object is detected within the light emission range, the scanning speed adjustment unit 25 reduces the scanning speed of the optical signal when scanning near the detection position of the object within the light emission range. Thereby, more optical signals can be emitted near the detection position of the object within the light emission range, and the depth shape of the object can be detected with higher accuracy.

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

[0069] Below Figure 14, a timing diagram for the case of scanning the light emission range twice is shown. Hereinafter, the first scanning period is referred to as the first scanning cycle, and the second scanning period is referred to as the second scanning cycle.

[0070] The horizontal axis of the timing diagram at the lower right of Figure 14 is time, and the vertical axis is the scanning position within the light emission range. Note that the vertical axis may also be the scanning angle. Times t1 to t4 in Figure 14 are the first scanning cycle, and times t4 to t9 are the second scanning cycle. In the first scanning cycle, since each light projecting unit 2 scans the optical signal at a constant scanning speed, the scanning position changes linearly with respect to time. Times t2 to t3 within the first scanning period are the periods for scanning the region where the vehicle exists within the light emission range. Since the signal level of the light reception signal received by the light receiving device 22 becomes high during this period, the object detection unit 24 detects the object 26.

[0071] In the second scanning cycle, initially, the optical signal is scanned at the same scanning speed as in the first scanning cycle. When the scanning position of the optical signal approaches the position of the object 26, the scanning speed adjustment unit 25 reduces the scanning speed of the optical signal. As described above, since each light projecting unit 2 emits the optical signal at a constant time interval, when the scanning speed of the optical signal decreases, more optical signals can be emitted while scanning the vicinity of the position of the object 26. Therefore, the depth shape of the object 26 can be detected more accurately.

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

[0073] FIG. 15 is a diagram showing an example in which a plurality of (two in the example of FIG. 15) objects 26 are detected within the light emission range. In this case, the plurality of light projecting units 2 are classified into a plurality of light projecting groups according to the number of the detected objects 26. In the case of FIG. 15, since two objects 26 are detected within the light emission range, they are classified into two light projecting groups. The number of light projecting units 2 belonging to each light projecting group is arbitrary.

[0074] The times t1 to t6 in FIG. 15 are the first scanning period, and the times t6 to t15 are the second scanning period. In the first scanning period, the entire area within the light emission range is scanned at a constant scanning speed. While scanning within the light emission range in the first scanning period, the object detection unit 24 detects two objects 26 within the light emission range. As described above, the object detection unit 24 detects the object 26 when the signal level of the light reception signal of the light reception device 22 exceeds a predetermined threshold value.

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

[0076] Since the object detection unit 24 has detected two objects (a first object and a second object) 26a and 26b, the first control unit 3 classifies the plurality of light projecting units 2 into, for example, two light projecting groups (a first light projecting group 2-1 and a second light projecting group 2-2), and reduces the scanning speed when the two light projecting units 2 belonging to the first light projecting group 2-1 scan near the position of the first object 26a, so as to more accurately detect the depth shape of the first object 26a. Further, when the two light projecting units 2 belonging to the second light projecting group 2-2 scan near the position of the second object 26b, the scanning speed is reduced to more accurately detect the depth shape of the second object 26b. In the example of FIG. 15, in the second scanning cycle, the first light projecting group 2-1 scans optical signals in the same period as the first scanning cycle during the periods from time t6 to t7 and from time t10 to t15. Since it is near the position of the object 26 during the period from time t7 to t10, the scanning speed of the optical signal is reduced. The object 26 is detected during the period from time t8 to t9. On the other hand, in the second scanning cycle, the second light projecting group 2-2 scans optical signals in the same period as the first scanning cycle during the periods from time t6 to t11 and from time t14 to t15. Since it is near the position of the object 26 during the period from time t11 to t14, the scanning speed of the optical signal is reduced. The object 26 is detected during the period from time t12 to t13.

[0077] As shown in FIG. 15, if the scanning speed is reduced for each object 26 detected within the light emission range with a separate light projecting group to detect the depth shape of the object 26, the depth shape of each object 26 can be accurately detected without making the second scanning cycle much longer than the first scanning cycle.

[0078] Thus, in the fourth embodiment, since the light projecting devices 1, 1a, 1b according to the first to third embodiments are applied to the distance measuring devices 21, 21a, objects 26 within a wide range can be accurately detected.

[0079] Also, in the distance measuring device 21a of FIG. 13, when an object 26 is detected within the light emission range, the scanning speed is reduced when scanning the vicinity of the detected position of the object 26 with an optical signal. Thereby, the depth shape of the object 26 can be detected more accurately.

[0080] Furthermore, when a plurality of objects 26 are detected within the light emission range, the plurality of light projecting units 2 are classified into a plurality of light projection groups according to the number of the detected objects 26, and the corresponding objects 26 can be detected at a reduced scanning speed in each light projection group. Therefore, the depth shape of the plurality of objects 26 within the light emission range can be accurately detected.

[0081] Aspects of the present disclosure are not limited to the individual embodiments described above, but also include various modifications that can be conceived by those skilled in the art, and the effects of the present disclosure are not limited to the content described above. That is, various additions, changes, and partial deletions are possible without departing from the conceptual ideas and spirits of the present disclosure derived from the content defined in the claims and their equivalents.

Explanation of Reference Numerals

[0082] 1 Light projecting device, 1a Light projecting device, 1b Light projecting device, 2 Light projecting 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. A light projecting device, a light receiving device that receives a reflected light signal obtained by reflecting a light signal emitted from the light projecting device by an object, a distance measurement unit that measures the distance to the object based on the light signal emitted from the light projecting device and the reflected light signal received by the light receiving device, an object detection unit that detects the position of the object based on the reflected light signal received by the light receiving device, a scanning speed adjustment unit that makes the scanning speed when scanning the light signal within the range where the object detected by the object detection unit exists slower than the scanning speed when scanning the light signal outside the range, and the light projecting device includes a plurality of light projecting units capable of individually controlling the emission direction and emission timing of the light signal, a plurality of first control units that control the emission direction and emission timing of the light signal emitted from the corresponding light projecting unit among the plurality of light projecting units, a second control unit that supplies an angle command signal regarding the emission direction of the light signal to each of the plurality of first control units, each of the plurality of light projecting units includes a light source that emits a light signal according to the control of the first control unit, an optical system that shapes the light signal emitted from the light source, a scanning unit that scans the light signal shaped by the optical system in a one-dimensional direction or a two-dimensional direction, when the object detection unit detects the positions of a plurality of the objects, the second control unit divides the plurality of light projecting units into a plurality of light projecting groups according to the number of the detected objects, and associates any one of the objects with each light projecting group, each of the light projecting units belonging to each of the plurality of light projecting groups makes the scanning speed when scanning the light signal within the range where the corresponding object exists slower than the scanning speed when scanning the light signal outside the range based on the control by the scanning speed adjustment unit, a distance measuring device.

2. A light projecting device, a light receiving device that receives a reflected light signal obtained by reflecting a light signal emitted from the light projecting device by an object, a distance measurement unit that measures the distance to the object based on the light signal emitted from the light projecting device and the reflected light signal received by the light receiving device, an object detection unit that detects the position of the object based on the reflected light signal received by the light receiving device, a scanning speed adjustment unit that makes the scanning speed when scanning the light signal within the range where the object detected by the object detection unit exists slower than the scanning speed when scanning the light signal outside the range, and the light projecting device includes a plurality of light projecting units capable of individually controlling the emission direction and emission timing of the light signal, Among the plurality of light projecting units, a plurality of first control units that control the emission direction and emission timing of the optical signals emitted from the corresponding light projecting units. A distance measuring device. **Claim 3** Each of the plurality of light projecting units A light source that emits an optical signal according to the control of the first control unit, An optical system that shapes the optical signal emitted from the light source, A scanning unit that scans the optical signal shaped by the optical system in a one-dimensional direction or a two-dimensional direction. The distance measuring device according to claim 2. **Claim 4** The light projecting device has a second control unit that supplies an angle command signal regarding the emission direction of the optical signal to each of the plurality of first control units. When the object detection unit detects the positions of the plurality of objects, the second control unit divides the plurality of light projecting units into a plurality of light projecting groups according to the number of the detected objects, associates any one of the objects with each light projecting group. For each of the light projecting units belonging to each of the plurality of light projecting groups, based on the control by the scanning speed adjustment unit, the scanning speed when scanning the optical signal within the range where the corresponding object exists is made slower than the scanning speed when scanning the optical signal outside the range. The distance measuring device according to claim 2 or 3. **Claim 5** The second control unit generates the angle command signal by adding an angle correction signal corresponding to each of the plurality of light projecting units to a reference command signal commonly used by the plurality of light projecting units. The distance measuring device according to claim 1 or 4. **Claim 6** 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 projecting units. For each of the plurality of light projecting units, the second control unit reads out the corresponding angle correction signal from the storage unit and adds it to the reference command signal to generate the angle command signal. The distance measuring device according to claim 5. **Claim 7** The storage unit stores a plurality of sets of the correspondence between the reference command signal and the plurality of angle correction signals, and the plurality of angle correction signals are different 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, for each of the plurality of light projecting units, reads out the corresponding angle correction signal from the storage unit and adds it to the reference command signal to generate the angle command signal. The distance measuring device according to claim 6. **Claim 8** A scanning control unit for collectively scanning a plurality of optical signals emitted from the plurality of light projecting units in a one-dimensional direction or a two-dimensional direction is provided. The distance measuring device according to claim 6 or 7.

9. The second control unit supplies each of the plurality of angle command signals to the corresponding light projecting unit so that the plurality of optical signals emitted from the plurality of light projecting units travel substantially in parallel. The distance measuring device according to any one of claims 1, 4 to 8.

10. The plurality of first control units emit the optical signals at substantially the same timing. The distance measuring device according to claim 9.

11. The light source repeatedly emits optical signals at a constant period. The scanning unit can change the scanning speed of the optical signal within a partial region within the scanning range of the optical signal. The distance measuring device according to claim 1 or 3.

12. The plurality of light projecting units emit optical signals conforming to laser safety standards, and at least a part of the optical signals overlap within a range separated from the plurality of light projecting units by a predetermined distance or more, and the optical intensity of the optical signals is set so as to conform to the laser safety standards in the overlapping state. The distance measuring device according to any one of claims 1 to 11.

13. The optical signals emitted from the plurality of light projecting units have a greater change in beam width with respect to the optical path length in the second direction than in the first direction. Among the plurality of light projecting units, at least two or more light projecting units are arranged at intervals in the second direction. The distance measuring device according to any one of claims 1 to 12.

14. A light projecting device, A distance measuring method using a light receiving device that receives a reflected optical signal obtained by reflecting an optical signal emitted from the light projecting device by an object, Based on the optical signal emitted from the light projecting device and the reflected optical signal received by the light receiving device, the distance to the object is measured. Based on the reflected optical signal received by the light receiving device, the position of the object is detected. When scanning the optical signal within the range where the detected object exists, the scanning speed is made slower than the scanning speed when scanning the optical signal outside the range. The light projecting device, Among a plurality of light projecting units capable of individually controlling the emission direction and emission timing of an optical signal, a plurality of first control processes for controlling the emission direction and emission timing of the optical signal emitted from the corresponding light projecting unit, For each of the plurality of first control processes, a second control process for supplying an angle command signal regarding the emission direction of the optical signal is performed. Each of the plurality of light projecting units, Emits an optical signal from a light source according to the corresponding first control process. Shape the optical signal emitted from the light source with an optical system, Scan the optical signal shaped by the optical system in a one-dimensional or two-dimensional direction, When the positions of a plurality of the objects are detected, the second control process divides the plurality of light projecting units into a plurality of light projecting groups according to the number of the detected objects, and associates any one of the objects with each light projecting group, Based on the control of the scanning speed, the light projecting units belonging to each of the plurality of light projecting groups 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, Distance measurement method.

15. A light projecting device, A distance measurement method using a light receiving device that receives a reflected optical signal obtained by reflecting an optical signal emitted from the light projecting device by an object, Measure the distance to the object based on the optical signal emitted from the light projecting device and the reflected optical signal received by the light receiving device, Detect the position of the object based on the reflected optical signal received by the light receiving device, Make the scanning speed when scanning the optical signal within the range where the detected object exists slower than the scanning speed when scanning the optical signal outside the range, The light projecting device, Individually control the emission direction and emission timing of the optical signal in a plurality of light projecting units, Among the plurality of light projecting units, control the emission direction and emission timing of the optical signal emitted from the corresponding light projecting unit, Distance measurement method.

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