JP2009156818A - Photoelectric sensor and holding member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric sensor for accurately detecting existence of a detecting object even when a background object has high reflectivity and the distance to the detecting object is varied. <P>SOLUTION: This photoelectric sensor 1 includes a light projecting means 3 for radiating light to an aluminum sheet W in the optical axis A1 direction, a regression reflecting plate 4 for folding the reflected light emitted from the light projecting means 3 and reflected by the aluminum sheet W in the optical axis A2 direction, and a light receiving means 3 for receiving the re-reflected light that is reflected by the regression reflecting plate 4 and re-reflected by the aluminum sheet W in the direction (optical axis A1 direction) coaxially to the outgoing light from the light projecting means 3. The photoelectric sensor 1 detects a thin mark M adhered on the aluminum sheet W based on the light receiving amount of the received re-reflected light. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a photoelectric sensor and a holding member preferably used for the photoelectric sensor.

  Conventionally, in a factory production line or the like, a so-called diffuse reflection type is used to detect the presence or absence of an object to be detected based on the amount of light reflected by the object to be detected that is placed on the object to be conveyed. May be used.

  This type of photoelectric sensor includes a light projecting element that irradiates light to an object to be detected and a light receiving element that receives reflected light reflected by the object to be detected. When the light receiving element receives the reflected light from the detected object and the reflected light from the background object (conveying object) existing behind the detected object, an amount by which the received light amount changes ( The presence or absence of an object to be detected is detected based on the amount of change in the amount of light received by the light receiving element.

  For this reason, if the background object has a glossy surface (metal luster) like an aluminum sheet and the object to be detected is easy to transmit light, the light is almost reflected by the background object. The amount of change in the amount of received light is reduced, making it difficult to detect the presence or absence of the detected object.

On the other hand, in the so-called limited reflection type photoelectric sensor, the optical axis of the light projecting element and the optical axis of the light receiving element are provided so as to intersect with each other, and an object to be detected is detected in a detection area where the optical axis intersects. The influence of reflected light from the background object is reduced, and the detected object is detected with good accuracy (see, for example, Patent Document 1).
JP 2000-81390 A

  However, in this limited reflection type photoelectric sensor, since the detection area is limited, for example, when the background object on which the detection object is placed vibrates in the vertical direction, the distance to the detection object fluctuates. Then, the detection of the detected object may not be performed with good accuracy.

  Further, in this type of photoelectric sensor, the presence / absence of the detected object is detected based on the amount of change in the amount of light received by the light receiving element between the detected object and the background object, similar to the diffuse reflection type photoelectric sensor described above. Therefore, it is necessary to ensure a sufficient amount of change in the amount of received light. However, if the object to be detected is a thin mark or a transparent plating solution attached on a highly reflective background object such as an aluminum sheet, the amount of change in the amount of received light becomes small, and the object to be detected is accurate. It becomes difficult to detect well.

  The present invention has been made in view of such circumstances, and its purpose is that the background object has a high reflectivity and the object is detected even when the distance to the object to be detected varies. An object of the present invention is to provide a photoelectric sensor that can detect a detected object with good accuracy and a holding member that is preferably used for the photoelectric sensor.

  In order to solve the above-mentioned problem, the invention described in claim 1 includes a light projecting unit that irradiates light to the object to be detected and a reflected light that is emitted from the light projecting unit and reflected by the object to be detected. A reflecting member that reflects light in a coaxial direction; and a light receiving means that receives re-reflected light that is reflected by the reflecting member and reflected again by the object to be detected in the coaxial direction with light emitted from the light projecting means; The reflection member is a regressive reflection plate that reflects the reflected light in the incident direction of the reflected light regardless of the incident angle of the reflected light incident on the reflecting member, and the amount of light received by the light receiving means is The gist is to detect the detected object based on the above.

  According to the present invention, the light receiving means is coaxial with the light emitted from the light projecting means even when the distance to the object to be detected varies (the detected object is displaced in the optical axis direction of the light projecting means). Since the re-reflected light reflected again by the detected object in the direction (the optical axis direction of the light projecting means) is continuously received, the presence / absence of the detected object is ensured regardless of the variation in the distance. Can be detected. In addition, since the light receiving means receives the light reflected twice by the object to be detected (re-reflected light), the influence of the object to be detected is increased and the background object existing behind the object to be detected is reflected. Even if the rate is high, the amount of change in the amount of light received by the light receiving means between the object to be detected and the background object can be increased. Thereby, the detected object can be detected with good accuracy. Furthermore, in the present invention, since the return reflection plate that reflects the reflected light in the incident direction of the reflected light is used as the reflecting member regardless of the incident angle of the reflected light incident on the reflecting member, the surface of the object to be detected Unlike the regular reflection mirror, the reflected light can be accurately reflected in the incident direction of the reflected light even when the inclination of the light changes and the incident angle of the reflected light incident on the reflecting member changes. Further, even when the return reflection plate has an assembly error with respect to the holding member or the like, the reflected light can be accurately reflected in the incident direction of the reflected light in the same manner as described above.

  The invention according to claim 2 is the photoelectric sensor according to claim 1, wherein the reflecting member is not affected by the change when the distance between the object to be detected and the light receiving means fluctuates by a small amount. The gist of the invention is that it has a reflecting surface having an area where the light reflected by the light receiving means can be received.

  According to the present invention, when the absolute position of the detected object fluctuates in the vertical direction, the reflecting member receives the re-reflected light reflected again by the detected object by the light receiving means regardless of the fluctuation. Therefore, when the distance to the object to be detected fluctuates, the re-reflected light can be more reliably received by the light receiving means.

  According to a third aspect of the present invention, in the photoelectric sensor according to the first or second aspect, a holding member that integrally holds the light projecting unit, the light receiving unit, and the reflecting member at respective specified positions. The gist is to further provide.

According to the present invention, the light projecting unit, the light receiving unit, and the reflecting member can be integrally and reliably held at the respective specified positions by the holding member provided in the photoelectric sensor.
According to a fourth aspect of the present invention, there is provided a holding member provided in the photoelectric sensor according to the first or second aspect, wherein the light projecting unit, the light receiving unit, and the reflecting member are integrated at respective specified positions. It is the gist of this.

  According to the present invention, the light projecting means, the light receiving means, and the reflecting member can be integrally and reliably held at their respective specified positions by the holding member provided in the photoelectric sensor.

  According to the present invention, there is provided a photoelectric sensor that can accurately detect the detected object without depending on the reflectance of the background object and the distance to the detected object, and a holding member that is preferably used for the photoelectric sensor. be able to.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings.
As shown in FIG. 1, the photoelectric sensor 1 of the present embodiment includes a plurality of objects to be detected that are adhered at predetermined intervals on an aluminum sheet W having a glossy surface as a background object that is conveyed by a roller R at a constant speed. (In this embodiment, the detected object whose presence or absence is detected by the photoelectric sensor 1 is the mark M,..., And is an aluminum sheet. W is a background object behind the mark M as a detection object, but the reflectance of the mark M,... Is extremely small compared to the reflectance of the aluminum sheet W. For example, the light that should be reflected by the object to be detected is treated as being reflected by the aluminum sheet W that is the background object).

  The photoelectric sensor 1 includes a holding member 2 as a holding unit supported and fixed to a support frame (not shown) provided above the aluminum sheet W, and light toward the aluminum sheet W and the marks M,. And a return reflection plate 4 as a reflecting member that reflects (reflects) the reflected light reflected by the aluminum sheet W in the same direction as that of the reflected light.

  Specifically, as shown in FIG. 2, the holding member 2 is supported and fixed to the support frame and extends in the width direction of the aluminum sheet W, and is provided at both ends of the fixing portion 11. Each of the support shafts 14 and 15 includes a long sensor holding portion 12 and a reflecting member holding portion 13 that are supported so as to be rotatable around the conveyance direction of the aluminum sheet W.

  In the sensor holding portion 12, a sensor placement surface 12a is formed in a flat shape so as to face the aluminum sheet W at the tip portion, and the sensor body 3 is placed and fixed on the placement surface 12a. Has been. Accordingly, the sensor body 3 can emit light in the direction of the normal A1 of the sensor placement surface 12a. This normal A1 forms an angle θ1 with the normal N of the surface of the aluminum sheet W when it is conveyed at the reference position.

  In addition, in the reflection member holding portion 13, a reflection member placement surface 13a is formed in a flat shape so as to face the aluminum sheet W at the tip portion thereof, and the regressive reflection plate 4 is placed on the placement surface 13a. Placed and fixed. Thereby, the regressive reflecting plate 4 can reflect the light incident in the direction of the normal A2 of the reflection member mounting surface 13a in the same direction as the direction of the normal A2. The normal A2 intersects the normal A1 on the surface so as to form an angle θ2 with the normal N of the surface of the aluminum sheet W.

  Further, as shown in FIG. 3, the sensor body 3 is configured as a so-called coaxial reflection type sensor, and is a light projecting element comprising a laser diode that emits linearly polarized light L1 toward the aluminum sheet W. 21, a half mirror 23 provided on the optical axis of the light L1 and transmitting the light L1, and a light L3 incident from the outside in the same direction as the optical axis of the light L1 and reflected by the half mirror 23 And a light receiving element 22 made of a photodiode for receiving light.

  The sensor body 3 further includes a control circuit 25 for controlling the operation of the sensor body 3, and a light projecting circuit 24 inserted between the control circuit 25 and the light projecting element 21 and the light receiving element 22, respectively. And a light receiving circuit 26.

  As shown in FIG. 2, the holding member 2 integrally holds the light projecting element 21, the light receiving element 22, and the regressive reflection plate 4 at respective specified positions. As a result, the light emitted from the light projecting element 21 of the sensor body 3 in the direction of the normal A1 and specularly reflected by the aluminum sheet W (θ1 = θ2 in the figure) is reflected by the regressive reflection plate 4 in the method. Reflection is possible in the same direction as the line A2.

  The control circuit 25 outputs a light projection pulse signal for illuminating the light projecting element 21 to the light projecting circuit 24, and the light projecting circuit 24 receives the signal to cause the light projecting element 21 to emit a predetermined light. Turn on the pulse at a cycle. When the light L1 emitted from the light projecting element 21 is reflected by the aluminum sheet W and the return reflection plate 4 and received by the light receiving element 22 as light L3, the light receiving element 22 receives the received light L3. Is photoelectrically converted and output to the light receiving circuit 26 as an electric signal. The light receiving circuit 26 amplifies the electric signal to a predetermined level and outputs it to the control circuit 25. In this way, an electric signal (analog signal) having a level corresponding to the amount of light received by the light receiving element 22 is input to the control circuit 25. Then, the control circuit 25 detects the presence / absence of the marks M,... Attached on the aluminum sheet W based on the electrical signal, that is, based on the amount of light received by the light receiving element 22, and an external device (not shown). A detection signal is output to

  On the other hand, the regressive reflecting plate 4 includes a reflecting surface 4a in which a large number of corner cubes 4c,. The regressive reflection plate 4 shifts the light L2 incident on the reflection surface 4a in parallel by the pitch interval of the corner cube and reflects the light L2 in the direction opposite to the incident direction of the light L2. That is, the regressive reflection plate 4 can accurately reflect the light L2 in the direction opposite to the incident direction regardless of the incident angle of the light L2 incident on the reflecting surface 4a. For this reason, the retroreflective plate 4 emits the light L2 (reflected light) emitted from the light projecting element 21 of the sensor body 3 and reflected by the aluminum sheet W, regardless of the incident angle. It is possible to reflect in the coaxial direction. In such a retroreflecting plate 4, the P-polarized component and the S-polarized component are reversed (replaced) by the reflection of light. Therefore, the reflected light is separated into the P-polarized component and the S-polarized component to detect the detected object. It is not suitable for the detection sensor etc. which perform. Thus, in order to detect an object to be detected based on the ratio of the P-polarized component and the S-polarized component, it is necessary to use a regular reflection mirror instead of the retroreflecting plate 4 as a reflecting member.

  The area of the reflection surface 4a is determined by the absolute position of the aluminum sheet W due to vibrations transmitted from a drive motor (not shown) that rotationally drives the roller R that conveys the aluminum sheet W, bending of the aluminum sheet W itself, or the like. Is set to such a size that the light L2 reflected by the aluminum sheet W can be received by the reflecting surface 4a even when the amount of fluctuation fluctuates in the vertical direction (see FIG. 6).

  In the present embodiment, as described above, the sensor main body 3 and the return reflection plate 4 are each provided with the sensor holding portion 12 and the reflection member holding portion that are provided on the holding member 2 so as to be rotatable with respect to the fixing portion 11. 13, the direction of the light L <b> 1 emitted from the sensor body 3 and the inclination angle of the regressive reflection plate 4 with respect to the aluminum sheet W are set so that the holding portions 12 and 13 are fixed to the fixing portion 11. On the other hand, it can be easily changed by rotating it by a necessary angle. Thereby, the sensor main body 3 (the light projecting element 21 and the light receiving element 22) and the retroreflecting plate 4 can be changed according to the state of the sensor main body 3, the state of the detected object, the state of the conveyance speed, or the type of the reflecting member. , It can be arranged easily and reliably at each specified position.

The photoelectric sensor 1 of the present embodiment is configured as described above and has the following effects.
That is, as shown in FIG. 5, the light L2 (reflected light) emitted from the sensor main body 3 (light projecting element 21) and specularly reflected by the aluminum sheet W (θ1 = θ2 in the figure) is reflected to the regressive reflection plate 4 Are reflected by the reflecting surface 4a and reflected in the coaxial direction with the light L2.

  Then, the light L2 is reflected again by the aluminum sheet W to become re-reflected light, and reversely follows the path of the light L1 emitted from the sensor main body 3 (light projecting element 21), so that the sensor main body 3 (light receiving element 22). ). Therefore, the sensor body 3 (light receiving element 22) transmits the mark M,... And receives the light L3 (re-reflected light) reflected twice by the aluminum sheet W, so that the mark M,. The influence on the re-reflected light is increased, and the background object to which the marks M,... Are attached is the aluminum sheet W, and even between the marks M,. The amount of change in the amount of light received by the light receiving element 22 can be increased. Thereby, the presence or absence of the marks M,... Can be detected with good accuracy.

  Further, as shown in FIG. 6, the sensor main body 3 (light receiving element 22) is moved from the state of FIG. 5 to the sensor main body 3 and the aluminum sheet W by vibration transmitted from a drive motor or the like, or bending of the aluminum sheet W itself. Even when the distance between them varies (the marks M,... Are displaced in the direction of the optical axis of the light projecting element 21), the light L1 emitted from the light projecting element 21 is coaxial (the optical axis of the light projecting element 21). The light L3 (re-reflected light) reflected again by the aluminum sheet W is continuously received in the direction), so that the presence / absence of the mark M,... Is reliably detected regardless of the change in the distance. It becomes like this.

  Furthermore, when the absolute position of the aluminum sheet W fluctuates in the vertical direction, the regressive reflecting plate 4 has a reflecting surface having an area where the light L3 (re-reflected light) can be received by the light receiving element 22 regardless of the fluctuation. 4a, when the distance from the sensor body 3 to the marks M,... (Aluminum sheet W) fluctuates due to vertical vibration of the aluminum sheet W, the light L3 is transmitted by the sensor body 3 (light receiving element 22). Can be received more reliably.

  Moreover, the retroreflecting plate 4 emits the light L2 (reflected light) emitted from the sensor body 3 (light projecting element 21) and regularly reflected by the aluminum sheet W, regardless of the angle of incidence on the reflecting surface 4a. It can reflect in the said incident direction (refer FIG. 4). For this reason, as shown in FIG. 7, even when the inclination of the surface of the aluminum sheet W changes due to vibration transmitted from the drive motor or the like or the deflection of the aluminum sheet W itself, the incident angle of light is a right angle (90 °). Unlike the regular reflection mirror that reflects light in the same direction as the incident direction only, the light L2 can be accurately reflected (turned back) in the incident direction. Further, as shown in FIG. 8, even when the regressive reflecting plate 4 has an assembly error with respect to the holding member 2, the light L2 can be accurately reflected in the incident direction as described above.

  Further, in the case where a regular reflection mirror is used as the reflection member, the regular reflection mirror causes an assembly error with respect to the holding member 2 in contrast to the case where the regression reflection plate 4 is used as in the photoelectric sensor 1 of the present embodiment. Not required. On the other hand, as in the photoelectric sensor 1 of the present embodiment, in the case of detecting using the amount of light received by the light receiving element 22 (total amount of received light) regardless of the polarization component, the regressive reflector is used as a reflecting member. Since 4 can be used, an assembly error with respect to the holding member 2 hardly poses a problem.

Below, the effect show | played by the photoelectric sensor 1 of this embodiment is described.
(1) The light receiving element 22 of the sensor body 3 can be used even when the distance to the marks M,... Attached on the aluminum sheet W varies due to vertical vibrations of the aluminum sheet W. Since the light L3 reflected again by the aluminum sheet W in the same direction as the light L1 emitted from the light projecting element 21 (re-reflected light) L3 is received, the marks M, The presence or absence of ... can be reliably detected. In addition, since the light receiving element 22 receives the light (re-reflected light) that is transmitted through the marks M,... And reflected twice by the aluminum sheet W, the marks M,. Even if the background object to which the marks M,... Are attached has a glossy surface such as the aluminum sheet W, the light receiving element 22 between each mark M and the aluminum sheet W increases. The amount of change in the amount of received light due to can be increased. Thereby, the presence or absence of the marks M,... Can be detected with good accuracy.

  (2) Since the regressive reflection plate 4 that reflects the light L2 in the incident direction is used regardless of the incident angle of the incident light L2 (reflected light), the surface of the aluminum sheet W is vibrated in the vertical direction or the like. Even when the inclination of the light L2 changes and the incident angle of the light L2 (reflected light) incident on the return reflector 4 changes, the light L2 can be accurately reflected in the incident direction. Further, even when the return reflection plate 4 has an assembly error with respect to the holding member 2, the light L2 can be accurately reflected in the incident direction as described above.

  (3) When the absolute position of the aluminum sheet W fluctuates by a small amount in the vertical direction, the retroreflector 4 reflects the light L3 reflected again by the light receiving element 22 of the sensor body 3 on the aluminum sheet W regardless of the fluctuation. Since the reflective surface 4a has an area capable of receiving (re-reflected light), when the distance from the sensor body 3 to the marks M,... The light L3 can be more reliably received by the light receiving element 22.

The above embodiment may be modified as follows.
In the above embodiment, as the holding member 2, the sensor holding portion 12 that holds the sensor body 3 and the reflection member holding portion 13 that holds the return reflection plate 4 are connected to the fixed portion 11 so as to be rotatable. Was used. However, the present invention is not limited to this, and for example, a holding member in which one of the sensor holding unit 12 and the reflection member holding unit 13 is fixed to the fixing unit 11 so as not to rotate may be used. You may use the holding member in which all the reflection member holding parts 13 are being fixed to the fixing | fixed part 11 so that rotation is impossible.

  In the above embodiment, in the photoelectric sensor 1, the sensor main body 3 and the return reflection plate 4 are provided apart from each other. However, the present invention is not limited to this. For example, the photoelectric sensor 1 may be configured such that the return reflection plate 4 is integrally accommodated in a casing (housing) that accommodates the sensor body 3.

  In the above embodiment, the so-called coaxial reflection type photoelectric sensor 1 is used. However, the present invention is not limited to this, and other types of photoelectric sensors may be used as long as they can receive light L3 (re-reflected light) reflected again by the aluminum sheet W in the same direction as the optical axis direction of the light projecting element 21. You can also

  In the above embodiment, a laser diode that emits light that is linearly polarized light is used as the light projecting element 21 of the sensor body 3. Instead, another light projecting element such as a red light emitting diode is used instead. Is also possible.

The perspective view which shows the whole structure of the photoelectric sensor which concerns on embodiment of this invention. It is the figure seen from the A direction of FIG. 1, Comprising: In the photoelectric sensor which concerns on embodiment of this invention, the arrow line view which shows the state by which the sensor main body and the retroreflection board are arrange | positioned by each holding position with the holding member. The block diagram which shows the electrical constitution of the sensor main body of the photoelectric sensor which concerns on embodiment of this invention. The side view of the regression reflector of the photoelectric sensor. The side view explaining operation | movement of the photoelectric sensor. The side view explaining another operation | movement of the photoelectric sensor. The side view explaining operation | movement of the regression reflector of the photoelectric sensor. The side view explaining another operation | movement of the regression reflector of the photoelectric sensor.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Photoelectric sensor, 2 ... Holding member, 4 ... Regression reflection plate (reflection member), 4a ... Reflecting surface of regression reflection plate, 21 ... Light projection element (light projection means), 22 ... Light reception element (light reception means), M ... Mark (object to be detected), L1 ... outgoing light, L2 ... reflected light, L3 ... re-reflected light.

Claims (4)

A light projecting means for irradiating the object to be detected;
A reflective member that reflects the reflected light emitted from the light projecting means and reflected by the object to be detected in a direction coaxial with the reflected light;
Receiving light that is reflected by the reflecting member and receives re-reflected light that is reflected again by the object to be detected in the same direction as the light emitted from the light projecting means;
The reflective member is a retroreflector that reflects the reflected light in the incident direction of the reflected light regardless of the incident angle of the reflected light incident on the reflective member;
A photoelectric sensor for detecting the object to be detected based on an amount of light received by the light receiving means.   The reflecting member has a reflecting surface having an area where the re-reflected light can be received by the light receiving unit regardless of the change when the distance between the object to be detected and the light receiving unit is changed by a minute amount. The photoelectric sensor according to claim 1.   3. The photoelectric sensor according to claim 1, further comprising a holding member that integrally holds the light projecting unit, the light receiving unit, and the reflecting member at respective specified positions. A holding member provided in the photoelectric sensor according to claim 1 or 2,
A holding member, wherein the light projecting means, the light receiving means, and the reflecting member are integrally held at their respective prescribed positions.

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