Safety monitoring device, method for control, and program

Abstract

To reduce the frequency of missing an object.SOLUTION: A safety monitoring device includes: a light-emission element; a first light-reception element; a second light-reception element arranged to receive at least a part of laser beams emitted from the light-emission element; a polarization unit for scanning the direction of radiation of laser beams periodically; and a control unit. The control unit controls a supply current to the light-emission element so that the light-emission amount of the light-emission element is closer to an ideal amount, on the basis of the light reception amount of the second light reception element. The control unit measures the distance to an object on the basis of the time since the light-emission element emits a laser beam until the first light-reception element receives reflection light from the object after the supply current is controlled, and detects the presence or absence of an object in a preset monitor area on the basis of the distance to the object and the direction of radiation of a laser beam.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a safety monitoring device, a control method, and a program. [Background technology]

[0002] Safety monitoring devices that detect when a person approaches dangerous machinery or equipment at a production site are known. For example, German Utility Model No. 202019100793 (Patent Document 1) discloses a laser scanner equipped with a light-emitting element and a light-receiving element. This laser scanner measures the distance to an object based on the time of flight (time of flight) between when the light-emitting element emits laser light and when the light-receiving element receives the reflected light from the object. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] German Utility Model No. 202019100793 Summary of the Invention [Problem to be solved by the invention]

[0004] The light emission amount of the light emitting element may change depending on the influence of deterioration of the light emitting element over time, etc. If the light emission amount of the light emitting element decreases, the safety monitoring device may fail to detect an object (person).

[0005] The present disclosure has been made in consideration of the above circumstances, and its purpose is to provide a safety monitoring device, a control method, and a program that can reduce the frequency of missing object detection. [Means for solving the problem]

[0006] A safety monitoring device according to one aspect of the present disclosure includes a light-emitting element, a first light-receiving element, a second light-receiving element arranged to receive at least a portion of the laser light emitted from the light-emitting element, a deflection unit that periodically scans the direction of irradiation of the laser light, and a control unit. The control unit controls a current supplied to the light-emitting element based on the amount of light received by the second light-receiving element so that the amount of light emitted by the light-emitting element approaches a target amount. After controlling the supply current, the control unit measures the distance to the object based on the time from when the light-emitting element emits the laser light to when the first light-receiving element receives the light reflected from the object, and detects the presence or absence of an object within a predetermined monitoring area based on the distance to the object and the direction of irradiation of the laser light.

[0007] According to this disclosure, the amount (intensity) of laser light irradiated to the outside when measuring the distance to an object is stabilized, thereby preventing missed object detection due to a decrease in the amount of laser light.

[0008] In the above disclosure, the safety monitoring device further includes a window through which light can pass. A scanning cycle of the irradiation direction of the laser light includes a first period during which the laser light does not pass through the window and a second period during which the laser light passes through the window. The control unit controls the supply current during the first period and measures the distance during the second period.

[0009] According to this disclosure, the control of the supply current to the light-emitting element is executed during a first period separate from a second period in which the distance to the object is measured, thereby suppressing the effect of the control of the supply current on delays in the process of measuring the distance to the object.

[0010] In the above disclosure, the second light receiving element generates charges by photoelectric conversion, and the control unit determines the supply current according to a difference between a first amount of charge generated in the second light receiving element when the light emitting element emits laser light and a second amount of charge generated in the second light receiving element when the light emitting element does not emit laser light.

[0011] According to this disclosure, the influence of individual variations in the dark current of the second light receiving element and noise is cancelled out.

[0012] In the above disclosure, the light-emitting element is disposed in a shielded space that is shielded from light except for the cylindrical passage through which the laser light travels. The second light-receiving element is disposed in the shielded space. According to this disclosure, the influence of stray light on the second light-receiving element is reduced.

[0013] In the above disclosure, the cylindrical passage has an annular portion on the inner wall surface that protrudes inward. According to this disclosure, the proportion of light that is incident on the second light receiving element out of the laser light emitted from the light emitting element is increased.

[0014] In the above disclosure, the safety monitoring device is provided with a reflecting member that is provided at a fixed position on the optical path of the laser light and reflects the laser light. The control unit determines whether the time from when the light-emitting element emits the laser light to when the first light-receiving element receives the reflected light from the reflecting member is within a reference range. The reflecting member has a notch that allows the laser light to pass. The second light-receiving element may be positioned to receive the laser light that has passed through the notch. According to this disclosure, the space behind the reflecting member is effectively utilized.

[0015] A control method according to one aspect of the present disclosure is a control method for a safety monitoring device having a light-emitting element, a first light-receiving element, a second light-receiving element arranged to receive at least a portion of the laser light emitted from the light-emitting element, and a deflection unit that periodically scans the irradiation direction of the laser light. The control method includes controlling a current supplied to the light-emitting element based on an amount of light received by the second light-receiving element so that an amount of light emitted by the light-emitting element approaches a target amount, measuring a distance to the object based on a time from when the light-emitting element emits the laser light to when the first light-receiving element receives the light reflected from the object after controlling the supply current, and detecting the presence or absence of an object within a predetermined monitoring area based on the distance to the object and the irradiation direction of the laser light.

[0016] A program according to one aspect of the present disclosure causes a computer to execute the above control method. These disclosures also reduce the frequency of overlooking object detection. [Effects of the Invention]

[0017] According to the present disclosure, it is possible to reduce the frequency of missing object detection. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is an external perspective view showing a safety laser scanner as an example of a safety monitoring device according to an embodiment; [Figure 2] FIG. 1 is a diagram illustrating an example of the configuration of a safety laser scanner. [Figure 3] 1 is a cross-sectional view of a safety laser scanner according to an embodiment. [Figure 4] FIG. 2 is a diagram showing an optical path of a laser beam irradiated onto a reference target. [Figure 5] 1 is a cross-sectional perspective view of a safety laser scanner showing a first example of the arrangement of a second light receiving element. FIG. [Figure 6] FIG. 10 is a cross-sectional view of a safety laser scanner showing a second example of the arrangement of the second light receiving element. [Figure 7] FIG. 2 is a perspective view showing a reference target and its surrounding configuration. [Figure 8] FIG. 4 is a diagram illustrating a processing cycle of a control unit. [Figure 9] 10 is a flowchart showing the flow of processing by a control unit. [Figure 10] FIG. 10 is a diagram illustrating a specific subroutine of step S1. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the accompanying drawings, in which the same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.

[0020] §1 Application Examples A safety laser scanner 1, which is an example of a safety monitoring device according to an embodiment, will be described using Figures 1 and 2. Figure 1 is an external perspective view showing a safety laser scanner, which is an example of a safety monitoring device according to an embodiment. Figure 2 is a diagram showing an example of the configuration of a safety laser scanner. Note that the "safety monitoring device" of the present disclosure is not limited to the safety laser scanner 1, and may be any device that measures distance using a time-of-flight (ToF) method.

[0021] The safety laser scanner 1 detects objects (including people) in the field of FA (Factory Automation), for example. The safety laser scanner 1 detects that an object has entered a preset monitoring area (for example, monitoring area 5a or monitoring area 5b) and outputs a signal to stop the device.

[0022] 1, the safety laser scanner 1 includes an upper housing 10 having a generally inverted truncated cone shape. A light-transmitting window 10a is provided on a portion of the side surface of the upper housing 10. The window 10a is provided, for example, over approximately 270° of the side surface of the upper housing 10 having an inverted truncated cone shape.

[0023] As shown in FIG. 2, the safety laser scanner 1 includes a light emitting element 11, a deflection unit 12, a first light receiving element 13, a second light receiving element 14, a control unit 15, and a communication interface 18.

[0024] The light emitting element 11 is, for example, a laser diode. The light emitting element 11 emits pulsed laser light (hereinafter simply referred to as "laser light 3") at predetermined intervals (regular or irregular intervals) (for example, 10 to 20 μs intervals). The pulse width of the laser light 3 is, for example, 3 to 4 ns. The amount (intensity) of the laser light 3 depends on the current supplied to the light emitting element 11.

[0025] The deflection unit 12 periodically scans the irradiation direction of the laser beam 3. Specifically, the deflection unit 12 rotates and irradiates the laser beam 3 along a rotation direction D about an axis 10b (see FIG. 1) that coincides with or is parallel to the central axis of the upper housing 10, which has a substantially inverted truncated cone shape. If a window 10a is present in the irradiation direction of the laser beam 3, the laser beam 3 passes through the window 10a and is irradiated to the outside.

[0026] The first light receiving element 13 is an element that generates electric charges through photoelectric conversion, and is, for example, an avalanche photodiode. The first light receiving element 13 is disposed so as to receive reflected light 4 from an object 2 present outside.

[0027] The second light receiving element 14 is an element that generates electric charges through photoelectric conversion, and is, for example, a photodiode. The second light receiving element 14 is disposed so as to receive at least a portion of the laser light 3 emitted from the light emitting element 11.

[0028] The control unit 15 controls the operation of each component within the safety laser scanner 1. Specifically, the control unit 15 controls the current supplied to the light-emitting element 11 based on the amount of light received by the second light-receiving element 14 so that the amount of light emitted by the light-emitting element 11 approaches a target amount. After controlling the current supplied to the light-emitting element 11, the control unit 15 measures the distance to the object 2 based on the time (time of flight) from when the light-emitting element 11 emits the laser beam 3 to when the first light-receiving element 13 receives the reflected light 4 from the object 2. The control unit 15 detects the presence or absence of the object 2 within a predetermined monitoring area based on the distance to the object 2 and the irradiation direction of the laser beam 3. For example, when the monitoring area 5a shown in FIG. 1 is set, the control unit 15 determines that the object 2 is present within the monitoring area 5a when the distance to the object 2 is equal to or less than the radius r of the monitoring area 5a. When the monitoring area 5b shown in FIG. 1 is set, the control unit 15 determines that the object 2 is present within the monitoring area 5b when the distance to the object 2 is within the distance range R corresponding to the irradiation direction of the laser beam 3. The distance range R according to the irradiation direction of the laser light 3 is determined in advance based on the monitoring area 5b.

[0029] The control unit 15 includes a processor 151, such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit), a memory 152, and a storage 153, and controls each component in accordance with information processing. The processor 151 loads a program 154 installed in the storage 153 into the memory 152 and executes it. The processor 151 executes the program 154, thereby realizing the functions of the control unit 15. The memory 152 is typically a volatile storage device such as a DRAM (Dynamic Random Access Memory). The storage 153 is configured, for example, with a hard disk drive, a solid state drive, or the like. The storage 153 stores the program 154 and monitoring area definition data 155. The monitoring area definition data 155 defines the shape and size of the monitoring area.

[0030] The communication interface 18 can be connected to an external computer 6. The computer 6 includes a setting tool 610 for setting the operation of the safety laser scanner 1. The setting tool 610 creates or edits the monitoring area definition data 155, for example, in accordance with input from a user, and installs the monitoring area definition data 155 in the safety laser scanner 1. The setting tool 610 may be built into the safety laser scanner 1.

[0031] 2 shows an example of a configuration in which the processor 151 executes the program 154 to provide the necessary processes. However, some or all of the processes provided may be implemented using dedicated hardware circuits (for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array)).

[0032] According to the safety laser scanner 1 of this embodiment, the current supplied to the light-emitting element 11 is controlled based on the amount of light received by the second light-receiving element 14 so that the amount of light emitted by the light-emitting element 11 approaches a target amount. As described above, the amount of light emitted by the light-emitting element 11 may change depending on the deterioration of the light-emitting element 11 over time. The amount of light emitted by the light-emitting element 11 also varies depending on individual variations in performance of the light-emitting element 11. Furthermore, the amount of light emitted by the light-emitting element 11 may also change depending on the temperature of the light-emitting element 11. However, according to the above configuration, the amount (intensity) of the laser light 3 irradiated to the outside when measuring the distance to the object 2 is stabilized. As a result, missed object detection due to a decrease in the amount of laser light 3 is avoided. This improves the safety monitoring performance of the safety laser scanner 1.

[0033] Furthermore, Patent Document 1 discloses a technique for adjusting the light emission power according to the intensity of light reflected from an object in order to obtain a wide dynamic range. In this case, adjusting the light emission power requires eye safety measures to prevent strong laser light from reaching the human eyes. However, with the above configuration, the amount (intensity) of the laser light 3 is stabilized, thereby reducing the need for eye safety measures. Note that even if the light emission amount of the light-emitting element 11 is stabilized, a wide dynamic range can be achieved by using a logarithmic amplifier, as will be described later.

[0034] §2 Specific examples <Internal structure of the safety laser scanner> 3 is a cross-sectional view of a safety laser scanner according to an embodiment. As shown in FIG. 3, the safety laser scanner 1 includes, as main components, a light-emitting unit 110, a deflection unit 12, a light-receiving unit 130, a control board 150, a power supply board 16, and a reference target 17.

[0035] The light-emitting unit 110 includes components related to light emission. Specifically, the light-emitting unit 110 includes a light-emitting element 11, a substrate 111, a shielding member 112, a lens holder 113, a lens 114, and a half mirror 115.

[0036] The light emitting element 11 is mounted on a substrate 111. The shielding member 112 is cylindrical and attached to the substrate 111 so as to surround the light emitting element 11. The lens holder 113 is cylindrical, one end of which is inserted inside the shielding member 112, and the other end of which supports a lens 114.

[0037] A part of the shielding member 112 and the lens holder 113 form a cylindrical passage 117 through which the laser light 3 travels. The substrate 111, the shielding member 112, and the lens holder 113 are made of a material that does not transmit light. Therefore, the substrate 111 and the shielding member 112 form a light-shielded shielded space 116 except for the cylindrical passage 117. Note that a spacer (for example, spacer 118 shown in FIG. 5) may be provided between the substrate 111 and the shielding member 112 to improve adhesion between the substrate 111 and the shielding member 112. The light-emitting element 11 is disposed in the shielded space 116.

[0038] The half mirror 115 bends the traveling direction of the laser light 3 that has passed through the lens 114 to a direction parallel to the axis 10 b, and guides the laser light 3 to the deflection unit 12 .

[0039] The deflection unit 12 includes a main mirror 121 , a motor 122 , and a shaft 123 .

[0040] The main mirror 121 has a reflecting surface 121a that forms an angle of 45° with the axis 10b. The reflecting surface 121a faces the half mirror 115. Therefore, the main mirror 121 bends the laser light 3 received from the half mirror 115 in a direction perpendicular to the axis 10b. The shaft 123 is attached to the rear surface of the main mirror 121 along the axis 10b. The motor 122 rotates the shaft 123. As a result, the main mirror 121 rotates around the axis 10b while maintaining the angle between the main mirror 121 and the axis 10b at 45°. As a result, the laser light 3 is irradiated in a rotational manner around the axis 10b.

[0041] When the laser light 3 is irradiated to the outside through the window 10a, the main mirror 121 can receive the reflected light 4 from the object 2 through the window 10a. The main mirror 121 guides the reflected light 4 to the light receiving unit .

[0042] The light receiving unit 130 includes a first light receiving element 13, an amplifier 131, a substrate 132 on which the first light receiving element 13 and the amplifier 131 are mounted, a filter 133, and a lens 134.

[0043] The lens 134 focuses the light guided by the main mirror 121 onto the first light receiving element 13. The filter 133 transmits light within a predetermined wavelength range and blocks light having wavelengths outside the predetermined wavelength range. The predetermined wavelength range includes the wavelength of the laser light 3 emitted from the light emitting element 11. For example, if the laser light 3 is infrared light, an IR filter is used as the filter 133.

[0044] The amplifier 131 amplifies the signal output from the first light receiving element 13. The signal output from the first light receiving element 13 represents the amount of light received by the first light receiving element 13. The control unit 15 (see FIG. 2) can measure the distance to the object 2 using the signal amplified by the amplifier 131.

[0045] IEC 61496-3, the product safety standard for safety laser scanners, requires that objects with a reflectivity of 1.6% be detectable. However, the objects 2 whose distances are measured by the safety laser scanner 1 may include not only low-reflectivity objects but also shiny floors or walls. Therefore, it is desirable to widen the dynamic range so that the distance to objects 2 with various reflectivities can be measured. To achieve a wide dynamic range, it is preferable to use a logarithmic amplifier as the amplifier 131. The amplifier 131, which is a logarithmic amplifier, converts the signal output from the first light-receiving element 13 into a logarithmic scale. This allows the amplifier 131 to provide high gain for low-level input signals and to provide a gain that gradually decreases as the signal level increases. As a result, the dynamic range of the safety laser scanner 1 is widened.

[0046] The control board 150 is equipped with various components (for example, the processor 151, memory 152, storage 153, ASIC, FPGA, etc. shown in FIG. 2 ) that constitute the control unit 15. The power supply board 16 is equipped with various components for supplying power to the components of the safety laser scanner 1.

[0047] The reference target 17 is a reflective member disposed between the main mirror 121 and a side of the upper housing 10 on which the window 10a is not formed. The reference target 17 reflects the laser light 3 received from the main mirror 121 toward the main mirror 121.

[0048] Fig. 4 is a diagram showing the optical path of the laser light irradiated onto the reference target. Fig. 4 shows a cross-sectional view of the safety laser scanner 1 when the reflective surface 121a of the main mirror 121 faces the reference target 17. As shown in Fig. 4, the reference target 17 has two reflective surfaces 171 and 172. The reflective surface 171 guides the laser light 3 from the main mirror 121 to the reflective surface 172. The reflective surface 172 guides the laser light 3 from the reflective surface 171 to the main mirror 121. The main mirror 121 guides the laser light 3 from the reflective surface 172 to the light-receiving unit 130.

[0049] The light-emitting unit 110, the deflection unit 12, the reference target 17, and the light-receiving unit 130 are installed at fixed positions. Therefore, the optical path length of the laser light 3 shown in FIG. 4 is constant. Therefore, in order to diagnose the distance measurement accuracy, the control unit 15 (see FIG. 1) periodically determines whether the time from when the light-emitting element 11 emits the laser light 3 to when the first light-receiving element 13 receives the reflected light from the reference target 17 is within a reference range. The reference range includes the time required for the laser light 3 to travel from the light-emitting element 11 to the first light-receiving element 13 along the optical path shown in FIG. 4. The control unit 15 may notify an error if the time from when the light-emitting element 11 emits the laser light 3 to when the first light-receiving element 13 receives the reflected light from the reference target 17 is outside the reference range.

[0050] <Example of arrangement of second light receiving element> The second light receiving element 14 is arranged inside the safety laser scanner 1 so as to receive at least a portion of the laser light 3 emitted from the light emitting element 11. Below, examples of the arrangement of the second light receiving element 14 will be described. Note that the second light receiving element 14 may be arranged according to either the first or second arrangement examples below, or may be arranged in a position different from the first or second arrangement examples.

[0051] (First arrangement example) Fig. 5 is a cross-sectional perspective view of a safety laser scanner showing a first arrangement example of the second light receiving element 14. As shown in Fig. 5, the second light receiving element 14 is mounted on the substrate 111 so as to be disposed in the shielded space 116. By disposing the second light receiving element 14 in the shielded space 116, the effect of external stray light on the second light receiving element 14 is reduced.

[0052] The second light receiving element 14 receives a portion of the laser light 3 emitted from the light emitting element 11 and reflected by the wall surfaces of the shielding member 112 and the lens holder 113. In order to increase the amount of laser light 3 guided to the second light receiving element 14, as shown in FIG. 5, the cylindrical passage 117 through which the laser light 3 travels preferably has an annular portion 113a protruding inward on its inner wall surface. In the example shown in FIG. 5, the annular portion 113a is formed at the end of the lens holder 113 on the shielding member 112 side. As a result, a portion of the laser light 3 emitted from the light emitting element 11 is reflected by the annular portion 113a and guided to the second light receiving element 14. As a result, the amount of laser light 3 guided to the second light receiving element 14 increases.

[0053] The proportion of the laser light 3 emitted from the light-emitting element 11 that is received by the second light-receiving element 14 depends on the positional relationship between the second light-receiving element 14, the light-emitting element 11, the shielded space 116, and the cylindrical passage 117, and is approximately constant.

[0054] (Second arrangement example) A second example of the arrangement of the second light-emitting element will be described with reference to Figures 6 and 7. Figure 6 is a cross-sectional view of a safety laser scanner showing the second example of the arrangement of the second light-receiving element. Figure 7 is a perspective view showing a reference target and its surrounding configuration.

[0055] As shown in FIGS. 6 and 7, the reference target 17 has a notch 173 that allows the laser light 3 from the main mirror 121 to pass through.

[0056] The second light receiving element 14 is arranged to receive the laser light 3 that has passed through the notch 173 of the reference target 17. Specifically, the second light receiving element 14 is mounted on a substrate 141 that is arranged on the back side of the reference target 17. By being arranged on the back side of the reference target 17, the influence of external stray light on the second light receiving element 14 is reduced.

[0057] <Processing cycle of the control unit> FIG. 8 is a diagram showing the processing cycle of the control unit. As described above, the deflection unit 12 periodically scans the irradiation direction of the laser beam 3. The scanning cycle of the irradiation direction of the laser beam 3 is the period during which the main mirror 121 rotates once around the axis 10b. As shown in FIG. 8, the scanning cycle includes a back scan period 51 during which the laser beam 3 does not pass through the window 10a, and a front scan period 52 during which the laser beam 3 passes through the window 10a and is irradiated to the outside. The back scan period 51 is an example of a "first period" in the present disclosure. The front scan period 52 is an example of a "second period" in the present disclosure.

[0058] During the front scan period 52, the control unit 15 measures the distance to the object 2 based on the time from when the light emitting element 11 emits the laser light 3 to when the first light receiving element 13 receives the reflected light from the object 2. The laser light 3 is emitted at predetermined intervals. Therefore, during the front scan period 52, the control unit 15 repeatedly performs a measurement process 61 for measuring the distance to the object 2 every time the laser light 3 is emitted.

[0059] As described above, the reference target 17 is disposed between the side of the upper housing 10 where the window 10a is not formed and the main mirror 121. Therefore, during the backscan period 51, the control unit 15 performs a determination process 62 to determine whether the time from when the light-emitting element 11 emits the laser light 3 to when the first light-receiving element 13 receives the reflected light from the reference target 17 is within a reference range.

[0060] Furthermore, the control unit 15 performs a current control process 63 for controlling the current supplied to the light emitting element 11 based on the amount of light received by the second light receiving element 14 so that the amount of light emitted by the light emitting element 11 approaches the target amount.

[0061] When the second light receiving element 14 is arranged according to the above-described first arrangement example, the second light receiving element 14 can receive a part of the laser light 3 emitted from the light emitting element 11 in both the back scan period 51 and the front scan period 52. Therefore, the control unit 15 may perform the current control process 63 in the back scan period 51, or may perform the current control process 63 in the front scan period 52.

[0062] However, during the front scan period 52, the measurement process 61 is repeatedly performed. For example, if the scanning period in the irradiation direction of the laser light 3 is 60 ms and the measurement process 61 is performed every time the laser light scans by 0.1°, the control unit 15 completes one measurement process 61 in approximately 17 μs. Such high-speed response is particularly required for the safety laser scanner 1. To meet this requirement, it is preferable to reduce the load of processes other than the measurement process 61 as much as possible during the front scan period 52. Therefore, it is preferable for the control unit 15 to perform the current control process 63 during the back scan period 51.

[0063] When the second light receiving element 14 is arranged according to the second arrangement example described above, the second light receiving element 14 receives a part of the laser light 3 emitted from the light emitting element 11 during the back scan period 51. Therefore, the control unit 15 performs a current control process 63 during the back scan period 51.

[0064] <Processing flow> Fig. 9 is a flowchart showing the processing flow of the control unit. Steps S1 to S4 shown in Fig. 9 are repeatedly performed for each processing cycle. Typically, steps S1 and S2 are performed during the back scan period 51 shown in Fig. 8, and steps S3 and S4 are performed during the front scan period 52.

[0065] In step S1, the control unit 15 measures the monitor voltage Vm corresponding to the amount of light received by the second light receiving element .

[0066] 10 is a diagram illustrating a specific subroutine of step S1. As shown in FIGS. 9 and 10, step S1 includes steps S11 to S13. In step S11, control unit 15 causes light to be emitted multiple times during a light-emitting period Ta having a predetermined charging time (e.g., 300 μs). Then, control unit 15 measures an integrated voltage Va corresponding to the first charge amount generated in second light receiving element 14 during light-emitting period Ta. The number of times light is emitted by light-emitting element 11 during light-emitting period Ta is set in advance according to a target voltage, which will be described later, and positional variations during optical alignment of lens 114, lens holder 113, and light-emitting element 11.

[0067] In step S12, the control unit 15 stops the light emission of the light-emitting element 11 during a non-light-emitting period Tb having the same charging time as the light-emitting period Ta. Then, the control unit 15 stops the light emission of the light-emitting element 11 during the non-light-emitting period Tb, and measures an integrated voltage Vb corresponding to the second amount of charge generated in the second light-receiving element 14.

[0068] The integrated voltage Vb represents a value corresponding to the dark current of the second light receiving element 14. Dark current is also generated in the second light receiving element 14 during the light emission period Ta. Therefore, in step S13, the control unit 15 calculates the difference (Va-Vb) between the integrated voltages Va and Vb as the monitor voltage Vm to cancel out the effects of individual variations in the dark current of the second light receiving element 14 and noise. That is, the monitor voltage Vm represents the difference between the first amount of charge generated by the second light receiving element 14 during the light emission period Ta and the second amount of charge generated by the second light receiving element 14 during the non-light emission period Tb. This allows the monitor voltage Vm to more accurately represent the predetermined proportion of the amount of light emitted from the light emitting element 11 during the light emission period Ta.

[0069] In the next step S2, the control unit 15 controls the current supplied to the light emitting element 11 based on the monitor voltage Vm corresponding to the amount of light received by the second light receiving element 14 so that the amount of light emitted from the light emitting element 11 approaches the target amount.

[0070] Specifically, the control unit 15 calculates an offset value corresponding to the difference between the monitor voltage Vm and the target voltage, and corrects the current supplied to the light-emitting element 11 during light emission by the offset value. The target voltage is an integrated voltage corresponding to the amount of charge generated by the second light-receiving element 14 in response to receiving the target amount of laser light 3. This allows the control unit 15 to control the current supplied to the light-emitting element 11 so that the amount of light emitted by the light-emitting element 11 approaches the target amount.

[0071] In the next step S3, the control unit 15 measures the distance to the object 2 based on the time (time of flight) from when the light-emitting element 11 emits the laser light 3 to when the first light-receiving element 13 receives the reflected light 4 from the object 2. In the next step S4, the control unit 15 detects the presence or absence of the object 2 in a predetermined monitoring area based on the distance to the object 2 and the irradiation direction of the laser light 3. Steps S3 and S4 are repeatedly performed every time the light-emitting element 11 emits the laser light 3 during the front scan period 52.

[0072] §3 Supplementary Note As described above, the present embodiment includes the following disclosures.

[0073] (Configuration 1) A safety monitoring device (1), A light-emitting element (11), a first light receiving element (13); a second light receiving element (14) arranged to receive at least a portion of the laser light (3) emitted from the light emitting element (11); a deflection unit (12) that periodically scans the irradiation direction of the laser light (3); and a control unit (15), controlling a current supplied to the light-emitting element (11) based on the amount of light received by the second light-receiving element (14) so that the amount of light emitted by the light-emitting element (11) approaches a target amount; After controlling the supply current, the distance to the object (2) is measured based on the time from when the light emitting element (11) emits the laser light (3) until the first light receiving element (13) receives the reflected light (4) from the object (2); and A safety monitoring device (1) that detects the presence or absence of the object (2) within a preset monitoring area (5a, 5b) based on the distance to the object (2) and the direction of irradiation of the laser light (3).

[0074] (Configuration 2) Further provided with a window (10a) through which light can pass, a scanning period of the laser beam (3) in the irradiation direction includes a first period in which the laser beam (3) does not pass through the window (10a) and a second period in which the laser beam (3) passes through the window (10a); The safety monitoring device (1) according to configuration 1, wherein the control unit (15) controls the supply current in the first period and measures the distance in the second period.

[0075] (Configuration 3) The second light receiving element (14) generates an electric charge by photoelectric conversion, The safety monitoring device (1) according to configuration 1 or 2, wherein the control unit (15) determines the supply current according to the difference between a first charge amount generated in the second light-receiving element (14) when the light-emitting element (11) is emitting the laser light (3) and a second charge amount generated in the second light-receiving element (14) when the light-emitting element (11) is not emitting the laser light (3).

[0076] (Configuration 4) The light-emitting element (11) is disposed in a shielded space (116) that is shielded from light except for a cylindrical passage (117) through which the laser light (3) travels, The safety monitoring device (1) according to any one of configurations 1 to 3, wherein the second light receiving element (14) is disposed in the shielded space (116).

[0077] (Configuration 5) 5. The safety monitoring device (1) according to configuration 4, wherein the cylindrical passage (117) has an annular portion (113a) protruding inward on the inner wall surface.

[0078] (Configuration 6) a reflecting member (17) provided at a fixed position on the optical path of the laser light (3) and reflecting the laser light (3); the control unit (15) determines whether or not a time period from when the light emitting element (11) emits the laser light (3) until when the first light receiving element (13) receives the reflected light from the reflecting member (17) is within a reference range; The reflecting member (17) has a notch (173) that allows the laser light (3) to pass through, The safety monitoring device (1) according to any one of configurations 1 to 3, wherein the second light receiving element (14) is arranged to receive the laser light (3) that has passed through the cutout portion (173).

[0079] (Configuration 7) A control method for a safety monitoring device (1) having a light-emitting element (11), a first light-receiving element (13), a second light-receiving element (14) arranged to receive at least a part of a laser beam (3) emitted from the light-emitting element (11), and a deflection unit (12) that periodically scans the irradiation direction of the laser beam (3), comprising: controlling a current supplied to the light-emitting element (11) based on the amount of light received by the second light-receiving element (14) so that the amount of light emitted by the light-emitting element (11) approaches a target amount; measuring a distance to the object (2) based on a time from when the light emitting element (11) emits a laser beam (3) until when the first light receiving element (13) receives the reflected light from the object (2) after controlling the supply current; and detecting the presence or absence of the object (2) within a preset monitoring area (5a, 5b) based on the distance to the object (2) and the irradiation direction of the laser light (3).

[0080] (Configuration 8) A processor of a safety monitoring device (1) having a light-emitting element (11), a first light-receiving element (13), a second light-receiving element (14) arranged to receive at least a part of the laser light (3) emitted from the light-emitting element (11), and a deflection unit (12) that periodically scans the irradiation direction of the laser light (3), controlling a current supplied to the light-emitting element (11) based on the amount of light received by the second light-receiving element (14) so that the amount of light emitted by the light-emitting element (11) approaches a target amount; measuring a distance to the object (2) based on a time from when the light emitting element (11) emits a laser beam (3) until when the first light receiving element (13) receives the reflected light from the object (2) after controlling the supply current; and detecting the presence or absence of the object (2) within a preset monitoring area (5a, 5b) based on the distance to the object (2) and the irradiation direction of the laser light (3).

[0081] Although the embodiments of the present invention have been described, the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is defined by the claims, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0082] 1 safety laser scanner, 2 object, 3 laser light, 4 reflected light, 5a, 5b monitoring area, 6 computer, 10 upper housing, 10a window, 10b axis, 11 light emitting element, 12 deflection unit, 13 first light receiving element, 14 second light receiving element, 15 control unit, 16 power supply board, 17 reference target, 51 back scan period, 52 front scan period, 61 measurement processing, 62 judgment processing, 63 current control processing, 110 light emitting unit, 111, 132, 141 board, 112 shielding member, 113 lens holder, 113a annular portion, 114, 134 lens, 115 half mirror, 116 shielded space, 117 cylindrical passage, 118 spacer, 121 main mirror, 121a, 171, 172 reflective surface, 122 motor, 123 Shaft, 130 light receiving unit, 131 amplifier, 133 filter, 150 control board, 151 processor, 152 memory, 153 storage, 154 program, 155 monitoring area definition data, 173 cutout portion.

Claims

1. A safety monitoring device, A light-emitting element; a first light receiving element; a second light receiving element disposed to receive at least a portion of the laser light emitted from the light emitting element; a deflection unit that periodically scans the irradiation direction of the laser light; a control unit, controlling a current supplied to the light emitting element based on the amount of light received by the second light receiving element so that the amount of light emitted by the light emitting element approaches a target amount; After controlling the supply current, the distance to the object is measured based on the time from when the light-emitting element emits the laser light to when the first light-receiving element receives the reflected light from the object; A safety monitoring device that detects the presence or absence of an object within a preset monitoring area based on the distance to the object and the direction of irradiation of the laser light.

2. Further comprising a window through which light can pass; a scanning period of the laser beam in the irradiation direction includes a first period in which the laser beam does not pass through the window and a second period in which the laser beam passes through the window; The safety monitoring device according to claim 1 , wherein the control unit controls the supply current during the first period and measures the distance during the second period.

3. the second light receiving element generates charges by photoelectric conversion; The safety monitoring device of claim 1, wherein the control unit determines the supply current based on the difference between a first charge amount generated in the second light-receiving element when the light-emitting element is emitting the laser light and a second charge amount generated in the second light-receiving element when the light-emitting element is not emitting the laser light.

4. the light-emitting element is disposed in a shielded space that is shielded from light except for a cylindrical passage through which the laser light travels, The safety monitoring device according to claim 1 , wherein the second light receiving element is disposed in the shielded space.

5. The safety monitoring device according to claim 4 , wherein the cylindrical passage has an annular portion on an inner wall surface thereof that protrudes inward.

6. a reflecting member provided at a fixed position on an optical path of the laser light and configured to reflect the laser light; the control unit determines whether or not a time from when the light emitting element emits the laser light to when the first light receiving element receives the reflected light from the reflecting member is within a reference range; the reflecting member has a notch that allows the laser light to pass through, The safety monitoring device according to claim 1 , wherein the second light receiving element is disposed so as to receive the laser light that has passed through the notch.

7. A control method for a safety monitoring device having a light-emitting element, a first light-receiving element, a second light-receiving element arranged to receive at least a part of a laser beam emitted from the light-emitting element, and a deflection unit that periodically scans an irradiation direction of the laser beam, controlling a current supplied to the light emitting element based on the amount of light received by the second light receiving element so that the amount of light emitted by the light emitting element approaches a target amount; measuring a distance to the object based on a time from when the light-emitting element emits a laser beam to when the first light-receiving element receives the reflected light from the object after controlling the supply current; and detecting the presence or absence of the object within a predetermined monitoring area based on the distance to the object and the direction of irradiation of the laser light.

8. a processor of a safety monitoring device having a light-emitting element, a first light-receiving element, a second light-receiving element arranged to receive at least a part of the laser light emitted from the light-emitting element, and a deflection unit that periodically scans the irradiation direction of the laser light; controlling a current supplied to the light emitting element based on the amount of light received by the second light receiving element so that the amount of light emitted by the light emitting element approaches a target amount; measuring a distance to the object based on a time from when the light-emitting element emits a laser beam to when the first light-receiving element receives the reflected light from the object after controlling the supply current; and detecting the presence or absence of the object within a preset monitoring area based on the distance to the object and the direction of irradiation of the laser light.

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