Light Curtain

Abstract

This improves the ease of wiring when installing operation indicator lights in light-synchronized light curtains. [Solution] The light curtain 1 is equipped with synchronization means (optical axes Oax1 and Oax6 for timing synchronization) that synchronize the light emission timing of the light emitter 100 and the light receiving timing of the light receiver 200 by optical communication. A safety signal generated based on whether or not the optical axes Oax1 to Oax6 formed between the light emitter 100 and the light receiver 200 are in a light-shielding state is output to the outside. The light curtain 1 is equipped with a first operation indicator light 140 provided on the light emitter 100, a second operation indicator light 240 provided on the light receiver 200, optical elements (optical axes Com1 and Com2 for linked display control) provided on the light emitter 100 and the light receiver 200 respectively for linked display of the first operation indicator light 140 and the second operation indicator light 240, and a control circuit that uses at least one set of optical elements to linked display of the first operation indicator light 140 and the second operation indicator light 240.

Description

Technical Field

[0001] The present invention relates to a light curtain.

Background Art

[0002] A light curtain is a form of a multi-axis photoelectric sensor. The light curtain detects a person or an object according to whether the optical axes formed between a projector and a receiver are blocked.

[0003] Some light curtains have an operation indicator light. The operation indicator light is used to display information such as, for example, (1) the on / off state of the power supply, (2) the on / off state of the OSSD [Output Signal Switching Device] output, that is, the light reception / shading state, and (3) the error state. For example, the operation indicator light turns off when all of the plurality of light receiving elements provided in the receiver receive the light emitted from the plurality of light projecting elements provided in the projector, and turns on otherwise. Also, the lighting state of the operation indicator light changes when an error occurs in the light curtain. An operator can visually recognize the operation state of the light curtain by looking at the operation indicator light of the light curtain.

[0004] Also, in a light curtain, due to the detection principle of the optical axis, it is necessary to match the driving timings of the light projecting element and the light receiving element, that is, to synchronize the light projecting timing and the light receiving timing. As synchronization methods, two types are known: a wired synchronization method and an optical synchronization method.

[0005] In the wired synchronization method, the projector and the 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 method is more resistant to optical interference than the optical synchronization method. However, the wired synchronization method requires cable wiring work. In particular, when the projector and the receiver are separated, the wiring work tends to be complicated.

[0006] In the optical synchronization method, a synchronization pulse is emitted from the light emitter. The synchronization pulse is a pulse signal used for timing synchronization and has a unique pulse pattern. The light receiver synchronizes its receiving timing to match the emission timing of the synchronization pulse. The optical synchronization method does not require wiring between the light emitter and the light receiver, offering high wiring flexibility. However, the optical synchronization method is more susceptible to optical interference than the wired synchronization method.

[0007] In recent years, efforts have been made to improve resistance to optical interference by increasing the speed of detection circuits, making detection pulses redundant, and improving resistance to disturbances. As a result, many light curtains now employ optical synchronization methods. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2002-124169 [Overview of the project] [Problems that the invention aims to solve]

[0009] Incidentally, the operation indicator lights for light curtains are generally provided on both the light emitter and the light receiver. In this case, there is a need to synchronize the illumination state of the operation indicator lights on both the light emitter and the light receiver. For example, regarding the previously mentioned (1) power on / off state and (3) error state, the states of the light emitter and the light receiver may differ. On the other hand, regarding (2) OSSD output on / off state, i.e., light in / out state, the illumination state of the operation indicator lights on both the light emitter and the light receiver must be the same.

[0010] Therefore, in order to improve the visibility of the operation indicator light, it is desirable to synchronize the operation indicator light display on both the transmitter and receiver. To achieve such synchronized display of the operation indicator light, it is necessary to inform the transmitter of the on / off status of the OSSD output from the receiver.

[0011] For example, in a light curtain employing a wired synchronization method, as described in Patent Document 1, the light emitter and light receiver are originally connected via a cable. Therefore, it is sufficient to simply add a communication line for synchronized display control within that cable.

[0012] On the other hand, in light curtains employing an optical synchronization method, there is no communication path from the receiver to the emitter. Therefore, in order to synchronize the operation indicator lights on both the emitter and receiver, a separate communication line for synchronized display control must be laid between the emitter and receiver. In other words, wiring work between the emitter and receiver becomes necessary, which negates the advantages of the optical synchronization method.

[0013] In view of the above problems, the present invention aims to improve the wiring workability when an operation indicator light is provided in a light curtain using an optical synchronization method. [Means for solving the problem]

[0014] The light curtain according to the present invention comprises, for example, a light emitter having a plurality of first light-emitting elements, a light receiver having a plurality of first light-receiving elements arranged opposite to the light emitter and receiving light emitted from the plurality of first light-emitting elements, and a synchronization means for synchronizing the light emission timing of the light emitter and the light-receiving timing of the light receiver by optical communication, and outputs a safety signal to the outside based on whether a plurality of optical axes formed between the light emitter and the light receiver are in a light-shielding state, and comprises a first operation indicator light provided on the light emitter for displaying the operating state of the light curtain, a second operation indicator light provided on the light receiver for displaying the operating state of the light curtain, at least one set of optical elements provided on the light emitter and the light receiver respectively for displaying the first operation indicator light and the second operation indicator light in conjunction, and a control circuit for displaying the first operation indicator light and the second operation indicator light in conjunction using the at least one set of optical elements.

[0015] Other features, elements, steps, advantages, and characteristics will become more apparent from the following embodiments for carrying out the invention and the accompanying drawings related thereto.

Effects of the Invention

[0016] According to the present invention, dedicated wiring for interlocking the operation indicator lights provided on both the projector and the light receiver becomes unnecessary. Therefore, it becomes possible to improve the wiring workability when providing operation indicator lights for a light curtain of an optical synchronization system.

Brief Description of the Drawings

[0017] [Figure 1] It is a diagram showing a schematic configuration of a light curtain. [Figure 2] It is a perspective view showing an overall configuration of a projector. [Figure 3] It is a front view showing an overall configuration of a projector. [Figure 4] It is a perspective view showing one end of a projector. [Figure 5] It is a functional block diagram of a light curtain. [Figure 6] It is a diagram showing a first embodiment of a projector. [Figure 7] It is a diagram showing an arrangement example of a light source for an indicator light in the first embodiment. [Figure 8] It is a diagram showing the relationship between the emission color and the operation mode. [Figure 9] It is a diagram showing an arrangement example of a light source for an indicator light in the second embodiment. [Figure 10] It is a diagram showing an example of a display pattern in the second embodiment. [Figure 11] It is a diagram showing an arrangement example of a light source for an indicator light and an example of a display pattern in the third embodiment. [Figure 12] It is a diagram showing an arrangement example of a light source for an indicator light and an example of a display pattern in the fourth embodiment. [Figure 13] It is a diagram showing the relationship between the average light reception amount and the display pattern. [Figure 14]This figure shows the relationship between the minimum light reception level and the display pattern. [Figure 15] This figure shows an example of how the light curtain will look when lit. [Figure 16] This figure shows an image of the light curtain lit up (second example). [Figure 17] This is a functional block diagram of a light curtain equipped with a display pattern control function. [Figure 18] This diagram shows the processing flow for display pattern control. [Figure 19] This figure shows an example of the configuration of a light curtain in the fifth embodiment. [Figure 20] This is a schematic diagram showing an example of optical axis formation. [Figure 21] This diagram shows the processing flow for linked display control. [Figure 22] This is a plan view showing one example of a photodetector configuration. [Figure 23] This is a perspective view showing one example of a light receiver configuration. [Figure 24] This figure shows an example of light interference between multiple light curtains. [Figure 25] This figure shows an example of optical axis drive control. [Figure 26] This is a longitudinal cross-sectional view showing an example of a photodetector equipped with a light leakage suppression mechanism. [Modes for carrying out the invention]

[0018] <Light Curtain> Figure 1 shows a schematic configuration of a light curtain. The light curtain 1 in this example configuration is one form of a multi-optical axis photoelectric sensor and generally comprises a pair of light emitters 100 and light receivers 200.

[0019] The light curtain 1 detects a person or object depending on whether at least one of the multiple optical axes (six optical axes Oax1 to Oax6 in this figure) that are spaced apart between the parallel-arranged light emitters 100 and light receivers 200 is blocked from light. For example, the light curtain 1 can be installed at the entrance or exit of a hazardous area where hazardous sources such as press equipment are placed, and used as a safety device to detect the intrusion or presence of workers.

[0020] The light emitter 100 and the light receiver 200 each comprise a long (maximum of 2m or more) housing 110 and 210, and cables 120 and 220 connected thereto.

[0021] The housing 110 has a hollow metal case 111 extending in the longitudinal direction, and hollow end caps 112 and 113 (corresponding to end members) connected to both ends of the metal case 111, respectively. Similarly, the housing 210 has a hollow metal case 211 extending in the longitudinal direction, and hollow end caps 212 and 213 (corresponding to end members) connected to both ends of the metal case 211, respectively. In this embodiment, the longitudinal direction is a direction substantially parallel to the direction in which the multiple optical axes formed between the light emitter 100 and the light receiver 200 are spaced apart from each other.

[0022] Thus, by using high-rigidity metal cases 111 and 211 as the cases for housings 110 and 210, the long housings 110 and 210 become less prone to deformation. Consequently, adjusting the placement of the light emitter 100 and light receiver 200 (for example, adjusting the angle to position them parallel) becomes relatively easy. Alternatively, inexpensive and lightweight extruded aluminum products may be used as the metal cases 111 and 211. In that case, the cross-section of the metal cases 111 and 211 will be the same shape regardless of where they are cut in the extrusion direction (=longitudinal direction).

[0023] The end caps 112, 113, 212, and 213 may each be formed by injection molding using a resin material, or by die casting using a metal material such as zinc. The lower end caps 113 and 213 in this figure may be fitted with interfaces for cables 120 and 220. Therefore, the end caps 113 and 213 may be larger than the upper end caps 112 and 212 in this figure.

[0024] <Floodlight> Figures 2 and 3 are perspective and front views, respectively, showing the overall configuration of the floodlight 100. Figure 4 is a perspective view showing one end of the floodlight 100.

[0025] As mentioned earlier, the floodlight 100 comprises a housing 110 and a cable 120. The housing 110 also includes a metal case 111 and end caps 112 and 113. Furthermore, the floodlight 100 includes a front cover 130, an indicator light 140, and a bumper section 150.

[0026] The front cover 130 is a long, translucent plate attached to cover the front opening (=detection window) of the housing 110. In the front opening of the housing 110, light-emitting elements 161 to 166, each for forming multiple optical axes Oax1 to Oax6, are arranged at equal intervals along the longitudinal direction. In other words, the front cover 130 is attached to the housing 110 so as to intersect with the multiple optical axes Oax1 to Oax6. The front cover 130 may be an extruded translucent resin plate (such as an acrylic plate) or a glass plate. In this embodiment, the translucency of the material used as the front cover 130 refers to a translucency such that the light from the light-emitting elements 161 to 166 forming the multiple optical axes Oax1 to Oax6 is not excessively diffused outside the optical axis, and is received by the light-receiving elements 261 to 266 (described later) with a certain amount of light or more. Since the front cover 130 is made of a light-transmitting material, the worker can see the light-emitting elements 161-166 through the front cover 130.

[0027] Furthermore, it is preferable that the end cap 113 has a light-emitting element (light-emitting element 166 in Figure 3) corresponding to at least one of the multiple optical axes Oax1 to Oax6. That is, it is preferable that the light-emitting elements 161 to 166 be arranged at equal intervals in the longitudinal direction over the entire length of the floodlight 100 from one end to the other. Also, it is preferable that the cable 120 extends from the back (or side) of the end cap 113 rather than from the bottom surface of the end cap 113. With this configuration, the floodlight 100 can be installed very close to the installation surface (floor, etc.). Therefore, dead space can be eliminated.

[0028] The indicator light 140 is controlled to flash on and off with a light color corresponding to, for example, the operating status of the light curtain 1 (such as the optical axis detection status and self-diagnosis results) or work instructions regarding the loading and unloading of objects. In other words, the indicator light 140 functions as an operation indicator light or a work instruction light. Therefore, by looking at the indicator light 140 of the light curtain 1, the worker can visually recognize the operating status of the light curtain 1 or work instructions.

[0029] In particular, the indicator light 140 is positioned longitudinally outward from at least one of the outer surfaces of the front cover 130 and the housing 110, or is formed in series with the front cover 130 (details of the structure will be described later). Referring to this figure, the indicator light 140 is provided on both sides of the front cover 130. With the indicator light 140 positioned or formed in this manner, a highly visible display can be provided without impairing the rigidity of the housing 110. More specifically, the indicator light 140 is a long extruded product, and is positioned so that the longitudinal direction of the indicator light 140 is aligned with the longitudinal direction of the housing 110. Note that the indicator light 140 only needs to be positioned 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 long. For example, a configuration in which multiple members that function as indicator lights 140 are positioned along the longitudinal direction of the housing 110 is also possible.

[0030] Furthermore, the indicator light 140 is a light-diffusing member that diffuses light incident from an indicator light source 170 (not shown) housed inside the housing 110 in various directions. More specifically, the indicator light 140 contains a light diffuser that diffuses light in various directions. In a configuration where the light-diffusing member of the indicator light 140 contains a light diffuser, the indicator light 140 can be illuminated relatively uniformly even if the indicator light source 170 is small relative to the surface size of the indicator light 140, thus enabling a highly visible display. In this embodiment, the indicator light 140 is made of a transparent resin to which fine particles have been added, and is therefore milky white. If the base resin is not transparent but a specific color, the color will be a mixture of that specific color and milky white. In addition to the configuration containing a light diffuser, the indicator light 140 can also be made of a milky white resin (such as silicone) to achieve relatively uniform illumination. The light-diffusing member for the indicator light 140 can be any member that diffuses the light from the indicator light source 170 so that it can be seen from more directions, or any member that diffuses the light from the indicator light source 170 to such an extent that the outline of the indicator light source 170 is difficult to see from outside the indicator light 140. For example, a light-diffusing member whose surface is processed to diffuse the light from the indicator light source 170 may be arranged as the indicator light 140. As a surface processing that diffuses light, for example, texturing is known. With a configuration in which a light-diffusing member with a processed surface is arranged as the indicator light 140, it becomes easier to manufacture a member that has a region that diffuses light relatively easily and a region that does not diffuse light relatively easily.

[0031] The bumper section 150 protrudes outward from the region of the front cover 130's outer surface that intersects with multiple optical axes Oax1 to Oax6, and is positioned along the longitudinal direction of the housing 110 (details of the structure will be described later).

[0032] As shown in the figure, the bumper sections 150 are formed in pairs, protruding from both sides of the front cover 130. In other words, the front cover 130 is positioned in a narrow valley between the pair of bumper sections 150 (the twin bumpers proposed by the applicant) located on both sides and rising forward. Therefore, even if an object collides with the front of the floodlight 100, the impact is absorbed by the bumper sections 150. Consequently, the front cover 130 is less likely to be damaged. The bumper sections 150 may be made of a hard material such as metal.

[0033] Furthermore, the configuration of the light receiver 200 is basically the same as that of the light emitter 100. Therefore, in the explanatory text for Figures 2 to 4, the configuration of the light receiver 200 can be understood by appropriately substituting light emitter 100 and light-emitting elements 161 to 166 with light receiver 200 and light-receiving elements 261 to 266, respectively, and appropriately substituting other 100-series codes with 200-series codes. The same applies to the explanations that follow.

[0034] <Function Block> Figure 5 is a functional block diagram of the light curtain 1. In the light curtain 1 of this configuration example, the floodlight 100 includes an indicator light 140, light-emitting elements 161 to 166, a light source 170 for the indicator light, a control circuit 181, and a communication circuit 182.

[0035] The light-emitting elements 161 to 166 are arranged at equal intervals along the longitudinal direction of the light emitter 100 at a predetermined pitch. Based on the light emission control signal input from the control circuit 181, the light-emitting elements 161 to 166 sequentially emit multiple light beams toward the light receiver 200 (particularly the light-receiving elements 261 to 266) in a time-division manner to form multiple optical axes Oax1 to Oax6, respectively. Note that the light-emitting elements 161 to 166 may be, for example, light-emitting diodes that emit infrared light.

[0036] The indicator light source 170 supplies light to the indicator light 140 for display purposes based on the display control signal input from the control circuit 181. The indicator light source 170 may be capable of switching between multiple light emission colors (e.g., red, green, and orange) depending on the operating state of the light curtain 1 or work instructions.

[0037] Furthermore, the indicator light source 170 is preferably pulsed on at a timing that is temporally offset from the light emission / reception timing of each of the multiple optical axes Oax1 to Oax6. With this type of on / off control, interference with optical axis detection by the indicator light source 170 can be suppressed.

[0038] The indicator light 140 diffuses the light incident from the indicator light source 170 in various directions. By looking at the indicator light 140, the worker can visually recognize the operating status of the light curtain 1 or work instructions.

[0039] The control circuit 181 receives instructions from the light receiver 200 and generates a light emission control signal to sequentially drive the light-emitting elements 161 to 166 in a time-division manner. The control circuit 181 also generates a display control signal to turn the indicator light source 170 on and off with an arbitrary emission color. Furthermore, the control circuit 181 exchanges various information with the communication circuit 182.

[0040] The communication circuit 182 communicates with the light receiver 200 (particularly the communication circuit 282) via wired or wireless means. For example, the communication circuit 182 receives input from the light receiver 200 regarding the operating status of the light curtain 1 (such as the optical axis detection status and self-diagnosis results) and transmits it to the control circuit 181.

[0041] On the other hand, the light receiver 200 includes an indicator light 240, light receiving elements 261 to 266, a light source 270 for the indicator light, a control circuit 281, a communication circuit 282, an output circuit 283, and an input circuit 284.

[0042] The light-receiving elements 261 to 266 are arranged at equal intervals along the longitudinal direction of the light receiver 200, with the same pitch as the light-emitting elements 161 to 166. Based on the light-receiving control signal input from the control circuit 281, the light-receiving elements 261 to 266 sequentially receive multiple light beams in a time-division manner to form multiple optical axes Oax1 to Oax6. The light-receiving elements 261 to 266 may also be, for example, photodiodes or phototransistors that output an electrical signal corresponding to the amount of infrared light received.

[0043] The indicator light source 270 supplies light to the indicator light 240 for display based on the display control signal input from the control circuit 281. Like the indicator light source 170, the indicator light source 270 may be able to switch between multiple light emission colors (e.g., red, green, and orange) depending on the operating status of the light curtain 1 or work instructions.

[0044] Furthermore, the indicator light source 270 is preferably pulsed on at a timing that is temporally offset from the light emission / reception timing of each of the multiple optical axes Oax1 to Oax6. With this type of on / off control, interference with optical axis detection by the indicator light source 270 can be suppressed.

[0045] Furthermore, consider the case where the indicator light source 270 is continuously lit. In this case, even if the DC light from the indicator light source 270 is received by the light receiving elements 261 to 266, it is desirable to provide a saturation prevention circuit (= DC component subtraction circuit) so that the electrical signals output from the light receiving elements 261 to 266 do not become saturated.

[0046] The indicator light 240 diffuses the light incident from the indicator light source 270 in various directions. By looking at the indicator light 240, the worker can visually recognize the operating status of the light curtain 1 or work instructions.

[0047] Furthermore, since indicator lights 140 and 240 are provided on both the light emitter 100 and the light receiver 200, a highly visible display can be achieved.

[0048] The control circuit 281 generates a light receiving control signal to sequentially activate the light receiving elements 261 to 266 in a time-division manner, synchronized with the drive timing of each of the light-emitting elements 161 to 166. The control circuit 281 also generates a display control signal to turn the indicator light source 270 on and off with an arbitrary emission color. Furthermore, the control circuit 281 exchanges various information with the communication circuit 282, the output circuit 283, and the input circuit 284.

[0049] Furthermore, the control circuit 281 monitors the light-ingress / light-blocking state of each of the multiple optical axes Oax1 to Oax6. For example, the control circuit 281 may output an operation permission signal (ON signal) when all of the multiple optical axes Oax1 to Oax6 are in the light-ingress state. On the other hand, the control circuit 281 may output an operation disallowance signal (OFF signal) when at least one of the multiple optical axes Oax1 to Oax6 is in the light-blocking state.

[0050] Furthermore, the control circuit 281 may be equipped with a self-diagnosis function to determine whether it is in a state where it can correctly monitor the light-ingress / light-blocking state of each of the multiple optical axes Oax1 to Oax6. As a self-diagnosis method, for example, the control circuit 281 and the output circuit 283 (e.g., OSSD [Output Signal Switching Device] output) may be multiplexed, and the match / mismatch of the multiplexed signals may be determined.

[0051] For example, if the multiplexed signals match, an OK diagnosis (a diagnosis result indicating that the system is in a state where it can be properly monitored) is issued. On the other hand, if the multiplexed signals do not match, an NG diagnosis (a diagnosis result indicating that the system is not in a state where it can be properly monitored) is issued. In the event of an NG diagnosis, an operation prohibition signal (OFF signal) may be output regardless of the light input status of each of the multiple optical axes Oax1 to Oax6.

[0052] Information that can be used for safety control is designated as safety information, while general information that cannot be used for safety control is designated as non-safety information. For example, the OSSD output is a type of safety information. The signals used to control the on / off state of the indicator light sources 170 and 270 may be signals indicating safety information or signals indicating non-safety information.

[0053] The communication circuit 282 communicates with the floodlight 100 (particularly the communication circuit 182) by wire or wireless means. The communication circuit 282 receives information from the control circuit 281 regarding the operating status of the light curtain 1 (such as the optical axis detection status and self-diagnosis results) and transmits it to the floodlight 100.

[0054] The output circuit 283 communicates with external devices (e.g., safety controllers) 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 (such as the optical axis detection status and self-diagnosis results) and transmits it to the external devices.

[0055] The input circuit 284 communicates with external devices (e.g., safety controllers) via wired or wireless means. For example, the input circuit 284 receives input from external devices regarding work instructions for loading and unloading objects and transmits them to the control circuit 281.

[0056] <First Embodiment> Figure 6 is a diagram showing a first embodiment of the floodlight 100 (a schematic cross-sectional view when the metal case 111 of the floodlight 100 is cut at an arbitrary position in the longitudinal direction). The floodlight 100 of this embodiment comprises a housing 110 (only the metal case 111 is depicted in this figure), a front cover 130, an indicator light 140, a bumper portion 150, a light source for the indicator light 170, a circuit board 190, and a light shielding plate 191.

[0057] The metal case 111 is an extruded product that extends in the longitudinal direction of the floodlight 100. As shown in the figure, the metal case 111 consists of a main body 111a, a pair of first protrusions 111b, and a pair of second protrusions 111c.

[0058] The main body 111a is a hollow member with a U-shaped cross-section and an opening on the upper side of the paper (= the front side of the floodlight 100). The internal space of the main body 111a houses the indicator light source 170, the substrate 190, and the light shielding plate 191.

[0059] A pair of first protruding strips 111b project inward from the inner surfaces of the left and right walls of the main body 111a toward the inside of the opening. That is, the pair of first protruding strips 111b are arranged facing each other at a predetermined distance, straddling the optical axis intersection region X (= the region where multiple optical axes Oax1 to Oax6 intersect). The pair of first protruding strips 111b also function as cover mounting parts for supporting the front cover 130. As described above, a translucent material is used for the front cover 130, but it is sufficient that at least the optical axis intersection region X is translucent and the optical axes Oax1 to Oax6 are not obstructed. For example, in this embodiment, the portion that contacts the pair of first protruding strips 111b does not necessarily have to be translucent.

[0060] A pair of second protrusions 111c extend further upward from the upper ends of the left and right walls of the main body 111a. Furthermore, the tips of each of the second protrusions 111c are bent inward towards the opening. The pair of second protrusions 111c function as a bumper portion 150 to protect the front cover 130. In this embodiment, the aforementioned bumper portion 150 is formed from the metal case 111. Therefore, the robustness of the floodlight 100 can be increased.

[0061] The front cover 130 is supported (suspended) at both ends, straddling a pair of first protruding strips 111b. The front cover 130 allows light to pass through that forms multiple optical axes Oax1 to Oax6 in the optical axis intersection region X. The area between the front cover 130 and the pair of first protruding strips 111b (see thick line α) is treated to improve liquid resistance. For example, a packing is placed, or it is bonded with a liquid-resistant adhesive. As will be described later, the indicator light 140 increases the adhesion between the front cover 130 and the first protruding strips 111b, further improving liquid resistance.

[0062] The indicator lights 140 are positioned on both sides of the front cover 130, adjacent to the bumper section 150. Referring to this figure, the indicator lights 140 are positioned along the longitudinal direction of the floodlight 100 in the area sandwiched between the tip (bent portion) of the first protruding strip 111b and the second protruding strip 111c, that is, in the area sandwiched between the bumper section 150 and the front cover 130.

[0063] The indicator light 140 diffuses the light incident from the indicator light source 170 through the front cover 130 in various directions. For example, the indicator light 140 may be provided with a taper to refract and diffuse the light incident from the indicator light source 170 toward the inside of the opening.

[0064] With the indicator lights 140 arranged in this manner, they are easily visible even from the side of the floodlight 100. Therefore, in a small (slim-diameter) light curtain 1 using a metal case 111, highly visible displays can be provided without compromising the rigidity of the housing 110. In particular, when a pair of bumper sections 150 are provided protruding from both sides of the front cover 130, the improvement in visibility due to the above arrangement can become even more pronounced.

[0065] Furthermore, in the floodlight 100 of this embodiment, the indicator light 140 also functions as a pressing member for pressing and fixing the front cover 130 downward (towards the first protruding strip 111b). Therefore, the airtightness between the front cover 130 and the first protruding strip 111b is increased, which prevents liquid from entering the inside of the metal case 111 and improves liquid resistance. In order for the indicator light 140 to function as a pressing member, it is desirable that the indicator light 140 has appropriate elasticity.

[0066] The indicator light source 170 is mounted on the main surface of the substrate 190 (= the surface facing the front cover 130). The indicator light source 170 supplies light for display to the indicator light 140 via the front cover 130. As shown in this figure, the light emitted from the indicator light source 170 passes between the pair of first protruding strips 111b without being obstructed by the pair of first protruding strips 111b and is supplied to the indicator light 140 via the front cover 130.

[0067] The number of indicator light sources 170 is not limited. For example, the indicator light sources 170 may be arranged intermittently in multiple locations along the longitudinal direction of the floodlight 100, or they may be formed in a continuous series.

[0068] Furthermore, the indicator light source 170 may be equipped with a lens for controlling the direction of the emitted light. For example, a lens may be provided that is optically designed to reduce the angle of light spread in the left-right direction of the figure and increase the angle of light spread in the depth direction of the figure. Such a lens makes it possible to reduce the number of indicator light sources 170 while suppressing interference with multiple optical axes Oax1 to Oax6.

[0069] The type of lens may be a point-symmetric lens (single arrangement) or a cylindrical lens (series arrangement of extruded products).

[0070] The light-shielding plate 191 is provided 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 less likely to interfere with the multiple optical axes Oax1 to Oax6.

[0071] Furthermore, consider the case where the optical axis Oax1 to Oax6 is formed by infrared light, and visible light (red light, green light, or orange light, etc.) is emitted from the indicator light source 170. In this case, a filter that transmits infrared light and blocks visible light may be provided in the light receiver 200. In particular, when an indicator light 240 is provided in the light receiver 200, it is sufficient to have a configuration in which a filter that transmits infrared light and blocks visible light is arranged so as not to obstruct the display of the indicator light 240. The filter may be provided in the light receiving elements 261 to 266, or it may be provided in the lens that guides light to the light receiving elements 261 to 266.

[0072] Figure 7 shows an example of the arrangement of the indicator light source 170 in the first embodiment. As shown in this figure, the light-emitting elements 161 to 166 may be arranged at equal intervals along the longitudinal direction of the substrate 190 in the central region 190a of the substrate 190. On the other hand, the indicator light source 170 may be arranged at equal intervals along the longitudinal direction of the substrate 190 in the end region 190b of the substrate 190.

[0073] In particular, the light-emitting elements 161-166 and the indicator light source 170 may be arranged so that their positions in the longitudinal direction of the substrate 190 are offset from each other (staggered). With such an arrangement, mutual interference between the light-emitting elements 161-166 and the indicator light source 170 is suppressed.

[0074] 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 may be reduced so that there is some unevenness in the light supplied to the indicator lights 140.

[0075] <Display contents> Figure 8 shows the relationship between the light emission color of the indicator light 140 and its operating mode. As shown in this figure, the indicator light 140 can be switched between operation indicator light mode and work indicator light mode. For example, the control signal for switching the operating mode of the indicator light 140 may be a 2-bit (4-value) digital signal input to the input circuit 284.

[0076] First, let's explain the case where the indicator light 140 is set to operation indicator light mode. When the indicator light 140 is set to operation indicator light mode, it is controlled to turn on and off with a light color corresponding to the operating status of the light curtain 1.

[0077] Referring to this diagram, for example, when the light curtain 1 is in a normal state (for example, when none of the multiple optical axes Oax1 to Oax6 are blocked), the indicator light 140 lights up green. On the other hand, when the light curtain 1 is in an abnormal state (for example, an emergency stop state where at least one of the multiple optical axes Oax1 to Oax6 is blocked), the indicator light 140 lights up red. Also, when the light curtain 1 is in an alarm notification state (for example, an NG diagnosis state by the self-diagnosis function), the indicator light 140 flashes red.

[0078] Next, we will describe the case when the indicator light 140 is set to work instruction light mode. When the indicator light 140 is set to work instruction light mode, it is controlled to turn on and off with a light color corresponding to the work instruction signal received by the input circuit 284.

[0079] Referring to this diagram, for example, when the work instruction signal indicates "work permitted," the indicator light 140 lights up green. On the other hand, when the work instruction signal indicates "work prohibited," the indicator light 140 lights up red. Also, when the work instruction signal indicates "self-diagnosis," the indicator light 140 blinks red. In addition, in work instruction light mode, the indicator light 140 may light up orange. The way in which these lighting states are used may vary depending on the user.

[0080] Furthermore, if the light curtain 1 is used in an environment where the illumination of the indicator light 140 is undesirable, it is possible to keep the indicator light 140 constantly off.

[0081] <Considerations regarding the decrease in light intensity of optical bearings> As explained earlier, a light curtain consists of two components: a light emitter and a light receiver, with multiple light-emitting and light-receiving elements arranged axially. When using a light curtain, the light emitter and light receiver should be positioned parallel to each other, and their angles adjusted so that light is received by all elements. The greater the distance between the light emitter and light receiver, the more difficult it becomes to determine if the orientation is correct, and the harder it is to see the display. Therefore, adjusting the angles becomes more difficult.

[0082] Light curtains are sometimes used in harsh environments where they may be exposed to dirt or impacts. Therefore, some products feature a bumper-shaped protrusion extending beyond the front cover to protect the detection unit's front cover. However, preventing dirt from accumulating on the front cover is difficult. If dirt builds up and the light-receiving element can no longer receive sufficient light, the optical axis may become obscured, potentially causing the device to shut down due to a safety output from the light curtain. Therefore, maintenance cleaning of the front cover's glass surface is necessary before it affects the optical axis detection results.

[0083] In environments where dirt accumulates, it is necessary to install light curtains to ensure sufficient optical bearing light intensity to compensate for the decrease in optical bearing light intensity (= the amount of light received by each optical axis, which is the criterion for determining whether or not the optical axis is in a state of light blocking) due to dirt. Furthermore, it is necessary to monitor the decrease in optical bearing light intensity over time and perform maintenance before the optical axis becomes completely blocked.

[0084] In response to the above requirements, there are models of light curtains that allow you to check the light bearing intensity on the unit itself. For example, some existing models express the light bearing intensity by the number of lit LEDs (light-emitting diodes) or by a 7-segment digital display. However, these displays are small and difficult to see from a distance. Therefore, it can be difficult to check the display when installing and adjusting the light curtain. Also, even during operation of the light curtain, it is difficult to notice a decrease in the light bearing intensity unless you consciously check the small display mentioned above.

[0085] On the other hand, the light curtain 1 described herein is equipped with large indicator lights 140 and 240 so that the operating status of the light curtain 1 can be easily seen, while maintaining both miniaturization and high visibility.

[0086] In light of the above considerations, we propose a novel embodiment below in which the highly visible indicator lights 140 and 240 described above can display information linked to the light intensity of the optical bearing.

[0087] <Second Embodiment> Figure 9 shows an example of the arrangement of light sources for indicator lights in the second embodiment. In this embodiment, multiple (two in this figure) substrates 190 having the same structure are cascaded along the longitudinal direction. With such a configuration, the length of the light curtain 1 can be easily increased simply by increasing the number of cascaded substrates 190.

[0088] In this figure illustrating the light emitter 100, the light-emitting elements 161 to 166 may be arranged at equal intervals along the longitudinal direction of the substrate 190 in the central region 190a of the substrate 190, as in Figure 7 above. Referring to this figure, on the substrate 190 on the right side of the page, the light-emitting elements 161 to 163 are arranged from right to left in the order shown in the figure. On the other hand, on the substrate 190 on the left side of the page, the light-emitting elements 164 to 166 are arranged from right to left in the order shown in the figure. When understanding the configuration of the light receiver 200, the light-emitting elements 161 to 166 can be replaced with light-receiving elements 261 to 266, respectively.

[0089] On the other hand, the indicator light sources 170 may be arranged at equal intervals along the longitudinal direction of the substrate 190 in the edge region 190b of the substrate 190. In particular, the indicator light sources 170 can be distinguished as indicator light sources 170a, 170b, and 170c depending on the differences in their respective control systems. Referring to this figure, the indicator light sources 170a, 170b, and 170c are arranged on the two substrates 190 in the order shown, from left to right on the page. Although not shown in this figure, the light curtain 1 is equipped with an OSSD indicator light whose display mode changes according to the OSSD output, separate from the indicator light sources 170. Therefore, the display mode of the indicator light sources 170 changes to indicate the light receiving state of the light receiving elements 261 to 266.

[0090] As described above, the light-emitting elements 161-163 (or 164-166) and the indicator light sources 170a, 170b, and 170c are arranged as a single unit on a common substrate 190. In particular, the indicator light sources 170a, 170b, and 170c are unitized as a set of three.

[0091] As a variation, the light-emitting elements 161-163 (or 164-166) and the indicator light sources 170a, 170b, and 170c may each be separate units. That is, the unit in which the light-emitting elements 161-163 (or 164-166) are arranged and the unit in which the indicator light sources 170a, 170b, and 170c are arranged may be independent.

[0092] Figure 10 shows an example of a display pattern in the second embodiment. The upper part of this figure depicts the "a-lighted state". In this "a-lighted state", the indicator light source 170a is lit, while both indicator light sources 170b and 170c are off. Therefore, the display pattern is one light on, two lights off, repeated from left to right on the page.

[0093] The middle section of this diagram depicts the "ab-lighted state." In this "ab-lighted state," both indicator light sources 170a and 170b are lit, while indicator light source 170c is off. Therefore, the display pattern repeats from left to right on the page, with "two lights on, one off."

[0094] The lower part of this diagram depicts the "abc lit state." In this "abc lit state," the indicator light sources 170a, 170b, and 170c are all lit.

[0095] Thus, in the example display pattern of this embodiment, the indicator light sources 170a, 170b, and 170c are illuminated at appropriate intervals. Therefore, by switching the display pattern to one of the three above according to the optical bearing light intensity, the optical bearing light intensity can be determined simply by looking at the large indicator lights 140 and 240. As a result, a light curtain 1 is provided that is easy to adjust during initial setup and has high maintainability.

[0096] <Third Embodiment> Figure 11 shows an example of the arrangement of indicator light sources and an example of a display pattern in the third embodiment. In this embodiment, two each of the indicator light sources 170a, 170b, and 170c are arranged on a common substrate 190 as a single unit. That is, the indicator light sources 170a, 170b, and 170c are unitized in sets of six.

[0097] Referring to this figure, the circuit board 190 has two indicator light sources 170a, 170b, and 170c arranged in the order shown, from left to right on the page.

[0098] The upper part of this diagram depicts the "a-lighting state." In this "a-lighting state," indicator light source 170a is lit, while indicator light sources 170b and 170c are both off. Therefore, the display pattern repeats from left to right on the page, with "two lights on, four lights off."

[0099] The middle section of this diagram depicts the "ab-lighted state." In this "ab-lighted state," both indicator light sources 170a and 170b are lit, while indicator light source 170c is off. Therefore, the display pattern repeats from left to right on the page, with "four lights on, two off."

[0100] The lower part of this diagram depicts the "abc lit state." In this "abc lit state," the indicator light sources 170a, 170b, and 170c are all lit.

[0101] In the second embodiment described above (Figure 10), the number of indicator light sources 170a, 170b, and 170c, which are in a non-lit state (off state), is increased or decreased by one for each display pattern, such as 2, 1, and 0.

[0102] On the other hand, in the example arrangement of indicator light sources and display patterns of this embodiment, the number of indicator light sources 170a, 170b, and 170c that are not lit increases or decreases by two for each display pattern, to 4, 2, and 0, respectively. Therefore, compared to the second embodiment described above (Figure 10), the difference in distance between the light sources that are partially lit becomes larger. As a result, it becomes easier to recognize the switching of the display pattern (and consequently the change in the amount of light in the optical bearing) even when passing through the light diffuser.

[0103] <Fourth Embodiment> Figure 12 shows an example of the arrangement of indicator light sources and an example of the display pattern in the fourth embodiment. In this embodiment, as in the second embodiment (Figure 10) described above, the indicator light sources 170a, 170b, and 170c are unitized as a set of three. However, the arrangement order of the indicator light sources 170a, 170b, and 170c differs for each substrate 190.

[0104] Referring to this figure, on the circuit board 190 on the left side of the figure, indicator light sources 170a, 170b, and 170c are arranged in the order shown, from left to right on the page. On the other hand, on the circuit board 190 on the right side of the figure, indicator light sources 170a, 170b, and 170c are arranged in the order shown, from right to left on the page.

[0105] The upper part of this diagram depicts the "a-lighting state." In this "a-lighting state," indicator light source 170a is lit, while indicator light sources 170b and 170c are both off. Therefore, the display pattern repeats from left to right on the page: "one lit, four off, one lit."

[0106] The middle section of this diagram depicts the "ab-lighted state." In this "ab-lighted state," both indicator light sources 170a and 170b are lit, while indicator light source 170c is off. Therefore, the display pattern repeats from left to right on the page: "one off, four on, one off."

[0107] Thus, with the example arrangement of indicator light sources and display patterns in this embodiment, while maintaining a set of three units, the number of indicator light sources 170a, 170b, and 170c that are not illuminated increases or decreases by two for each display pattern, such as 4, 2, and 0. Therefore, as with the third embodiment described above (Figure 11), it becomes easier to recognize the switching of the display pattern (and consequently the change in the light intensity of the optical bearing).

[0108] <Relationship between optical bearing light intensity and display pattern> Figure 13 shows the relationship between the optical bearing light intensity (average light received) and the display pattern. The optical bearing light intensity is converted by an A / D converter and compared with a threshold. The criterion for determining the display pattern may also be the average value of the light received at each optical axis (= average light received).

[0109] First, the ON state of the OSSD indicates that the condition "the amount of light received by all optical axes is above the first threshold" is met for the photodetectors 261 to 266, and the OSSD output is ON. In this embodiment, for convenience, the state in which the photodetectors 261 to 266 meet this condition and the OSSD output can be turned ON is defined as the ON state, and the ON state is the state in which "the amount of light received by all optical axes is above the first threshold." The first threshold mentioned above is the same as the threshold used to determine whether each individual optical axis is in a light-shielding state or not. Therefore, the average amount of light received in that state is relatively high and cannot be as low as a value considered to be "completely shielded." In other words, since the amount of light received by all optical axes is above the first threshold, it is impossible for the average amount of light received to fall below the first threshold.

[0110] Therefore, the "off" display when the average light reception amount falls below the first threshold can be understood as a display mode that exists only when the light-receiving elements 261-266 do not satisfy the condition that "the light reception amount for all optical axes is above the first threshold," i.e., when the judgment is OFF. In this figure, a horizontal axis is introduced to clarify this. The horizontal axis shows the result of the individual light reception amount judgment for each optical axis (= the number of optical axes judged to be in a shaded state by the individual optical axis judgment). Note that the OSSD OFF state indicates that the condition that "the light reception amount for all optical axes is above the first threshold" is not satisfied for the light-receiving elements 261-266, and the OSSD output is OFF. In this embodiment, for convenience, the judgment OFF state is defined as the state when the light-receiving elements 261-266 do not satisfy the condition that "the light reception amount for all optical axes is above the first threshold," i.e., when "the light reception amount for at least one optical axis is below the first threshold." In other words, in the judgment ON state, the number of shaded optical axes is 0. On the other hand, in the judgment OFF state, the number of shaded optical axes is 1 or more.

[0111] It should be noted that the individual light reception amount judgment for each optical axis is solely for switching between the judgment ON state (display color: green) and the judgment OFF state (display color: red). Therefore, the step for making this judgment in the flowchart shown later is the same step as the step for comparing the average light reception amount with the threshold.

[0112] Furthermore, the thresholds used to determine the number of illuminated indicator light sources 170a, 170b, and 170c are shifted between the ON and OFF states. First, let's explain the ON state. As mentioned earlier, the ON state is when the amount of light received by all optical axes is above the first threshold. Therefore, in the ON state, thresholds for switching the number of illuminated lights (the fourth and fifth thresholds in this diagram) are set in the region where the average amount of light received is relatively high.

[0113] As shown in this diagram, when the judgment is ON and the average light received is lower than the fourth threshold, one green light will illuminate (meaning only the indicator light source 170a will be illuminated green). When the average light received is higher than the fourth threshold but lower than the fifth threshold, two green lights will illuminate (meaning both indicator light sources 170a and 170b will be illuminated green). When the average light received is higher than the fifth threshold, three green lights will illuminate (meaning indicator light sources 170a, 170b, and 170c will be illuminated green). In other words, the number of illuminated green lights increases as the average light received increases.

[0114] Furthermore, the amount of light received by each optical axis decreases as the distance between the light emitter 100 and the light receiver 200 increases. It is conceivable that even if the light emitter 100 and the light receiver 200 are installed parallel to each other as specified, and are free of dirt and receiving light normally, the amount of light received may decrease solely due to an increase in the distance between the light emitter 100 and the light receiver 200.

[0115] In this situation, reducing the number of illuminated indicator light sources 170a, 170b, and 170c would prevent the correct transmission of information related to installation and maintenance. Therefore, it is desirable to set the threshold so that the range in which three indicator light sources 170a, 170b, and 170c are illuminated is wide. Referring to this figure, in the ON state of the judgment, the fifth threshold for switching between three illuminated indicator light sources 170a, 170b, and 170c and two illuminated is set relatively low.

[0116] Next, we will explain the OFF state. Switching the display pattern in the OFF state is useful when installing the light emitter 100 and light receiver 200. For example, consider the case where you start from an off state with 0 lights on and adjust the installation positions of the light emitters 100 and 200. In this case, it is desirable that the display pattern switches even if the average light received increases or decreases only slightly, in order to understand the direction of the adjustment (i.e., whether or not you are approaching the correct installation position).

[0117] Therefore, in the OFF state, thresholds for switching the number of lights on (first threshold, second threshold, and third threshold in this figure) are set in a region where the average light reception is relatively low. For example, the relationship between the thresholds may be first threshold < second threshold < third threshold < fourth threshold < fifth threshold, as shown in this figure. In the embodiment shown in this figure, the first threshold, second threshold, and third threshold do not affect the switching of the number of lights on in the ON state.

[0118] As shown in the diagram, when the judgment is OFF and the average light received is lower than the first threshold, the lights will be off as previously described (= the indicator light sources 170a, 170b, and 170c will be turned off). When the average light received is higher than the first threshold but lower than the second threshold, one red light will be on (= only indicator light source 170a will be lit red). When the average light received is higher than the second threshold but lower than the third threshold, two red lights will be on (= indicator light sources 170a and 170b will be lit red). When the average light received is higher than the third threshold, three red lights will be on (= indicator light sources 170a, 170b, and 170c will be lit red). In other words, the number of red lights increases as the average light received increases.

[0119] Thus, the purpose of switching the display pattern according to the light intensity of the optical bearing differs between the ON and OFF states. Specifically, the green light display pattern switch in the ON state is expected to be useful for identifying dirt accumulation (the need for maintenance) after the start of operation of Light Curtain 1. On the other hand, the red light display pattern switch in the OFF state is expected to be useful for adjusting the optical axis when installing Light Curtain 1. Therefore, in order to individually set the optimal threshold for the ON and OFF states, it is desirable to stagger the thresholds between the ON and OFF states.

[0120] However, conversely, there are also advantages to setting the thresholds to match the ON and OFF states. For example, in this diagram, looking only at the average light reception, the "one green light" in the ON state and the "three red lights (or two red lights)" in the OFF state are adjacent. Therefore, when the optical axis is blocked while maintaining the average light reception, and the system switches from the ON state to the OFF state, the display pattern switches from "one green light" to "three red lights (or two red lights)".

[0121] In other words, if we focus solely on the number of lights illuminated, there is a risk of an unnatural display pattern switching where the number of lights illuminated increases even though the optical axis is blocked. Therefore, if the priority is to clearly communicate the optical axis light intensity, it is desirable to keep the threshold the same for the ON and OFF states of the judgment to prevent the aforementioned reversal of the number of lights illuminated.

[0122] Figure 14 shows the relationship between the light intensity of the optical bearing (minimum light intensity) and the display pattern. As shown in this figure, the criterion for determining the display pattern may be the minimum value of the amount of light received at each optical axis (= minimum light intensity).

[0123] In this case, for example, a first threshold, a second threshold, and a third threshold may be set. The relationship between each threshold may be first threshold < second threshold < third threshold.

[0124] As shown in this diagram, when the minimum light intensity is lower than the first threshold, three red lights illuminate (= indicator light sources 170a, 170b, and 170c are illuminated in red). This state corresponds to the OFF state. Thus, in the OFF state, the number of illuminated red lights is fixed at three. When the minimum light intensity is higher than the first threshold but lower than the second threshold, one green light illuminates (= only indicator light source 170a is illuminated in green). When the minimum light intensity is higher than the second threshold but lower than the third threshold, two green lights illuminate (= indicator light sources 170a and 170b are illuminated in green). When the minimum light intensity is higher than the third threshold, three green lights illuminate (= indicator light sources 170a, 170b, and 170c are illuminated in green). In other words, the number of illuminated green lights increases as the minimum light intensity increases.

[0125] Thus, as a criterion for determining the display pattern, either the average value of the amount of light received in each optical axis (= average light received) or the minimum value (= minimum light received) may be used.

[0126] <Image of lights up> Figure 15 shows an image of the lighting of the light curtain 1 (first example). In this figure, the arrangement example of the indicator light sources 170a, 170b, and 170c and the display pattern are the same as those of the second embodiment described above (Figures 9 and 10). Furthermore, the relationship between the light intensity of the optical bearing and the display pattern is the same as the display pattern switching control described above in Figure 13.

[0127] First, let's explain the OFF state (the four states on the left side of this diagram). In the completely blackout state, light curtain 1 is turned off (= indicator light sources 170a, 170b, and 170c are turned off). At low light intensity, one red light is lit (= only indicator light source 170a is lit red). At medium light intensity, two red lights are lit (= indicator light sources 170a and 170b are lit red). At high light intensity, three red lights are lit (= indicator light sources 170a, 170b, and 170c are lit red).

[0128] Next, let's explain the ON state (the three states on the right in this diagram). At low light intensity, one green light is illuminated (= only indicator light source 170a is illuminated in green). At medium light intensity, two green lights are illuminated (= indicator light sources 170a and 170b are illuminated in green). At high light intensity, three green lights are illuminated (= indicator light sources 170a, 170b, and 170c are illuminated in green).

[0129] Furthermore, diffusers are placed above each of the indicator light sources 170a, 170b, and 170c. Therefore, it is desirable to appropriately set the arrangement and display patterns of the indicator light sources 170a, 170b, and 170c so that the change in the display pattern can be recognized even through the diffusers. This point has been mentioned earlier.

[0130] Figure 16 shows an image of the lighting of the light curtain 1 (second example). In this figure, the light curtain 1 displays a bar according to the light intensity of the optical bearing. Specifically, the three circuit boards 190x, 190y, and 190z (more precisely, a group of indicator light sources 170 incorporated into each) that are cascaded in the longitudinal direction of the light curtain 1 are each controlled to turn on and off as individual units.

[0131] First, let's explain the OFF state (the four states on the left side of this diagram). In the completely darkened state, light curtain 1 is turned off (= the circuit board 190x, 190y, and 190z are turned off). At low light intensity, 1 / 3 of light curtain 1 is illuminated in red (= only circuit board 190x is illuminated in red). At medium light intensity, 2 / 3 of light curtain 1 is illuminated in red (= circuit board 190x and 190y are illuminated in red). At high light intensity, the entire (3 / 3) of light curtain 1 is illuminated in red (= circuit board 190x, 190y, and 190z are illuminated in red).

[0132] Next, let's explain the ON state (the three states on the right in this diagram). With low light intensity, 1 / 3 of light curtain 1 will light up in green (= only circuit board 190x will light up in green). With medium light intensity, 2 / 3 of light curtain 1 will light up in green (= circuit boards 190x and 190y will light up in green). With high light intensity, the entire (3 / 3) of light curtain 1 will light up in green (= circuit boards 190x, 190y and 190z will light up in green).

[0133] Thus, with the lighting image of the second example (Figure 16), the switching of the display pattern according to the light intensity of the optical bearing is easier to understand compared to the first example (Figure 15). However, if the above lighting image is to be realized based on a configuration in which multiple circuit boards 190x, 190y, and 190z are cascaded, the design difficulty and cost may increase.

[0134] <Examples of display patterns according to the light intensity of the optical bearing> The above example illustrates a configuration in which the number of indicator light sources 170 illuminated (especially the decimation interval) is switched according to the light intensity of the optical bearing, but various other modifications are also possible.

[0135] For example, the indicator light 140 may be switched to change over time according to the amount of light from the optical bearing (for example, keeping the indicator light 140 constantly lit, flashing at 1-second intervals, or flashing at 2-second intervals). Alternatively, the amount of light emitted or the color of light emitted by the indicator light 140 may be switched according to the amount of light from the optical bearing. When these embodiments are adopted, it becomes unnecessary to individually control multiple indicator light sources 170 when switching display patterns. Therefore, it becomes possible to use, for example, an optical fiber as the indicator light 140.

[0136] <Functional block (with display pattern control function)> Figure 17 is a functional block diagram of the light curtain 1 equipped with a display pattern control function. Note that this figure is based on the previously mentioned Figure 5, but focuses on the control systems of the indicator light sources 170a, 170b, and 170c, and the indicator light sources 270a, 270b, and 270c, rather than the light emission / receiving systems of the optical axes Oax1 to Oax6.

[0137] Furthermore, in this figure, following the second embodiment described above (Figures 9 and 10), the indicator light sources 170a, 170b, and 170c, and the indicator light sources 270a, 270b, and 270c, are each arranged in sets of three in the order shown in the figure (a, b, c, a, b, c from the top of the page).

[0138] The control circuit 181 controls the two indicator light sources 170a with a common control signal. The same applies to the indicator light sources 170b and 170c. Similarly, the control circuit 281 controls the two indicator light sources 270a with a common control signal. The same applies to the indicator light sources 270b and 270c.

[0139] The amount of light received by each of the optical axes Oax1 to Oax6 is compared with a threshold value by the control circuit 281. In this case, the control circuit 281 may include an analog-to-digital conversion circuit that converts the analog signals output from each of the photodetectors 261 to 266 into digital signals. The control circuit 281 may also include a calculation circuit that calculates the average value (=average light received) or the minimum value (=minimum light received) from the light received by each of the optical axes Oax1 to Oax6.

[0140] The control circuit 281 controls the on / off states of the indicator light sources 270a, 270b, and 270c based on the comparison result between the average light received (or minimum light received) and a threshold. The control circuit 281 also transmits the above comparison result to the control circuit 181 via the communication circuits 282 and 182. The control circuit 181 controls the on / off states of the indicator light sources 170a, 170b, and 170c based on the above comparison result transmitted from the control circuit 281.

[0141] <Processing Flow> Figure 18 shows the processing flow for display pattern control based on the average light reception amount. When the processing flow shown in this figure starts, in step S1, the optical axis to be driven, Oax(i) (where i=1, 2, ... imax(6), and the initial setting value is i=1), is set.

[0142] In the following step S2, the light-emitting element 16i is turned on. Specifically, the light-emitting element 161, which forms the optical axis Oax1, is turned on first.

[0143] In step S3, it is determined whether the amount of light received by the light-receiving element 26i, Li, is greater than the first threshold. As mentioned earlier, the first threshold corresponds to the threshold used to determine whether each of the optical axes Oax1 to Oax6 is in a light-shielding state. If the result is yes, the flow proceeds to step S4. On the other hand, if the result is no, the flow 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 be completed. Therefore, it is possible to quickly stop hazardous sources such as press equipment. In addition to switching the safety output (OSSD) to the OFF state in step S8, the display pattern of the OSSD indicator light may also be changed in accordance with the switch to the OFF state of the safety output (OSSD). Steps S3 and S8 are not directly related to the display pattern control. For this reason, steps S3 and S8 are depicted with dashed lines in this figure.

[0144] If a "yes" determination is made in step S3, the amount of light received, Li, is recorded in a register or similar device in step S4.

[0145] In the following step S5, it is determined whether the optical axis is at its final position (i.e., i = imax(6)). If the result is yes, the flow proceeds to step S6. On the other hand, if the result is no, the variable i is incremented by one (++i), and the flow returns to step S1. From here on, steps S1 to S5 are repeated until the result in step S5 is yes.

[0146] If a "yes" determination is made in step S5, step S6 performs a comparison process between the average (=average light received) or minimum (=minimum light received) value of the received light and several threshold values. The comparison process in this step has already been explained in Figures 13 and 14 above. Therefore, a redundant explanation will be omitted.

[0147] In the following step S7, the illumination state (display pattern) of indicator lights 140 and 240 is updated according to the comparison result obtained in step S6. The flow then returns to step S1, and the above series of processes is repeated.

[0148] This diagram is drawn with the understanding that in step S6, a comparison process may be performed between the average value of the received light (=average received light) and multiple thresholds. In other words, the comparison process in step S6 is not performed for each optical axis, but rather after the received light for all optical axes has been recorded.

[0149] However, if a comparison process is performed between the minimum light-receiving amount (= minimum light-receiving amount) and multiple thresholds, step S5 may be omitted. In other words, the comparison process in step S6 may be performed sequentially for each optical axis without waiting for the light-receiving amounts of all optical axes to be recorded.

[0150] For example, if the amount of light received by the first light-receiving element 261 is below the second threshold, it is sufficient to switch to a single green light (i.e., only the indicator light source 170a is lit green) without comparing the amount of light received by each of the other light-receiving elements 262 to 266 with the threshold (see Figure 14). Therefore, subsequent comparison processing can be omitted.

[0151] <Summary> In Figures 9 to 18 above, we proposed a light curtain 1 equipped with a function to switch display patterns according to the light intensity of the optical bearing. To briefly describe this configuration, "In order to form multiple optical axes spaced apart from each other, one of the pair of light-emitting and light-receiving elements forming the multiple optical axes is arranged inside along the longitudinal direction, and the housing has a metal case extending in the longitudinal direction and end members connected to both ends of the metal case, respectively." A cover that transmits light from the light-emitting element and is attached to the housing so as to intersect with the plurality of optical axes, An indicator light, which is a light-diffusing member, is positioned outward along the longitudinal direction from at least one of the outer surfaces of the cover and the housing, or is formed in series with the cover. The enclosure comprises a light source for an indicator light, which is housed inside the enclosure and supplies light for displaying to the indicator light, The light source for the indicator light is controlled to turn on and off in a color corresponding to the operating state of the light curtain and in a display pattern corresponding to the amount of light received by the light receiving element when the light curtain is set to operation indicator light mode.

[0152] <Fifth Embodiment> Figure 19 shows an example of the configuration of the light curtain 1 in the fifth embodiment. The light curtain 1 in this embodiment comprises a pair of light emitters 100 and light receivers 200.

[0153] As mentioned above, the light emitter 100 has multiple light-emitting elements 161 to 166. The light receiver 200 is positioned opposite the light emitter 100 and has multiple light-receiving elements 261 to 266, each receiving light emitted from the multiple light-emitting elements 161 to 166. However, for illustrative purposes, only the optical axes Oax1 to Oax6 formed between the light-emitting elements 161 to 166 and the light-receiving elements 261 to 266 are depicted in this figure. For details on the light-emitting elements 161 to 166 and the light-receiving elements 261 to 266, please refer to Figures 3 and 5 mentioned earlier.

[0154] The light curtain 1 outputs a safety signal, i.e., the aforementioned OSSD output, to the outside, which is generated based on whether or not each of the multiple optical axes Oax1 to Oax6, which are formed between the light emitter 100 and the light receiver 200, is in a light-blocking state. It goes without saying that the number of optical axes Oax1 to Oax6 is arbitrary.

[0155] Furthermore, the light curtain 1 is equipped with a synchronization means that synchronizes the light emission timing of each light emission element 161 to 166 in the light emitter 100 with the light reception timing of each light receiving element 261 to 266 in the light receiver 200 via optical communication. In other words, the light curtain 1 employs an optical synchronization method as the synchronization method for light emission and reception timing.

[0156] Referring to this figure, of the optical axes Oax1 to Oax6 used for detecting incoming / outgoing light, optical axes Oax1 and Oax6, which are formed at the upper and lower ends of the light curtain 1, may be reused for timing synchronization. For example, the light emitter 100 may transmit a synchronization pulse via optical axis Oax1 prior to starting an optical axis scan that sequentially detects incoming / outgoing light for each of optical axes Oax1 to Oax6. As mentioned above, the synchronization pulse is a pulse signal for timing synchronization and has a unique pulse pattern. The light receiver 200 synchronizes its light reception timing to match the light emission timing of the synchronization pulse.

[0157] By adopting an optical synchronization method, wiring between the light emitter 100 and the light receiver 200 becomes unnecessary. Therefore, the wiring flexibility of the light curtain 1 can be increased.

[0158] Furthermore, the light curtain 1 is equipped with indicator lights 140 and 240. Indicator light 140 is provided on the floodlight 100. Indicator light 240 is provided on the light receiver 200. Indicator lights 140 and 240 can function as operation indicator lights that display the operating status of the light curtain 1. By looking at the indicator lights 140 and 240 of the light curtain 1, the operator can visually recognize the operating status of the light curtain 1, for example, the on / off state of the OSSD output.

[0159] Furthermore, the light curtain 1 also includes an interlocking display means that synchronizes the display of indicator lights 140 and 240 through optical communication from the light receiver 200 to the light emitter 100. Referring to this figure, between the light emitter 100 and the light receiver 200, in addition to the optical axes Oax1 to Oax6 for detecting incoming / outgoing light and timing synchronization, optical axes Com1 and Com2 for controlling the interlocking display are formed.

[0160] Furthermore, optical axes Com1 and Com2 may be formed, for example, near the upper and lower ends of the light curtain 1. Referring to this figure, optical axis Com1 is formed between optical axis Oax1 and optical axis Oax2. Optical axis Com2 is formed between optical axis Oax5 and optical axis Oax6. However, one of optical axes Com1 or Com2 may be omitted. Also, optical axes Com1 and Com2 may be formed in the upper and lower central region of the light curtain 1.

[0161] Figure 20 is a schematic diagram showing an example of optical axis formation. As shown in this figure, the light curtain 1 of this embodiment includes, in addition to at least one pair of light-emitting elements 160 and light-receiving elements 260 provided for light-ingress / light-blocking detection, at least one pair of light-emitting elements 310 and light-receiving elements 320 provided for interlocking display control of indicator lights 140 and 240. Furthermore, the aforementioned control circuits 181 and 281 are depicted in this figure as means for coordinating the overall operation of the light emitter 100 and light receiver 200, respectively.

[0162] The light-emitting element 160 is an optical element provided on the light emitter 100. The light-emitting element 160 can be understood as the previously mentioned light-emitting elements 161 to 166. The light-emitting element 160 may be, for example, a light-emitting diode. The light-receiving element 260 is an optical element provided on the light-receiving element 200. The light-receiving element 260 may be understood as the previously mentioned light-receiving elements 261 to 266. The light-receiving element 260 may be, for example, a photodiode or a phototransistor. An optical axis Oax for detecting incoming / outgoing light or for timing synchronization is formed between the light-emitting element 160 and the light-receiving element 260. The optical axis Oax corresponds to the previously mentioned optical axes Oax1 to Oax6.

[0163] The light-emitting element 310 is an optical element provided on the light-receiving device 200. The light-emitting element 310 may be, for example, a light-emitting diode. The light-receiving element 320 is an optical element provided on the light-emitting device 100. The light-receiving element 320 may be, for example, a photodiode or a phototransistor. Between the light-emitting element 310 and the light-receiving element 320, an optical axis Com is formed, which is different from the optical axis Oax and is used for interlocking display control. The optical axis Com corresponds to the optical axes Com1 and Com2 mentioned above.

[0164] Control circuits 181 and 281 perform optical communication for synchronized display control using the optical axis Com formed between the light-emitting element 310 and the light-receiving element 320, thereby synchronizing the display of indicator lights 140 and 240. The optical axis Com can be understood as an optical communication path from the light receiver 200 to the light emitter 100.

[0165] For example, the control circuit 281 of the light receiver 200 determines the on / off state of the OSSD output depending on whether the optical axis Oax formed between the light-emitting element 160 and the light-receiving element 260 is in a light-shielding state. Then, the control circuit 281 controls the on / off state of the indicator light source 270 according to the on / off state of the OSSD output. At this time, the control circuit 281 drives the light-emitting element 310 to transmit the on / off state of the OSSD output to the light emitter 100. The control circuit 181 of the light emitter 100 controls the on / off state of the indicator light source 170 according to the on / off information of the OSSD output received by the light-receiving element 320.

[0166] With the light curtain 1 of this embodiment, the indicator lights 140 and 240 can be displayed in conjunction without requiring wiring work between the light emitter 100 and the light receiver 200. Therefore, the visibility of the indicator lights 140 and 240 can be improved while enjoying the advantages of the optical synchronization method.

[0167] As mentioned earlier, the optical axis Com for linked display control may be formed as a dedicated optical axis, separate from the optical axis Oax used for light ingress / blockage detection or timing synchronization. This configuration increases the design flexibility of both the light-emitting element 310 and the light-receiving element 320. Furthermore, if the optical axis Oax and optical axis Com are formed individually, the design flexibility of the number of light-emitting pulses or pulse intervals for each also increases.

[0168] For example, with respect to the optical axis Oax used for detecting incoming / outgoing light, the projection divergence angle of the light-emitting element 160, the light-receiving field of view of the light-receiving element 260, and the size of the lenses provided in the light guide paths of the light-emitting element 160 and the light-receiving element 260 can be strictly limited by safety standards in order to accurately detect the outgoing state.

[0169] On the other hand, the optical axis Com for linked display control is not subject to the above restrictions. For example, the light-emitting element 310 may be designed to have a larger light-emitting divergence angle than the light-emitting element 160. Similarly, the light-receiving element 320 may be designed to have a larger light-receiving field of view than the light-receiving element 260. Furthermore, the size of the lenses provided in the light guide paths of the light-emitting element 310 and the light-receiving element 320 may be designed to be larger than the size of the lenses provided in the light guide paths of the light-emitting element 160 and the light-receiving element 260.

[0170] This design makes it easier to establish the optical axis Com between the light emitter 100 and the light receiver 200. Therefore, for example, when aligning the optical axis during the installation of the light curtain 1, it becomes possible to quickly synchronize the indicator lights 140 and 240. As a result, it becomes possible to display the status linked to the optical bearing light intensity (see Figure 13 or Figure 14), which can make optical axis alignment easier.

[0171] For example, in Figure 5 shown above, if at least one pair of light-emitting elements and light-receiving elements from among the light-emitting elements 161-166 and light-receiving elements 261-266 are swapped between the light emitter 100 and the light receiver 200, it is not impossible to use one optical axis for both light input / blocking detection and linked display control in a time-division manner. According to this modified example, the light-emitting element 310 and light-receiving element 320 are omitted, which can contribute to cost reduction of the light curtain 1. However, the light input / blocking information for at least one of the optical axes Oax1-Oax6 will be obtained by the light emitter 100 instead of the light receiver 200. Therefore, in order for the light receiver 200 to output OSSD, optical communication is also required to transmit the light input / blocking information obtained by the light emitter 100 to the light receiver 200.

[0172] Furthermore, multiple sets of light-emitting elements 310 and light-receiving elements 320 may be provided. For example, as shown in Figure 19 above, multiple optical axes Com1 and Com2 may be formed for interlocking display control. With this configuration, even if one of the optical axes Com1 and Com2 is blocked, information transmission from the light receiver 200 to the light emitter 100 can continue.

[0173] Figure 21 shows the processing flow for linked display control. This processing flow is based on Figure 18, but the operation in step S7 is modified, and steps S9 to S11 are added following step S7. The following section will focus on explaining the processing content from step S7 onwards.

[0174] In step S7, the light receiver 200 determines the lighting state (display pattern) of indicator lights 140 and 240, respectively, according to the comparison result obtained in step S6. The flow then proceeds to step S9 without returning to step S1.

[0175] In step S9, the light receiver 200 emits pulse information corresponding to the illumination state (display pattern) determined in step S7 by pulse driving the optical axis Com. That is, after detecting the light-in / light-out state of all optical axis Oax(i), the light receiver 200 performs optical communication reflecting the detection results. The pulse information may be, for example, a specific pulse pattern.

[0176] Subsequently, in step S10, the light emitter 100 receives pulse information via the optical axis Com and compares the pulse information with predetermined internal information. The internal information may be a table that associates the pulse information with the on / off state of the indicator light 140.

[0177] In the subsequent step S11, the light emitter 100 updates the illumination state (display pattern) of the indicator light 140 according to the verification result in step S10, and consequently, the decision made in step S7. Similarly, the light receiver 200 updates the illumination state (display pattern) of the indicator light 240 according to the comparison result in step S6, and consequently, the decision made in step S7. Through this control, synchronized display of indicator lights 140 and 240 can be achieved.

[0178] After the illumination status (display pattern) of indicator lights 140 and 240 is updated, the flow returns to step S1, and the above series of processes is repeated.

[0179] Figures 22 and 23 are a plan view and a perspective view, respectively, showing one example configuration of the light receiver 200. In both figures, 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.

[0180] Figure 22 can be understood as an xy-plane view of the light receiver 200 as seen from the front. Figure 23 can also be understood as a perspective view of Figure 22 with the z-axis tilted towards the back of the paper, and the light receiver 200 rotated slightly around the x-axis.

[0181] However, Figure 23 depicts the receiver 200 with its metal case 211 and end cap 212 removed. Therefore, Figure 23 shows the circuit board 190 and holder 216 housed inside the metal case 211 and end cap 212.

[0182] As shown in both figures, multiple lenses 214 are arranged at equal intervals along the longitudinal direction of the light receiver 200 on the front surface of the light receiver 200. Each of the multiple lenses 214 forms a light guide path (light receiving path) along the optical axis Oax. All of the multiple lenses 214 are supported by a holder 216. Some of the multiple lenses 214 may be provided in a position corresponding to the front surface of the end cap 212.

[0183] Furthermore, among the multiple lenses 214, a lens 215 may be provided between two adjacent lenses 214. The lens 215 forms a light guide path (light projection path) for the optical axis Com. The lens 215 is supported by a holder 216. The optical axis Com may be formed, for example, near both ends of the light curtain 1. Referring to this figure, the lens 215 is provided at a position corresponding to the front of the end cap 212. The size of the lens 215 may be designed to be larger than the size of each of the multiple lenses 214.

[0184] Figure 24 shows an example of light interference between light curtain 1A and light curtain 1B. Light curtain 1A comprises a pair of light emitters 100A and light receivers 200A. Light curtain 1B comprises a pair of light emitters 100B and light receivers 200B.

[0185] Light curtains 1A and 1B are installed so that the floodlight 100A of light curtain 1A and the floodlight 100B of light curtain 1B are back to back. Alternatively, light curtains 1A and 1B are installed so that the light receiver 200A of light curtain 1A and the light receiver 200B of light curtain 1B are facing each other.

[0186] With this installation, the optical axis OaxA emitted from the floodlight 100A of light curtain 1A is less likely to be received by the light receiver 200B of light curtain 1B. Also, the optical axis OaxB emitted from the floodlight 100B of light curtain 1B is less likely to be received by the light receiver 200A of light curtain 1A.

[0187] However, as mentioned 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. Also, 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. Consequently, there is a risk of interference with the detection of incoming / outgoing light axes OaxA and OaxB, respectively.

[0188] In light of the above considerations, the following proposes an optical axis drive control that can suppress optical interference.

[0189] Figure 25 shows an example of optical axis drive control. As shown in this figure, the light curtain 1 of this embodiment repeats the drive periods T1 and T2 in a time-division manner as the drive control of the optical axis Oax and Com, respectively. Optical axis Oax may be understood as either optical axis OaxA or OaxB as described above. Optical axis Com may be understood as either optical axis ComA or ComB as described above.

[0190] The drive period T1 can be understood as the period during which the light-emitting element 160 and the light-receiving element 260 are driven, that is, the period during which an optical axis Oax is formed between the light-emitting element 160 and the light-receiving element 260, and its light ingress / blockage is detected. The drive period T1 can be a length that depends on the number i of optical axes Oax, for example, several ms (= tens of microseconds × i axes).

[0191] The drive period T2 can be understood as the period during which the light-emitting elements 310 and 320 are driven, that is, the period during which an optical axis Com is formed between the light-emitting element 310 and the light-receiving element 320, and pulse information for interlocking display control is transmitted. The drive period T2 can be a length that depends on the amount of information being transmitted, for example, several hundred microseconds.

[0192] Furthermore, as shown in this figure, one scan period Ts may include drive periods T1 and T2. However, the drive period T2 may be skipped once for every two or more scan periods Ts. In other words, optical communication using the optical axis Com may be performed after the detection of light entry / exclusion of the optical axis Oax has been repeated two or more times. In other words, the interval for optical communication may be set to be longer than the interval for optical axis detection.

[0193] In this case, the light receiver 200 may operate in a way that ignores the effect of interference from the optical axis Com, since the frequency of interference from the optical axis Com with the detection of the optical axis Oax is less than once every two times.

[0194] This control method makes it possible to suppress potential optical interference between light curtain 1A and light curtain 1B, even under the conditions shown in Figure 24.

[0195] For the sake of clarity, the skipped drive period T2 is depicted in this figure with a dashed line. Therefore, it appears that the length of the scan period Ts is always constant, regardless of whether the drive period T2 is skipped or not. In reality, the scan period Ts may be shortened by the amount of the skipped drive period T2 so that the next drive period T1 arrives earlier.

[0196] This type of optical axis drive control makes it possible to achieve synchronized display control of indicator lights 140 and 240 while keeping the response time of the OSSD output as short as possible. Note that the skip frequency of the drive period T2 only affects the response time of indicator lights 140 and 240, i.e., the update frequency of the on / off state. Therefore, the skip frequency of the drive period T2 can be designed relatively freely.

[0197] Another method for suppressing optical interference is to use different wavelengths for the optical axis Oax and Com. For example, the optical axis Oax may be formed with infrared light, and the optical axis Com may be formed with red light. In this case, the lens that guides the optical axis Com to the light-receiving element 320 of the light emitter 100 may be filtered to cut out infrared light. With this configuration, the intrusion of the optical axis Oax into the light-receiving element 320 can be suppressed.

[0198] <Failure to establish optical communication> Incidentally, if the optical axis Com is blocked or otherwise causes the photodetector 320 to fail to receive a specific pulse pattern, optical communication using the optical axis Com may fail. Also, if an unexpected pulse pattern is received by the photodetector 320 due to optical interference or other reasons, optical communication using the optical axis Com may fail.

[0199] If optical communication via the optical axis Com fails during the driving period T2, the light emitter 100 will be unable to know the light-receiving / blocking state of the light receiver 200. In such a case, the indicator light 140 may be maintained in its previous display state. With this type of control, if the failure of optical communication is temporary, it is less likely to interfere with the synchronized display of indicator lights 140 and 240.

[0200] However, if optical communication via the optical axis Com fails consecutively over multiple driving periods T2, the indicator light 140 may be switched to the off state. This type of control allows the operator to be notified of the failure of optical communication. By switching to the off state, the user can be directly informed of the fact that optical communication via the optical axis Com has not been established.

[0201] Furthermore, if optical axis Com is positioned between optical axis Oax(i) and optical axis Ox(i+1), it is unlikely that only optical axis Com will be blocked from light. Therefore, if optical communication via optical axis Com fails for multiple driving periods T2, the indicator light 140 may be switched to an indicator state that shows the OSSD output is off, for example, a red light. However, if the indicator light is set to a red light when optical communication with optical axis Com is not established when aligning the light curtain, it may confuse the user about the meaning of the color red. Therefore, as mentioned above, it is preferable to switch to an off state when optical communication with optical axis Com is not established. The indicator light 140 may also blink green when interlocked (blinking green instead of solid green allows the user to easily understand that it is interlocked), or it may blink orange when muted. Also, since the information on the indicator light 140 is non-safety information, failure of optical communication with optical axis Com is permitted. In other words, the OSSD is not turned off just because optical communication with optical axis Com fails.

[0202] When light emitters and light receivers are added in series, the indicator lights 140 may each operate independently. Specifically, for example, when three light emitters (light receivers) are connected in series, if optical communication of the optical axis Com in the middle light emitter (light receiver) fails, only that middle light emitter (light receiver) may be made to fail (for example, it may be switched to the off state). In addition to operating each one independently, all indicator lights 140 may be operated according to the optical communication status of the optical axis Com in a predetermined light emitter (light receiver). For example, when three light emitters (light receivers) are connected in series, if optical communication of one predetermined optical axis Com fails, all indicator lights 140 may be switched to the off state.

[0203] Furthermore, as described above, two optical axis Coms are provided for each light emitter (light receiver) according to this embodiment. If the information of the two optical axis Coms does not match, it is conceivable to switch between various lighting states. For example, if only one of the optical axis Coms is valid, the indicator light 140 may be switched based on the information of the valid optical axis Com. Alternatively, for example, if both optical axis Coms are valid but the information of the optical axis Coms does not match, the previous state of the indicator light 140 may be maintained.

[0204] <Light leakage> Furthermore, if the optical axis Oax for detecting incoming / outgoing light and the optical axis Com for linked display control are installed adjacent to each other, light leakage may occur through the respective optical guide paths of optical axis Oax and Com.

[0205] Figure 26 is a longitudinal cross-sectional view showing an example of a photodetector 200 equipped with a light leakage suppression mechanism. This figure can be understood as a diagram showing the α-α cross-section in Figure 22, in particular, a partially enlarged view of the area around the lens 215.

[0206] In the photodetector 200 of this configuration example, a plurality of photodetectors 260 are arranged on the surface of the substrate 190 at regular intervals d1 along the longitudinal direction of the photodetector 200. Each of the plurality of photodetectors 260 can be understood as an optical element for detecting the optical axis Oax that enters the photodetector 200 from outside through a plurality of lenses 214.

[0207] Furthermore, on the surface of the substrate 190, a light-emitting element 310 is provided between two adjacent light-receiving elements 260. The light-emitting element 310 can be understood as an optical element that emits an optical axis Com for interlocking display control to the outside of the light receiver 200 via the lens 215.

[0208] In this case, as shown by the solid arrow in the figure, light leakage of the optical axis Oax can occur by entering in the reverse direction from the light guide path of the light-emitting element 310 and wrapping around to the light-receiving element 260. When such light leakage occurs, the light-receiving element 260 adjacent to the light-emitting element 310 may misdetect the optical axis Oax. Specifically, even though the optical axis Oax that should be entering the light-receiving element 260 is blocked by object M, its entry is misdetected. When this situation occurs, the correct OSSD output cannot be generated, which can be a very dangerous situation.

[0209] Therefore, the light receiver 200 in this configuration example is equipped with a light-shielding wall 330. The light-shielding wall 330 is formed to block light that wraps around the light-guiding path of the light-emitting element 310 to the light-receiving element 260. For example, the light-shielding wall 330 may be formed to surround the light-emitting element 310. With this configuration, light leakage of the optical axis Oax is suppressed. Consequently, it is possible to reduce false detection of the optical axis Oax in the light-receiving element 260 and improve the reliability of the light curtain 1.

[0210] The light-shielding wall 330 may be integrally formed as part of the holder 216. Alternatively, the light-shielding wall 300 may be formed as an additional part attached to the holder 216.

[0211] Furthermore, the light-shielding wall 330 and its surrounding components should ideally reflect as little of the optical axis Oax as possible. For example, it is desirable that the substrate 190 and holder 216 be blackened.

[0212] Another method for suppressing light leakage is to use different wavelengths for the optical axis Oax and Com, similar to the method for suppressing optical interference. For example, the optical axis Oax may be formed with infrared light, and the optical axis Com may be formed with red light. In this case, the lens 215 that guides the optical axis Com to the outside of the photodetector 200 may be filtered to cut out infrared light. With this configuration, the intrusion of the optical axis Oax through the lens 215 can be suppressed.

[0213] <Other variations> Furthermore, the various technical features disclosed herein can be modified in various ways, in addition to the embodiments described above, without departing from the spirit of the technical creation. In other words, the embodiments described above should be considered in all respects to be illustrative and not restrictive, and the technical scope of the present invention should be defined by the claims and understood to include all modifications that fall within the meaning and scope equivalent to the claims. [Explanation of symbols]

[0214] 1, 1A, 1B Light Curtain (Multi-axis Photoelectric Sensor) 100, 100A, 100B floodlights 200, 200A, 200B receiver 110, 210 cabinets 111, 211 Metal Case 111a Main Unit 111b 1st protruding strip 111c 2nd protruding strip 112, 113, 212, 213 End caps (end members) 214, 215 lenses 216 Holder 120, 220 cables 130 Front Cover 140, 240 indicator light 150 Bumper section 160, 161-166 Light-emitting elements 260, 261-266 Photodetector 170, 170a / b / c, 270, 270a / b / c light source for indicator light 181, 281 Control circuits 182, 282 Communication Circuits 283 Output Circuit 284 Input Circuit 190, 190x, 190y, 190z circuit board 190a central area 190b End area 191 Light-shielding plate 310 Light-emitting element (for interlocking display control) 320 Light-receiving elements (for linked display control) 330 Light-blocking wall Com, Com1, Com2, ComB Optical axis (for linked display control) M object Oax, Oax1~Oax6, OaxB Optical axis (for light ingress / death detection) T1, T2 operating period TS scan period X optical axis intersection area

Claims

1. A light emitter having multiple first light-emitting elements, A light receiver is positioned opposite the light emitter and has a plurality of first light receiving elements that receive light emitted from the plurality of first light-emitting elements, A synchronization means for synchronizing the light emission timing of the light emitter and the light reception timing of the light receiver by optical communication, Equipped with, A light curtain that outputs a safety signal to the outside, generated based on whether or not each of the multiple optical axes formed between the light emitter and the light receiver is in a light-shielding state, The floodlight is provided with a first operation indicator light that displays the operating status of the light curtain, The light receiver is provided with a second operation indicator light that displays the operating status of the light curtain, Each of the light emitter and the light receiver is provided with at least one set of optical elements for synchronized display of the first operation indicator light and the second operation indicator light, A control circuit that uses at least one set of optical elements to synchronize the display of the first operation indicator light and the second operation indicator light, A light curtain equipped with this feature.

2. The light curtain according to claim 1, wherein the at least one set of optical elements comprises a second light-emitting element provided on the light-receiving element and a second light-receiving element provided on 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 the second light-emitting element has a larger light-emitting divergence angle and lens size than the first light-emitting element, and the second light-receiving element has a larger light-receiving field of view and lens size than the first light-receiving element.

6. A light curtain according to claim 2, wherein a first optical axis for detecting incoming / outgoing light or for timing synchronization is configured between the first light-emitting element and the first light-receiving element, and a second optical axis different from the first optical axis for interlocking display control is configured between the second light-emitting element and the second light-receiving element.

7. A first period in which the first light-emitting element and the first light-receiving element are driven, and a second period in which the second light-emitting element and the second light-receiving element are driven, are repeated in a time-division manner. The light curtain according to claim 6, wherein the light receiver drives the second optical axis in a second period according to the detection result of the first optical axis obtained in each of the multiple first periods.

8. The light curtain according to claim 7, wherein if optical communication via the second optical axis fails during the second period, the first operation indicator light is maintained in its previous display state.

9. The light curtain according to claim 8, wherein if optical communication via the second optical axis fails to occur consecutively over multiple periods, the first operation indicator light is switched to an off state or a display state indicating the safety signal is off.

10. The light curtain according to claim 6, wherein the light receiver is provided with a light-shielding wall formed to block light that wraps around from the light guide path of the second light-emitting element to the first light-receiving 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.

Images