Control device, optical scanning system, control method, and control program

Abstract

To provide a control device capable of accurately discriminating an abnormality factor in an optical scanning unit.SOLUTION: The control device includes a processor for controlling an optical scanning unit including a scanning mirror that rotationally adjusts a scanning azimuth for each scanning cycle in a scanning field of view and a rotation angle sensor that senses a rotation angle of the scanning mirror. The processor is configured to repeatedly control a scanning time interval Ts triggered by detection of a scanning azimuth corresponding to a rotation angle sensed at each reference angle interval, and determine an abnormality cause in the optical scanning unit according to abnormality detection patterns F1, F2, and F3 as detection patterns in which a detection interval of the scanning azimuth deviates from the reference angle interval.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to a control technique for controlling an optical scanning unit. [Background technology]

[0002] In the technology disclosed in Patent Document 1, the rotation angle of the scanning mirror is sensed by a rotation angle sensor. Therefore, by repeatedly controlling the scanning time interval in accordance with the sensing of the rotation angle at predetermined angular intervals, it becomes possible to scan the external world in the scanning direction corresponding to the sensed rotation angle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7468661 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the technology disclosed in Patent Document 1, there is a concern that due to the occurrence of an abnormality such as an impact, physical failure, or adhesion of foreign matter, the scanning time interval may not be set appropriately for the scanning orientation corresponding to the rotation angle at each predetermined angular interval, and external scanning in that scanning orientation may be skipped. When an abnormality like this occurs, it is necessary to accurately identify the cause of the abnormality in order to determine whether maintenance is required to restore the optical scanning unit to normal.

[0005] An object of the present disclosure is to provide a control device capable of accurately determining an abnormality factor in an optical scanning unit, and an optical scanning system configured including the control device. Another object of the present disclosure is to provide a control method capable of accurately determining an abnormality factor in an optical scanning unit. Yet another object of the present disclosure is to provide a control program capable of accurately determining an abnormality factor in an optical scanning unit. [Means for solving the problem]

[0006] The technical means of the present disclosure for solving the problems will be described below. Note that the claims and the reference characters in parentheses in this section indicate the correspondence with the specific means described in the embodiments described later in detail, and do not limit the technical scope of the present disclosure.

[0007] A first aspect of the present disclosure is A control device including a processor (52) for controlling an optical scanning unit (10) having a scanning mirror (120) that rotates and adjusts a scanning orientation (Rs) for each scanning cycle (Cs) within a scanning field (Vs) and a rotation angle sensor (122) that senses a rotation angle (θs) of the scanning mirror, The processor Repeatedly controlling a scanning time interval (Ts) triggered by the detection of a scanning direction corresponding to the rotation angle sensed at each reference angle interval (Δθ); and determining the cause of the abnormality in the optical scanning unit according to the abnormality detection patterns (F1, F2, F3) as detection patterns in which the detection interval in the scanning orientation deviates from the reference angle interval.

[0008] An optical scanning system according to a second aspect of the present disclosure comprises: an optical scanning unit (10) having a scanning mirror (120) that rotates and adjusts a scanning direction (Rs) within a scanning field (Vs) for each scanning cycle (Cs) and a rotation angle sensor (122) that senses a rotation angle (θs) of the scanning mirror; and a first embodiment control device (50) comprising a processor (52) for controlling the optical scanning unit.

[0009] A third aspect of the present disclosure is A control method executed by a processor (52) for controlling an optical scanning unit (10) having a scanning mirror (120) that rotates and adjusts a scanning orientation (Rs) within a scanning field (Vs) for each scanning cycle (Cs) and a rotation angle sensor (122) that senses a rotation angle (θs) of the scanning mirror, the method comprising: Repeatedly controlling a scanning time interval (Ts) triggered by the detection of a scanning direction corresponding to the rotation angle sensed at each reference angle interval (Δθ); and determining the cause of the abnormality in the optical scanning unit according to the abnormality detection patterns (F1, F2, F3) as detection patterns in which the detection interval in the scanning orientation deviates from the reference angle interval.

[0010] A fourth aspect of the present disclosure is A control program is stored in a storage medium (51) for controlling an optical scanning unit (10) having a scanning mirror (120) that rotates and adjusts a scanning direction (Rs) within a scanning field (Vs) for each scanning cycle (Cs) and a rotation angle sensor (122) that senses a rotation angle (θs) of the scanning mirror, the control program including instructions for causing a processor (52) to execute said control, Repeatedly controlling a scanning time interval (Ts) triggered by the detection of a scanning direction corresponding to the rotation angle sensed at each reference angle interval (Δθ); and determining the cause of the abnormality in the optical scanning unit according to the abnormality detection patterns (F1, F2, F3) as detection patterns in which the detection interval in the scanning orientation deviates from the reference angle interval.

[0011] According to the first to fourth aspects, the scanning time interval triggered by the detection of the scanning orientation corresponding to the rotation angle sensed at each reference angle interval is repeatedly controlled. As a result, the abnormality detection pattern, which is a detection pattern in which the detection interval of the scanning orientation deviates from the reference angle interval, can differ depending on the abnormality cause in the optical scanning unit. Therefore, it is possible to accurately determine the abnormality cause in the optical scanning unit based on the abnormality detection pattern. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a block diagram illustrating an optical scanning system according to a first embodiment. [Figure 2] FIG. 2 is a plan view schematically showing a scanning field of the optical scanning system according to the first embodiment. [Figure 3] FIG. 2 is a block diagram showing the functional configuration of the optical scanning system according to the first embodiment. [Figure 4] 4 is a time chart showing the processing of the optical scanning system according to the first embodiment. [Figure 5] 4 is a flowchart showing a control flow according to the first embodiment. [Figure 6] 4 is a time chart for explaining a control flow according to the first embodiment. [Figure 7] 4 is a time chart for explaining a control flow according to the first embodiment. [Figure 8] 4 is a time chart for explaining a control flow according to the first embodiment. [Figure 9] 4 is a time chart for explaining a control flow according to the first embodiment. [Figure 10] 4 is a time chart for explaining a control flow according to the first embodiment. [Figure 11] 10 is a flowchart showing a control flow according to a second embodiment. [Figure 12] 10 is a flowchart showing a control flow according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, multiple embodiments of the present disclosure will be described with reference to the drawings. Note that corresponding components in each embodiment are designated by the same reference numerals, and redundant description may be omitted. Furthermore, when only a portion of the configuration is described in each embodiment, the configuration of another previously described embodiment may be applied to the remaining portions of the configuration. Furthermore, in addition to the combinations of configurations explicitly stated in the description of each embodiment, configurations of multiple embodiments may be partially combined together even if not explicitly stated, provided that there is no particular problem with the combination.

[0014] (First embodiment) As shown in Fig. 1, the optical scanning system 1 of the first embodiment includes an optical scanning unit 10 and a control device 50. As shown in Fig. 2, the optical scanning system 1 uses the control device 50 to control optical scanning within a scanning field Vs by the optical scanning unit 10. The optical scanning unit 10 may be installed on a stationary object such as a structure or infrastructure facility. The optical scanning unit 10 may also be installed on a moving object such as a vehicle.

[0015] 1 and 3, the optical scanning unit 10 is a LiDAR (Light Detection and Ranging / Laser Imaging Detection and Ranging) device capable of optically scanning a scanning field of view Vs. The optical scanning unit 10 includes a light-emitting unit 11, a scanning unit 12, and a light-receiving unit 13. The light-emitting unit 11 is mainly composed of a plurality of light-emitting elements, such as laser diodes, that emit directional laser light in the infrared range. The light-emitting unit 11 generates pulsed beam-like irradiation light directed toward the scanning field of view Vs by intermittently emitting light from each light-emitting element.

[0016] The scanning unit 12 is mainly composed of a scanning mirror 120 and a scanning drive source 121. The scanning mirror 120 is formed in the shape of a rotating plate with a reflective film deposited on one side of a base material and is pivotally supported so as to be able to swing and rotate. The scanning mirror 120 reflects the light emitted from the light-emitting unit 11 into the scanning field of view Vs. As a result, as shown in FIG. 2 , the scanning direction Rs corresponding to the rotation angle θs of the scanning mirror 120 within the scanning field of view Vs is optically scanned temporally and spatially by the illumination light reflected by the scanning mirror 120. Here, in the optical scanning unit 10 of this embodiment, the horizontal angle of view of the scanning field of view Vs is determined by the scanning direction Rs being rotationally changed by the scanning mirror 120 being rotationally driven. Note that the vertical angle of view of the scanning field of view Vs may also be determined by the scanning direction Rs being rotationally changed by the scanning mirror 120 being rotationally driven.

[0017] In the optical scanning unit 10, the scanning field of view Vs in one scanning cycle Cs (see FIG. 5 described later) is determined by changing the rotation angle θs of the scanning mirror 120 in the forward direction from the starting orientation Rss to the terminal orientation Rse. During the period in one scanning cycle Cs when the rotation angle θs of the scanning mirror 120 changes in the backward direction from the terminal orientation Rse to the starting orientation Rss, the generation of irradiation light by the light-emitting unit 11 is interrupted, and optical scanning within the scanning field of view Vs is essentially stopped.

[0018] 1 and 3 is mainly composed of an electric motor capable of driving and oscillating the scan mirror 120. The scan drive source 121 may be provided with a reducer capable of amplifying the output of the electric motor and transmitting the amplified output to the scan mirror 120. The scan drive source 121 drives and oscillates the scan mirror 120 within a drive angle range corresponding to the start orientation Rss and end orientation Rse of the scan field Vs shown in FIG.

[0019] The scanning unit 12 shown in FIGS. 1 and 3 includes a rotation angle sensor 122 for sensing the rotation angle θs of the scanning mirror 120, along with the scanning mirror 120 and the scanning drive source 121. The rotation angle sensor 122 is configured, for example, mainly using an absolute or incremental rotary encoder. The rotation angle sensor 122 senses the rotation angle θs of the scanning mirror 120. As shown in FIG. 4, the rotation angle sensor 122 generates at least two types of pulses Psa and Psb whose outputs are turned on and off each time the sensed rotation angle θs changes by a fixed angular interval, with the on-off phases shifted from each other. Thus, during optical scanning in the forward direction, the interval of the rotation angle θs corresponding to the on timings and off timings of the sequentially appearing pulses Psa and Psb is recognized as the set angular interval δθ at which the rotation angle θs is sensed by the rotation angle sensor 122.

[0020] The light receiving unit 13 shown in FIGS. 1 and 3 is configured by combining a light receiving element, such as a SPAD (Single Photon Avalanche Diode), highly sensitive to irradiated light with an integrated circuit. The light receiving unit 13 receives reflected light from a target present in a scanning direction Rs within the scanning field of view Vs, with each light receiving pixel constituting the light receiving element receiving the reflected light by the scanning mirror 120 according to the rotation angle θs. As a result, the light receiving unit 13 generates a light receiving signal corresponding to the scanning position of the target for each light receiving pixel within a predetermined scanning time interval Ts at the scanning direction Rs at each reference angular interval Δθ, which is repeated as shown in FIGS. 4 and 5 within one scanning cycle Cs. Therefore, during one scanning cycle Cs, the light receiving unit 13 generates scan output data representing a scanning point cloud of the scanned target based on the received signals sampled within the scanning time interval Ts at each scanning direction R at each reference angular interval Δθ within the scanning field of view Vs.

[0021] 1, the dedicated computer constituting the control device 50 includes at least one memory 51 and one processor 52. The memory 51 is at least one type of non-transitory tangible storage medium, such as a semiconductor memory, a magnetic medium, or an optical medium, that non-temporarily stores computer-readable programs, data, and the like.

[0022] In the control device 50, the processor 52 includes at least one type of core, such as a central processing unit (CPU), a graphics processing unit (GPU), or a reduced instruction set computer (RISC)-CPU. The processor 52 executes a plurality of instructions included in a control program stored in the memory 51 to control optical scanning by the optical scanning unit 10. In this way, the control device 50 configures a plurality of functional blocks for controlling optical scanning by the optical scanning unit 10. The plurality of functional blocks configured in the control device 50 include a cycle control block 500 and an abnormality determination block 510, as shown in FIG. 3 .

[0023] The control method for controlling optical scanning by the optical scanning unit 10 is executed in accordance with the control flow shown in Fig. 6 by the cooperation of these blocks 500 and 510. This control flow is repeatedly executed for each scanning cycle Cs while the optical scanning system 1 is running. Note that each "S" in the control flow represents a step executed by a plurality of instructions included in the control program stored in the memory 51.

[0024] In S10, the cycle control block 500 repeatedly controls the scan time interval Ts in the current scan cycle Cs. At this time, the scan time interval Ts shown in FIG. 5 is defined as an interval for performing synchronous control of light emission by the light-emitting unit 11 and light reception by the light-receiving unit 13, triggered by the scan orientation Rs at the reference angle interval Δθ shown in FIG. 4 within the scan field of view Vs. Of the rotation angles θs sensed by the rotation angle sensor 122 and outputting pulses Psa and Psb, the corresponding scan orientation Rs is detected for each trigger rotation angle θst, which is spaced apart by the reference angle interval Δθ from the rotation angle θss corresponding to the starting orientation Rss. At this time, the set angle interval δθ between the rotation angles θs at which the pulses Psa and Psb are output is smaller than the reference angle interval Δθ between the trigger rotation angles θst.

[0025] In this way, the scanning time interval Ts is repeatedly controlled so that the start of scanning is triggered by the detection of the scanning orientation Rs within the scanning field of view Vs based on the pulses Psa and Psb from the rotation angle sensor 122. However, in S10, it is assumed that a detection miss event will occur in which the detection interval of the scanning orientation Rs deviates from the reference angle interval Δθ due to a failure to detect the scanning orientation Rs caused by an abnormality due to a variety of factors in the optical scanning unit 10, as shown in Figures 7 to 9.

[0026] 7, one example of a missed detection event is when, during the most recent scanning time interval Ts, at least one abnormal rotation angle θs is sensed as an abnormal angle θsf following sensing of the trigger rotation angle θst that triggers the next scanning time interval Ts. When this event occurs, the cycle control block 500 will no longer accept the scanning orientation Rs corresponding to the abnormal angle θsf as a trigger for the next scanning time interval Ts, resulting in a missed detection. This occurs because once the most recent scanning time interval Ts is started in response to the trigger rotation angle θst, the light-emitting unit 11 and the light-receiving unit 13 enter a busy state in which they will not accept a trigger for the next scanning time interval Ts until the most recent scanning time interval Ts ends.

[0027] 8 and 9, another type of missed detection event occurs when, during or after the most recent scan time interval Ts, at least one of the rotation angles θs corresponding to the scan orientation Rs that triggers the next or subsequent scan time interval Ts is not sensed, resulting in a missed output. When this type of event occurs, the cycle control block 500 is unable to detect the scan orientation Rs corresponding to the rotation angle θs for which the output was missed, resulting in a missed detection.

[0028] 6, the abnormality determination block 510 determines whether a detection failure occurred in the scanning direction Rs in the current scanning cycle Cs in S10. If a negative determination is made, the current execution of the control flow ends. On the other hand, if a positive determination is made, the control flow proceeds to S30.

[0029] In S30, the abnormality determination block 510 determines whether the detection pattern for the scanning orientation Rs in the current scanning cycle Cs, which was determined to be a detection miss in the scanning orientation Rs in S20, is the first abnormality detection pattern F1. In this case, the first abnormality detection pattern F1 in Fig. 7 is defined as a detection pattern in which a detection miss occurred during any of the scanning time intervals Ts in the current scanning cycle Cs, by sensing the trigger rotation angle θst corresponding to the scanning orientation Rs in the next scanning time interval Ts and the subsequent abnormal angle θsf.

[0030] Specifically, as shown in FIG. 10 , the first abnormality detection pattern F1 occurs when the angular velocity ωs between the rotation angles θs sensed by the rotation angle sensor 122 at set angular intervals δθ falls outside the allowable range. In particular, the first abnormality detection pattern F1, which is based on the consecutive sensing of the trigger rotation angle θst and the abnormal angle θsf within the scanning time interval Ts, is predicted when the angular velocity ωs between the rotation angles θs rises outside the allowable range. Therefore, the angular velocity ωs is recognized from the rotation angle θs at set angular intervals δθ and compared with an upper threshold value of the allowable range to determine whether the first abnormality detection pattern F1 has occurred. The upper threshold value of the allowable range, which serves as the basis for this determination, is set to, for example, the maximum value of the angular velocity ωs when consecutive sensing of the trigger rotation angle θst and the abnormal angle θsf does not occur within the scanning time interval Ts. In FIG. 10, the angular velocity ωs within the allowable range is indicated by the symbol ωsi, and the angular velocity ωs outside the allowable range is indicated by the symbol ωso.

[0031] 6, if a positive determination is made in S30, the control flow proceeds to S40. In S40, the abnormality determination block 510 determines that the cause of the abnormality in the optical scanning unit 10 is an impact to the optical scanning unit 10, based on the determination result of the first abnormality detection pattern F1 in S30. At this time, the abnormality determination block 510 may generate diagnostic output data that is output to indicate the determination result that the cause of the abnormality is an impact to the optical scanning unit 10. When S40 is completed, the current execution of the control flow ends.

[0032] If a negative determination is made in S30, the control flow proceeds to S50. In S50, an abnormality determination block 510 determines whether the detection pattern for the scanning orientation Rs in the current scanning cycle Cs, which was determined to be a detection miss in the scanning orientation Rs in S20, is a second abnormality detection pattern F2. In this case, the second abnormality detection pattern F2 in Fig. 8 is defined as a detection pattern in which detection of the scanning orientation Rs is missed consecutively at every reference angle interval Δθ in the current scanning cycle Cs.

[0033] 6, if a positive determination is made in S50, the control flow proceeds to S60. In S60, the abnormality determination block 510 determines that the cause of the abnormality in the optical scanning unit 10 is a physical failure of the rotation angle sensor 122, depending on the determination result of S60 that the second abnormality detection pattern F2 has occurred. At this time, the abnormality determination block 510 may generate diagnostic output data that is output to indicate the determination result that the physical failure of the rotation angle sensor 122 has occurred. Upon completion of execution of S60, the current execution of the control flow ends.

[0034] If a negative determination is made in S50, the control flow proceeds to S70. In S70, the abnormality determination block 510 determines whether the detection pattern for the scanning orientation Rs in the current scanning cycle Cs, which was determined to be a detection miss in the scanning orientation Rs in S20, is the third abnormality detection pattern F3. In this case, the third abnormality detection pattern F3 in Fig. 9 is defined as a detection pattern in which the scanning orientation Rs in which detection is missed at every reference angle interval Δθ is common between the current scanning cycle Cs and the previous scanning cycle Cs from the previous execution of the control flow, which are consecutive scanning cycles Cs.

[0035] 6, if a positive determination is made in S70, the control flow proceeds to S80. In S80, the abnormality determination block 510 determines that the cause of the abnormality in the optical scanning unit 10 is the adhesion of a foreign substance to the rotation angle sensor 122, depending on the determination result of S70 that the third abnormality detection pattern F3 has occurred. At this time, the abnormality determination block 510 may generate diagnostic output data that is output to indicate the determination result that the adhesion of a foreign substance to the rotation angle sensor 122 has occurred. When S80 is completed, the current execution of the control flow ends.

[0036] If a negative determination is made in S70, the control flow proceeds to S90. In S90, the abnormality determination block 510 suspends the determination of the cause of the abnormality. At this time, the abnormality determination block 510 may generate diagnostic output data that is output to indicate the occurrence of a detection failure for which the determination of the cause of the abnormality has been suspended. Completion of execution of S90 marks the end of the current execution of the control flow.

[0037] (Action and effect) The effects of the first embodiment described above will be explained below.

[0038] According to the first embodiment, the scanning time interval Ts triggered by the detection of the scanning orientation Rs, which corresponds to the trigger rotation angle θst as the rotation angle θs sensed every reference angle interval Δθ, is repeatedly controlled. As a result, the abnormality detection patterns F1, F2, and F3, which are detection patterns in which the detection interval of the scanning orientation Rs deviates from the reference angle interval Δθ, may differ depending on the cause of the abnormality in the optical scanning unit 10. Therefore, it is possible to accurately determine the cause of the abnormality in the optical scanning unit 10 according to the abnormality detection patterns F1, F2, and F3.

[0039] In the first embodiment, if an abnormal angle θsf is sensed following the trigger rotation angle θst corresponding to the scanning orientation Rs that triggers the next scanning time interval Ts during any one of the scanning time intervals Ts, the scanning orientation Rs corresponding to the abnormal angle θsf will not be detected. In this case, the first abnormality detection pattern F1 appears due to an impact on the optical scanning unit 10. Therefore, in the case of the first abnormality detection pattern F1 in which the scanning orientation Rs corresponding to the abnormal angle θsf within the scanning time interval Ts is not detected, it is possible to accurately determine that the cause of the abnormality is a temporary or accidental impact.

[0040] According to the first embodiment, if an abnormal angle θsf is sensed within a scanning time interval Ts, it is assumed that the angular velocity ωs appearing between the rotation angles θs sensed by the rotation angle sensor 122 falls outside the allowable range. In particular, an abnormal angle θsf within a scanning time interval Ts is sensed when the angular velocity ωs appearing between the rotation angles θs sensed at set angular intervals δθ, which are smaller than the reference angular interval Δθ, falls outside the allowable range. Therefore, by monitoring the angular velocity ωs, it is possible to detect the first abnormality detection pattern F1, which is an impact factor, early and quickly identify the impact factor.

[0041] In the first embodiment, it is assumed that a physical failure of the rotation angle sensor 122 will result in consecutive failures in detection of the scanning orientation Rs at every reference angle interval Δθ. Therefore, in the case of the second abnormality detection pattern F2 in which consecutive failures in detection of the scanning orientation Rs at every reference angle interval Δθ occur, it is possible to accurately determine that the cause of the abnormality is a physical failure that requires maintenance of the rotation angle sensor 122.

[0042] In the first embodiment, it is assumed that when foreign matter adheres to the rotation angle sensor 122, the scanning orientation Rs at which detection is missed at every reference angle interval Δθ will be the same in consecutive scanning cycles Cs. Therefore, in the case of the third abnormality detection pattern F3 in which the scanning orientation Rs at which detection is missed at every reference angle interval Δθ is the same in consecutive scanning cycles Cs, it is possible to accurately determine that the abnormality is caused by the adhesion of foreign matter that requires maintenance of the rotation angle sensor 122.

[0043] Second Embodiment The second embodiment is a modification of the first embodiment. As shown in Figures 11 and 12, in the control flow of the second embodiment, if a positive determination is made in S30, the flow proceeds to S2040. In S2040, the abnormality determination block 510 determines whether the detection pattern for the scanning orientation Rs in the current scanning cycle Cs, in which a detection miss in the scanning orientation Rs is determined in S20, is a consecutive pattern F1_1 of the first abnormality detection pattern F1. Here, the consecutive pattern F1_1 is defined as a detection pattern in which the angular velocity ωs between the rotation angles θs increases beyond the allowable range in both the consecutive current scanning cycle Cs and the previous scanning cycle Cs.

[0044] 12, in the control flow of the second embodiment, the determination result of the first abnormality detection pattern F1 in S30 is limited to the current scanning cycle Cs alone, and therefore if a negative determination is made in S2040, the flow proceeds to S40. As a result, the cause of the abnormality in the optical scanning unit 10 is determined to be an impact to the unit 10, narrowing it down to cases where the first abnormality detection pattern F1 appears only in the current scanning cycle Cs.

[0045] On the other hand, if the determination result of S30 for the first abnormality detection pattern F1 is consecutive over multiple scanning cycles Cs, resulting in a positive determination in S2040, the flow proceeds to S2041. In S2041, the abnormality determination block 510 determines that the cause of the abnormality in the optical scanning unit 10 is a physical failure of the scanning unit 12 including the scan drive source 121 and the scanning mirror 120, based on the determination result of the consecutive pattern F1_1 in S2040. At this time, the abnormality determination block 510 may generate diagnostic output data that is output to indicate the determination result that there is a physical failure of the scanning unit 12. Completion of execution of S2041 marks the end of the current execution of the control flow.

[0046] This second embodiment also considers an abnormality caused by a physical failure of the scanning unit 12, which includes the scanning drive source 121 that drives the scanning mirror 120 in the optical scanning unit 10, along with the scanning mirror 120. Such a physical failure of the scanning unit 12 results in an event in which the angular velocity ωs between the rotation angles θs falls outside the allowable range in all consecutive scanning cycles Cs. Therefore, when the first abnormality detection pattern F1 is a consecutive pattern F1_1 in multiple scanning cycles Cs, it is possible to accurately determine that the abnormality is caused by a physical failure requiring maintenance of the scanning unit 12. On the other hand, when the first abnormality detection pattern F1 is limited to a single scanning cycle Cs, it is possible to accurately determine that the abnormality is caused by a temporary or accidental impact to the optical scanning unit 10, distinguishing it from a physical failure of the scanning unit 12.

[0047] (Other embodiments) Although several embodiments have been described above, the present disclosure should not be construed as being limited to the embodiments described above, and can be applied to various embodiments within the scope of the gist of the present disclosure.

[0048] In the modifications of the first and second embodiments, the dedicated computer constituting the control device 50 may have at least one of a digital circuit and an analog circuit as a processor. Here, the digital circuit is at least one of an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a system on a chip (SOC), a programmable gate array (PGA), and a complex programmable logic device (CPLD). Such a digital circuit may also have a memory that stores a program.

[0049] In a modification of the first embodiment, one or two of the sets of S30 and S40, S50 and S60, and S70 and S80 may be skipped. In a modification of the second embodiment, one or two of the sets of S30, S2040, S2041, and S40, S50 and S60, and S70 and S80 may be skipped. In the modifications of the first and second embodiments, S90 may be skipped. In addition to the embodiments described above, the above-described embodiments and modifications may be implemented in the form of a semiconductor device (e.g., a semiconductor chip) as a control device 50 including at least one processor 52 and one memory 51. [Explanation of symbols]

[0050] 1: Optical scanning system, 10: Optical scanning unit, 12: Scanning section, 50: Control device, 51: Memory, 52: Processor, 120: Scanning mirror, 121: Scanning drive source, 122: Rotation angle sensor, Cs: Scanning cycle, F1: First abnormality detection pattern, F2: Second abnormality detection pattern, F3: Third abnormality detection pattern, F1_1: Continuous pattern, Rs: Scanning direction, Ts: Scanning time interval, Vs: Scanning field of view, Δθ: Reference angle interval, δθ: Set angle interval, θs: Rotation angle, θsf: Abnormal angle, ωs: Angular velocity

Claims

1. A control device including a processor (52) for controlling an optical scanning unit (10) having a scanning mirror (120) that rotates and adjusts a scanning orientation (Rs) within a scanning field (Vs) for each scanning cycle (Cs) and a rotation angle sensor (122) that senses a rotation angle (θs) of the scanning mirror, The processor: repeatedly controlling a scanning time interval (Ts) triggered by detection of the scanning orientation corresponding to the rotation angle sensed at each reference angle interval (Δθ); and determining an abnormality factor in the optical scanning unit according to an abnormality detection pattern (F1, F2, F3) as a detection pattern in which the detection interval of the scanning orientation deviates from the reference angle interval.

2. The determining of the abnormality factor includes:

2. The control device according to claim 1, further comprising: determining that the cause of the abnormality is an impact to the optical scanning unit in the case of an abnormal detection pattern in which, during any one of the scanning time intervals, an abnormal angle (θsf) that is an abnormal rotation angle is sensed following the rotation angle corresponding to the scanning orientation that triggers the next scanning time interval, thereby missing detection of the scanning orientation corresponding to the abnormal angle.

3. The determining of the abnormality factor includes:

3. The control device according to claim 2, further comprising: determining that the cause of the abnormality is an impact to the optical scanning unit when the abnormality detection pattern that appears between the rotation angles sensed by the rotation angle sensor is such that the angular velocity (ωs) is outside an allowable range.

4. The determining of the abnormality factor includes:

4. The control device according to claim 3, further comprising: determining that the cause of the abnormality is an impact to the optical scanning unit when the abnormality detection pattern appears between the rotation angles sensed by the rotation angle sensor at set angle intervals (δθ) smaller than the reference angle interval, and the angular velocity is outside the allowable range.

5. The determining of the abnormality factor includes: determining that the cause of the abnormality is an impact on the optical scanning unit when the abnormality detection pattern in which the angular velocity between the rotation angles is outside the allowable range is limited to a single scanning cycle; 4. The control device according to claim 3, further comprising: determining that the abnormal cause, when the abnormality detection pattern in which the angular velocity between the rotation angles is outside the allowable range, occurs continuously in a plurality of the scanning cycles, is a physical failure of a scanning section (12) that has a scanning drive source (121) that drives the scanning mirror in the optical scanning unit together with the scanning mirror.

6. The determining of the abnormality factor includes:

2. The control device according to claim 1, further comprising: determining that the cause of the abnormality is a physical failure of the rotation angle sensor when the abnormal detection pattern is one in which detection of the scanning orientation at each reference angle interval is missed consecutively.

7. The determining of the abnormality factor includes:

2. The control device according to claim 1, further comprising: determining that the cause of the abnormality is adhesion of a foreign matter to the rotation angle sensor when the abnormality detection pattern has a common scanning orientation in which detection is missed at each reference angle interval between consecutive scanning cycles.

8. an optical scanning unit (10) having a scanning mirror (120) that rotates and adjusts a scanning direction (Rs) within a scanning field (Vs) for each scanning cycle (Cs) and a rotation angle sensor (122) that senses a rotation angle (θs) of the scanning mirror; and a control device (50) according to any one of claims 1 to 6, comprising a processor (52) for controlling the optical scanning unit.

9. A control method executed by a processor (52) for controlling an optical scanning unit (10) having a scanning mirror (120) that rotates and adjusts a scanning orientation (Rs) within a scanning field (Vs) for each scanning cycle (Cs) and a rotation angle sensor (122) that senses a rotation angle (θs) of the scanning mirror, the method comprising: repeatedly controlling a scanning time interval (Ts) triggered by detection of the scanning orientation corresponding to the rotation angle sensed at each reference angle interval (Δθ); and determining an abnormality factor in the optical scanning unit according to an abnormality detection pattern (F1, F2, F3) as a detection pattern in which the detection interval in the scanning orientation deviates from the reference angle interval.

10. A control program is stored in a storage medium (51) for controlling an optical scanning unit (10) having a scanning mirror (120) that rotates and adjusts a scanning orientation (Rs) for each scanning cycle (Cs) within a scanning field (Vs) and a rotation angle sensor (122) that senses a rotation angle (θs) of the scanning mirror, the control program including instructions for causing a processor (52) to execute the control, repeatedly controlling a scanning time interval (Ts) triggered by detection of the scanning orientation corresponding to the rotation angle sensed at each reference angle interval (Δθ); and determining an abnormality factor in the optical scanning unit according to an abnormality detection pattern (F1, F2, F3) as a detection pattern in which the detection interval of the scanning orientation deviates from the reference angle interval.

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