Light curtain

Abstract

The invention relates to a light curtain. The wiring workability under the condition that an operation indicating lamp is arranged on a light curtain of an optical synchronization system is improved. The light curtain includes a synchronization unit (optical axis for timing synchronization) for synchronizing the light projection timing of the light projector and the light reception timing of the light receiver by optical communication. A safety signal generated on the basis of whether or not an optical axis formed between the light projector and the light receiver is in a light-shielding state is output to the outside. The light curtain comprises a first operation indicating lamp arranged in the light projector; the second operation indicating lamp is arranged in the light receiver; an optical element (optical axis) provided in each of the light projector and the light receiver and configured to display the first operation indicator light and the second operation indicator light in conjunction with each other; and a control circuit configured to display the first operation indicating lamp and the second operation indicating lamp in linkage by using at least one group of optical elements.

Description

TECHNICAL FIELD

[0001] The present application relates to a light curtain. BACKGROUND

[0002] A light curtain is one aspect of a multi-optical-axis photosensor. A light curtain detects a person or an object based on whether a plurality of optical axes formed between a light projector and a light receiver are blocked.

[0003] Some light curtains include an operation indicator light. The operation indicator light is used to display information such as (1) an on or off state of a power supply, (2) an on or off state of an output signal switching device [OSSD] output (that is, a light incidence and light blocking state), and (3) an error state, for example. For example, the operation indicator light is turned off in a case where a plurality of light receiving elements provided in the light receiver all receive light beams emitted from a plurality of light projecting elements provided in the light projector, and the operation indicator light is turned on in other cases. In addition, when an error occurs in the light curtain, the on state of the operation indicator light also changes. An operator can visually recognize the operation state of the light curtain by looking at the operation indicator light of the light curtain.

[0004] In addition, in a light curtain, in terms of the detection principle of the optical axes, it is necessary to match the drive timings of the light projecting elements and the light receiving elements (that is, to synchronize the light projecting timing and the light receiving timing). There are two types of synchronization systems, a wired synchronization system and an optical synchronization system, which are known.

[0005] In the wired synchronization system, the light projector and the light receiver are connected by a cable, and the light projecting timing and the light receiving timing are synchronized by wired communication via the cable. The wired synchronization system is stronger in terms of light mutual interference than the optical synchronization system. However, in the wired synchronization system, wiring work of the cable is essential. In particular, in a case where the light projector and the light receiver are separated from each other, the wiring work easily becomes complicated.

[0006] In the optical synchronization system, a synchronization pulse is projected from the light projector. The synchronization pulse is a pulse signal used for timing synchronization and has a unique pulse pattern. The light receiver synchronizes the light receiving timing based on the light projecting timing of the synchronization pulse. The optical synchronization system does not require wiring work between the light projector and the light receiver, and has a high degree of wiring freedom. However, the optical synchronization system is weaker in terms of light mutual interference than the wired synchronization system.

[0007] Note that in recent years, in order to improve resistance to light mutual interference, the redundancy of detection pulses by increasing the speed of a detection circuit, and the improvement of interference resistance, and the like have been promoted.

[0008] Thus, the number of light curtains that adopt the optical synchronization system is increasing.

[0009] The operation indicator light is generally provided in both the light projector and the light receiver. In this case, it is necessary to link the lighting state of the operation indicator light in both the light projector and the light receiver. For example, for the (1) on or off state of the power supply and the (3) error state described above, the states of the light projector and the light receiver can be different from each other. On the other hand, for the (2) on or off state of the OSSD output (that is, the light incident and light shielding states), the lighting state of the operation indicator light needs to be common between the light projector and the light receiver.

[0010] Therefore, in order to improve the visibility of the operation indicator light, it is desirable to link the operation indicator light and display in both the light projector and the light receiver. In order to achieve such linked display of the operation indicator light, it is necessary to notify the light projector of the on or off state of the OSSD output from the light receiver.

[0011] For example, as disclosed in Japanese Patent Application Laid-Open No. 2002-124169, in a light curtain employing a wired synchronization system, the light projector and the light receiver are initially connected via a cable. Thus, it is sufficient to add a communication line for linked display control in the cable.

[0012] On the other hand, in a light curtain employing an optical synchronization system, there is no communication path from the light receiver to the light projector. Therefore, in order to link the operation indicator light and display in both the light projector and the light receiver, it is necessary to separately lay a communication line for linked display control between the light projector and the light receiver. That is, wiring work between the light projector and the light receiver is required, and the advantage of the optical synchronization system is weakened. SUMMARY

[0013] In view of the above problems, an object of the present application is to improve the wiring workability in the case where the operation indicator light is provided in a light curtain of an optical synchronization system.

[0014] The light curtain according to the present invention includes, for example: a projector comprising a plurality of first light-emitting elements; a receiver arranged facing the projector and comprising a plurality of first light-receiving elements configured to receive light beams projected from the plurality of first light-emitting elements; and a synchronization unit configured to synchronize the light-emitting timing of the projector with the light-receiving timing of the receiver via optical communication, wherein a safety signal generated based on whether each of the plurality of optical axes formed between the projector and the receiver is in a light-blocking state is output to the outside. The light curtain further includes: a first operation indicator light disposed in the projector and configured to display the operation status of the light curtain; a second operation indicator light disposed in the receiver and configured to display the operation status of the light curtain; at least one set of optical elements disposed in each of the projector and the receiver and configured to cause the first and second operation indicator lights to be displayed in conjunction; and a control circuit configured to use the at least one set of optical elements to cause the first and second operation indicator lights to be displayed in conjunction.

[0015] Note that other features, components, steps, advantages, and characteristics will become more apparent from the following detailed description and accompanying drawings.

[0016] According to the present invention, dedicated wiring for linking the operation indicator lights installed in both the projector and the receiver is no longer required. Therefore, wiring operability can be improved when operation indicator lights are installed within the light curtain of an optical synchronization system. Attached Figure Description

[0017] Figure 1 This is a schematic diagram illustrating the structure of a light curtain;

[0018] Figure 2 This is a three-dimensional diagram illustrating the overall structure of the projector;

[0019] Figure 3 This is a front view illustrating the overall structure of the projector;

[0020] Figure 4 This is a three-dimensional view illustrating one end of a projector;

[0021] Figure 5 This is a functional block diagram of the light curtain;

[0022] Figure 6 This is a diagram illustrating a first embodiment of the projector;

[0023] Figure 7 This is a diagram illustrating an example of the arrangement of the indicator light source according to the first embodiment;

[0024] Figure 8This is a diagram illustrating the relationship between the emitted light color and the operating mode;

[0025] Figure 9 This is a diagram illustrating an example of the arrangement of the indicator light source according to the second embodiment;

[0026] Figure 10 This is a diagram illustrating an example of a display pattern according to the second embodiment;

[0027] Figure 11 This is a diagram illustrating an example of the arrangement of indicator light sources and an example of the display pattern according to the third embodiment;

[0028] Figure 12 These are illustrations of an example of the arrangement of indicator light sources and an example of a display pattern according to the fourth embodiment;

[0029] Figure 13 This is a graph illustrating the relationship between average light intake and the displayed pattern;

[0030] Figure 14 This is a diagram illustrating the relationship between minimum light intake and the displayed pattern;

[0031] Figure 15 This is a diagram illustrating the illuminated image of the light screen (first example);

[0032] Figure 16 This is a diagram illustrating the illuminated image of the light screen (second example);

[0033] Figure 17 This is a functional block diagram of a light screen with display pattern control function;

[0034] Figure 18 This is a diagram illustrating the processing flow of display pattern control;

[0035] Figure 19 This is a diagram illustrating an example of the structure of a light curtain according to the fifth embodiment;

[0036] Figure 20 This is a schematic diagram illustrating an example of optical axis formation;

[0037] Figure 21 This is a diagram illustrating the processing flow of the linked display control;

[0038] Figure 22 This is a plan view illustrating an example structure of a light receiver;

[0039] Figure 23 This is a perspective view illustrating an example of the structure of a light receiver;

[0040] Figure 24 This is a diagram illustrating an example of light interference between multiple light curtains;

[0041] Figure 25 This is a diagram illustrating an example of optical axis drive control; and

[0042] Figure 26 This is a longitudinal cross-sectional view illustrating an example of a light receiver including a light leakage suppression mechanism. Detailed Implementation

[0043] <Light Curtain>

[0044] Figure 1 This is a schematic diagram illustrating the structure of a light curtain. The light curtain 1 in this example structure is one aspect of a multi-axis photoelectric sensor and generally includes a pair of projectors 100 and receivers 200.

[0045] The light curtain 1 detects people or objects based on whether at least one of the multiple optical axes (six optical axes Oax1 to Oax6 in the figure) formed at intervals between the parallel-arranged projectors 100 and receivers 200 is blocked. For example, the light curtain 1 is installed at the entrance of a hazardous area where a hazard source such as a press is located, and can be used as a safety device to detect the intrusion or presence of workers.

[0046] The projector 100 and the receiver 200 each include an elongated housing 110 and 210 (up to 2m or greater than 2m) and cables 120 and 220 connected to these housings.

[0047] The housing 110 includes a hollow metal outer shell 111 extending in the longitudinal direction, and hollow end caps 112 and 113 (corresponding to end members) respectively connected to both ends of the metal outer shell 111. Similarly, the housing 210 includes a hollow metal outer shell 211 extending in the longitudinal direction, and hollow end caps 212 and 213 (corresponding to end members) respectively connected to both ends of the metal outer shell 211. In this embodiment, the longitudinal direction is a direction that is substantially parallel to the direction in which a plurality of optical axes formed between the projector 100 and the receiver 200 are arranged at intervals.

[0048] As described above, when high-rigidity metal shells 111 and 211 are used as the outer shells of housings 110 and 210, the slender housings 110 and 210 are less likely to deform. Therefore, adjusting the arrangement of the projector 100 and receiver 200 (e.g., angular adjustment for arranging the two housings in parallel) becomes relatively easy. Note that, for example, inexpensive and lightweight extruded aluminum products can be used as the metal shells 111 and 211. In this case, regardless of where the metal shells are cut in the extrusion direction (= longitudinal direction), the metal shells 111 and 211 have the same cross-section.

[0049] Each of end caps 112, 113, 212, and 213 can be formed by injection molding using a resin material, or by die casting using a metal material such as zinc. Note that the interfaces with cables 120 and 220 can be mounted on end caps 113 and 213 on the lower side of the figure. Therefore, end caps 113 and 213 can be larger than end caps 112 and 212 on the upper side of the figure.

[0050] <Light emitter>

[0051] Figure 2 and Figure 3 These are, respectively, a perspective view and a front view illustrating the overall structure of the projector 100. Additionally, Figure 4 This is a perspective view illustrating one end of the projector 100.

[0052] As described above, the projector 100 includes a housing 110 and a cable 120. Additionally, the housing 110 includes a metal casing 111 and end caps 112 and 113. Furthermore, the projector 100 includes a front cover 130, an indicator light 140, and a buffer 150.

[0053] The front cover 130 is an elongated light-transmitting plate attached to cover the front opening (=detection window) of the housing 110. In the front opening of the housing 110, projection elements 161 to 166, forming multiple optical axes Oax1 to Oax6, are arranged at equal intervals along the longitudinal direction. That is, the front cover 130 is attached to the housing 110 to intersect with the multiple optical axes Oax1 to Oax6. The front cover 130 can be an extruded light-transmitting resin plate (acrylic plate, etc.) or a glass plate. In this embodiment, the light-transmitting properties of the component used as the front cover 130 refer to light-transmitting properties that achieve the following level: the light beams of the projection elements 161 to 166 forming the multiple optical axes Oax1 to Oax6 do not excessively diffuse beyond the optical axes and are received by the light-receiving elements 261 to 266, which will be described later, with a certain amount or more of light. As described above, since the light-transmitting component is used for the front cover 130, the operator can visually identify the projection elements 161 to 166 through the front cover 130.

[0054] Note that the projection element corresponds to at least one of the multiple optical axes Oax1 to Oax6. Figure 3 The projection elements 161 to 166 can be arranged within the end cap 113. That is, the projection elements 161 to 166 can be arranged at equal intervals in the longitudinal direction over the entire area from one end of the projector 100 to the other. Furthermore, instead of extending from the lower surface of the end cap 113, the cable 120 can extend from the back surface (or side surface) of the end cap 113. With this structure, the projector 100 can be mounted close to the mounting surface (floor surface, etc.). Therefore, a dead zone-free installation is possible.

[0055] The indicator light 140 is controlled to illuminate or extinguish in a color corresponding to, for example, the operating status of the light curtain 1 (optical axis detection status or self-diagnostic results, etc.) or work instructions related to placing and removing objects. In other words, the indicator light 140 serves as an operation indicator or work instruction light. Therefore, operators can visually identify the operating status or work instructions of the light curtain 1 by looking at the indicator light 140 of the light curtain 1.

[0056] Specifically, the indicator light 140 is arranged outward from the outer surface of at least one of the front cover 130 and the housing 110 along the longitudinal direction, or is formed in series with the front cover 130 (details of the construction will be described later). Referring to the figure, the indicator light 140 is disposed on both sides of the front cover 130. Using the indicator light 140 arranged or formed in this way, highly visible displays can be achieved without compromising the rigidity of the housing 110. More specifically, the indicator light 140 is an elongated extruded product and is arranged such that the longitudinal direction of the indicator light 140 is along the longitudinal direction of the housing 110. Note that the indicator light 140 can be arranged along the longitudinal direction of the housing 110, and its manufacturing method is not limited to extrusion molding, and the shape of the indicator light 140 does not have to be elongated. For example, multiple components serving as the indicator light 140 can be arranged along the longitudinal direction of the housing 110.

[0057] Furthermore, the indicator light 140 is a light-diffusing member that diffuses light incident from the indicator light source 170 (not shown) housed inside the housing 110 in various directions. More specifically, the indicator light 140 includes a light diffuser that diffuses light in various directions. In a structure where the light-diffusing member of the indicator light 140 includes a light diffuser, even if the number of indicator light sources 170 is small relative to the surface size of the indicator light 140, the indicator light 140 can be illuminated relatively uniformly, thus enabling a highly visible display. In this embodiment, the indicator light 140 is milky white because it is made of a transparent resin with added fine particles. In the case where the base resin is opaque and has a specific color, this specific color is mixed with the milky white. When the indicator light 140 is made of a milky white resin (such as silicone resin) in addition to a structure where the light-diffusing member includes a light diffuser, an operation for illuminating the indicator light 140 relatively uniformly can be obtained. The light-diffusing component of the indicator light 140 can be a component used to diffuse light from the indicator light source 170 so that the light can be visually identified from more directions, or a component used to diffuse light from the indicator light source 170 to a degree that makes it difficult to visually identify the outline of the indicator light source 170 from the outside of the indicator light 140. For example, a light-diffusing component having a surface processed to diffuse light from the indicator light source 170 can be arranged as the indicator light 140. For example, embossing is known as a surface processing method for diffusing light. By arranging a light-diffusing component with a processed surface as the indicator light 140, it is easy to manufacture such a component when a region in which light is relatively easy to diffuse and a region in which light is relatively difficult to diffuse are provided in a single component.

[0058] The buffer 150 protrudes outward from the area on the outer surface of the front cover 130 that intersects with the plurality of optical axes Oax1 to Oax6, and is arranged along the longitudinal direction of the housing 110 (the details of its construction will be described later).

[0059] Referring to the figure, a pair of buffers 150 are formed to protrude from both sides of the front cover 130. That is, the front cover 130 is positioned within a narrow valley between the pair of buffers 150 (a double buffer proposed by the applicant of this application) located on its sides and protruding forward. Therefore, even if an object collides with the front surface of the projector 100, its impact is absorbed by the buffers 150. Thus, the front cover 130 is unlikely to be damaged. Note that the buffers 150 can be made of a hard material such as metal.

[0060] Furthermore, the structure of the light receiver 200 is basically similar to that of the light projector 100. Therefore, in Figures 2 to 4In the description, the structure of the light receiver 200 can be understood by appropriately interpreting the light transmitter 100 and the light transmitter elements 161 to 166 using the light receiver 200 and the light receiving elements 261 to 266 respectively, and by appropriately replacing the reference numerals of the other 100 series with the reference numerals of the 200 series. Furthermore, this also applies to the following description.

[0061] <Function Block>

[0062] Figure 5 This is a functional block diagram of light curtain 1. In light curtain 1 of this structural example, projector 100 includes indicator light 140, projection elements 161 to 166, indicator light source 170, control circuit 181, and communication circuit 182.

[0063] The light-emitting elements 161 to 166 are arranged at equal intervals along the longitudinal direction of the light emitter 100 at predetermined spacing. Based on a light-emitting control signal input from the control circuit 181, the light-emitting elements 161 to 166 sequentially project multiple light beams, respectively forming multiple optical axes Oax1 to Oax6, toward the light receiver 200 (specifically, the light-receiving elements 261 to 266), in a time-division manner. Note that the light-emitting elements 161 to 166 may, for example, be light-emitting diodes that emit infrared light beams.

[0064] The indicator light source 170 supplies light for display to the indicator light 140 based on the display control signal input from the control circuit 181. The indicator light source 170 can switch between multiple light emission colors (e.g., red, green, and orange) according to the operating status or work instructions of the light screen 1.

[0065] Note that the indicator light source 170 can be pulsed at a timing offset relative to the timing of illumination or reception of each of the plurality of optical axes Oax1 to Oax6. This illumination or extinguishing control can suppress interference with optical axis detection using the indicator light source 170.

[0066] Indicator light 140 diffuses light incident from indicator light source 170 in all directions. Operators can visually identify the operating status or work instructions of light curtain 1 by checking indicator light 140.

[0067] In response to a command from the light receiver 200, the control circuit 181 generates a light-emitting control signal to sequentially drive the light-emitting elements 161 to 166 in a time-division multiplexing manner. Additionally, the control circuit 181 generates a display control signal to turn the indicator light source 170 on or off with any color. Furthermore, the control circuit 181 exchanges various types of information with the communication circuit 182.

[0068] The communication circuit 182 communicates with the light receiver 200 (specifically, the communication circuit 282) via wired or wireless communication. For example, the communication circuit 182 receives input from the light receiver 200 regarding information related to the operating status of the light curtain 1 (optical axis detection status and self-diagnostic results, etc.) and sends this information to the control circuit 181.

[0069] On the other hand, the light receiver 200 includes an indicator light 240, light receiving elements 261 to 266, an indicator light source 270, a control circuit 281, a communication circuit 282, an output circuit 283, and an input circuit 284.

[0070] Light-receiving elements 261 to 266 are arranged at equal intervals along the longitudinal direction of the light receiver 200, with the same spacing as the light-emitting elements 161 to 166. The light-receiving elements 261 to 266 sequentially receive multiple light beams for forming multiple optical axes Oax1 to Oax6 in a time-division manner based on a light-receiving control signal input from the control circuit 281. Note that the light-receiving elements 261 to 266 may be, for example, photodiodes or phototransistors that output an electrical signal corresponding to the amount of infrared light received.

[0071] The indicator light source 270 supplies light for display to the indicator light 240 based on the display control signal input from the control circuit 281. Similar to the indicator light source 170, the indicator light source 270 can switch between multiple light emission colors (e.g., red, green, and orange) according to the operating status or work instructions of the light screen 1.

[0072] Note that the indicator light source 270 can be pulsed at a timing offset relative to the timing of illumination or reception of each of the plurality of optical axes Oax1 to Oax6. This illumination or extinguishing control can suppress interference with optical axis detection using the indicator light source 270.

[0073] In addition, the case where the indicator light source 270 is continuously lit will be considered. In this case, it is desirable to provide a saturation prevention circuit (= DC component subtraction circuit) so that even if the DC light from the indicator light source 270 is received by the light receiving elements 261 to 266, the electrical signals output from the light receiving elements 261 to 266 will not be saturated.

[0074] Indicator light 240 diffuses light incident from indicator light source 270 in all directions. Operators can visually identify the operating status or work instructions of light curtain 1 by checking indicator light 240.

[0075] In addition, since indicator lights 140 and 240 are respectively located on the projector 100 and the receiver 200, a highly visible display can be achieved.

[0076] Control circuit 281 generates a light-receiving control signal to sequentially activate light-receiving elements 261 to 266 in a time-division manner, synchronized with the driving timing of each of the light-emitting elements 161 to 166. Additionally, control circuit 281 generates a display control signal to turn indicator light source 270 on or off with any emission color. Furthermore, control circuit 281 exchanges various types of information with communication circuit 282, output circuit 283, and input circuit 284.

[0077] In addition, the control circuit 281 monitors the light incidence or blocking state of each of the plurality of optical axes Oax1 to Oax6. For example, when all of the plurality of optical axes Oax1 to Oax6 are in the light incidence state, the control circuit 281 can output an operation permission signal (ON signal). On the other hand, when at least one of the plurality of optical axes Oax1 to Oax6 is in the blocking state, the control circuit 281 can output an operation disallow signal (OFF signal).

[0078] Furthermore, the control circuit 281 may have the function of self-diagnosing whether it can correctly monitor the light incidence state or shading state of each of the multiple optical axes Oax1 to Oax6. Note that, as a self-diagnostic method, for example, the control circuit 281 and the output circuit 283 (e.g., the output signal switching device [OSSD] output) may be multiplexed, and the consistency or inconsistency of the multiplexed signals may be determined.

[0079] For example, when the multiplexed signals are consistent with each other, an OK diagnosis is made (=a diagnosis indicating that the status can be monitored correctly). On the other hand, when the multiplexed signals are inconsistent with each other, an NG diagnosis is made (=a diagnosis indicating that the status cannot be monitored correctly). Note that in the case of an NG diagnosis, regardless of the light incident state of each of the multiple optical axes Oax1 to Oax6, an operation non-permit signal (OFF signal) can be output.

[0080] Note that information that can be used for safety control is safety information, and general information that cannot be used for safety control is unsafe information. For example, the OSSD output is a safety message. The signal used to control the lighting or extinguishing of each of the indicator lights 170 and 270 can be a signal indicating safety information or a signal indicating unsafe information.

[0081] The communication circuit 282 performs wired or wireless communication with the projector 100 (specifically, the communication circuit 182). For example, the communication circuit 282 receives input from the control circuit 281 regarding information related to the operating status of the light curtain 1 (optical axis detection status and self-diagnostic results, etc.) and sends that information to the projector 100.

[0082] The output circuit 283 communicates with an external machine (e.g., a safety controller) via wired or wireless means. For example, the output circuit 283 receives input from the control circuit 281 regarding the operating status of the light curtain 1 (optical axis detection status or self-diagnostic results, etc.) and sends this information to the external machine.

[0083] The input circuit 284 communicates with an external machine (e.g., a safety controller) via wired or wireless means. For example, the input circuit 284 receives an input of a work instruction related to placing and retrieving an object from the external machine and sends the work instruction to the control circuit 281.

[0084] <First Embodiment>

[0085] Figure 6 This is a diagram illustrating a first embodiment of the projector 100 (= schematic cross-sectional view when the metal housing 111 of the projector 100 is cut at any position in the longitudinal direction). The projector 100 of this embodiment includes a housing 110 (only the metal housing 111 is depicted in this figure), a front cover 130, an indicator light 140, a buffer 150, an indicator light source 170, a substrate 190, and a light shield 191.

[0086] The metal casing 111 is an extruded product extending in the longitudinal direction of the projector 100. Referring to the figure, the metal casing 111 includes a body 111a, a pair of first protruding strips 111b, and a pair of second protruding strips 111c.

[0087] The main body 111a is a hollow member with a U-shaped cross-section and an opening on the upper side (the front side of the projector 100) of the figure. The indicator light source 170, the substrate 190, and the light shield 191 are housed in the internal space of the main body 111a.

[0088] A pair of first protruding strips 111b protrude from the inner surfaces of the left and right side walls of the main body 111a toward the interior of the opening. That is, the pair of first protruding strips 111b are arranged to face each other at a predetermined interval, thereby clamping the optical axis intersection region X (the region intersecting with the plurality of optical axes Oax1 to Oax6). Note that the pair of first protruding strips 111b serve as a cover attachment for supporting the front cover 130. As described above, a light-transmitting member is used for the front cover 130, provided that the light-transmitting member is at least provided in the optical axis intersection region X and the optical axes Oax1 to Oax6 are unobstructed. For example, in this embodiment, the portion in contact with the pair of first protruding strips 111b does not necessarily need to be light-transmitting.

[0089] A pair of second protruding strips 111c extend further upward from the upper ends of the left and right side walls of the body 111a in this figure. Additionally, each of the pair of second protruding strips 111c has a distal end that curves inward toward the opening. Note that the pair of second protruding strips 111c serve as a buffer 150 for protecting the front cover 130. That is, in this embodiment, the buffer 150 is formed of a metal housing 111. Therefore, the robustness of the projector 100 can be enhanced.

[0090] The front cover 130 is supported (suspended) at both ends across a pair of first protruding strips 111b. The front cover 130 allows light beams forming multiple optical axes Oax1 to Oax6 to pass through the optical axis intersection region X. A treatment to improve liquid resistance is performed between the front cover 130 and the pair of first protruding strips 111b (see thick line α). For example, a treatment is performed for arranging filler and bonding using a liquid-resistant adhesive. As described later, the liquid resistance is further improved by using the indicator light 140 to enhance the adhesive properties between the front cover 130 and the first protruding strips 111b.

[0091] Indicator lights 140 are arranged on both sides of the front cover 130 adjacent to the buffer 150. Referring to the figure, the indicator lights 140 are arranged along the longitudinal direction of the projector 100 in the area sandwiched between the distal ends (bends) of the first protrusion 111b and the second protrusion 111c, that is, in the area sandwiched between the buffer 150 and the front cover 130.

[0092] Note that the indicator light 140 diffuses light incident from the indicator light source 170 via the front cover 130 in various directions. For example, the indicator light 140 may have a trapezoidal shape for refracting and diffusing light incident from the indicator light source 170 toward the interior of the opening.

[0093] The indicator lights 140, arranged in this manner, are easily visible even from the side of the projector 100. Therefore, in a small (small diameter) light screen 1 using a metal housing 111, highly visible displays can be achieved without compromising the rigidity of the housing 110. In particular, the effect of improving visibility through the above arrangement is even more significant when a pair of buffers 150 are configured to protrude from both sides of the front cover 130.

[0094] Furthermore, in the projector 100 of this embodiment, the indicator light 140 also serves as a pressing member for pressing down (in the direction toward the first protruding strip 111b) and securing the front cover 130. Therefore, due to the enhanced adhesive properties between the front cover 130 and the first protruding strip 111b, liquid resistance can be improved by preventing liquid from entering the interior of the metal housing 111. Note that in order for the indicator light 140 to function as a pressing member, it is desirable for the indicator light 140 to have appropriate elasticity.

[0095] The indicator light source 170 is mounted on the main surface (the surface facing the front cover 130) of the substrate 190. The indicator light source 170 supplies light for display to the indicator light 140 via the front cover 130. Referring to this figure, the light emitted from the indicator light source 170 passes between the pair of first protrusions 111b without being blocked by them, and is supplied to the indicator light 140 via the front cover 130.

[0096] Note that the number of indicator light sources 170 is not limited. For example, multiple indicator light sources 170 can be arranged intermittently or connected in series along the longitudinal direction of the projector 100.

[0097] Additionally, the indicator light source 170 may include a lens for controlling the direction of the emitted light. For example, a lens may be provided that is optically designed to reduce the divergence angle of light in the left-right direction and increase the divergence angle of light in the depth direction of the figure. With such a lens, the number of indicator light sources 170 can be reduced while suppressing interference with multiple optical axes Oax1 to Oax6.

[0098] Note that the lens type can be a point-symmetric lens (single lens arrangement) or a cylindrical lens (using a series arrangement of extruded products).

[0099] A light shield 191 is disposed between the indicator light source 170 and the optical axis intersection region X. Therefore, since the light from the indicator light source 170 toward the optical axis intersection region X is blocked, the light emitted from the indicator light source 170 is unlikely to interfere with the multiple optical axes Oax1 to Oax6.

[0100] Additionally, consider the following scenario: optical axes Oax1 to Oax6 are formed by infrared light and visible light (red, green, or orange, etc.) is emitted from the indicator light source 170. In this case, a filter that allows infrared light to pass through and blocks visible light can be provided in the light receiver 200. Specifically, when the indicator light 240 is provided in the light receiver 200, a filter that allows infrared light to pass through and blocks visible light can be arranged so as not to obstruct the display of the indicator light 240. The filter can be provided in the light receiving elements 261 to 266, or it can be provided in the lens that guides the light to the light receiving elements 261 to 266.

[0101] Figure 7 This is a diagram illustrating an example arrangement of the indicator light source 170 according to the first embodiment. As illustrated in the diagram, the light-emitting elements 161 to 166 can be arranged at equal intervals in the central region 190a of the substrate 190 along the longitudinal direction of the substrate 190. On the other hand, the indicator light source 170 can be arranged at equal intervals in the end region 190b of the substrate 190 along the longitudinal direction of the substrate 190.

[0102] Specifically, the light-emitting elements 161 to 166 and the indicator light source 170 can be arranged such that their positions in the longitudinal direction of the substrate 190 are shifted (interlaced) relative to each other. According to such an arrangement example, mutual interference between the light-emitting elements 161 to 166 and the indicator light source 170 is suppressed.

[0103] Note that the number and arrangement of the indicator light sources 170 are not limited to the arrangement example shown in this figure. For example, the number of indicator light sources 170 can be reduced, resulting in some unevenness in the beam supplied to the indicator light 140.

[0104] <Display content>

[0105] Figure 8 This is a diagram illustrating the relationship between the light color of indicator light 140 and the operating mode. As illustrated in the diagram, indicator light 140 can be switched between an operation indicator light mode and a work instruction light mode. For example, the control signal used to switch the operating mode of indicator light 140 can be a 2-bit (quad-value) digital signal input to input circuit 284.

[0106] First, the scenario where indicator light 140 is set to operation indicator light mode will be described. When operation indicator light mode is set, indicator light 140 is controlled to illuminate or extinguish with a light emission color corresponding to the operation state of light curtain 1.

[0107] Referring to the figure, for example, when the light curtain 1 is in a normal state (e.g., all optical axes Oax1 to Oax6 are unobstructed), indicator light 140 illuminates in green. On the other hand, when the light curtain 1 is in an abnormal state (e.g., an emergency stop state where at least one of the optical axes Oax1 to Oax6 is obstructed), indicator light 140 illuminates in red. Additionally, when the light curtain 1 is in an alarm notification state (e.g., an NG diagnostic state utilizing the self-diagnostic function), indicator light 140 flashes in red.

[0108] Next, the scenario where indicator light 140 is set to work instruction light mode will be described. When work instruction light mode is set, indicator light 140 is controlled to light up or turn off with a light color corresponding to the work instruction signal received by input circuit 284.

[0109] Referring to the diagram, for example, when the work instruction signal indicates "work permitted status," indicator light 140 illuminates in green. Conversely, when the work instruction signal indicates "work prohibited status," indicator light 140 illuminates in red. Additionally, when the work instruction signal indicates "self-diagnosis," indicator light 140 flashes red. Note that in work instruction light mode, indicator light 140 can illuminate in orange. The method used to determine the illumination status can be varied depending on the user.

[0110] In addition, when the light curtain 1 is used in an environment where the illumination of the indicator light 140 is not desired, the indicator light 140 can always be turned off.

[0111] <Considerations related to the reduction of light received by the optical axis>

[0112] As described above, a light curtain comprises two components: a projector and a receiver, with multiple projecting elements and multiple receiving elements arranged along the axial direction. When using a light curtain, the projector and receiver are arranged in parallel, and their angles are adjusted so that all elements receive sufficient light. The greater the distance between the projector and receiver, the more difficult it is to determine if the orientation is correct, and the harder it is to see the display. Consequently, adjusting the angle becomes difficult.

[0113] Light curtains can be used in harsh environments such as dusty or bumpy conditions. Therefore, products with a buffer shape protruding from the front cover exist to protect the front cover of the detection unit. However, it is difficult to prevent dust from adhering to the front cover. When dust accumulates and the light-receiving element cannot receive sufficient light, the optical axis is blocked, and there is a possibility that the device's activation will stop due to the safety output from the light curtain. Therefore, maintenance is required to clean the glass surface of the front cover before the detection results of the optical axis are affected.

[0114] In dusty environments, light curtains are required to ensure sufficient light intake along the optical axes to compensate for reductions in light intake (the amount of light received by each optical axis, used as a criterion for determining whether the optical axis is in a shaded state) due to dust. Additionally, maintenance is necessary before the optical axes become shaded by monitoring the reduction in light intake over time.

[0115] In response to the above requirements, there are models that can use the main body of the light curtain to confirm the amount of light received along the optical axis. For example, in existing models, the amount of light received along the optical axis is represented by the number of lit LEDs or a seven-segment digital display. However, these displays are small and difficult to see from a distance. Therefore, it may be difficult to confirm the display when adjusting the installation of the light curtain. In addition, even during the operation of the light curtain, it is difficult to notice the reduction in the amount of light received along the optical axis unless the small display is consciously checked.

[0116] On the other hand, large indicator lights 140 and 240 are provided in the light curtain 1 described in this specification so far, so that the activation state of the light curtain 1 can be easily identified visually while achieving both reduced size and high visibility.

[0117] In view of the above considerations, a novel embodiment is proposed below in which a display linked to the amount of light received along the optical axis can be made using highly visible indicator lights 140 and 240.

[0118] <Second Embodiment>

[0119] Figure 9 This is a diagram illustrating an example arrangement of the indicator light source according to the second embodiment. In this embodiment, multiple substrates 190 (two in this figure) having the same structure are cascaded together along the longitudinal direction. Using such a structure, the light curtain 1 can be easily extended by simply increasing the number of cascaded substrates 190.

[0120] In this diagram illustrating the projector 100, similar to the above... Figure 7 The light-emitting elements 161 to 166 can be arranged at equal intervals along the longitudinal direction of the substrate 190 in the central region 190a of the substrate 190. Referring to the figure, on the substrate 190 on the right side of the figure, the light-emitting elements 161 to 163 are arranged from right to left in the illustrated order. On the other hand, on the substrate 190 on the left side of the figure, the light-emitting elements 164 to 166 are arranged from right to left in the illustrated order. Note that, in understanding the structure of the light receiver 200, each of the light-emitting elements 161 to 166 can be interpreted as a light-receiving element 261 to 266.

[0121] On the other hand, the indicator light sources 170 can be arranged at equal intervals along the longitudinal direction of the substrate 190 in the end region 190b of the substrate 190. Specifically, depending on the differences in each control system, the indicator light sources 170 can be distinguished as indicator light sources 170a, 170b, and 170c. Referring to the figure, on both substrates 190, the indicator light sources 170a, 170b, and 170c are arranged from left to right in the illustrated order. Note that, although not illustrated in the figure, separate from the indicator light sources 170, the light curtain 1 includes OSSD indicator lights whose display aspect changes according to the OSSD output. Therefore, the display aspect of the indicator light sources 170 changes to indicate the light-receiving state of the light-receiving elements 261 to 266.

[0122] As described above, the light-emitting elements 161 to 163 (or 164 to 166) and the indicator light sources 170a, 170b and 170c are arranged as a unit on a common substrate 190. In particular, the indicator light sources 170a, 170b and 170c are unified into a group of three light sources.

[0123] Note that, as a variation, the light-emitting elements 161 to 163 (or 164 to 166) and the indicator light sources 170a, 170b and 170c can be separate units. That is, the unit with the light-emitting elements 161 to 163 (or 164 to 166) and the unit with the indicator light sources 170a, 170b and 170c can be independent of each other.

[0124] Figure 10This is a diagram illustrating an example of a display pattern according to the second embodiment. At the top of the diagram, a "lit state" (a) is depicted. In this "lit state," indicator light source 170a is lit, while indicator light sources 170b and 170c are both off. Thus, a display pattern of "lit 1, off 2" repeating from left to right in this diagram is obtained.

[0125] In the center of the diagram, the "ab lit state" is depicted. In this "ab lit state," both indicator lights 170a and 170b are lit, while indicator light 170c is off. Thus, a display pattern of "lit 2, off 1" repeats from left to right in the diagram is obtained.

[0126] At the bottom of the diagram, the "abc illuminated state" is depicted. In this "abc illuminated state," indicator lights 170a, 170b, and 170c are all lit.

[0127] As described above, in the display pattern example according to this embodiment, the indicator light sources 170a, 170b, and 170c are appropriately illuminated intermittently. Therefore, the display pattern is switched to any of the three patterns based on the amount of light received along the optical axis, thus allowing the amount of light received along the optical axis to be distinguished simply by looking at the large indicator lights 140 and 240. As a result, a light curtain 1 that is easy to adjust during initial setup and has high maintainability is provided.

[0128] <Third Embodiment>

[0129] Figure 11 This diagram illustrates an example of the arrangement of indicator light sources and an example of the display pattern according to the third embodiment. In this embodiment, two indicator light sources 170a, two indicator light sources 170b, and two indicator light sources 170c are arranged as a unit on a common substrate 190. That is, the indicator light sources 170a, 170b, and 170c are unified into a group of six light sources.

[0130] Referring to the figure, on the substrate 190, two indicator light sources 170a, two indicator light sources 170b and two indicator light sources 170c are arranged from left to right in the illustrated order.

[0131] At the top of the diagram, the "a-lit state" is depicted. In this "a-lit state," indicator light source 170a is lit, while indicator light sources 170b and 170c are both off. Thus, a display pattern of "lit 2, off 4" repeating from left to right in the diagram is obtained.

[0132] In the center of the diagram, the "ab lit state" is depicted. In this "ab lit state," both indicator lights 170a and 170b are lit, while indicator light 170c is off. Thus, a display pattern of "lit 4, off 2" repeats from left to right on the paper is obtained.

[0133] At the bottom of the diagram, the "abc illuminated state" is depicted. In this "abc illuminated state," indicator lights 170a, 170b, and 170c are all lit.

[0134] Note that in the second embodiment described above ( Figure 10 In the display pattern, the number of indicator light sources 170a, 170b and 170c that are in the non-lit state (off state) increases or decreases by one for each display pattern, such as 2, 1 and 0.

[0135] On the other hand, in the example arrangement of the indicator light sources and the example display pattern according to this embodiment, the number of indicator light sources 170a, 170b, and 170c in the non-lit state is increased or decreased by two for each display pattern, such as 4, 2, and 0. Therefore, compared with the second embodiment described above ( Figure 10 In contrast, the difference in distance between light sources that are intermittently lit becomes larger. As a result, the switching of the display pattern (and the change in the amount of light received by the optical axis) can be easily identified by the light diffuser.

[0136] <Fourth Embodiment>

[0137] Figure 12 This is a diagram illustrating an example of the arrangement of indicator light sources and an example of the display pattern according to the fourth embodiment. Similar to the second embodiment described above ( Figure 10 In this embodiment, the indicator light sources 170a, 170b, and 170c are grouped into three. However, the arrangement order of the indicator light sources 170a, 170b, and 170c varies for each substrate 190.

[0138] Referring to the figure, on the substrate 190 on the left side of the figure, indicator light sources 170a, 170b, and 170c are arranged from left to right in the illustrated order. On the other hand, on the substrate 190 on the right side of the figure, indicator light sources 170a, 170b, and 170c are arranged from right to left in the illustrated order.

[0139] At the top of the diagram, the "a-lit state" is depicted. In this "a-lit state," indicator light source 170a is lit, while indicator light sources 170b and 170c are both off. Thus, a display pattern of "lit 1, off 4, lit 1" repeats from left to right in the diagram.

[0140] At the bottom of the diagram, the "bc lit state" is depicted. In this "bc lit state," indicator light 170a is lit, while indicator lights 170b and 170c are both off. Thus, a display pattern of "off 1, lit 4, off 1" is obtained, repeating from left to right in the diagram.

[0141] As described above, in the example arrangement and display pattern of the indicator light sources according to this embodiment, while maintaining a group of three units, the number of indicator light sources 170a, 170b, and 170c in the non-lit state is increased or decreased by two per display pattern, such as 4, 2, and 0. Therefore, similar to the third embodiment described above ( Figure 11 It is easy to identify the switching of the display pattern (and the change in the amount of light received by the optical axis).

[0142] <The Relationship Between Light Received Along the Optical Axis and the Displayed Pattern>

[0143] Figure 13 This is a graph illustrating the relationship between the light received along the optical axis (average light received) and the displayed pattern. The light received along the optical axis is converted by an A / D converter and compared with a threshold. The criterion used to determine the displayed pattern can be the average light received along the optical axis (= average light received).

[0144] First, the ON (on) state of the OSSD indicates the following state: for light-receiving elements 261 to 266, the condition "the amount of light received by all optical axes is a first threshold or greater than a first threshold" is met, and the OSSD output is ON. In this embodiment, for convenience, the state where light-receiving elements 261 to 266 meet this condition and the OSSD output can become ON is set to a determined ON (on) state, and the determined ON state is the state where "the amount of light received by all optical axes is a first threshold or greater than a first threshold". The first threshold is the same as the threshold used to determine whether each individual optical axis is in a light-blocking state. Therefore, the average amount of light received in this state is high to a certain extent and cannot be low enough to be considered a "completely light-blocking" value. That is, since the amount of light received by all optical axes is a first threshold or greater than a first threshold, the average amount of light received cannot drop below the first threshold.

[0145] Therefore, the "OFF" display when the average light received amount drops below the first threshold can be understood as the following display aspect: the light receiving elements 261 to 266 do not meet the condition that "the light received amount of all optical axes is the first threshold or greater than the first threshold" (that is, they are only in the determined OFF state). In this figure, a horizontal axis is introduced to clarify this display aspect. The horizontal axis indicates the result of the individual light received amount determination for each optical axis (= the number of optical axes determined to be in the light-blocking state by individual optical axis determination). Note that the OFF state of the OSSD indicates the following state: the light receiving elements 261 to 266 do not meet the condition that "the light received amount of all optical axes is the first threshold or greater than the first threshold", and the OSSD output is OFF. In this embodiment, for convenience, the state in which the light receiving elements 261 to 266 do not meet the condition that "the light received amount of all optical axes is the first threshold or greater than the first threshold" (that is, the state in which "the light received amount of at least one or more optical axes is less than the first threshold") is considered to be the determined OFF state. In other words, when the ON state is determined, the number of optical axes in the light-blocking state is 0. On the other hand, when the OFF state is determined, the number of optical axes in the light-blocking state is 1 or more.

[0146] Note that the individual light intake determination for each optical axis is performed only when the ON state (display color: green) and OFF state (display color: red). Therefore, the step of performing this determination on the flowchart described later is the same as the step of comparing the average light intake with a threshold.

[0147] Furthermore, in determining the ON and OFF states, the threshold used as the criterion for determining the number of indicator lights 170a, 170b, and 170c illuminated is shifted. First, the ON state will be described. As mentioned above, the ON state is determined when the light received along all optical axes is at or greater than the first threshold. Therefore, in determining the ON state, thresholds (the fourth and fifth thresholds in this figure) are set in areas with relatively high average light received light for determining the number of indicator lights illuminated.

[0148] Referring to the diagram, when the average light intensity in the ON state is below the fourth threshold, one green light is illuminated (i.e., only indicator light source 170a is illuminated in green). When the average light intensity is above the fourth threshold but below the fifth threshold, two green lights are illuminated (i.e., indicator light sources 170a and 170b are illuminated in green). When the average light intensity is above the fifth threshold, three green lights are illuminated (i.e., indicator light sources 170a, 170b, and 170c are illuminated in green). In other words, as the average light intensity increases, the number of illuminated green lights increases.

[0149] Note that as the distance between the projector 100 and the receiver 200 increases, the amount of light received along each optical axis decreases. Although the projector 100 and the receiver 200 are arranged in parallel and can generally receive light without contamination, it is conceivable that the amount of light received decreases only due to the increase in the distance between the projector 100 and the receiver 200.

[0150] When the number of indicator lights 170a, 170b, and 170c illuminated decreases under such circumstances, information related to installation and maintenance cannot be transmitted correctly. Therefore, it is desirable to set a threshold to widen the area where the number of indicator lights 170a, 170b, and 170c illuminated is three. Referring to the figure, in the ON state, the fifth threshold used to switch the number of indicator lights 170a, 170b, and 170c illuminated between three and two is set to a relatively low value.

[0151] Next, the OFF state will be described. Controlling the switching of the display pattern in the OFF state is useful when installing the projector 100 and receiver 200. For example, consider the following scenario: starting from an off state where the number of indicator lights is 0, the installation positions of the projectors 100 and 200 are adjusted. In this case, to ensure the directionality of the adjustment (i.e., whether the installation position is close to the correct installation position), it is desirable to switch the display pattern even if the average amount of light received increases or decreases slightly.

[0152] Therefore, in the OFF state, thresholds (the first threshold, the second threshold, and the third threshold in this figure) are set in areas with relatively low average light intensity to switch the number of indicator lights illuminated. For example, as illustrated in the figure, the relationship between the thresholds could be: first threshold < second threshold < third threshold < fourth threshold < fifth threshold. In the embodiment illustrated in the figure, the first threshold, the second threshold, and the third threshold do not affect the switching of the number of indicator lights illuminated in the ON state.

[0153] Referring to the diagram, when the average light intensity in the OFF state is below the first threshold, the state becomes off (i.e., indicator lights 170a, 170b, and 170c are off), as described above. When the average light intensity is above the first threshold but below the second threshold, one red light is illuminated (i.e., only indicator light 170a is illuminated in red). When the average light intensity is above the second threshold but below the third threshold, two red lights are illuminated (i.e., indicator lights 170a and 170b are illuminated in red). When the average light intensity is above the third threshold, three red lights are illuminated (i.e., indicator lights 170a, 170b, and 170c are illuminated in red). In other words, as the average light intensity increases, the number of illuminated red lights increases.

[0154] As described above, the purpose of switching the display pattern differs depending on the amount of light received along the optical axis in the ON and OFF states. Specifically, it is assumed that switching to a green light display pattern in the ON state is useful for monitoring dust adhesion (necessity of maintenance) after the operation of the light screen 1 has begun. On the other hand, it is assumed that switching to a red light display pattern in the OFF state is useful for adjusting the optical axis during the installation of the light screen 1. Therefore, in order to set an optimal threshold separately for the ON and OFF states, it is desirable to shift the threshold between the ON and OFF states.

[0155] However, contrary to the above description, it is also advantageous to match the thresholds between the ON and OFF states. For example, in this figure, from the viewpoint of only the average amount of light received, "one green light spot lit" in the ON state and "three red light spots lit (or two red light spots lit)" in the OFF state are adjacent to each other. Therefore, when the optical axis is blocked while maintaining the average amount of light received and the ON state switches to the OFF state, the display pattern changes from "one green light spot lit" to "three red light spots lit (or two red light spots lit)".

[0156] In other words, focusing solely on the number of illuminated lights presents the possibility of switching display patterns while experiencing discomfort due to an increased number of illuminated lights despite the optical axis being blocked. Therefore, when prioritizing the transmission of light received along the optical axis in an easily understandable manner, it is desirable to align the thresholds between the ON and OFF states to prevent a reversal in the number of illuminated lights.

[0157] Figure 14 This is a diagram illustrating the relationship between the amount of light received along the optical axis (minimum light intensity) and the displayed pattern. As illustrated in the diagram, the criterion for determining the displayed pattern can be the minimum amount of light received along each optical axis (= minimum light intensity).

[0158] In this scenario, for example, a first threshold, a second threshold, and a third threshold are set. The relationship between the thresholds can be: first threshold < second threshold < third threshold.

[0159] Referring to the diagram, when the minimum light intensity is below the first threshold, three red lights illuminate (i.e., indicator lights 170a, 170b, and 170c are illuminated in red). This state corresponds to the OFF state. As mentioned above, in the OFF state, the number of red lights is fixed at three. When the minimum light intensity is above the first threshold but below the second threshold, one green light illuminates (i.e., only indicator light 170a is illuminated in green). When the minimum light intensity is above the second threshold but below the third threshold, two green lights illuminate (i.e., indicator lights 170a and 170b are illuminated in green). When the minimum light intensity is above the third threshold, three green lights illuminate (i.e., indicator lights 170a, 170b, and 170c are illuminated in green). In other words, as the minimum light intensity increases, the number of green lights illuminates increases.

[0160] As described above, the average value of the amount of light received along the optical axis (= average amount of light received) or the minimum value (= minimum amount of light received) can be used as the criteria for determining the display pattern.

[0161] <Light up the image>

[0162] Figure 15 This is a diagram illustrating the illuminated image of light screen 1 (first example). In this diagram, the second embodiment described above is used. Figure 9 and Figure 10 Examples of the arrangement and display patterns for indicator light sources 170a, 170b, and 170c are provided. Furthermore, the relationship between the amount of light received along the optical axis and the display pattern is based on the above reference. Figure 13 The description describes the switching control of the display pattern.

[0163] First, the OFF state will be described (the four states on the left side of the diagram). In the fully shaded state, light curtain 1 is off (= indicator lights 170a, 170b, and 170c are off). In low light intensity, one red light is lit (= only indicator light 170a is lit in red). In medium light intensity, two red light are lit (= indicator lights 170a and 170b are lit in red). In high light intensity, three red light are lit (= indicator lights 170a, 170b, and 170c are lit in red).

[0164] Next, the ON state will be described (the three states on the right side of the diagram). In low light intensity (small), one green light is illuminated (=only indicator light source 170a is illuminated in green). In medium light intensity (medium), two green lights are illuminated (=indicator light sources 170a and 170b are illuminated in green). In high light intensity (large), three green lights are illuminated (=indicator light sources 170a, 170b, and 170c are illuminated in green).

[0165] Note that the light diffuser is arranged above each of the indicator light sources 170a, 170b, and 170c. Therefore, it is desirable to appropriately arrange the arrangement and display pattern of the indicator light sources 170a, 170b, and 170c so that the switching of the display pattern can also be identified through the light diffuser. This is also as stated above.

[0166] Figure 16 This is a diagram illustrating the illuminated image of light curtain 1 (second example). In this diagram, light curtain 1 is displayed in bars corresponding to the amount of light received along the optical axis. Specifically, each of the three substrates 190x, 190y, and 190z (more precisely, a set of indicator light sources 170 incorporated therein) cascaded in the longitudinal direction of light curtain 1 is controlled to be lit or turned off as an individual unit.

[0167] First, the OFF state will be described (the four states on the left side of the diagram). In the fully light-blocking state, light curtain 1 is off (= substrates 190x, 190y, and 190z are off). In low light intensity, 1 / 3 of light curtain 1 is illuminated by the red bar (= only substrate 190x is illuminated in red). In medium light intensity, 2 / 3 of light curtain 1 is illuminated by the red bar (= substrates 190x and 190y are illuminated in red). In high light intensity, the entire light curtain 1 (3 / 3) is illuminated by the red bar (= substrates 190x, 190y, and 190z are illuminated in red).

[0168] Next, the ON state will be described (the three states on the right side of the diagram). In low light intensity (small), 1 / 3 of the light curtain 1 is illuminated by the green bar (=only substrate 190x is illuminated in green). In medium light intensity (medium), 2 / 3 of the light curtain 1 is illuminated by the green bar (=substrates 190x and 190y are illuminated in green). In high light intensity (large), the entire light curtain 1 (3 / 3) is illuminated by the green bar (=substrates 190x, 190y, and 190z are illuminated in green).

[0169] As mentioned above, in the second example ( Figure 16 In the illuminated image of ), compared with the first example above ( Figure 15 Compared to other methods, it is easier to control the switching of display patterns corresponding to the amount of light received along the optical axis. Note that when implementing the above-mentioned illuminated image based on a structure of multiple substrates cascaded at 190x, 190y, and 190z, the design difficulty and cost may increase.

[0170] <Example of a variation of the display pattern corresponding to the amount of light received along the optical axis>

[0171] In the above description, the following structure has been illustrated: the number of indicator light sources 170 illuminated (especially the intermittent intervals) is switched according to the amount of light received along the optical axis. However, various other variations are conceivable.

[0172] For example, the timing of the indicator light 140 can be switched based on the amount of light received along the optical axis (e.g., whether the indicator light 140 is always on, flashes at 1-second intervals, or flashes at 2-second intervals). Additionally, the light intensity or color of the indicator light 140 can be switched based on the amount of light received along the optical axis. With these features, it is not necessary to individually control multiple indicator light sources 170 when switching display patterns. Therefore, for example, optical fibers can be used as the indicator light 140.

[0173] <Function Block (with display pattern control function)>

[0174] Figure 17 This is a functional block diagram of a light screen 1 with pattern display control function. Note that in this diagram, refer to the above... Figure 5 The light-emitting and light-receiving systems that replace the optical axes Oax1 to Oax6 are used to focus on the control systems of indicator light sources 170a, 170b and 170c and indicator light sources 270a, 270b and 270c.

[0175] Furthermore, according to the second embodiment described above ( Figure 9 and Figure 10 The indicator light sources 170a, 170b and 170c and the indicator light sources 270a, 270b and 270c are arranged in groups of three in the order shown (a, b, c, a, b and c from the top of the figure).

[0176] Control circuit 181 uses a common control signal to control two indicator light sources 170a. The same applies to indicator light sources 170b and 170c. Additionally, control circuit 281 uses a common control signal to control two indicator light sources 270a. The same applies to indicator light sources 270b and 270c.

[0177] Note that the amount of light received by each of the optical axes Oax1 to Oax6 is compared with a threshold in the control circuit 281. In this case, the control circuit 281 may include an analog-to-digital converter circuit that converts the analog signal output from each of the light-receiving elements 261 to 266 into a digital signal. Additionally, the control circuit 281 may include an arithmetic circuit that calculates an average value (= average light received amount) or a minimum value (= minimum light received amount) based on the amount of light received by each of the optical axes Oax1 to Oax6.

[0178] Control circuit 281 controls the lighting or extinguishing of each of the indicator light sources 270a, 270b, and 270c based on a comparison between the average light received (or minimum light received) and a threshold. Additionally, control circuit 281 transmits the comparison result to control circuit 181 via communication circuits 282 and 182. Control circuit 181 then controls the lighting or extinguishing of each of the indicator light sources 170a, 170b, and 170c based on the comparison result transmitted from control circuit 281.

[0179] <Processing Flow>

[0180] Figure 18 This is a diagram illustrating the processing flow of display pattern control based on average light received. When the processing flow of this diagram is started, in step S1, the optical axis to be driven Oax(i) is set (where i = 1, 2, ..., and imax(6), and the initial setting value is i = 1).

[0181] In the subsequent step S2, the projection element 16i is illuminated. That is, firstly, the projection element 161 used to form the optical axis Oax1 is illuminated.

[0182] In step S3, it is determined whether the amount of light received by the light-receiving element 26i is greater than a first threshold. Note that, as described above, the first threshold corresponds to the threshold used to determine whether each of the optical axes Oax1 to Oax6 is in a light-blocking state. Here, if a "yes" determination is made, the process proceeds to step S4. On the other hand, if a "no" determination is made, the process proceeds to step S8. In step S8, the safety output (OSSD) is switched to the OFF state without waiting for the display pattern control to complete. Therefore, hazardous sources such as presses can be stopped quickly. In addition, in step S8, besides switching the safety output (OSSD) to the OFF state, the display aspect of the OSSD indicator can also be changed according to the safety output (OSSD) being switched to the off state. Note that steps S3 and S8 are not directly related to the display pattern control. Therefore, steps S3 and S8 are depicted by dashed lines in this figure.

[0183] When a "yes" confirmation is made in step S3, the amount of light received, Li, is recorded in a register or similar device in step S4.

[0184] In the subsequent step S5, it is determined whether the optical axis is the final optical axis (that is, i = imax(6)). Here, if a "yes" determination is made, the process proceeds to step S6. On the other hand, if a "no" determination is made, the process returns to step S1 after incrementing the variable i by one (++i). Then, steps S1 to S5 are repeated until a "yes" determination is made in step S5.

[0185] When a "yes" decision is made in step S5, step S6 involves comparing the average or minimum amount of light received with multiple threshold values. (This has already been referred to above.) Figure 13 and 14 The comparison process in this step is described. Therefore, redundant descriptions have been omitted.

[0186] In the subsequent step S7, the illumination status (display pattern) of each of the indicator lights 140 and 240 is updated based on the comparison result obtained in step S6. After that, the process returns to step S1 and repeats this series of processes.

[0187] Note that this figure is drawn with the following fact in mind: In step S6, a comparison can be made between the average amount of light received (= average light received) and multiple thresholds. That is, the comparison in step S6 is not performed for each optical axis, but after the amount of light received for all optical axes has been recorded.

[0188] However, when comparing the minimum amount of light received (= minimum amount of light received) with multiple thresholds, step S5 can be omitted. That is, the comparison process in step S6 can be performed sequentially for each optical axis without waiting to record the amount of light received for all optical axes.

[0189] For example, when the amount of light received by the first light-receiving element 261 is at or below the second threshold, it is sufficient to switch a green light to on (=only the indicator light source 170a is on in green) without having to compare the amount of light received by each of the other light-receiving elements 262 to 266 with the threshold (see [link]). Figure 14 Therefore, subsequent comparison processing can be omitted.

[0190] Summary

[0191] In the above Figures 9 to 18 In the present invention, a light curtain 1 has been proposed that has the function of switching display patterns corresponding to the amount of light received by the optical axis. When briefly describing the structure, it can be represented as "a light curtain comprising a housing to form a plurality of optical axes spaced apart from each other, the housing having a metal outer shell and end members connected to both ends of the metal outer shell, wherein, in the metal outer shell, one of a pair of light-emitting elements and a light-receiving element forming the plurality of optical axes is arranged inside along the longitudinal direction and extends in the longitudinal direction;

[0192] The cover is used to allow light from the projection element to pass through and is attached to the housing to intersect multiple optical axes;

[0193] As a light-diffusing component, the indicator light is arranged outward from the outer surface of at least one of the cover and the housing along the longitudinal direction, or is formed in series with the cover; and

[0194] The indicator light source, housed inside the housing, supplies light for display towards the indicator light.

[0195] When the operation indicator light mode is set, the indicator light source is controlled to be lit or turned off in the following display pattern, which corresponds to the light emission color and the amount of light received by the light receiving element corresponding to the operation state of the light curtain.

[0196] <Fifth Embodiment>

[0197] Figure 19 This is a diagram illustrating an example of the structure of a light curtain 1 according to a fifth embodiment. The light curtain 1 of this embodiment includes a pair of projectors 100 and receivers 200.

[0198] As described above, the projector 100 includes a plurality of projecting elements 161 to 166. Additionally, the receiver 200 is arranged facing the projector 100 and includes a plurality of receiving elements 261 to 266, which receive light beams projected from the plurality of projecting elements 161 to 166. However, in this figure, for ease of illustration, only the optical axes Oax1 to Oax6 formed between the projecting elements 161 to 166 and the receiving elements 261 to 266 are illustrated. The projecting elements 161 to 166 and the receiving elements 261 to 266 refer to the above-described... Figure 3 and Figure 5 To describe.

[0199] The light curtain 1 outputs a safety signal (i.e., the OSSD output mentioned above) to the outside based on whether each of the multiple optical axes Oax1 to Oax6 formed between the projector 100 and the receiver 200 is in a light-blocking state. Needless to say, the number of optical axes Oax1 to Oax6 is arbitrary.

[0200] In addition, the light curtain 1 includes a synchronization unit that synchronizes the projection timing of each of the projection elements 161 to 166 in the projector 100 with the light receiving timing of each of the light receiving elements 261 to 266 in the receiver 200 via optical communication. That is, in the light curtain 1, an optical synchronization system is used as the synchronization system for the projection timing and the light receiving timing.

[0201] Referring to the figure, among the optical axes Oax1 to Oax6 used for light incidence and shading detection, the optical axes Oax1 and Oax6 formed at both the upper and lower ends of the light curtain 1 can be used for timing synchronization. For example, the projector 100 can send a synchronization pulse via optical axis Oax1 before the start of the optical axis scan for sequentially detecting each of the optical axes Oax1 to Oax6. As described above, the synchronization pulse is a pulse signal used for timing synchronization and has a unique pulse pattern. The receiver 200 synchronizes the light reception timing to match the light projection timing of the synchronization pulse.

[0202] An optical synchronization system is used, eliminating the need for wiring between the projector 100 and the receiver 200. This increases the wiring flexibility of the light curtain 1.

[0203] Additionally, the light curtain 1 includes indicator lights 140 and 240. Indicator light 140 is located in the projector 100. Indicator light 240 is located in the receiver 200. Indicator lights 140 and 240 can be used as operation indicator lights to indicate the operating status of the light curtain 1. Operators can visually identify the operating status of the light curtain 1 (e.g., the on or off status of the OSSD output) by observing indicator lights 140 and 240 on the light curtain 1.

[0204] Furthermore, the light curtain 1 includes a linkage display unit for linking the indicator lights 140 and 240 through optical communication from the light receiver 200 to the projector 100. Referring to the figure, optical axes Com1 and Com2 for linkage display control are formed between the projector 100 and the light receiver 200, separate from the optical axes Oax1 to Oax6 used for light incidence and shading detection and timing synchronization.

[0205] Note that optical axes Com1 and Com2 can be formed, for example, near the upper and lower ends of light curtain 1. Referring to the figure, optical axis Com1 is formed between optical axes Oax1 and Oax2. Additionally, optical axis Com2 is formed between optical axes Oax5 and Oax6. However, either optical axis Com1 or Com2 can be omitted. Furthermore, optical axes Com1 and Com2 can be formed in the upper and lower central regions of light curtain 1.

[0206] Figure 20 This is a schematic diagram illustrating an example of optical axis formation. As illustrated in the figure, separate from the at least one pair of light-emitting elements 310 and light-receiving elements 320 provided for light incidence and shading detection, the light curtain 1 of this embodiment includes at least one pair of light-emitting elements 160 and light-receiving elements 260 provided for the linked display control of indicator lights 140 and 240. Furthermore, in this figure, the aforementioned control circuits 181 and 281 are illustrated as units for integrating the overall operation of each of the light emitter 100 and the light receiver 200.

[0207] The light-emitting element 160 is an optical element disposed in the light emitter 100. The light-emitting element 160 can be understood as the light-emitting elements 161 to 166 described above. The light-emitting element 160 can be, for example, a light-emitting diode (LED). The light-receiving element 260 is an optical element disposed in the light receiver 200. The light-receiving element 260 can be understood as the light-receiving elements 261 to 266 described above. The light-receiving element 260 can be, for example, a photodiode or a phototransistor. An optical axis Oax is formed between the light-emitting element 160 and the light-receiving element 260 for light incidence and shading detection or timing synchronization. The optical axis Oax corresponds to the optical axes Oax1 to Oax6 described above.

[0208] The light-emitting element 310 is an optical element disposed in the light receiver 200. The light-emitting element 310 may be, for example, a light-emitting diode (LED). The light-receiving element 320 is an optical element disposed in the light emitter 100. The light-receiving element 320 may be, for example, a photodiode or a phototransistor. An optical axis Com, different from the optical axis Oax, is formed between the light-emitting element 310 and the light-receiving element 320 for linkage display control. The optical axis Com corresponds to the aforementioned optical axes Com1 and Com2.

[0209] Control circuits 181 and 281 use optical communication via the optical axis Com formed between the light-emitting element 310 and the light-receiving element 320 to enable the indicator lights 140 and 240 to display in tandem. Note that the optical axis Com can be understood as the optical communication path from the light receiver 200 to the light emitter 100.

[0210] For example, the control circuit 281 of the light receiver 200 determines the on / off state of the OSSD output based on whether the optical axis Oax formed between the light-emitting element 160 and the light-receiving element 260 is in a light-blocking state. Then, the control circuit 281 controls the indicator light source 270 to turn on or off based on the on / off state of the OSSD output. At this time, the control circuit 281 drives the light-emitting element 310 to send the on / off state of the OSSD output to the light transmitter 100. The control circuit 181 of the light transmitter 100 controls the indicator light source 170 to turn on or off based on the on / off information of the OSSD output received by the light-receiving element 320.

[0211] In the light curtain 1 of this embodiment, indicator lights 140 and 240 can be displayed in tandem without the need for wiring between the projector 100 and the receiver 200. Therefore, the visibility of indicator lights 140 and 240 can be improved while enjoying the advantages of an optical synchronization system.

[0212] Note that, as described above, the optical axis Com used for linkage display control can be formed separately as a dedicated optical axis from the optical axis Oax used for light incidence and shading detection or timing synchronization. This structure increases the degrees of freedom in designing each of the light-emitting element 310 and the light-receiving element 320. Furthermore, in the structure where the optical axes Oax and Com are formed separately, design freedom, such as the number of light-emitting pulses or the pulse interval, is increased.

[0213] For example, for the optical axis Oax used in light incidence and shading detection, in order to accurately detect the shading state, safety standards can be used to strictly limit the light projection divergence angle of the projection element 160, the light receiving angle of the light receiving element 260, and the size of the lens in the light guide path of each of the projection element 160 and the light receiving element 260.

[0214] On the other hand, the aforementioned restrictions are not imposed on the optical axis Com used for linkage display control. Therefore, for example, the projection element 310 can be designed to have a larger projection divergence angle compared to the projection element 160. Additionally, the light-receiving element 320 can be designed to have a larger light-receiving angle compared to the light-receiving element 260. Furthermore, the size of the lens disposed in the light guide path of each of the projection element 310 and the light-receiving element 320 can be designed to be larger than the size of the lens disposed in the light guide path of each of the projection element 160 and the light-receiving element 260.

[0215] Based on this design, an optical axis Com can be easily established between the projector 100 and the receiver 200. Therefore, for example, when aligning the optical axis during the installation of the light curtain 1, the indicator lights 140 and 240 can be quickly synchronized. As a result, a status display linked to the amount of light received along the aforementioned optical axis can be performed (see reference). Figure 13 or Figure 14 Therefore, optical axis alignment can be easily performed.

[0216] Note, for example, in the above Figure 5 In this embodiment, when at least one pair of light-emitting elements 161 to 166 and light-receiving elements 261 to 266 are exchanged between the projector 100 and the receiver 200, it is not impossible to use a single optical axis in a time-division manner for both light incidence and shading detection and linked display control. According to this variation, since the projector element 310 and the light-receiving element 320 are omitted, this can help reduce the cost of the light screen 1. However, at least one light incidence and shading information of optical axes Oax1 to Oax6 is obtained by the projector 100, not the receiver 200. Therefore, in order to output the OSSD using the receiver 200, optical communication is also required to send the light incidence and shading information obtained by the projector 100 to the receiver 200.

[0217] Additionally, multiple sets of light-emitting elements 310 and light-receiving elements 320 can be provided. For example, as described above. Figure 19 As illustrated, multiple optical axes Com1 and Com2 can be formed for linked display control. Using this structure, even if one of the optical axes Com1 and Com2 is blocked, information transmission from the receiver 200 to the projector 100 can continue.

[0218] Figure 21 This is a diagram illustrating the processing flow of linked display control. In the processing flow of this diagram, for the above... Figure 18 The operation in step S7 is modified, and steps S9 to S11 are added after step S7. The following text will mainly describe the processing content of step S7 and subsequent steps.

[0219] In step S7, the light receiver 200 determines the illumination state (display pattern) of each of the indicator lights 140 and 240 based on the comparison result obtained in step S6. Afterward, the process proceeds to step S9 without returning to step S1.

[0220] In step S9, the light receiver 200 performs pulse driving on the optical axis Com to project pulse information corresponding to the illumination state (display pattern) determined in step S7. That is, after detecting the light incidence and blocking states of all optical axes Oax(i), the light receiver 200 performs optical communication reflecting the detection result. The aforementioned pulse information can, for example, be a specific pulse pattern.

[0221] Subsequently, in step S10, the projector 100 receives pulse information via the optical axis Com and compares the pulse information with predetermined internal information. Note that the internal information may be a table that associates the pulse information with the on or off state of the indicator light 140.

[0222] In the subsequent step S11, the projector 100 updates the illumination state (display pattern) of the indicator light 140 based on the comparison result in step S10 (that is, the determination content in step S7). Additionally, the receiver 200 updates the illumination state (display pattern) of the indicator light 240 based on the comparison result in step S6 and the determination content in step S7. Through this control, the linked display of indicator lights 140 and 240 can be achieved.

[0223] Note that after updating the illumination status (display pattern) of each of the indicator lights 140 and 240, the process returns to step S1 and repeats the series of processes.

[0224] Figure 22 and Figure 23These are plan and perspective views illustrating an example structure of the light receiver 200. In both views, the longitudinal direction of the light receiver 200 is the x-axis, the transverse direction is the y-axis, and the thickness direction (depth direction) is the z-axis.

[0225] Figure 22 This can be understood as an xy-plane view of the light receiver 200 viewed from the front side. Additionally, Figure 23 This can be understood as a light receiver 200. Figure 22 A three-dimensional image in which the z-axis is tilted towards the back side of the image and rotated slightly around the x-axis.

[0226] However, Figure 23 This example illustrates the state where the metal casing 211 and end cap 212 of the light receiver 200 have been removed. Therefore, Figure 23 The substrate 190 and the retainer 216 are depicted within the metal housing 211 and the end cap 212.

[0227] As illustrated in these two figures, on the front surface of the light receiver 200, a plurality of lenses 214 are arranged at equal intervals along the longitudinal direction of the light receiver 200. Each of the plurality of lenses 214 forms the light guiding path (light receiving path) of the optical axis Oax. All of the plurality of lenses 214 are supported by the retainer 216. Note that some of the plurality of lenses 214 may be positioned at a location corresponding to the front surface of the end cap 212.

[0228] Additionally, among the plurality of lenses 214, a lens 215 may be disposed between two adjacent lenses 214. The lens 215 forms the light guide path (projection path) of the optical axis Com. The lens 215 is supported by a retainer 216. The optical axis Com may, for example, be formed near both ends of the light curtain 1. With reference to this figure, the lens 215 is positioned corresponding to the front surface of the end cap 212. The size of the lens 215 may be designed to be larger than the size of each of the plurality of lenses 214.

[0229] Figure 24 This diagram illustrates an example of light interference between light curtains 1A and 1B. Light curtain 1A includes a pair of projectors 100A and receivers 200A. Light curtain 1B includes a pair of projectors 100B and receivers 200B.

[0230] Light curtains 1A and 1B are mounted such that the projector 100A of light curtain 1A and the projector 100B of light curtain 1B are back to back. From another viewpoint, light curtains 1A and 1B are mounted such that the receiver 200A of light curtain 1A and the receiver 200B of light curtain 1B face each other.

[0231] With this installation, the optical axis OaxA emitted from the projector 100A of the light curtain 1A is unlikely to be received by the receiver 200B of the light curtain 1B. Furthermore, the optical axis OaxB emitted from the projector 100B of the light curtain 1B is unlikely to be received by the receiver 200A of the light curtain 1A.

[0232] However, as described above, in light curtains 1A and 1B, the light receiver 200A of light curtain 1A and the light receiver 200B of light curtain 1B face each other. Therefore, the optical axis ComA emitted from the light receiver 200A of light curtain 1A can be received by the light receiver 200B of light curtain 1B. Furthermore, the optical axis ComB emitted from the light receiver 200B of light curtain 1B can be received by the light receiver 200B of light curtain 1A. Therefore, there is a possibility that problems may arise in the detection of light incidence and shading of optical axes OaxA and OaxB.

[0233] In view of the above considerations, the optical axis drive control that can suppress mutual interference of light is proposed below.

[0234] Figure 25 This is a diagram illustrating an example of optical axis drive control. As illustrated in the diagram, in this embodiment, the light curtain 1 repeatedly drives time periods T1 and T2 in a time-division manner as drive control for optical axes Oax and Com. Optical axis Oax can be understood as either optical axes OaxA or OaxB as described above. Optical axis Com can be understood as either optical axes ComA or ComB as described above.

[0235] The driving time period T1 can be understood as the time period during which the light-emitting element 160 and the light-receiving element 260 are driven (that is, the time period during which the optical axis Oax is formed between the light-emitting element 160 and the light-receiving element 260 and the light incident and blocked are detected). The driving time period T1 can have a length that depends on the number i of optical axes Oax (e.g., several ms (= tens of μs × i)).

[0236] The driving time period T2 can be understood as the time period during which the light-emitting elements 310 and 320 are driven (that is, the time period during which an optical axis Com is formed between the light-emitting element 310 and the light-receiving element 320 and pulse information used for linked display control is transmitted). The driving time period T2 can have a length that depends on the amount of information to be transmitted (e.g., hundreds of μs).

[0237] Additionally, as illustrated in the figure, a scan time period Ts can include drive time periods T1 and T2. However, for two or more scan time periods Ts, drive time period T2 can be skipped once. That is, optical communication using the optical axis Com can be performed after repeating the light incidence and shading detection of the optical axis Oax two or more times. In other words, the interval of optical communication can be set to be longer than the interval of optical axis detection.

[0238] In this case, since the frequency of interference with the optical axis Oax and the optical axis Com is once or less than once every two detections, the receiver 200 can be operated to ignore the influence of the interference with the optical axis Com.

[0239] According to this control, even in Figure 24 In the illustrated case, possible light interference between light curtain 1A and light curtain 1B can also be suppressed.

[0240] Note that in this figure, for ease of description, the skipped drive time period T2 can be depicted with a dashed box. Therefore, the length of the scan time period Ts appears constant regardless of whether drive time period T2 is skipped. In reality, the scan time period Ts can shorten the skipped drive time period T2, allowing the next drive time period T1 to arrive earlier.

[0241] Based on this optical axis drive control, the coordinated display control of indicator lights 140 and 240 can be achieved while maintaining the shortest possible response time for the OSSD output. Note that the skipping frequency of the drive time period T2 only affects the response time of each of indicator lights 140 and 240 (that is, the update frequency of the on or off state). Therefore, the skipping frequency of the drive time period T2 can be designed relatively freely.

[0242] Additionally, as another method to suppress mutual interference of light, the optical axes Oax and Com can be different wavelengths. For example, the optical axis Oax can be formed by infrared light, and the optical axis Com can be formed by red light. In this case, the lens that guides the optical axis Com to the light-receiving element 320 of the projector 100 can be filtered to remove infrared light. According to this structure, the entry of the optical axis Oax into the light-receiving element 320 can be suppressed.

[0243] <The lack of established optical communication>

[0244] On the other hand, if the light-receiving element 320 does not receive a specific pulse pattern due to light blocking of the optical axis Com, optical communication using the optical axis Com cannot be established. In addition, even if the light-receiving element 320 receives an unexpected pulse pattern due to light interference, optical communication using the optical axis Com may not be established.

[0245] If optical communication via optical axis Com is not established during the drive period T2, the projector 100 enters a state where it cannot know the light incidence and blocking status of the receiver 200. In this case, the indicator light 140 can maintain its current display state. Based on this control, the coordinated display of indicator lights 140 and 240 is unlikely to be disturbed when optical communication is temporarily not established.

[0246] However, if optical communication via optical axis Com is not established continuously within multiple drive time periods T2, indicator light 140 can be switched to an off state. This control allows the operator to be notified that optical communication has not been established. By switching to the off state, the user can be directly informed that optical communication via optical axis Com has not been established.

[0247] Furthermore, when the optical axis Com is positioned between the optical axes Oax(i) and Ox(i+1), it is unlikely that only the optical axis Com will be blocked. Therefore, when optical communication via the optical axis Com is not established continuously for multiple drive time periods T2, the indicator light 140 can switch to a display state indicating the disconnected state of the OSSD output (e.g., a red light illuminated state). However, when the light screen is aligned with the optical axis, if the screen is in a red light illuminated state when optical communication via the optical axis Com is not established, the user may be confused about the meaning of red. Therefore, as described above, it is preferable to switch to an off state when optical communication via the optical axis Com is not established. Note that the indicator light 140 can flash green when in operation (by flashing green instead of illuminating green, the user can easily grasp the in-operation state), or it can illuminate orange when silent. In addition, since the information in the indicator light 140 is unsafe information, it is permissible for optical communication via the optical axis Com to not be established. In other words, the OSSD will not disconnect even if optical communication via the optical axis Com is not established.

[0248] When projectors and receivers are connected in series, indicator lights 140 can operate independently. Specifically, for example, when three projectors (receivers) are connected in series, if optical communication of the optical axis Com in the middle projector (receiver) is not established, only the middle projector (receiver) can be switched to an off state (e.g., it can be switched to an off state). In addition to the independent operation of each unit, all indicator lights 140 can also operate according to a predetermined optical communication state of the optical axis Com in the projector (receiver). For example, when three projectors (receivers) are connected in series, if optical communication of a predetermined optical axis Com is not established, all indicator lights 140 can be switched to an off state.

[0249] Furthermore, as described above, two optical axes Com are provided for a single projector (receiver) according to this embodiment. In the event of inconsistency between the information of the two optical axes Com, various illumination states can be switched. For example, if only one optical axis Com is established, the indicator light 140 can be switched based on the information of the established optical axis Com. Alternatively, for example, if two optical axes Com are established but the information of the optical axes Com is inconsistent, the previous state of the indicator light 140 can be maintained.

[0250] <Light Leakage>

[0251] Note that if the optical axis Oax used for light incidence and light shading detection and the optical axis Com used for linkage display control are set to be adjacent to each other, light leakage may occur through the light guide path of the optical axes Oax and Com.

[0252] Figure 26 This is a longitudinal cross-sectional view illustrating an example of a light receiver 200 including a light leakage suppression mechanism. This figure can be understood as illustrating the above. Figure 22 The diagram shows the α-α section, especially the partially magnified diagram of the periphery of lens 215.

[0253] In the photodetector 200 of this structural example, a plurality of photodetector elements 260 are arranged on the surface of substrate 190 at constant intervals d1 along the longitudinal direction of photodetector 200. Each of the plurality of photodetector elements 260 can be understood as an optical element for detecting the optical axis Oax incident from the outside of photodetector 200 through a plurality of lenses 214.

[0254] Additionally, on the surface of the substrate 190, a light-emitting element 310 is disposed between two adjacent light-receiving elements 260. The light-emitting element 310 can be understood as an optical element used to project the optical axis Com used for linkage display control through the lens 215 to the outside of the light receiver 200.

[0255] In this situation, as indicated by the solid arrow in the figure, light leakage along the optical axis Oax may occur in the form of light entering from the light-guiding path of the projection element 310 in the opposite direction and bypassing it to enter the light-receiving element 260. When such light leakage occurs, false detection of the optical axis Oax may occur in the light-receiving element 260 adjacent to the projection element 310. Specifically, although the optical axis Oax to be incident on the light-receiving element 260 is blocked by the object M, the incident light is falsely detected. In such a case, a very dangerous situation may occur because the correct OSSD output is not generated.

[0256] Therefore, the light receiver 200 of this structural example includes a light-shielding wall 330. The light-shielding wall 330 is formed to block light entering the light receiver 260 from the light guide path of the light-projecting element 310. For example, the light-shielding wall 330 can be formed to surround the periphery of the light-projecting element 310. With this structure, light leakage along the optical axis Oax is suppressed. Therefore, the reliability of the light curtain 1 can be improved by reducing false detections of the optical axis Oax in the light receiver 260.

[0257] Note that the light-shielding wall 330 may be integrally formed as part of the retainer 216. Alternatively, the light-shielding wall 300 may be formed as an additional part attached to the retainer 216.

[0258] Additionally, the light-shielding wall 330 and its surrounding components are unlikely to reflect the optical axis Oax as much as possible. For example, it is desirable to darken the substrate 190 and the retainer 216.

[0259] Alternatively, as another method to suppress light leakage, such as methods for suppressing mutual light interference, the optical axes Oax and Com can be of different wavelengths. For example, the optical axis Oax can be formed by infrared light, and the optical axis Com can be formed by red light. In this case, the lens 215 that guides the optical axis Com to the outside of the receiver 200 can be filtered to remove infrared light. According to this structure, the entry of the optical axis Oax through the lens 215 can be suppressed.

[0260] <Other variations>

[0261] Note that, apart from the embodiments, various modifications can be made to the various technical features disclosed in this specification without departing from the spirit of the invention. That is, it should be understood that the above embodiments are illustrative in all respects and not restrictive, and the scope of the invention is defined by the claims and includes all modifications falling within the meaning and scope equivalent to the claims.

Claims

1. A light curtain, comprising: A light projector comprising a plurality of first light-projecting elements; A light receiver is arranged to face the light projector and includes a plurality of first light-receiving elements configured to receive a light beam projected from the plurality of first light-projecting elements; as well as A synchronization unit is configured to synchronize the light projection timing of the projector with the light reception timing of the receiver via optical communication. Specifically, a safety signal generated based on whether each optical axis among the multiple optical axes formed between the projector and the receiver is in a light-blocking state is output to the outside. The light curtain also includes: A first operation indicator light is disposed in the projector and configured to display the operation status of the light screen; A second operation indicator light is disposed in the light receiver and configured to display the operation status of the light screen; At least one set of optical elements is disposed in each of the projector and the receiver, and is configured to cause the first operation indicator light and the second operation indicator light to display in conjunction; and A control circuit is configured to use the at least one set of optical elements to cause the first operation indicator and the second operation indicator to be displayed in tandem.

2. The light curtain according to claim 1, wherein, The at least one set of optical elements includes a second light-emitting element disposed in the light receiver and a second light-receiving element disposed in the light-emitting element.

3. The light curtain according to claim 2, wherein, Multiple sets of the second light-emitting element and the second light-receiving element are provided.

4. The light curtain according to claim 2, wherein, The second light-emitting element is a light-emitting diode, and the second light-receiving element is a photodiode or a phototransistor.

5. The light curtain according to claim 2, wherein, In the second light-emitting element, at least one of the light-emitting divergence angle and the lens size is larger than that of the first light-emitting element, and in the second light-receiving element, at least one of the light-receiving angle and the lens size is larger than that of the first light-receiving element.

6. The light curtain according to claim 2, wherein, A first optical axis is formed between the first light-emitting element and the first light-receiving element for light incidence and shading detection or timing synchronization, and a second optical axis, different from the first optical axis, is formed between the second light-emitting element and the second light-receiving element for linkage display control.

7. The light curtain according to claim 6, in, The first time period driving each of the first light-emitting element and the first light-receiving element, and the second time period driving each of the second light-emitting element and the second light-receiving element, are repeated in a time-division manner. The light receiver drives the second optical axis in the second time period based on the detection results of the first optical axis obtained in each of the plurality of first time periods.

8. The light curtain according to claim 7, wherein, When optical communication via the second optical axis is not established during the second time period, the first operation indicator light remains in the current display state.

9. The light curtain according to claim 8, wherein, If optical communication via the second optical axis is not established continuously during multiple second time periods, the first operation indicator light is switched to an off state or a display state indicating the disconnection state of the safety signal.

10. The light curtain according to claim 6, wherein, The light receiver includes a light-shielding wall that is configured to block light from entering the first light receiver via the light guide path of the second light-emitting element.

11. The light curtain according to claim 2, wherein, The second light-emitting element is arranged between the plurality of first light-receiving elements, and the second light-receiving element is arranged between the plurality of first light-emitting elements.

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