Photoelectric sensor

Abstract

To provide a photoelectric sensor with which it is possible to suppress occurrence of a dead band in a detection target region and decrease in light receiving efficiency.SOLUTION: There is provided a photoelectric sensor for outputting a signal indicating that a target (TA) has been detected on the basis of a change of the received light amount of the light having been received and provided with a floodlight for emitting light toward a detection target region (F) and a photoreceiver for receiving light. The floodlight (10) is configured to emit first polarized light, second polarized light differing from the first polarized light in characteristics and not interfering with each other, and non-polarized light differing from the first and second polarized light in characteristics and not interfering with each other, from a light projection surface. The floodlight further includes: a first polarizing plate (23P) for passing the first polarized light through and provided on the light receiving surface of the photoreceiver (20); a second polarizing plate (23S) for passing the second polarized light through and provided on the light receiving surface; and a filterless region (23U) for leading the non-polarized light to the inside of the photoreceiver (20) and provided between the first polarizing plate (23P) and the second polarizing plate (23S) on the light receiving surface.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a photoelectric sensor. [Background technology]

[0002] Conventionally, as a photoelectric sensor of this type, a type is known in which a light projector and a light receiver of a transmission type photoelectric sensor are arranged facing each other across a detection target area, and a decrease in the amount of received light is detected when part of the light traveling from the light projector to the light receiver is blocked by a substrate in the detection target area (Patent Document 1). When detecting the thickness part of a thin object transported horizontally at a predetermined position on the transport path, as in the photoelectric sensor of Patent Document 1, it is difficult to cause a complete light blocking state by the detection target, so the sensor is set to turn on the detection signal when the amount of received light falls below a certain threshold value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-216489 A (Prior Art Document 1) Summary of the Invention [Problem to be solved by the invention]

[0004] Meanwhile, in order to stably detect thin objects, a device has been proposed in which two types of light with different characteristics that do not interfere with each other are emitted from the light-projecting surface toward the detection target area. These two types of light are guided to the light-receiver by two filters that are placed a certain distance away from the light-projecting surface across the detection target area.

[0005] However, since a partition member that enables the filter to be fixed or positioned is provided at the joint between the filters and does not transmit light, a dead zone occurs near the partition member in the space that is the detection target area. As a result, when a thin target is placed in the area including the dead zone, the amount of received light does not change sufficiently, and there is a risk that the target cannot be detected.

[0006] In addition, because the filter selectively transmits only two types of light, the amount of light received by the receiver tends to be lower than when no filter is used, resulting in a decrease in the light receiving efficiency relative to the intensity of the light emitted by the projector.

[0007] The present invention has been made in consideration of the above circumstances, and has an object to provide a photoelectric sensor that can suppress the occurrence of dead zones in a detection target area and the decrease in light receiving efficiency. [Means for solving the problem]

[0008] A photoelectric sensor according to one embodiment of the present disclosure includes a light projector that emits light toward a detection target area and a light receiver that receives the light, and outputs a signal indicating that an object has been detected based on a change in the amount of received light. The light projector is configured to emit from a light projecting surface a first light, a second light having characteristics different from the first light and not interfering with each other, and a third light having characteristics different from the first light and the second light and not interfering with each other, and further includes a first optical filter that is provided on the light receiving surface of the receiver and transmits the first light, a second optical filter that is provided on the light receiving surface and transmits the second light, and a first filterless region that is provided between the first optical filter and the second optical filter on the light receiving surface and guides the third light into the inside of the light receiver.

[0009] According to this aspect, the first filterless region is provided between the first optical filter and the second optical filter on the light receiving surface, and guides the third light to the inside of the light receiver. This makes it possible to irradiate the third light to the region between the first optical filter and the second optical filter on the light receiving surface, which was a cause of the occurrence of a dead zone, and guide it to the inside. In addition, since the first filterless region does not have a filter function, the irradiated third light is guided directly to the inside. Therefore, it is possible to suppress the occurrence of a dead zone in the detection target region, and to improve the light receiving efficiency compared to the conventional technology.

[0010] In the above-described embodiment, the first filterless region may include an aperture formed in the light receiving surface.

[0011] According to this aspect, the first filterless region includes an aperture formed in the light receiving surface, which makes it possible to easily realize the first filterless region that guides unpolarized light into the inside of the light receiver.

[0012] In the above-described aspect, a holder may be further provided that holds the first optical filter and the second optical filter in a state in which they are arranged along the light receiving surface.

[0013] According to this aspect, the holding section is provided to hold the first optical filter and the second optical filter in a state in which they are arranged along the light receiving surface, thereby making it possible to easily position the first optical filter and the second optical filter on the light receiving surface.

[0014] In the above-described aspect, the optical sensor may further include a cover glass that is provided on the light-receiving surface and to which the first optical filter and the second optical filter are adhered in a state of being disposed along the light-receiving surface.

[0015] According to this aspect, the cover glass is provided on the light receiving surface and is bonded to the first optical filter and the second optical filter in a state where the first optical filter and the second optical filter are arranged along the light receiving surface, thereby making it possible to easily position and fix the first optical filter and the second optical filter to the light receiving surface.

[0016] In the above-described aspect, the light projector may further include an optical axis setting unit provided inside the light projector for setting the optical axis direction of the first light to a direction diagonally across the detection target area toward the first optical filter, and for setting the optical axis direction of the second light to a direction diagonally across the detection target area toward the second optical filter.

[0017] According to this aspect, an optical axis setting unit is provided inside the projector, which sets the optical axis direction of the first light to a direction diagonally across the detection target area toward the first optical filter, and the optical axis direction of the second light to a direction diagonally across the detection target area toward the second optical filter. This makes it possible to irradiate the first light onto the entire surface of the first optical filter and the second light onto the entire surface of the second optical filter, even when the distance between the projector and the receiver is short (close). Therefore, it is possible to easily accommodate changes in the detection distance.

[0018] In the above-mentioned aspect, the optical receiver may further include a first light receiving element, a second light receiving element, and a third light receiving element, and may be configured to guide the first light that has passed through the first optical filter to the first light receiving element, the second light that has passed through the second optical filter to the second light receiving element, and the third light from the first filterless region to the third light receiving element.

[0019] According to this aspect, the light receiver is configured to guide the first light transmitted through the first optical filter to the first light receiving element, the second light transmitted through the second optical filter to the second light receiving element, and the third light from the first filterless region to the third light receiving element. This makes it possible to detect an object based on a change in the amount of light received in the detection region even if the object enters only one of the detection region by the first light, the detection region by the second light, and the detection region by the third light. This makes it possible to increase the detection sensitivity and accurately detect even small objects.

[0020] In the above-mentioned aspect, the light projection surface may further include a third optical filter provided on the light projection surface, through which transmitted light is emitted as a first light, a fourth optical filter provided on the light projection surface, through which transmitted light is emitted as a second light, and a second filterless region provided between the third optical filter and the fourth optical filter on the light projection surface, through which the third light is emitted.

[0021] According to this aspect, the second filterless region is provided between the third optical filter and the fourth optical filter on the light projection surface, and the third light is emitted from the second filterless region. This makes it possible to make the third light from the light source incident on the region between the third optical filter and the fourth optical filter on the light projection surface, which was a cause of the occurrence of the dead zone. In addition, since the second filterless region does not have a filter function, the incident third light can be emitted as it is. Therefore, the occurrence of the dead zone in the detection target region can be further suppressed, and the light receiving efficiency can be further improved compared to the conventional technology.

[0022] In the above-mentioned aspect, the device may further include a first housing that houses the light projector therein, the first housing having a surface that is positioned opposite the area to be detected as a light projecting surface, and a second housing that houses the light receiver therein, the second housing having a surface that is positioned opposite the surface of the first housing across the area to be detected as a light receiving surface.

[0023] According to this aspect, a first housing that houses a light projector and has a surface that faces the detection target area as a light projecting surface, and a second housing that houses a light receiver and has a surface that faces the surface of the first housing across the detection target area as a light receiving surface are separated from each other. This makes it possible to separate the detection target area into two housings, the first housing on one side and the second housing on the other side, and to place the light projector and the light receiver opposite each other. Therefore, for example, it is possible to easily detect an object that is transported through the detection target area.

[0024] In the above-described aspect, the device may further include a housing that houses the light projector and the light receiver therein, the housing having surfaces that are disposed to face the detection target area as a light projecting surface and a light receiving surface.

[0025] According to this aspect, a housing is provided that houses the light emitter and the light receiver therein, and has surfaces that are arranged to face the detection target area as a light-emitter surface and a light-receiving surface, thereby making it possible to easily realize a reflective photoelectric sensor in which the light emitter and the light receiver are integrally housed in the same housing.

[0026] In the above-described aspect, the projector may be configured to emit from the projection surface a first polarized light as the first light, a second polarized light that vibrates in a direction different from that of the first polarized light as the second light, and unpolarized light as the third light.

[0027] According to this aspect, the projector is configured to emit, from the light projection surface, a first polarized light as the first light, a second polarized light that vibrates in a direction different from the first polarized light as the second light, and non-polarized light as the third light. This makes it possible to stably detect an object by utilizing the characteristics of the lights vibrating in different directions, for example, by using a first polarizing filter that transmits the first polarized light as the first optical filter and a second polarizing filter that transmits the second polarized light as the second optical filter.

[0028] A photoelectric sensor according to another aspect of the present disclosure is a photoelectric sensor comprising a light projector that emits light toward a detection target area and a light receiver that receives the light, and outputs a signal indicating that an object has been detected based on a change in the amount of the received light, wherein the light projector is configured to emit a first light having a first wavelength range, a second light having a second wavelength range different from the first wavelength range, and a third light having a third wavelength range different from the first wavelength range and the second wavelength range, and further comprises a first color filter that transmits the first light and guides it to the light receiver, a second color filter that transmits the second light and guides it to the light receiver, and a third color filter that transmits the third light and guides it to the light receiver, and is configured to output a signal in response to a decrease in the amount of at least one of the first light, the second light, and the third light received by the light receiver.

[0029] According to this aspect, the optical receiver is configured to output a signal in response to a decrease in the amount of at least one of the first, second, and third lights received by the optical receiver. This allows for stable detection of an object even if the object's position varies, compared to a case where the detection is based on a change in the total amount of received light of each light. Effect of the Invention

[0030] According to the present invention, it is possible to suppress the occurrence of dead zones in a detection target area and the decrease in light receiving efficiency. [Brief description of the drawings]

[0031] [Figure 1] FIG. 1 is a diagram showing an example of application of a photoelectric sensor according to a first embodiment. [Diagram 2] FIG. 2 is a diagram for explaining the detection principle of the photoelectric sensor according to the first embodiment. [Diagram 3] FIG. 3 is a configuration diagram showing an example of the configuration of an optical system of the photoelectric sensor according to the first embodiment. [Figure 4] FIG. 4 is a diagram showing the configuration of an optical system of a virtual photoelectric sensor. [Diagram 5]FIG. 5 is a diagram for explaining an example of the range of spread of each light beam when the light beam is emitted without setting the optical axis. [Figure 6] FIG. 6 is an enlarged cross-sectional view of a main portion showing the configuration of a light-projecting surface of a light projector of the photoelectric sensor according to the first embodiment. [Figure 7] FIG. 7 is a configuration diagram showing a first modified example of the configuration of the optical system of the photoelectric sensor according to the first embodiment. [Figure 8] FIG. 8 is a configuration diagram showing a second modified example of the configuration of the optical system of the photoelectric sensor according to the first embodiment. [Figure 9] FIG. 9 is a configuration diagram showing a third modified example of the configuration of the optical system of the photoelectric sensor according to the first embodiment. [Figure 10] FIG. 10 is a configuration diagram showing an example of the configuration of an optical system of a photoelectric sensor according to the second embodiment. [Figure 11] FIG. 11 is a diagram for explaining detection of an object by the photoelectric sensor according to the second embodiment. [Figure 12] FIG. 12 is a configuration diagram showing another example of the configuration of the optical system of the photoelectric sensor according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] An embodiment of the present invention will be described below. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the drawings are schematic. Therefore, specific dimensions, etc. should be judged in light of the following description. In addition, it goes without saying that the drawings include parts with different dimensional relationships and ratios. Furthermore, the technical scope of the present invention should not be interpreted as being limited to the embodiment.

[0033] [First embodiment] <Application Examples> An application example of the photoelectric sensor according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing an application example of the photoelectric sensor 100 according to the first embodiment. In Fig. 1, Fig. 1(A) in the upper part is a plan view, and Fig. 1(B) in the lower part is a cross-sectional view taken along the dashed line shown in Fig. 1(A).

[0034] 1, the photoelectric sensor 100 includes a light emitter 10, a light receiver 20, and a signal processing device 30. The signal processing device 30 accommodates a light emitter element and a light receiver element inside a housing. A light guide path formed by an optical fiber 41 is provided between the signal processing device 30 and the light emitter 10, and a light guide path formed by an optical fiber 42 is provided between the signal processing device 30 and the light receiver 20.

[0035] The photoelectric sensor 100 is used for the purpose and application of detecting an object TA conveyed by, for example, conveyors CVa and CVb. The object TA to be detected is, for example, a thin, small structure such as a board. The light projector 10 is disposed on the side of one conveyor CVa, and the light receiver 20 is disposed on the side of the other conveyor CVb, such that the light projecting window 16 of the housing 15 and the light receiving window 26 of the housing 25 face each other.

[0036] The light projector 10 emits light guided by an optical fiber 41 from a light projecting element in the signal processing device 3 through a light projecting window 16 provided on the front surface of the housing 15. The light receiver 20 collects light incident through a light receiving window 26 provided on the front surface of the housing 25, and guides the collected light via an optical fiber 42 to a light receiving element in the signal processing device 3. The signal processing device 30 controls the light emitting operation of the light projecting element, processes the output signal of the light receiving element to detect the amount of received light, and detects the object TA based on the detected amount of received light.

[0037] Here, a description will be given of the detection principle of the photoelectric sensor 100 according to the first embodiment. Fig. 2 is a diagram for explaining the detection principle of the photoelectric sensor 100 according to one embodiment.

[0038] 2, the space SP between the light projector 10 and the light receiver 20, which are disposed opposite to each other, is the detectable range. When an object TA is present in this space SP, the object TA blocks the light emitted from the light projector 10, and the amount of light incident on the light receiver 20 decreases. This change in the amount of light is detected and a detection signal of the object TA is generated.

[0039] 1 compares the amount of light received by the light receiver 20 with a judgment threshold. Then, while the amount of light received is equal to or greater than the threshold, the signal processing device 30 sets the signal level of the detection signal output from the signal processing device 3 to a level indicating an OFF state, for example, a low level. On the other hand, when the light from the projector 10 to the light receiver 20 is blocked by the object TA and the amount of light received falls below the threshold, the signal processing device 30 sets the signal level of the detection signal to a level indicating an ON state, for example, a high level.

[0040] 1 and 2 show an optical fiber type photoelectric sensor, but the present invention is not limited to this example, and the photoelectric sensor of the present invention can be applied to sensors other than the optical fiber type. In the following, unless otherwise specified, the optical fibers 41, 42 are not shown, and an example will be described in which the configuration of the projector 10 includes a light projecting element 50 and the configuration of the receiver 20 includes a light receiving element 60.

[0041] Next, the configuration of the optical system of the photoelectric sensor according to the first embodiment will be described with reference to Fig. 3. Fig. 3 is a configuration diagram showing an example of the configuration of the optical system of the photoelectric sensor 100 according to the first embodiment.

[0042] In addition, in addition to the optical system, the photoelectric sensor 100 also has components such as an electrical system, a mechanical system, and a control system. However, the following description will focus on the optical system configuration, and illustrations and descriptions of components other than the optical system will be omitted.

[0043] As shown in Fig. 3, floodlight 10 is configured to emit first polarized light, second polarized light, and non-polarized light (also called non-polarized light) from a light-projecting surface. More specifically, floodlight 10 incorporates collimator lens 11 and prism 12 together with light-projecting element 50 such as an LED. Also, third polarizing plate 13P, fourth polarizing plate 13S, and filterless region 13U are disposed on the light emission side of prism 12 (right side in Fig. 3). Third polarizing plate 13P, fourth polarizing plate 13S, and filterless region 13U are arranged side by side in a direction perpendicular to the traveling direction of light (up and down direction in Fig. 3).

[0044] The third polarizing plate 13P and the fourth polarizing plate 13S are each configured to transmit polarized light (also called polarized light) that vibrates in a specific direction. More specifically, the third polarizing plate 13P is configured to transmit polarized light whose electric field vibrates in a horizontal direction relative to the paper surface of FIG. 3. The fourth polarizing plate 13S is configured to transmit polarized light whose electric field vibrates in a vertical direction relative to the paper surface of FIG. 3. The third polarizing plate 13P and the fourth polarizing plate 13S are attached to the surface of the light projection window 16 shown in FIG. 1 and FIG. 2, and the surfaces of the third polarizing plate 13P and the fourth polarizing plate 13S are substantially the light projection surface of the projector 10. The first polarized light that has passed through the third polarizing plate 13P is emitted from the light projection surface of the projector 10, and the second polarized light that has passed through the fourth polarizing plate 13S is emitted from the light projection surface of the projector 10.

[0045] The filterless region 13U is configured so that non-polarized light is emitted from the light-projecting surface of the projector 10. More specifically, the filterless region 13U is configured so that the light incident from the light-projecting element 50 through the collimating lens 11 and the prism 12 can pass or be transmitted without being partially selected or removed. In other words, the filterless region 13U is a region that does not have a filter function. The filterless region 13U is disposed between the third polarizing plate 13P and the fourth polarizing plate 13S, and constitutes the light-projecting surface of the projector 10 together with the third polarizing plate 13P and the fourth polarizing plate 13S. The non-polarized light that has passed through or been transmitted through the filterless region 13U is emitted from the light-projecting surface of the projector 10. Details of the filterless region 13U will be described later.

[0046] The light receiver 20 is provided with a light receiving element 60 such as a photodiode, a lens 21, and a prism 22. A second polarizing plate 23S, a first polarizing plate 23P, and a filterless region 23U are provided on the light incident side of the prism 22 (the left side in FIG. 3). The second polarizing plate 23S, the first polarizing plate 23P, and the filterless region 23U are arranged side by side in a direction perpendicular to the traveling direction of the light (the up and down direction in FIG. 3).

[0047] The second polarizing plate 23S and the first polarizing plate 23P are each configured to transmit polarized light that vibrates in a specific direction. More specifically, the second polarizing plate 23S is configured to transmit polarized light whose electric field vibrates in a vertical direction relative to the paper surface of FIG. 3. The first polarizing plate 23P is configured to transmit polarized light whose electric field vibrates in a horizontal direction relative to the paper surface of FIG. 3. The second polarizing plate 23S and the first polarizing plate 23P are attached to the surface of the light receiving window 26 shown in FIG. 1 and FIG. 2, and the surfaces of the second polarizing plate 23S and the first polarizing plate 23P are substantially the light receiving surface of the light receiver 20. The second polarized light that has passed through the second polarizing plate 23S is guided to the inside of the light receiver 20, and the first polarized light that has passed through the first polarizing plate 23P is guided to the inside of the light receiver 20.

[0048] The filterless region 23U is configured to guide non-polarized light to the inside of the optical receiver 20. More specifically, the filterless region 23U is configured to allow the incident light to pass or transmit without selecting or removing a part of the light. In other words, the filterless region 23U is a region that does not have a filter function. The filterless region 23U is disposed between the second polarizing plate 23S and the first polarizing plate 23P, and constitutes the light receiving surface of the optical receiver 20 together with the second polarizing plate 23S and the first polarizing plate 23P. The non-polarized light that passes through or transmits the filterless region 23U is guided to the inside of the optical receiver 20. Details of the filterless region 23U will be described later.

[0049] The first polarized light of this embodiment corresponds to an example of the "first light" of the present invention, the second polarized light of this embodiment corresponds to an example of the "second light" of the present invention, and the non-polarized light of this embodiment corresponds to an example of the "third light" of the present invention. That is, the second polarized light is light that has characteristics different from the first polarized light and does not interfere with each other. Moreover, the non-polarized light is light that has characteristics different from the first polarized light and the second polarized light and does not interfere with each other, that is, with both the first polarized light and the second polarized light. Furthermore, the filterless region 23U of this embodiment corresponds to an example of the "first filterless region" of the present invention, and the filterless region 13U of this embodiment corresponds to an example of the "second filterless region" of the present invention.

[0050] The light-projecting window 16 of the projector 10 and the light-receiving window 26 of the receiver 20 have the same or approximately the same dimensions and shape. The projector 10 and the receiver 20 are arranged so that the light-projecting window 16 and the light-receiving window 26 are located at the same height when they are opposed to each other. At this time, the third polarizing plate 13P on the projector 10 side and the second polarizing plate 23S on the receiver 20 side are located at the same height, the fourth polarizing plate 13S on the projector 10 side and the first polarizing plate 23P on the receiver 20 side are located at the same height, and the filterless region 13U on the projector 10 side and the filterless region 23U on the receiver 20 side are located at the same height.

[0051] That is, the first polarizing plate 23P and the second polarizing plate 23S are disposed so as to face the emission region of light different from the transmissible light, across the space (hereinafter referred to as the detection target region F) between the light projector 10 and the light receiver 20 when they are disposed opposite each other. Specifically, the first polarizing plate 23P is disposed opposite the fourth polarizing plate 13S that emits the second polarized light, and the second polarizing plate 23S is disposed opposite the third polarizing plate 13P that emits the first polarized light. On the other hand, the filterless region 23U is disposed so as to face the emission region of the transmissible light across the detection target region F. Specifically, the filterless region 23U is disposed opposite the filterless region 13U that emits non-polarized light.

[0052] The light projecting element 50 emits light (also called natural light or unpolarized light) that vibrates in various directions. The collimator lens 11 converts the light emitted from the light projecting element 50 into parallel light.

[0053] Prism 12 is provided inside projector 10 and is configured to set the optical axis direction of the first polarized light to a direction diagonally across detection target area F toward first polarizing plate 23P, and the optical axis direction of the second polarized light to a direction diagonally across detection target area F toward second polarizing plate 23S.

[0054] Specifically, the light converted into parallel light by collimator lens 11 is set in prism 12 such that the direction of the optical axis of the light in the range irradiated to third polarizing plate 13P is changed obliquely downward, and the direction of the optical axis of the light in the range irradiated to fourth polarizing plate 13S is changed obliquely upward. On the other hand, the direction of the optical axis of the light in the range irradiated to filterless region 13U is not changed in prism 12, and the light passes through filterless region 23U as parallel light.

[0055] In Fig. 3, the range of travel of the light that reaches the light receiving surface of the light receiver 20 and is guided to the light receiving element 60 among the actual light emitted from the third polarizing plate 13P, the fourth polarizing plate 13S, and the filterless region 13U is shown by different line types for each of the three types of light. In Fig. 3, the main travel direction of the first polarized light is shown by a dashed dotted line, and the main travel direction of the second polarized light is shown by a dotted line. Also, the main travel direction of the unpolarized light is shown by a solid line.

[0056] 3, in the photoelectric sensor 100 of this embodiment, the light that passes through the third polarizing plate 13P, travels in an obliquely downward direction, and is guided to the region corresponding to the first polarizing plate 23P enters the optical receiver 20. The light that passes through the fourth polarizing plate 13S, travels in an obliquely upward direction, and is guided to the region corresponding to the second polarizing plate 23S enters the optical receiver 20. The light that passes through the filterless region 13U, travels in the horizontal direction, and is guided to the region corresponding to the filterless region 23U enters the optical receiver 20. These three types of light that enter the optical receiver 20 are collected by the prism 22 and the lens 21, and are guided to the light receiving element 60.

[0057] When an object TA to be detected, such as a substrate, enters the detection target area F, of the light incident on the light receiver 20, the light from the third polarizing plate 13P is blocked by the top surface of the object TA, the light from the fourth polarizing plate 13S is blocked by the bottom surface of the object TA, and the light from the filterless area 13U is blocked by the side surface of the object TA, etc. As a result, the amount of light incident on the light receiver 20 is significantly reduced. Accordingly, the value of the signal indicating the amount of received light output from the light receiving element 60 falls below the threshold value, and the detection signal is set to the ON state.

[0058] Here, the configuration of the optical system of a virtual photoelectric sensor will be described. Fig. 4 is a configuration diagram showing the configuration of the optical system of a virtual photoelectric sensor. Note that the virtual photoelectric sensor is hypothetical for comparison with the photoelectric sensor 100 of the first embodiment, and the same or similar configuration as the photoelectric sensor 100 is given the same or similar reference numerals, and the description thereof will be omitted as appropriate. Also, in Fig. 4, for the sake of simplicity of explanation, the collimator lens 11 and the prism 12 of the projector 10 and the collimator lens 21 and the prism 22 of the receiver 20 in the photoelectric sensor 100 shown in Fig. 3 are omitted.

[0059] As shown in FIG. 4, the virtual photoelectric sensor includes a projector 10' and a receiver 20'. In the projector 10', a partition member DM1 is provided between a third polarizing plate 13P' and a fourth polarizing plate 13S'. The partition member DM1 is a member provided to facilitate fixing and positioning the third polarizing plate 13P' and the fourth polarizing plate 13S' to the light-projecting surface of the projector 10'. Similarly, in the receiver 20', a partition member DM2 is provided between a first polarizing plate 23P' and a second polarizing plate 23S'. The partition member DM2 is a member provided to facilitate fixing and positioning the first polarizing plate 23P' and the second polarizing plate 23S' to the light-receiving surface of the receiver 20'.

[0060] Since the partition members DM1 and DM2 do not transmit light, the light from the light projecting element 50' does not exit from the partition member DM1, and the partition member DM2 does not guide the light to the light receiving element 60'. Therefore, in the space that becomes the detection target area when the light projector 10' and the light receiver 20' are arranged opposite to each other, dead zones DB1 and DB2, which are areas outside the range where the light that reaches the light projecting surface of the light projector 10' and is guided to the light receiving element 60' travels, are generated near the partition members DM1 and DM2. If an object including a thin structure is arranged in the area including the dead zone, the amount of light received does not change sufficiently, and the object may not be detected.

[0061] In addition, since the third polarizing plate 13P', the fourth polarizing plate 13S', the second polarizing plate 23S', and the first polarizing plate 23P' have a filter function that selects and removes a part of the incident light, the amount of light received by the light receiving element 60' of the light receiver 20' tends to decrease compared to when these polarizing plates are not used. Therefore, the light receiving efficiency decreases with respect to the intensity of the light emitted by the light projecting element 50' of the light projector 10'.

[0062] In contrast, as shown in FIG. 3, the photoelectric sensor 100 of this embodiment includes a filterless region 23U that is provided between the first polarizing plate 23P and the second polarizing plate 23S on the light receiving surface of the light receiver 20 and guides non-polarized light to the inside of the light receiver 20. This makes it possible to irradiate the non-polarized light to the area between the first polarizing plate 23P' and the second polarizing plate 23S' on the light receiving surface, which was a cause of the generation of the dead zone DB2 in the virtual photoelectric sensor shown in FIG. 4, and guide it to the inside. In addition, since the filterless region 23U does not have a filter function, the irradiated non-polarized light can be guided directly to the inside. Therefore, it is possible to suppress the generation of the dead zone in the detection target area, and to improve the light receiving efficiency compared to the conventional art.

[0063] The photoelectric sensor 100 of this embodiment further includes a filterless region 13U that is provided between the third polarizing plate 13P and the fourth polarizing plate 13S on the light projection surface of the projector 10 and outputs non-polarized light. This allows non-polarized light from the light source to be incident on the region between the third polarizing plate 13P' and the fourth polarizing plate 13S' on the light projection surface, which was a cause of the generation of the dead zone DB1 in the virtual photoelectric sensor shown in FIG. 4. In addition, since the filterless region 13U does not have a filter function, it can directly output the incident non-polarized light. Therefore, it is possible to further suppress the generation of the dead zone in the detection target region and to further improve the light receiving efficiency compared to the conventional art.

[0064] Furthermore, the photoelectric sensor 100 of this embodiment is configured such that the projector 10 emits, from the light projection surface, a first polarized light as the first light, a second polarized light that oscillates in a direction different from the first polarized light as the second light, and non-polarized light as the third light. This makes it possible to stably detect the object TA by utilizing the characteristics of the lights that oscillate in different directions, for example, by using a first polarizing plate 23P that transmits the first polarized light as the first optical filter and a second polarizing plate 23S that transmits the second polarized light as the second optical filter.

[0065] Returning to the explanation of Fig. 3, when the object TA enters the detection target area F, at least one of the two types of light from the third polarizing plate 13P and the fourth polarizing plate 13S may be reflected on the surface of the object TA and guided toward the light receiver 20. In this case, a polarizing plate having properties that do not match the vibration direction of the light, that is, a polarizing plate that transmits light with a different vibration direction, is provided at the position where the reflected light reaches, so that the reflected light can be prevented from entering the light receiver 20. Therefore, it is possible to prevent the accuracy of detection of the object TA from being reduced due to the reflected light from the surface of the object TA.

[0066] Also, according to the example of FIG. 3, the amount of light incident on the optical receiver 20 decreases not only when the ranges corresponding to the three types of light intersect or overlap, but also when the object TA is located in an area where only the range corresponding to one of the lights is shown. In this way, the ranges shown in the figure correspond to the ranges in which the object TA can be detected. Therefore, in the following description, the ranges of each light are referred to as the "detection area by the first polarized light," the "detection area by the second polarized light," and the "detection area by the non-polarized light," and all the ranges of the three types of light are collectively referred to as the "detection area."

[0067] 3, the detection area by the first polarized light and the detection area by the second polarized light each cross the detection target area F diagonally and intersect within the detection target area F. Therefore, if the object TA is included in the height range corresponding to the intersection, the amount of light received by the light receiving element 60 is significantly reduced due to light blocking by both sides of the object TA, and the object TA can be stably detected.

[0068] Furthermore, since the detection areas using the two types of light, the first polarized light and the second polarized light, are distributed to the left and right, even if the object TA is located above or below the height range corresponding to the intersection, if the width of the detection target area F is set to correspond to the width of the object TA, it is possible for the object TA to create a light-blocking state within the detection area F regardless of the height position of the object TA within the detection target area F.

[0069] The actual light emitted by third polarizing plate 13P, fourth polarizing plate 13S, and filterless region 13U spreads to a certain extent due to the characteristics of collimator lens 11 and prism 12 as it travels.

[0070] 3, it is necessary that the first polarized light and the second polarized light are irradiated onto the entire surfaces of the first polarizing plate 23P and the second polarizing plate 23S, which correspond to the characteristics of the first polarized light and the second polarizing light, respectively, and that the non-polarized light is irradiated onto the entire corresponding filterless region 23U.

[0071] 3, a prism 12 is provided inside the projector 10, which sets the optical axis direction of the first polarized light to a direction diagonally crossing the detection target area F toward the first polarizing plate 23P and the optical axis direction of the second polarized light to a direction diagonally crossing the detection target area F toward the second polarizing plate 23S. This makes it possible to irradiate the entire surface of the second polarizing plate 23P with the first polarized light and the entire surface of the second polarizing plate 23S with the second polarized light, even when the distance between the projector 10 and the photoreceiver 20 is short (close). This makes it possible to easily accommodate changes in the detection distance.

[0072] That is, even if the distance between the projector 10 and the receiver 20 is set relatively short, the spreading range of each of the first polarized light and the second polarized light can be set to a size that corresponds exactly to the first polarizing plate 23P and the second polarizing plate 23S at the position of the light receiving surface, as in the example shown in Fig. 3. On the other hand, although not shown, if the distance between the projector 10 and the receiver 20 is set relatively long (farther) compared to the example of Fig. 3, the spreading range of each of the first polarized light and the second polarized light at the position of the light receiving surface becomes sufficiently larger than the second polarizing plate 23P and the second polarizing plate 23S at the light receiving surface.

[0073] In this way, if the light from the third polarizing plate 13P and the fourth polarizing plate 13S is irradiated to the entire surface of each of the first polarizing plate 23P and the second polarizing plate 23S on the light receiving surface of the light receiver 20, the first polarizing plate 23P and the second polarizing plate 23S on the light receiver 20 side can reliably receive the light to be selected on the entire surface and make it enter the light receiver 20, thereby stabilizing the size of each detection area. In addition, by setting the optical paths of the first polarized light and the second polarized light obliquely downward and upward, as shown in FIG. 3, it becomes possible to irradiate the entire surfaces of the first polarizing plate 23P and the second polarizing plate 23S on the light receiving surface with each light from the stage when the distance between the projector 10 and the light receiver 20 is short. Therefore, it becomes possible to handle both short-distance detection and long-distance detection.

[0074] Even if the distance between the light projector 10 and the light receiver 20 is closer than that shown in Figure 3, a detection area of ​​similar size to the example shown in Figure 3 can be secured as long as the condition that each light from the third polarizing plate 13P and the fourth polarizing plate 13S is irradiated to the entire surface of the corresponding first polarizing plate 23P and second polarizing plate 23S on the receiver 20 side is satisfied.

[0075] Meanwhile, by arranging filterless region 13U and filterless region 13U at the same height and having the same dimensions, it is possible for the light from filterless region 13U to irradiate the entire surface of filterless region 23U, regardless of the distance between projector 10 and receiver 20. Furthermore, because the light from filterless region 13U spreads over a certain range as it travels, even if filterless region 13U and filterless region 13U are approximately at the same height or approximately the same dimensions, it is possible for unpolarized light from filterless region 13U to irradiate the entire surface of filterless region 23U.

[0076] The photoelectric sensor 100 of this embodiment is not limited to the case where the projector 10 includes the prism 12. For example, when the distance between the projector 10 and the receiver 20 is appropriately set according to the configuration of the optical system in the photoelectric sensor 100, the projector 10 does not need to include the prism 12 for setting the optical axis.

[0077] Fig. 5 is a diagram for explaining an example of the spread range of each light when the light is emitted without setting the optical axis. Fig. 5(A) shows an example in which the light projector 10 and the light receiver 20 are installed at the same distance apart as in the example of Fig. 3, and Fig. 5(B) shows an example in which the light projector 10 and the light receiver 20 are installed at a relatively longer distance apart compared to the example of Fig. 3.

[0078] Even when the optical axis setting by the prism 12 is not performed in the projector 10, the first polarized light and the second polarized light advance while spreading over a certain range as described above. However, as shown in Fig. 5(A), when the distance between the projector 10 and the photoreceiver 20 is relatively short, the first polarized light and the second polarized light cannot be irradiated onto the entire surfaces of the corresponding first polarizing plate 23P and second polarizing plate 23S. This reduces the detection area, and an area where the detection of the target object TA is impossible is generated within the detection target area F, as shown by the rectangular frames NG1 and NG2 in Fig. 5(A).

[0079] 5(B), even if the light from the third polarizing plate 13P and the fourth polarizing plate 13S is caused to travel without being inclined, it is possible to irradiate the entire first polarizing plate 23P and the entire second polarizing plate 23S on the light receiving surface with the light, by setting a sufficiently long distance between the projector 10 and the receiver 20. Therefore, if the purpose is to detect an object TA at a long distance, even an example configuration not including a prism 12 as shown in FIG. 5 can meet the purpose of detecting the object TA.

[0080] Next, the configurations of the light-projecting surface of the projector and the light-receiving surface of the receiver will be described with reference to Fig. 6. Fig. 6 is an enlarged cross-sectional view of a main part showing the configuration of the light-projecting surface of projector 10 of photoelectric sensor 100 according to the first embodiment. Fig. 6(A) shows a first example of the configuration of the light-projecting surface of projector 10, and Fig. 6(B) shows a second example of the configuration of the light-projecting surface of projector 10.

[0081] The configuration of the light receiving surface in the receiver 20 is substantially the same as the configuration of the light projecting surface in the projector 10, except for the arrangement of the second polarizing plate 23S and the first polarizing plate 23P. Therefore, hereinafter, unless otherwise specified, the configuration of the light projecting surface in the projector 10 will be described, and the configuration of the light receiving surface in the receiver 20 will not be illustrated or described.

[0082] The third polarizing plate 13P and the fourth polarizing plate 13S and the filterless region 13U constituting the light projection surface of the floodlight 10 are disposed in the opening of the light projection window 16 formed on the front surface of the housing 15 of the floodlight 10 shown in Fig. 1 and Fig. 2. As shown in Fig. 6(A) and Fig. 6(B), the third polarizing plate 13P is disposed above the opening, and the fourth polarizing plate 13S is disposed above the opening. For example, the third polarizing plate 13P and the fourth polarizing plate 13S are formed in a rectangular shape whose horizontal length (perpendicular to the paper surface in Fig. 6) is the same or approximately the same as the opening of the light projection window 16, and whose vertical length (up and down direction in Fig. 6) is half or approximately half.

[0083] Filterless region 13U is disposed at a height between third polarizing plate 13P and fourth polarizing plate 13S with respect to the opening of light projection window 16. Filterless region 13U is formed, for example, on the light projection surface and includes an aperture through which unpolarized light passes. Similarly, filterless region 23U of receiver 20 is formed, for example, on the light receiving surface and includes an aperture through which unpolarized light passes.

[0084] In this manner, by including an aperture formed in the light receiving surface of filterless region 23U, filterless region 23U that guides unpolarized light into the inside of optical receiver 20 can be easily realized.

[0085] It should be noted that the filterless region 13U is not limited to including an aperture. For example, the filterless region 13U may be configured to include a hole (opening) formed in a part of each of the third polarizing plate 13P and the fourth polarizing plate 13S, or may be configured to include a linear (band-shaped) gap (slit) disposed between the third polarizing plate 13P and the fourth polarizing plate 13S.

[0086] As shown in FIG. 6(A), the upper holding portion 15a and the lower holding portion 15b are configured to hold the third polarizing plate 13P and the fourth polarizing plate 13S in a state in which they are aligned along the light-projecting surface. Specifically, the upper holding portion 15a and the lower holding portion 15b each constitute a frame portion of a light-projecting window in the housing 15 of the light-projector 10, and the third polarizing plate 13P is held in a state in which the upper end portion of the third polarizing plate 13P abuts on a step 15a1 formed in the upper holding portion 15a. The fourth polarizing plate 13S is held in a state in which the lower end portion of the fourth polarizing plate 13S abuts on a step 15b1 formed in the lower holding portion 15b. Similarly, a holding portion (not shown) constituting a frame portion of a light-projecting window in the housing 25 of the light-receiver 20 is configured to hold the first polarizing plate 23P and the fourth polarizing plate 23S in a state in which they are aligned along the light-receiving surface.

[0087] In this way, by providing a holding portion that holds the first polarizing plate 23P and the second polarizing plate 23S in a lined up state along the light receiving surface, the first polarizing plate 23P and the second polarizing plate 23S can be easily positioned on the light receiving surface.

[0088] It should be noted that the configuration for holding the third polarizing plate 13P and the fourth polarizing plate 13S, and the configuration for holding the first polarizing plate 23P and the second polarizing plate 23S are not limited to the example shown in FIG. 6(A).

[0089] For example, as shown in FIG. 6B, a cover glass 17 may be provided over the entire opening of the light projection window 16. The cover glass 17 is a light-transmitting member having the same or substantially the same shape and dimensions as the opening. The cover glass 17 is provided on the light projection surface, and is configured so that the third polarizing plate 13P and the fourth polarizing plate 13S are bonded in a state in which they are arranged along the light projection surface. Specifically, the cover glass 17 is held in a state in which the upper end of the cover glass 17 abuts against a step 15a1 formed in the upper holding portion 15a and the lower end of the cover glass 17 abuts against a step 15b1 formed in the lower holding portion 15b. The third polarizing plate 13P has its upper end abutted against the upper holding portion 15a and is bonded to the upper portion of the cover glass 17 via an adhesive. The fourth polarizing plate 13S has its lower end abutted against the lower holding portion 15b and is bonded to the lower portion of the cover glass 17 via an adhesive. Similarly, a cover glass (not shown) may be provided over the entire opening of the light receiving window 26 in the light receiver 20. The cover glass is provided on the light receiving surface and is configured to be bonded to the first polarizing plate 23P and the second polarizing plate 23S in a state where they are arranged along the light receiving surface.

[0090] In this way, by providing a cover glass that is provided on the light receiving surface and to which the first polarizing plate 23P and the second polarizing plate 23S are adhered while being arranged along the light receiving surface, the first polarizing plate 23P and the second polarizing plate 23S can be easily positioned and fixed to the light receiving surface.

[0091] The configuration of the optical system of the photoelectric sensor 100 of this embodiment is not limited to the examples shown in Figures 3, 5, and 6. For example, the optical system of the photoelectric sensor 100 of this embodiment may be configured as shown in the following Figures 7 to 9.

[0092] (Modification) Next, modified examples of the optical system of the photoelectric sensor in the first embodiment will be described with reference to Fig. 7 to Fig. 9. In each of Fig. 7 to Fig. 9, the same or similar components as those of the optical system of the photoelectric sensor 100 shown in Fig. 3 are denoted by the same or similar reference numerals, and the description thereof will be omitted as appropriate. Also, similar actions and effects due to similar components will not be mentioned one after another.

[0093] Fig. 7 is a configuration diagram showing a first modified example of the configuration of the optical system of the photoelectric sensor 100 according to the first embodiment. As shown in Fig. 7, the photoelectric sensor 100 in the first modified example sets a detection area using a third polarizing plate 13P, a fourth polarizing plate 13S, and a filterless region 13U, and a first polarizing plate 23P, a second polarizing plate 23S, and a filterless region 23U, similar to the example shown in Fig. 3.

[0094] In the first modified example shown in FIG. 7, instead of the lens 21 and the light receiving element 60 shown in FIG. 3, the light receiver 20 is provided with three lenses 21P, 21S, and 21U, and three light receiving elements 60P, 60S, and 60U, each of which is a photodiode or the like.

[0095] The photodetector 20 is configured to guide the first polarized light transmitted through the first polarizing plate 23P to the photodetector 60P, the second polarized light transmitted through the second polarizing plate 23S to the photodetector 60S, and the non-polarized light from the filterless region 23U to the photodetector 60U. Specifically, the lens 21P collects the first polarized light transmitted by the first polarizing plate 23P and guides it to the photodetector 60P, the lens 21S collects the second polarized light transmitted by the second polarizing plate 23S and guides it to the photodetector 60S, and the lens 21U collects the non-polarized light incident from the filterless region 23U and guides it to the photodetector 60U.

[0096] In this way, by configuring the light receiver 20 to guide the first polarized light transmitted through the first polarizing plate 23P to the light receiving element 60P, the second polarized light transmitted through the second polarizing plate 23S to the light receiving element 60U, and the non-polarized light from the filterless region 23U to the light receiving element 60U, even if the object TA enters only one of the detection regions using the first polarized light, the detection region using the second polarized light, and the detection region using the non-polarized light, it is possible to detect the object TA based on the change in the amount of light received in that detection region. Therefore, the detection sensitivity can be increased, and even a small object TA can be detected with high accuracy.

[0097] 1 to 3 and 5 to 7, the photoelectric sensor 100 has been described as an example including a housing 15 that houses the light projector 10 therein and has a surface that faces the detection target area F as a light projecting surface, and a housing 25 that houses the light receiver 20 therein and has a surface that faces the surface of the housing 15 across the detection target area F as a light receiving surface, in other words, a transmission type photoelectric sensor.

[0098] In this way, by providing housing 15 that houses light projector 10 therein and has a surface that faces detection target area F as a light projecting surface, and housing 25 that houses light receiver 20 therein and has a surface that faces the surface of housing 15 across detection target area F as a light receiving surface, it becomes possible to separate the detection target area F into two housings, housing 15 on one side and housing 25 on the other side, and to arrange light projector 10 and light receiver 20 opposite each other, with detection target area F in between. Therefore, for example, an object TA being transported passing through detection target area F can be easily detected.

[0099] Next, the optical system of the reflective photoelectric sensor according to the first embodiment will be described with reference to Fig. 8 and Fig. 9. Fig. 8 is a configuration diagram showing a second modified example of the configuration of the optical system of the photoelectric sensor 100 according to the first embodiment, and Fig. 9 is a configuration diagram showing a third modified example of the configuration of the optical system of the photoelectric sensor 100 according to the first embodiment.

[0100] As shown in Fig. 8, the photoelectric sensor 100 in the second modification includes a sensor head 310 that houses a light-projecting element 50 such as an LED and a light-receiving element 60 such as a photodiode, and a mirror unit 320 that includes a retroreflector 24. A third polarizing plate 13P, a fourth polarizing plate 13S, and a filterless region 13U are arranged on the front surface of the housing of the sensor head 310 in a state similar to that of the projector 10 shown in Fig. 3. A collimating lens 11 and a prism 12 are arranged inside the sensor head 310, similar to that of the projector 10 shown in Fig. 3. Furthermore, a half mirror 14 is provided inside the sensor head 310 between the light-projecting element 50 and the collimating lens 11.

[0101] The mirror section 320 is, for example, a holder (not shown) into which the retroreflector 24 is fitted, and a first polarizing plate 23P, a filterless region 23U, and a second polarizing plate 23S are arranged in a vertical direction and attached to the entire surface of the holder (not shown) into which the retroreflector 24 is fitted. When the mirror section 320 and the above-mentioned sensor head 310 are arranged opposite each other, the third polarizing plate 13P of the sensor head 310 is aligned with the second polarizing plate 23S of the mirror section 320, the fourth polarizing plate 13S of the sensor head 310 is aligned with the first polarizing plate 23P of the mirror section 320, and the filterless region 13U of the sensor head 310 is aligned with the filterless region 23U of the mirror section 320.

[0102] Light emitting element 50 emits light that vibrates in various directions. These lights are guided to collimator lens 11 via half mirror 14 and are changed into light along the horizontal direction. Furthermore, the direction of the optical axis of the light is changed by prism 12, and a first polarized light that is directed diagonally downward is emitted from third polarizing plate 13P, and a second polarized light that is directed diagonally upward is emitted from fourth polarizing plate 13S. In addition, the optical axis of a portion of the horizontal light is not changed by prism 12, and the non-polarized light is emitted as it is from filterless region 13U.

[0103] 8, by setting the sensor head 310 and the mirror unit 320 at a distance similar to that of the light projector 10 and the light receiver 20 shown in FIG. 3, the lights from the third polarizing plate 13P, the fourth polarizing plate 13S, and the filterless region 13U can be irradiated onto the entire surfaces of the first polarizing plate 23P, the second polarizing plate 23S, and the filterless region 23U in the mirror unit 320. Of these lights, the first polarized light irradiated to the first polarizing plate 23P, the second polarized light irradiated to the second polarizing plate 23S, and the non-polarized light irradiated to the filterless region 23U are guided to the retroreflector 24.

[0104] The retroreflector 24 has a function of reflecting the irradiated light in the irradiation direction. The reflection by the retroreflector 24 breaks the regularity of the vibration of the light, so that the reflected light vibrates in various directions. Of the light reflected toward the first polarizing plate 23P, the first polarized light passes through the first polarizing plate 23P and proceeds toward the third polarizing plate 13P on the sensor head 310 side, and then passes through the first polarizing plate 13P to enter the sensor head 310. Of the light reflected toward the second polarizing plate 23S, the second polarized light passes through the second polarizing plate 23S and proceeds toward the fourth polarizing plate 13S of the sensor head 310, and then passes through the fourth polarizing plate 13S to enter the sensor head 310. Furthermore, the light reflected toward filterless region 23U is emitted from filterless region 23U as unpolarized light, travels toward filterless region 13U of sensor head 310, and is further incident on sensor head 310 from filterless region 13U.

[0105] The light incident on the sensor head 310 is collected by the prism 12 and the collimator lens 11, and is guided toward the light receiving element 60 via the half mirror 14. In this way, the range through which the light travels back and forth between the sensor head 310 and the mirror section 320 becomes the detection area of ​​the photoelectric sensor shown in Fig. 9. Therefore, the reflective photoelectric sensor can detect the object TA in the same detection range as the above-mentioned transmissive photoelectric sensor.

[0106] 8 includes a sensor head 310 that houses the light projector 10 and the light receiver 20 therein and has surfaces that are disposed to face the detection target area F as a light projecting surface and a light receiving surface. This makes it possible to easily realize a reflective photoelectric sensor in which the light projector 10 and the light receiver 20 are integrally housed in the same housing.

[0107] 9, the photoelectric sensor 100 in the third modified example includes a mirror unit 320 having the same configuration as that of the second modified example shown in Fig. 8. Meanwhile, the photoelectric sensor 100 in the third modified example includes a sensor head 310, but unlike the second modified example shown in Fig. 8, the half mirror 14, the light projecting element 50, and the light receiving element 60 are not provided in the sensor head 310. Instead, a coaxial type optical fiber 330 connected to a signal processing device (not shown) similar to that of the example shown in Fig. 1 is drawn into the sensor head 310.

[0108] The optical fiber 330 is arranged with its tip aligned with the focal position of the collimator lens 11. As shown in the enlarged view at the lower left of the figure, the optical fiber 330 has a configuration in which, for example, a plurality of light receiving fibers 332 are arranged around a large-diameter light projecting fiber 331, and these are fixed by a coating material 333.

[0109] Light emitted by a light-projecting element (not shown) provided in the signal processing device is guided to the sensor head 310 by a light-projecting fiber 331, and is emitted to the mirror section 320 in the same principle as in the example shown in Fig. 8. Reflected light is also returned from the mirror section 320 to the sensor head 310 in the same principle as in the example shown in Fig. 8.

[0110] The light returned to the sensor head 310 is collected by the prism 12 and the collimator lens 11 and guided to the optical fiber 330, and the light incident on the light receiving fiber 332 is guided to a light receiving element (not shown) provided in the signal processing device.

[0111] 8 and 9, while light travels back and forth between the sensor head 310 and the mirror section 320, the third polarizing plate 13P and the fourth polarizing plate 13S select the light twice, and the first polarizing plate 23P and the second polarizing plate 23S select the light twice, for a total of four selections. As a result, the ratio of the amount of received light to the amount of light emitted from the light-projecting element 50 is relatively small compared to the case of a transmission-type photoelectric sensor. However, it becomes possible to sufficiently detect the light-blocking state by a method such as increasing the light emission intensity of the light-projecting element.

[0112] The photoelectric sensor 100 of this embodiment is not limited to the application example shown in FIG. 1, and can be used for detecting a wide variety of objects TA for various purposes. In the above embodiment, the first and fourth polarizing plates are configured to transmit polarized light in a direction horizontal to the paper surface of FIG. 3, and the second and third polarizing plates are configured to transmit polarized light in a vertical direction, but this is not limited to this, and the first and fourth polarizing plates may be vertical, and the second and third polarizing plates may be horizontal. Furthermore, the first and fourth polarizing plates may be arranged so that the direction of polarized light transmitted by the second and third polarizing plates is orthogonal to each other, that is, the direction is not limited to the horizontal / vertical direction to the paper surface of FIG. 3, and may be oblique to the paper surface.

[0113] Further, in the photoelectric sensor 100 of the present embodiment, an example has been shown in which a polarizing plate, that is, a polarizing filter, is used as an optical filter, but the present invention is not limited to this, and for example, a wavelength filter may be used.

[0114] [Second embodiment] Next, the configuration of the optical system of the photoelectric sensor according to the second embodiment will be described with reference to Figures 10 to 12. Note that, in the following, the same or similar components as those in the first embodiment will be denoted by the same or similar reference numerals, and differences from the first embodiment will be described. Also, similar effects due to similar components will not be mentioned one by one. Furthermore, since application examples and detection principles of the photoelectric sensor in the second embodiment are the same or substantially the same as those of the photoelectric sensor 100 in the first embodiment, illustrations and descriptions thereof will be omitted.

[0115] First, the configuration of the optical system of a photoelectric sensor according to the second embodiment will be described with reference to Fig. 10. Fig. 10 is a configuration diagram showing an example of the configuration of the optical system of a photoelectric sensor 100A according to the second embodiment.

[0116] 10, in the photoelectric sensor 100A of the second embodiment, a red color filter 13R, a blue color filter 13B, and a green color filter 13G are provided in the projector 10 instead of the third polarizing plate 13P, the fourth polarizing plate 13S, and the filterless region 13U of the first embodiment. Also, in place of the first polarizing plate 23P, the second polarizing plate 23S, and the filterless region 23U of the first embodiment, a red color filter 23R, a blue color filter 23B, and a green color filter 23G are provided in the receiver 20. Note that, like the first embodiment, the photoelectric sensor 100A of the second embodiment includes a signal processing device (not shown) and is configured to detect an object TA based on a change in the amount of light received by the light receiving element 60.

[0117] The light projecting element 50 of the second embodiment emits white light, not light that vibrates in various directions. White light is light that has a variety of colors, that is, light in a plurality of wavelength bands, continuously. In general, white light includes light with wavelengths from 380 nm to 780 nm.

[0118] The red color filter 13R and the red color filter 23R are filters that transmit and extract red light from the incident light. The red light emitted from the red color filter 13R and the red color filter 23R includes light with a wavelength of 640 nm to 770 nm. The blue color filter 13B and the blue color filter 23B are filters that transmit and extract blue light from the incident light. The blue light emitted from the blue color filter 13B and the blue color filter 23B includes light with a wavelength of 430 nm to 490 nm. The green color filter 13G and the green color filter 23G are filters that transmit and extract green light from the incident light. The green light emitted from the green color filter 13G and the green color filter 23G includes light with a wavelength of 490 nm to 550 nm.

[0119] The red color filter 13R, the blue color filter 13B, and the green color filter 13G may be integrally configured. In this case, the integrated color filter may be, for example, a thin glass substrate on which patterns of red, blue, and green color resists are formed. The red color filter 13R, the blue color filter 13B, and the green color filter 13G each have a rectangular shape having the same or approximately the same dimensions. Note that the red color filter 23R, the blue color filter 23B, and the green color filter 23G provided in the light receiver 20 are the same or approximately the same as the above-mentioned red color filter 13R, the blue color filter 13B, and the green color filter 13G, except for the arrangement on the light receiving surface, so that the description thereof will be omitted.

[0120] In photoelectric sensor 100A, red light is emitted diagonally downward from an upper region on the projection surface of projector 10, blue light is emitted diagonally upward from a lower region on the projection surface of projector 10, and green light is emitted horizontally from a central region on the projection surface of projector 10. Of these colored lights, the red light guided to the arrangement range of red color filter 23R of receiver 20, the blue light guided to the arrangement range of blue color filter 23B, and the green light guided to the arrangement range of green color filter 23G are guided to light receiving element 60.

[0121] Here, a description will be given of detection of an object by the photoelectric sensor according to the second embodiment. Fig. 11 is a diagram for explaining detection of an object TA by the photoelectric sensor 100A according to the second embodiment.

[0122] As shown in Figure 11, if the position of the object TA shifts vertically relative to the detection target area F, the proportion of light emitted from the light projection surface that is blocked by the object TA (hereinafter also referred to as the "light blocking rate") may not be reduced sufficiently.

[0123] For example, it is assumed that the red light emitted from the red color filter 13R, the blue light emitted from the blue color filter 13B, and the green light emitted from the green color filter 13G are each "100". When the position of the object TA shifts upward, the red light irradiated to the red color filter 23R and guided to the light receiver 20 becomes, for example, "80", the blue light irradiated to the blue color filter 23B and guided to the light receiver 20 becomes, for example, "90", and the green light irradiated to the green color filter 23G and guided to the light receiver 20 remains, for example, "100". In this example, the total light blocking rate of the three lights received by the light receiver 20 with respect to the light emitted from the projector 10 is "10%" (=(300-270) / 300). Therefore, if the threshold value of the light blocking rate for detection judgment is, for example, "15%," the object TA cannot be detected, and the detection of the object TA becomes unstable.

[0124] In contrast, the photoelectric sensor 100A of this embodiment is configured to output a detection signal in response to a decrease in the amount of at least one of red light, blue light, and green light received by the optical receiver 20. More specifically, the signal processing device is configured to measure the light blocking rate individually from the amount of light received of each color obtained by the light receiving element 60. Then, the signal processing device sets the detection signal to an ON state when at least one of the light blocking rates of each color exceeds a threshold value.

[0125] Specifically, as in the above example, the red light irradiated to the red color filter 23R and received by the light receiver 20 is "80", the blue light irradiated to the blue color filter 23B and received by the light receiver 20 is "90", and the green light irradiated to the green color filter 23G and received by the light receiver 20 is "100". The signal processing device measures the light blocking rate of the red light as "20%" (=(100-80) / 100), the light blocking rate of the blue light as "10%" (=(100-90) / 100), and the light blocking rate of the green light as "0%" (=(100-100) / 100). Since the light blocking rate of the red light is higher than the threshold value of the light blocking rate for detection judgment, which is "15%, the signal processing device sets the detection signal to an ON state and detects the object TA.

[0126] In this way, by configuring the receiver 20 to output a detection signal in response to a decrease in the amount of at least one of the red, blue, and green lights received, the receiver 20 can detect the object TA stably even if the position of the object TA varies, compared to when the detection signal is based on a change in the total amount of received light of each light.

[0127] Furthermore, by using red color filter 13R, blue color filter 13B, and green color filter 13G, and red color filter 23R, blue color filter 23B, and green color filter 23G shown in Figure 11 to realize a reflective configuration similar to that shown in Figures 8 and 9 in the first embodiment, it is possible to limit the selection of light to only the initial projection of light, and to suppress a decrease in the amount of received light.

[0128] Next, another configuration of the optical system of the photoelectric sensor according to the second embodiment will be described with reference to Fig. 12. Fig. 12 is a configuration diagram showing another example of the configuration of the optical system of the photoelectric sensor 100A according to the second embodiment.

[0129] 12, the photoelectric sensor 100A of the second embodiment may be provided with a light-projecting element 50R that emits red light, a light-projecting element 50B that emits blue light, and a light-projecting element 50G that emits green light, instead of providing the light-projecting element 10 with the red color filter 13R, the blue color filter 13B, and the green color filter 13G. Also, individual collimator lenses 11R, 11B, and 11G are provided between the light-projecting elements 50R, 50B, and 50G and the prism 12 so as to guide the respective lights from the light-projecting elements 50R, 50B, and 50G to the prism 12. The three light-projecting elements 50R, 50B, and 50G provided in the light-projecting element 10 may be accommodated in a signal processing device (not shown), and the respective lights may be guided to the light-projecting element 10 by separate optical fibers.

[0130] In the example shown in FIG. 12, the floodlight 10 is provided with light-projecting elements 50R, 50B, and 50G for each of the three types of light, and the light guided from these light-projecting elements 50R, 50B, and 50G is emitted without filtering, so that the intensity of the emitted light can be increased and detection of the object TA can be performed more stably.

[0131] In the example using color filters as shown in Fig. 11 or the example using a polarizing plate and a filterless region as in the first embodiment, a light source may be provided separately for each type of color light or for each emission direction, as in the example shown in Fig. 12. By adopting such a configuration, the intensity of the emitted light can be increased, and the stability of detection of the object TA can be improved.

[0132] Also, in the case where the object TA is detected using three types of colored light as in the examples shown in Fig. 10 and Fig. 12, each colored light may be guided to an individual light receiving element as in the example shown in Fig. 7 in the first embodiment. By adopting such a configuration, it is possible to configure so that the detection and determination process is performed for each light receiving element based on the light blocking rate of the amount of received light.

[0133] In each of the above-described embodiments, the three types of light emission regions of the light projector 10, the first polarizing plate 23P, the second polarizing plate 23S, and the filterless region 23U that receive the respective lights, or the red color filter 23R, the blue color filter 23B, and the green color filter 23G are arranged vertically, but the present invention is not limited to this. For example, when detecting a plate-shaped object TA that moves up and down with its plate surface vertical, the emission regions of the respective lights, and the first polarizing plate 23P, the second polarizing plate 23S, and the filterless region 23U, or the red color filter 23R, the blue color filter 23B, and the green color filter 23G are arranged horizontally in the left-right direction.

[0134] An exemplary embodiment of the present invention has been described above. According to the photoelectric sensor 100 in one embodiment, a filterless region 23U is provided between the first polarizing plate 23P and the second polarizing plate 23S on the light receiving surface of the light receiver 20, and guides non-polarized light to the inside of the light receiver 20. This makes it possible to irradiate the non-polarized light to the area between the first polarizing plate 23P' and the second polarizing plate 23S' on the light receiving surface, which was a cause of the generation of the dead zone DB2 in the virtual photoelectric sensor shown in FIG. 4, and guide it to the inside. In addition, since the filterless region 23U does not have a filter function, the irradiated non-polarized light can be guided directly to the inside. Therefore, it is possible to suppress the generation of the dead zone in the detection target region F, and to improve the light receiving efficiency compared to the conventional art.

[0135] Moreover, the photoelectric sensor 100A in another embodiment is configured to output a detection signal in response to a decrease in the amount of at least one of the red light, blue light, and green light received by the optical receiver 20. This allows the object TA to be detected stably even if the position of the object TA varies, compared to a case where the detection signal is based on a change in the total amount of received light of each light.

[0136] The above-described embodiments are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The present invention may be modified / improved without departing from the spirit thereof, and equivalents are also included in the present invention. In other words, even if a person skilled in the art appropriately modifies the design of the embodiments, the embodiment is included in the scope of the present invention as long as it has the characteristics of the present invention. For example, the elements of the embodiments and their arrangements, materials, conditions, shapes, sizes, etc. are not limited to those exemplified, and can be appropriately modified. In addition, the embodiments are merely examples, and it goes without saying that partial replacement or combination of the configurations shown in different embodiments is possible, and these are also included in the scope of the present invention as long as they include the characteristics of the present invention.

[0137] [Appendix 1] A photoelectric sensor (100) is provided with a light projector (10) that emits light toward a detection target area (F) and a light receiver (20) that receives the light, and outputs a signal indicating that an object (TA) has been detected based on a change in the amount of received light, the floodlight (10) is configured to emit, from a light-projecting surface, a first light, a second light having characteristics different from those of the first light and not interfering with each other, and a third light having characteristics different from those of the first light and the second light and not interfering with each other; a first optical filter (23P) provided on a light receiving surface of the light receiver (20) and transmitting the first light; a second optical filter (23S) provided on the light receiving surface and transmitting the second light; a first filterless region (23U) provided between the first optical filter (23P) and the second optical filter (23S) on the light receiving surface, for guiding the third light to an inside of the light receiver (20); A photoelectric sensor (100). [Appendix 11] A photoelectric sensor (100) is provided with a light projector (10) that emits light toward a detection target area (F) and a light receiver (20) that receives the light, and outputs a signal indicating that an object (TA) has been detected based on a change in the amount of received light, the light projector (10) is configured to emit a first light having a first wavelength range, a second light having a second wavelength range different from the first wavelength range, and a third light having a third wavelength range different from the first wavelength range and the second wavelength range; a first color filter (13R) that transmits the first light and guides it to a light receiver (20); a second color filter (13B) that transmits the second light and guides it to the light receiver (20); a third color filter (13G) that transmits the third light and guides it to the light receiver (20); The light receiver (20) is configured to output a signal in response to a decrease in the amount of at least one of the first light, the second light, and the third light received by the light receiver (20). A photoelectric sensor (100). [Explanation of symbols]

[0138] 10... projector, 10'... projector, 11, 11B, 11G, 11R... collimating lens, 12... prism, 13B... blue color filter, 13G... green color filter, 13P... third polarizing plate, 13P'... third polarizing plate, 13R... red color filter, 13S... fourth polarizing plate, 13S'... fourth polarizing plate, 13U... filterless area, 14... half mirror, 15... housing, 15a... upper holding portion, 15a1... step, 15b... lower holding portion, 15b1... step, 16... projector window, 17... cover glass, 20... receiver, 20'... receiver, 21, 21P, 21S, 21U... lens, 22... prism, 23B... blue color filter, 23G... green color filter, 23P... first polarizing plate, 23P' ...first polarizing plate, 23R...red color filter, 23S...second polarizing plate, 23S'...second polarizing plate, 23U...filterless area, 24...retroreflector, 25...housing, 26...light-receiving window, 30...signal processing device, 41...optical fiber, 42...optical fiber, 50, 50B, 50G, 50R...light-emitting element, 50'...light-emitting element, 60, 60P, 60S, 60U...light-receiving element, 60' ...light receiving element, 100...photoelectric sensor, 100A...photoelectric sensor, 310...sensor head, 320...mirror portion, 330...optical fiber, 331...fiber, 332...fiber, 333...coating material, CVa...conveyor, CVb...conveyor, DB1...dead zone, DB2...dead zone, DM1...component, DM2...component, F...detection target area, NG1...rectangular frame, NG2...rectangular frame, SP...space, TA...target.

Claims

1. A photoelectric sensor including a light projector that projects light toward a detection target area and a light receiver that receives the light, and outputs a signal indicating that an object has been detected based on a change in the amount of received light, the light projector is configured to emit, from a light projection surface, a first light, a second light having characteristics different from those of the first light and not interfering with each other, and a third light having characteristics different from those of the first light and the second light and not interfering with each other; a first optical filter provided on a light receiving surface of the light receiver and configured to transmit the first light; a second optical filter provided on the light receiving surface and configured to transmit the second light; a first filterless region provided between the first optical filter and the second optical filter on the light receiving surface, the first filterless region directing the third light into the inside of the light receiver; Photoelectric sensor.

2. the first filterless region includes an aperture formed in the light receiving surface; The photoelectric sensor according to claim 1.

3. a holder that holds the first optical filter and the second optical filter in a state in which the first optical filter and the second optical filter are arranged along the light receiving surface, The photoelectric sensor according to claim 1.

4. a cover glass provided on the light projection surface and bonded to the first optical filter and the second optical filter in a state where the first optical filter and the second optical filter are disposed along the light receiving surface; The photoelectric sensor according to claim 1.

5. an optical axis setting unit provided inside the light projector, which sets an optical axis direction of the first light to a direction obliquely crossing the detection target area toward the first optical filter, and sets an optical axis direction of the second light to a direction obliquely crossing the detection target area toward the second optical filter, The photoelectric sensor according to claim 1.

6. Further comprising a first light receiving element, a second light receiving element, and a third light receiving element; the optical receiver is configured to guide the first light transmitted through the first optical filter to the first light receiving element, the second light transmitted through the second optical filter to the second light receiving element, and the third light from the first filterless region to the third light receiving element, respectively. The photoelectric sensor according to claim 1.

7. a third optical filter provided on the light projection surface, the third optical filter transmitting light therethrough being emitted as the first light; a fourth optical filter provided on the light projection surface, the fourth optical filter transmitting light therethrough being emitted as the second light; a second filterless region provided between the third optical filter and the fourth optical filter on the light projection surface, through which the third light is emitted. The photoelectric sensor according to claim 1.

8. a first housing that accommodates the light projector therein, the first housing having a surface that faces the detection target area as the light projection surface; a second housing that houses the optical receiver therein, the second housing having a surface that is disposed opposite the surface of the first housing across the detection target area as the light receiving surface; The photoelectric sensor according to claim 1.

9. a housing that houses the light projector and the light receiver therein, the housing having a surface that faces the detection target area as the light projecting surface and the light receiving surface; The photoelectric sensor according to claim 1.

10. The light projector is configured to emit, from a light projection surface, a first polarized light as the first light, a second polarized light vibrating in a direction different from that of the first polarized light as the second light, and a non-polarized light as the third light. The photoelectric sensor according to any one of claims 1 to 9.

11. A photoelectric sensor including a light projector that projects light toward a detection target area and a light receiver that receives the light, and outputs a signal indicating that an object has been detected based on a change in the amount of received light, the light projector is configured to emit a first light having a first wavelength range, a second light having a second wavelength range different from the first wavelength range, and a third light having a third wavelength range different from the first wavelength range and the second wavelength range; a first color filter that transmits the first light and guides it to the light receiver; a second color filter that transmits the second light and guides it to the light receiver; a third color filter that transmits the third light and guides it to the light receiver; The optical receiver is configured to output the signal in response to a decrease in an amount of at least one of the first light, the second light, and the third light received by the optical receiver. Photoelectric sensor.

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