Optical scanning type safety sensor

Abstract

To provide an optical scanning type safety sensor which can be downsized, while continuously testing light projection and light reception.SOLUTION: An optical scanning type safety sensor comprises: a light projecting element; a light receiving element; a scanning mirror which causes a laser beam to scan in a circumferential direction, and guides reflection light of the laser beam to the light receiving element; a window capable of transmitting a laser beam; and a reference object which is disposed on an opposite side of the window relative to the scanning mirror, and on which the laser beam is reflected toward the scanning mirror. The reference object comprises a first reflective plane including a first area and a second area with lower reflectivity than the first area. The first area and the second area are arranged side by side in the circumferential direction. A first width of the first area along the circumferential direction is narrower than a second width of the second area along the circumferential direction. A spot width along the circumferential direction of a laser beam projected on the reference object is wider than the first width.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present disclosure relates to optical scanning safety sensors. [Background technology]

[0002] Optical scanning safety sensors are known to detect when people approach dangerous machinery or equipment in production sites. Optical scanning safety sensors scan the light emitted from the light-emitting element two-dimensionally and measure the direction and distance to an object based on the time it takes for the light-receiving element to receive the reflected light from the object (time of flight). Optical scanning safety sensors used for protecting people have the function of continuously testing the light-emitting and light-receiving elements.

[0003] For example, European Patent No. 2781938 (Patent Document 1) discloses a sensor having multiple reference sections arranged at different positions. Each reference section has a light-guiding element for guiding light emitted from a light-emitting element to a light-receiving element. The sensor performs a reference measurement to evaluate the amount of light received by the light-receiving element when light is incident on each reference section. In the reference measurement, the amount of received light depends on the type of reflectivity of the light-guiding element. Therefore, the sensor checks whether light is being projected and received normally by comparing the level of the amount of received light obtained in the reference measurement for each reference section with a target value corresponding to the light-guiding element. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] European Patent No. 2781938 Summary of the Invention [Problem to be solved by the invention]

[0005] In the technique described in Patent Document 1, the sensor becomes large due to the provision of multiple reference sections.

[0006] The present disclosure has been made in consideration of the above-described situation, and its purpose is to provide an optical scanning safety sensor that can be miniaturized while continuously determining whether light projection and light reception are normal or not. [Means for solving the problem]

[0007] An optical scanning safety sensor according to one aspect of the present disclosure includes a light-projecting element that emits laser light, a light-receiving element, a scanning mirror that scans the laser light in a circumferential direction around a rotation axis and directs reflected light of the laser light to the light-receiving element, a window that is arranged along the circumferential direction and allows the laser light to pass through, and a reference object that is arranged on the opposite side of the scanning mirror from the window and reflects the laser light toward the scanning mirror. The reference object has a first reflective surface that includes a first region and a second region having a lower reflectivity than the first region. The first region and the second region are arranged side by side along the circumferential direction. A first width of the first region along the circumferential direction is narrower than a second width of the second region along the circumferential direction. A spot width of the laser light projected on the reference object along the circumferential direction is wider than the first width.

[0008] According to this disclosure, a laser beam is scanned across a first region and a second region. When a large portion of the first region is included in the spot of the laser beam, the amount of light received by the light-receiving element depends on the reflectivity of the first region. On the other hand, when the area of ​​the first region included in the spot of the laser beam becomes small enough that the second region becomes dominant in the spot, the amount of light received by the light-receiving element depends on the reflectivity of the second region. Therefore, the optical scanning safety sensor can confirm whether light projection and reception are normal by evaluating the amount of light received for each of the two regions with different reflectivities. In addition, the optical scanning safety sensor can be made smaller by simply installing a reference object having a first reflective surface that satisfies the following conditions: first width < second width and spot width > first width.

[0009] In the above disclosure, the first region diffusely reflects the laser light. According to this disclosure, even if the light receiving element receives the light reflected from the first region, the output signal of the light receiving element does not saturate. Therefore, based on the amount of light received from the first region, the optical scanning safety sensor can determine whether the light reflected from the first region was received normally or whether the output signal of the light receiving element is saturated due to a failure of the light receiving element or its surrounding circuitry.

[0010] In the above disclosure, the reference object further includes a second reflecting surface orthogonal to the first reflecting surface, and one of the first reflecting surface and the second reflecting surface reflects the laser light and guides it to the other of the first reflecting surface and the second reflecting surface.

[0011] According to this disclosure, the reference object can retroreflect laser light, thereby increasing the tolerance for placement errors of the reference object.

[0012] In the above disclosure, the first reflective surface is formed by a single sheet. The first region is a region on the single sheet where a first color is printed. The second region is a region on the single sheet where a second color, which is less bright than the first color, is printed. According to this disclosure, the first reflective surface can be manufactured by a simple printing process. [Effects of the Invention]

[0013] According to the present disclosure, it is possible to provide an optical scanning safety sensor that can be miniaturized while continuously testing light projection and light reception. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a perspective view showing the appearance of an optical scanning safety sensor according to an embodiment; [Figure 2] 1 is a cross-sectional view of an optical scanning safety sensor according to an embodiment. [Figure 3] FIG. 2 is a diagram showing the optical path of a laser beam irradiated onto a reference object. [Figure 4] FIG. 2 is a perspective view showing a reference object. [Figure 5]FIG. 4 is a diagram showing a processing cycle of a control board. [Figure 6] 10 is a diagram showing the positional relationship between the reflecting surface of a reference object and the spot of laser light; FIG. [Figure 7] 10 is a diagram showing the relationship between the scanning position of the laser light and the amount of light received by the light receiving element. FIG. [Figure 8] FIG. 10 is a diagram showing the relationship between the scanning position of the laser light and the amount of light received by the light receiving element when the width Wa of the highly reflective region is 0.5 mm, 0.75 mm, 1 mm, 1.5 mm, and 2 mm. [Figure 9] FIG. 10 is a diagram showing the relationship between the scanning position of the laser light and the amount of light received by the light receiving element when the spot width W is 4.4 mm, 4.9 mm, 5.4 mm, 5.9 mm, and 6.4 mm. [Figure 10] 10 is a diagram showing the relationship between the scanning position of the laser light and the time (time of flight (ToF)) from when the laser light is emitted until the light receiving element receives the reflected light. FIG. [Figure 11] This figure shows the relationship between the scanning position of the laser light and the amount of light received by the light receiving element when high-reflection and low-reflection areas are provided on each of the two reflective surfaces, and when high-reflection and low-reflection areas are provided on one reflective surface and the entire surface of the other reflective surface has a uniform reflectivity. DETAILED DESCRIPTION OF THE INVENTION

[0015] 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.

[0016] Fig. 1 is a perspective view showing the appearance of an optical scanning safety sensor according to an embodiment. The optical scanning safety sensor 1 shown in Fig. 1 is, for example, a safety laser scanner.

[0017] For example, in the field of FA (Factory Automation), the optical scanning safety sensor 1 detects an object 2 (including a person) around the optical scanning safety sensor 1. The optical scanning safety sensor 1 detects that an object has entered a preset monitoring area. The detection result is used to stop the FA equipment.

[0018] 1, the optical scanning safety sensor 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.

[0019] The optical scanning safety sensor 1 scans with a laser beam 3 along a circumferential direction D centered on a rotation axis 10b that coincides with or is parallel to the central axis of an upper housing 10 having a generally inverted truncated cone shape. The laser beam 3 passes through a window 10a and is irradiated to the outside.

[0020] When an object 2 is present around the optical scanning safety sensor 1, the optical scanning safety sensor 1 receives reflected light 4 of the laser light 3. The optical scanning safety sensor 1 measures the distance to the object 2 based on the time (time of flight) between emitting the laser light 3 and receiving the reflected light 4. The optical scanning safety sensor 1 detects the presence or absence of the object 2 within a preset monitoring area based on the distance to the object 2 and the direction in which the laser light 3 is emitted.

[0021] Fig. 2 is a cross-sectional view of an optical scanning safety sensor according to an embodiment. As shown in Fig. 2, the optical scanning safety sensor 1 includes, as main components, a light-emitting unit 11, a deflection unit 12, a light-receiving unit 13, a control board 15, a power supply board 16, and a reference object 17.

[0022] The light-projecting unit 11 includes components related to light projection. Specifically, the light-projecting unit 11 includes a light-projecting element 110, a substrate 111, a shielding member 112, a lens holder 113, a lens 114, and a half mirror 115.

[0023] The light-projecting element 110 is, for example, a laser diode. The light-projecting element 110 emits 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-projecting element 110. The light-projecting element 110 is mounted on a substrate 111.

[0024] Shielding member 112 is cylindrical and is attached to substrate 111 so as to surround light-emitting element 110. Lens holder 113 is cylindrical and supports lens 114 therein. One end of lens holder 113 is inserted into shielding member 112. The other end of lens holder 113 supports half mirror 115.

[0025] A part of the shielding member 112 and the lens holder 113 form a cylindrical passage 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.

[0026] 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 rotation axis 10b, and guides the laser light 3 to the deflection unit 12. The lens holder 113 has an opening 116 above the half mirror 115. The laser light 3 reflected by the half mirror 115 passes through the opening 116 and is guided to the deflection unit 12.

[0027] 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 circumferential direction D (see FIG. 1) centered on the rotation axis 10b. If a window 10a exists in the irradiation direction of the laser beam 3, the laser beam 3 passes through the window 10a and is irradiated to the outside.

[0028] The deflection unit 12 includes a scanning mirror 121 , a motor 122 , and a shaft 123 .

[0029] The scanning mirror 121 has a reflecting surface 121a that forms an angle of 45° with the rotation axis 10b. The reflecting surface 121a faces the half mirror 115. Therefore, the scanning mirror 121 bends the laser light 3 received from the half mirror 115 in a direction perpendicular to the rotation axis 10b. The shaft 123 is attached to the back surface of the scanning mirror 121 along the rotation axis 10b. The motor 122 rotates the shaft 123. As a result, the scanning mirror 121 rotates around the rotation axis 10b while maintaining the angle between the scanning mirror 121 and the rotation axis 10b at 45°. As a result, the scanning mirror 121 scans the laser light 3 in the circumferential direction D around the rotation axis 10b.

[0030] Furthermore, the scanning mirror 121 receives the reflected light 4 of the laser light 3 and guides the reflected light 4 to the light receiving element 130 provided in the light receiving unit 13 .

[0031] The light receiving unit 13 includes a light receiving element 130, an amplifier 131, a substrate 132 on which the light receiving element 130 and the amplifier 131 are mounted, a filter 133, and a lens 134.

[0032] The lens 134 focuses the light guided by the scanning mirror 121 onto the light receiving element 130. 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 projecting element 110. For example, if the laser light 3 is infrared light, an IR filter is used as the filter 133.

[0033] The light receiving element 130 is an element that generates electric charges through photoelectric conversion, and is, for example, an avalanche photodiode. The light receiving element 130 outputs an output signal that represents the amount of received light. The amplifier 131 amplifies the output signal from the light receiving element 130.

[0034] IEC 61496-3, the product safety standard for safety laser scanners, requires that the sensor be able to detect objects with a reflectivity of 1.6%. However, the objects 2 whose distances are measured by the optical scanning safety sensor 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 sensor can measure the distance to objects 2 with various reflectivities. To achieve this 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 output signal from the light-receiving element 130 into a logarithmic scale. This allows the amplifier 131 to provide high gain for low-level signals and a gain that gradually decreases as the signal level increases. As a result, the optical scanning safety sensor 1 has a wide dynamic range.

[0035] The reference object 17 is disposed on the opposite side of the scanning mirror 121 from the window 10a, and reflects the laser light 3 received from the scanning mirror 121 toward the scanning mirror 121. In other words, the reference object 17 is a reflective member disposed between the scanning mirror 121 and the side of the upper housing 10 on which the window 10a is not formed.

[0036] FIG. 3 is a diagram showing the optical path of the laser light irradiated onto the reference object. FIG. 3 shows a cross-sectional view of the optical scanning safety sensor 1 when the reflecting surface 121a of the scanning mirror 121 faces the reference object 17. As shown in FIG. 3, the reference object 17 reflects the laser light 3 from the scanning mirror 121 and directs the reflected light 4 to the scanning mirror 121. The light-emitting unit 11, the deflection unit 12, the reference object 17, and the light-receiving unit 13 are installed in fixed positions. Therefore, the optical path length shown in FIG. 3 is constant.

[0037] The control board 15 controls the operation of each component inside the optical scanning safety sensor 1. The control board 15 includes, for example, a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit), a memory, and a storage, and controls each component in accordance with information processing.

[0038] During the period when the laser light 3 passes through the window 10a (hereinafter referred to as the "front scan period"), the control board 15 measures the distance to the object 2 based on the time from when the light projecting element 110 emits the laser light 3 to when the light receiving element 130 receives the reflected light 4. Based on the distance to the object 2 and the irradiation direction of the laser light 3, the control board 15 detects the presence or absence of the object 2 within a preset monitoring area.

[0039] The control board 15 determines whether the time (time of flight) from when the light projecting element 110 emits the laser light 3 to when the light receiving element 130 receives the reflected light 4 falls within a first reference range during a period in which the laser light 3 is irradiated onto the reference object 17. The first reference range includes the time required for the laser light 3 to travel from the light projecting element 110 to the light receiving element 130 along the optical path shown in FIG. 3. Furthermore, the control board 15 determines whether the amount of light received by the light receiving element 130 falls within a second reference range. The control board 15 may output an error signal if the time of flight falls outside the first reference range a predetermined number of times (e.g., two times) in succession, or if the amount of light received falls outside the second reference range a predetermined number of times (e.g., two times) in succession.

[0040] The power supply board 16 is mounted with various components for supplying power to the components of the optical scanning safety sensor 1 .

[0041] FIG. 4 is a perspective view showing a reference object. As shown in FIG. 4, reference object 17 includes a reflecting surface 171 and a reflecting surface 172 that is perpendicular to reflecting surface 171. This allows reference object 17 to retroreflect laser light 3. As a result, the tolerance for installation error of reference object 17 is increased. That is, as shown in FIG. 3, reflecting surface 171 guides laser light 3 from scanning mirror 121 to reflecting surface 172. Reflecting surface 172 reflects laser light 3 from reflecting surface 171 and guides reflected light 4 to scanning mirror 121. One of reflecting surfaces 171 and 172 is an example of a "first reflecting surface" in the present disclosure. The other of reflecting surfaces 171 and 172 is an example of a "second reflecting surface" in the present disclosure.

[0042] The reflective surface 171 includes a high-reflection region 171a and a low-reflection region 171b having a lower reflectivity than the high-reflection region 171a. The high-reflection region 171a and the low-reflection region 171b are adjacent to each other and in contact with each other. Similarly, the reflective surface 172 includes a high-reflection region 172a and a low-reflection region 172b having a lower reflectivity than the high-reflection region 172a. The high-reflection region 172a and the low-reflection region 172b are adjacent to each other and in contact with each other. The high-reflection regions 171a and 172a are examples of the "first region" in the present disclosure. The low-reflection regions 171b and 172b are examples of the "second region" in the present disclosure.

[0043] Laser light 3 from scanning mirror 121 is reflected by high reflection region 171a and travels to high reflection region 172a. Similarly, laser light 3 from scanning mirror 121 is reflected by low reflection region 171b and travels to low reflection region 172b.

[0044] The high-reflection regions 171a, 172a and the low-reflection regions 171b, 172b diffusely reflect the laser light. This allows the light-receiving element 130 to receive the reflected light 4 from the reference object 17 even if an error occurs in the placement of the reference object 17. In other words, robustness against an error in the placement of the reference object 17 is improved.

[0045] The reflectance of the high-reflection areas 171a and 172a is, for example, 80% or more, and the reflectance of the low-reflection areas 171b and 172b is, for example, 10% or less.

[0046] Each of reflective surfaces 171, 172 is formed, for example, by a single sheet. The sheet is printed in two colors. In the sheet forming reflective surface 171, high-reflection areas 171a are areas printed with a first color having a relatively high brightness, and low-reflection areas 171b are areas printed with a second color having a lower brightness than the first color. Similarly, in the sheet forming reflective surface 172, high-reflection areas 172a are areas printed with a first color having a relatively high brightness, and low-reflection areas 172b are areas printed with a second color having a lower brightness than the first color.

[0047] 5 is a diagram showing the processing cycle of the control board. As described above, the scanning mirror 121 scans the laser light 3 along the circumferential direction D. The scanning period of the laser light 3 is the period during which the scanning mirror 121 makes one rotation around the rotation axis 10b. The scanning period includes a front scanning period 51 during which the laser light 3 passes through the window 10a and is irradiated to the outside, and a back scanning period 52 during which the laser light 3 does not pass through the window 10a.

[0048] The control board 15 controls the light-projecting element 110 to emit the laser light 3, for example, every time the scanning mirror 121 rotates by 0.1°. In this case, the light-projecting element 110 emits the laser light 3 3,600 times in each scanning cycle. Hereinafter, the laser light 3 emitted first in the front scanning period 51 will be referred to as the laser light 3 with beam number "No. 0," and the laser light 3 emitted last in the front scanning period 51 will be referred to as the laser light 3 with beam number "No. 2699." Furthermore, the laser light 3 emitted first in the back scanning period 52 will be referred to as the laser light 3 with beam number "No. 2700." The laser light 3 emitted last in the back scanning period 52 will be referred to as the laser light 3 with beam number "No. 3599." Following the laser light 3 with beam number "No. k," the laser light 3 with beam number "No. k+1" is emitted.

[0049] The control board 15 repeatedly performs the measurement process 61 each time the laser light 3 having the beam numbers "No. 0" to "No. 2699" is emitted. The measurement process 61 is a process for measuring the distance to the object 2 based on the time from when the light-projecting element 110 emits the laser light 3 to when the light-receiving element 130 receives the reflected light 4.

[0050] As described above, the reference object 17 is disposed on the opposite side of the scanning mirror 121 from the window 10a. Therefore, the reference object 17 receives the laser light 3 during the backscan period 52. In the example shown in FIG. 5, the reference object 17 is disposed so as to receive the laser light 3 having the beam numbers "No. 3070" to "No. 3229." Therefore, the control board 15 performs a determination process 62 to determine whether the projection and reception of light are normal during the period when the laser light 3 having the beam numbers "No. 3070" to "No. 3229" is emitted. The determination process 62 includes a first process to determine whether the time (time of flight) from when the light-projecting element 110 emits the laser light 3 to when the light-receiving element 130 receives the reflected light 4 is within a first reference range, and a second process to determine whether the amount of light received by the light-receiving element 130 is within a second reference range.

[0051] 6 is a diagram showing the positional relationship between the reflecting surface of the reference object 17 and the spot of the laser light. The spot shape of the laser light 3 on the reflecting surface 171 of the reference object 17 depends on the shape of the opening 116 of the light projection unit 11. In the example shown in FIG. 6, the spot shape of the laser light 3 on the reflecting surface 171 is elliptical.

[0052] As shown in FIG. 6, on the reflecting surface 171, the high-reflection regions 171a and the low-reflection regions 171b are arranged side by side along the circumferential direction D, which is the scanning direction of the laser light 3. Therefore, the laser light 3 is scanned so as to traverse the high-reflection regions 171a and the low-reflection regions 171b. The width Wa of the high-reflection regions 171a along the circumferential direction D is narrower than the width Wb of the low-reflection regions 171b along the circumferential direction D. The spot width W of the laser light 3 projected onto the reference object 17 along the circumferential direction D is wider than the width Wa. Furthermore, the spot width W is wider than the width Wb. Furthermore, the spot width W is wider than the width of the sheet that constitutes the reflecting surface 171 (i.e., the sum of the width Wa and the width Wb, i.e., Wa+Wb).

[0053] In the reflecting surface 172, the width of the high reflecting region 172a along the circumferential direction D is Wa, and the width of the low reflecting region 172b along the circumferential direction D is Wb.

[0054] FIG. 7 is a diagram showing the relationship between the scanning position of the laser beam 3 and the amount of light received by the light receiving element. The scanning position of the laser beam 3 is represented by the beam number of the laser beam 3. Therefore, in the graph shown in FIG. 7, the horizontal axis represents the beam number of the laser beam 3, and the vertical axis represents the amount of light received. The amount of light received is represented by the output value of the amplifier 131. FIG. 7 shows the results of a simulation using the reference object 17 shown in FIGS. 4 and 6, where the width Wa is 1 mm, the width Wb is 3.5 mm, and the spot width is 5.4 mm.

[0055] 7, the period during which the laser beam 3 scans the reference object 17 includes a first stable period TA during which the amount of received light remains relatively large and stable, a fluctuating period TB during which the amount of received light gradually changes in response to the scanning of the laser beam 3, and a second stable period TC during which the amount of received light remains relatively small and stable. The fluctuating period TB is between the first stable period TA and the second stable period TC.

[0056] The first stable period TA includes the timing when laser light 3 with beam number "No. 3085" is emitted. As shown in FIG. 6, the spot center of laser light 3 with beam number "No. 3085" is located at the end of the reflective surface 171 on the side of the highly reflective region 171a. Therefore, the spot of laser light 3 includes most of the highly reflective region 171a. Therefore, it is estimated that the amount of light received during the first stable period TA depends on the reflectance of the highly reflective regions 171a and 172a.

[0057] The second stable period TC includes the timing when the laser beam 3 with beam number "No. 3214" is emitted. As shown in FIG. 6, the spot center of the laser beam 3 with beam number "No. 3214" is located at the end of the reflecting surface 171 on the low-reflection region 171b side. Therefore, the low-reflection region 171b is dominant in the spot of the laser beam 3. Therefore, it is estimated that the amount of light received during the second stable period TC depends on the reflectance of the low-reflection regions 171b and 172b.

[0058] Thus, even under the conditions where width Wa<width Wb and spot width W>width Wa are satisfied, the control board 15 can obtain, for example, the amount of light received by the light receiving element 130 when the laser beam 3 with beam number "No. 3085" is emitted as an amount of light received that depends on the reflectance of the high-reflection regions 171a and 172a. Furthermore, the control board 15 can obtain, for example, the amount of light received by the light receiving element 130 when the laser beam 3 with beam number "No. 3214" is emitted as an amount of light received that depends on the reflectance of the low-reflection regions 171b and 172b. Therefore, as the second process, the control board 15 can perform, for example, a process of determining whether the amount of light received by the light receiving element 130 when the laser beam 3 with beam number "No. 3085" is emitted is within a second reference range Ra that depends on the reflectance of the high-reflection regions 171a and 172a. Similarly, as the second process, the control board 15 can perform a process to determine whether the amount of light received by the light-receiving element 130 when emitting laser light 3 with beam number "No. 3214" is within a second reference range Rb corresponding to the reflectance of the low-reflection regions 171b and 172b. Therefore, with the optical scanning safety sensor 1 according to this embodiment, by performing the second process to evaluate the amount of light received for each of the two reflective regions with different reflectances, it is possible to confirm whether light projection and reception are normal. Furthermore, since it is only necessary to install a reference object 17 having a reflective surface 171 that satisfies the relationships: width Wa<width Wb and spot width W>width Wa, the optical scanning safety sensor 1 can be made smaller.

[0059] In order to eliminate the effects of measurement errors and noise in the amount of received light as much as possible, it is preferable that the control board 15 evaluates the amount of received light when laser beams 3 of multiple consecutive beam numbers (e.g., 24 beams) are emitted, rather than when laser beams 3 of a single beam number are emitted. For example, as shown in FIG. 7, the control board 15 may determine whether a representative value (e.g., average value) of the amount of received light by the light receiving element 130 when laser beams 3 of beam numbers "No. 3085" to "No. 3108" are emitted is within the second reference range Ra. Similarly, the control board 15 may determine whether a representative value of the amount of received light by the light receiving element 130 when laser beams 3 of beam numbers "No. 3191" to "No. 3214" are emitted is within the second reference range Rb. Furthermore, the control board 15 may evaluate the variation (e.g., variance) of the amount of received light when laser beams 3 of beam numbers "No. 3085" to "No. 3108" are emitted. Similarly, the control board 15 may evaluate the variation in the amount of received light (for example, the dispersion value) when the laser beams 3 with beam numbers "No. 3191" to "No. 3214" are emitted.

[0060] FIG. 8 shows the relationship between the scanning position of the laser beam and the amount of light received by the light receiving element when the width Wa of the highly reflective region is 0.5 mm, 0.75 mm, 1 mm, 1.5 mm, and 2 mm. Note that FIG. 8 also shows simulation results for the reference object 17 shown in FIGS. 4 and 6, where the sum of the widths Wa and Wb (Wa + Wb) is 4.5 mm and the spot width is 5.4 mm. As with FIG. 7, the period during which the laser beam 3 scans the reference object 17 includes a first stable period during which the amount of received light remains relatively large and stable, a fluctuating period TB during which the amount of received light gradually changes in response to the scanning of the laser beam 3, and a second stable period during which the amount of received light remains relatively small and stable. However, the lengths of the first stable period, fluctuating period TB, and second stable period vary depending on the width Wa.

[0061] When the width Wa is 0.5 to 1.5 mm, the fluctuation period TB does not overlap with the period for which the second process is to be performed (the period for beam numbers "No. 3085" to "No. 3108" and "No. 3191" to "No. 3214"). Therefore, it is preferable that the width Wa be 0.5 to 1.5 mm. In other words, it is preferable that the ratio (Wa / (Wa+Wb)) of Wa to the width of the reflecting surface 171 along the circumferential direction D (i.e., Wa+Wb) be 1 / 9 to 1 / 3.

[0062] When the width Wa is 0.75 to 1.5 mm, the difference between the fluctuation period TB and the period for which the second process is to be performed (the period for beam numbers "No. 3085" to "No. 3108" and "No. 3191" to "No. 3214") becomes even larger. Therefore, it is more preferable that the width Wa be 0.75 to 1.5 mm. In other words, it is more preferable that the ratio (Wa / (Wa+Wb)) of Wa to the width of the reflecting surface 171 along the circumferential direction D (i.e., Wa+Wb) be 1 / 6 to 1 / 3.

[0063] When the laser light 3 is specularly reflected by the high-reflection regions 171a and 172a, a strong amount of light may be guided to the light-receiving element 130. Generally, if the intensity of the light received by the light-receiving element 130 is too strong, the output signal of the light-receiving element 130 becomes saturated. Therefore, when the laser light 3 is specularly reflected by the high-reflection regions 171a and 172a, it is difficult to determine, based on the amount of light received by the light-receiving element 130 alone, whether the reflected light 4 from the high-reflection regions 171a and 172a was received normally or whether the output signal of the light-receiving element 130 has become saturated due to a malfunction of the light-receiving unit 13 (e.g., a circuit on the substrate 132). However, as described above, the high-reflection regions 171a and 172a diffusely reflect the laser light 3. Therefore, even when the light-receiving element 130 receives the reflected light 4 from the high-reflection regions 171a and 172a, the output signal of the light-receiving element 130 does not become saturated. This allows the control board 15 to determine, based on the amount of light received corresponding to beam numbers "No. 3085" to "No. 3108," whether the reflected light 4 from the highly reflective areas 171a, 172a has been received normally, or whether the light receiving unit 13 has malfunctioned and the output signal of the light receiving element 130 has become saturated.

[0064] FIG. 9 shows the relationship between the scanning position of the laser beam and the amount of light received by the light receiving element when the spot width W is 4.4 mm, 4.9 mm, 5.4 mm, 5.9 mm, and 6.4 mm. Note that FIG. 9 also shows simulation results for the reference object 17 shown in FIGS. 4 and 6, where the width Wa is 1 mm and the width Wb is 3.5 mm. As with FIG. 7, the period during which the laser beam 3 scans the reference object 17 includes a first stable period during which the amount of light received remains relatively large and stable, a fluctuating period during which the amount of light received gradually changes in response to the scanning of the laser beam 3, and a second stable period during which the amount of light received remains relatively small and stable. However, the lengths of the first stable period, fluctuating period, and second stable period vary depending on the spot width W.

[0065] 9, when the spot width W is in the range of 4.4 mm to 6.4 mm, the fluctuation period does not overlap with the period for which the second process is performed (the period for beam numbers "No. 3085" to "No. 3108" and "No. 3191" to "No. 3214"). Therefore, it is preferable that the spot width W is 4.4 mm to 6.4 mm. In other words, it is preferable that the ratio (W / (Wa+Wb)) of the spot width W to the width of the reflecting surface 171 along the circumferential direction D (i.e., Wa+Wb) is 0.98 to 1.42.

[0066] FIG. 10 is a diagram showing the relationship between the scanning position of the laser light and the time (time of flight (ToF)) from when the laser light is emitted until the light receiving element receives the reflected light. As shown in FIG. 10, when light projection and light reception are performed normally, the time of flight is stable. Therefore, as a first process, for example, the control board 15 determines whether the time of flight corresponding to the laser light 3 with beam numbers "No. 3085" to "No. 3108" and "No. 3191" to "No. 3214" is within a first reference range. This allows the control board 15 to confirm whether light projection and light reception are performed normally.

[0067] In the above description, reference object 17 has high-reflection regions and low-reflection regions on both reflecting surfaces 171 and 172. However, reference object 17 may have high-reflection regions and low-reflection regions on only one of reflecting surfaces 171 and 172, with the entire surface of the other surface designed to have a uniform reflectance. For example, the entire surface of reflecting surface 172 may have a uniform reflectance.

[0068] Fig. 11 shows the relationship between the scanning position of the laser beam and the amount of light received by the light receiving element when two reflecting surfaces each have a high-reflection region and a low-reflection region, and when one reflecting surface has a high-reflection region and a low-reflection region while the entire surface of the other reflecting surface has a uniform reflectance. That is, Fig. 11 shows the relationship between the scanning position of the laser beam and the amount of light received by the light receiving element when reflecting surfaces 171 and 172 have a high-reflection region and a low-reflection region, and when reflecting surface 171 has a high-reflection region and a low-reflection region while the entire surface of reflecting surface 172 has a uniform reflectance of 10%. Note that Fig. 11 shows the simulation results when width Wa is 1.0 mm and width Wb is 3.5 mm.

[0069] 11, in either case, there is a clear difference between the amount of light received by the light receiving element 130 when the laser beams 3 with beam numbers "No. 3085" to "No. 3108" are emitted and the amount of light received by the light receiving element 130 when the laser beams 3 with beam numbers "No. 3191" to "No. 3214" are emitted. Therefore, the control board 15 can determine whether the light projection and light reception are normal or not depending on whether the amount of light received by the light receiving element 130 when the laser beams 3 with beam numbers "No. 3085" to "No. 3108" are emitted is within the second reference range Ra based on the reflectivity of the high-reflection region 171a. Furthermore, the control board 15 can determine whether the light projection and light reception are normal depending on whether the amount of light received by the light receiving element 130 when emitting laser light 3 with beam numbers "No. 3191" to "No. 3214" is within a second reference range Rb corresponding to the reflectivity of the low-reflection region 171b.

[0070] <Additional Notes> As described above, the present embodiment includes the following disclosures.

[0071] (Configuration 1) An optical scanning safety sensor (1), a light-emitting element (110) that emits a laser beam (3); a light receiving element (130); a scanning mirror (121) that scans the laser light (3) in a circumferential direction around a rotation axis (10b) and guides reflected light (4) of the laser light (3) to the light receiving element (130); a window (10a) arranged along the circumferential direction and through which the laser light (3) can pass; a reference object (17) that is disposed on the opposite side of the window (121) with respect to the scanning mirror (121) and that reflects the laser light (3) toward the scanning mirror (121); the reference object (17) comprises a first reflecting surface (171, 172) including a first region (171a, 172a) and a second region (171b, 172b) having a reflectance lower than that of the first region (171a, 172a); The first regions (171a, 172a) and the second regions (171b, 172b) are arranged side by side along the circumferential direction, a first width (Wa) of the first region (171a, 172a) along the circumferential direction is narrower than a second width (Wb) of the second region (171b, 172b) along the circumferential direction; The optical scanning safety sensor (1) has a spot width (W) along the circumferential direction of the laser light (3) projected onto the reference object (17) that is wider than the first width (Wa).

[0072] (Configuration 2) 2. The optical scanning safety sensor according to configuration 1, wherein the first region (171a, 172a) diffusely reflects the laser light.

[0073] (Configuration 3) The reference object (17) further comprises a second reflecting surface (172, 171) perpendicular to the first reflecting surface (171, 172), The optical scanning safety sensor (1) according to configuration 1 or 2, wherein one of the first reflecting surface (171, 172) and the second reflecting surface (172, 171) reflects the laser light and guides it to the other of the first reflecting surface (171, 172) and the second reflecting surface (172, 171).

[0074] (Configuration 4) The first reflecting surface (171, 172) is formed of a single sheet, the first area (171a, 172a) is an area on the single sheet where a first color is printed, The optical scanning safety sensor (1) according to any one of configurations 1 to 3, wherein the second region (171b, 172b) is a region on the single sheet where a second color having a lower brightness than the first color is printed.

[0075] 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]

[0076] 1 optical scanning safety sensor, 2 object, 3 laser light, 4 reflected light, 10 upper housing, 10a window, 10b rotating shaft, 11 light emitting unit, 12 deflection unit, 13 light receiving unit, 15 control board, 16 power supply board, 17 reference object, 51 front scan period, 52 back scan period, 61 measurement processing, 62 judgment processing, 110 light emitting element, 111, 132 board, 112 shielding member, 113 lens holder, 114, 134 lens, 115 half mirror, 116 opening, 121 scanning mirror, 121a, 171, 172 reflective surface, 122 motor, 123 shaft, 130 light receiving element, 131 amplifier, 133 filter, 171a, 172a high reflection area, 171b, 172b low reflection area.

Claims

1. An optical scanning safety sensor, a light-emitting element that emits laser light; A light receiving element; a scanning mirror that scans the laser light in a circumferential direction around a rotation axis and guides reflected light of the laser light to the light receiving element; a window that is arranged along the circumferential direction and through which the laser light can pass; a reference object that is disposed on the opposite side of the scanning mirror from the window and that reflects the laser light toward the scanning mirror; the reference object has a first reflecting surface including a first region and a second region having a reflectance lower than that of the first region; The first region and the second region are arranged side by side along the circumferential direction, a first width of the first region along the circumferential direction is narrower than a second width of the second region along the circumferential direction; An optical scanning safety sensor, wherein a spot width along the circumferential direction of the laser light projected onto the reference object is wider than the first width.

2. The scanning optical safety sensor of claim 1 , wherein the first region diffusely reflects the laser light.

3. the reference object further comprises a second reflecting surface orthogonal to the first reflecting surface; 3. The optical scanning safety sensor according to claim 1, wherein one of the first reflecting surface and the second reflecting surface reflects the laser light and guides it to the other of the first reflecting surface and the second reflecting surface.

4. the first reflecting surface is formed by a single sheet, the first area is an area on the single sheet where a first color is printed, 3. The optical scanning safety sensor according to claim 1, wherein the second region is a region on the single sheet where a second color having a lower brightness than the first color is printed.

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