JP4266182B2 - Photoelectric switch - Google Patents

Description

  The present invention relates to a photoelectric switch for detecting an object.

  Conventionally, a photoelectric switch that detects the presence or absence of an object by projecting light onto a detection region and detecting the reflected light or transmitted light has been used.

  The photoelectric switch generally has a light source that projects red light. In addition, there may be a case where detection of red light alone has a small difference in the amount of received light between the object and the background, making detection difficult. In this case, a photoelectric switch having a light source that projects green light or a light source that projects blue light The photoelectric switch which has is used.

  On the other hand, it has a light source that projects red light, green light, and blue light, and detects the presence or absence of an object by sequentially projecting the light of these light sources onto the detection area and detecting the reflected or transmitted light A color identification device is used (see, for example, Patent Document 1).

In the above-described color identification device, the sum of received light amounts of red light, green light, and blue light (hereinafter referred to as three colors of light) is calculated based on information about the received reflected light or transmitted light. . An object having a predetermined color is detected by comparing the calculated sum of received light amounts with a threshold value preset by teaching processing.
JP 2000-121440 A

  In the case of a photoelectric switch that projects only light of a single wavelength onto an object, the difference in the amount of received light that is sufficient for detection, depending on the color of the object to be detected, even though the object color is different from the background color You may not get. As a result, the detection accuracy of the object is lowered.

  On the other hand, in the object detection process by the color identification device, first, the amount of received light of three colors when there is an object in the detection region, and the amount of received light of three colors when there is no object in the detection region, Is calculated as a difference in received light amount for each of the three colors of light. In this case, the difference in received light amount has a positive value or a negative value.

  Then, the sum of the received light amount differences calculated for the three colors of light is calculated as the received light amount sum. The presence / absence of an object having a predetermined color is determined based on the calculated total amount of received light and a threshold value preset by teaching processing.

  However, for example, the total received light amount, which is the sum of the received light amount difference of two colors having a positive value and the received light amount difference of one color having a negative value, may be close to zero. As a result, the detection accuracy of the object is lowered.

  An object of the present invention is to provide a photoelectric switch capable of easily detecting an object having a predetermined color with high accuracy.

  A photoelectric switch according to the present invention is a photoelectric switch that projects light onto a detection region and receives feedback light, and detects an object based on a threshold value and an amount of received light for detecting the object, and is different. A plurality of light sources that project light having a plurality of wavelengths, a light receiving element that receives feedback light based on the light of each wavelength, and light reception amount information based on the light reception amount obtained by the light receiving element for each wavelength of light are generated. The information generation means, a plurality of received light amount information corresponding to light of a plurality of wavelengths generated by the information generation means when the detection area is in the first state at the first teaching, and the detection area is the second A selection unit that selects one or a plurality of light sources among a plurality of light sources based on a magnitude relationship with a plurality of received light amount information corresponding to light of a plurality of wavelengths generated by the information generation unit when in a state; Second tee Setting means for setting a threshold value based on one or a plurality of received light quantity information corresponding to one or a plurality of light sources selected by the selection means at the time of selection, and selection by the selection means during the object detection operation Determination means for determining the detection state of the object based on one or a plurality of received light amount information corresponding to the one or a plurality of light sources and a threshold set by the setting means.

  In the photoelectric switch according to the present invention, at the time of the first teaching, a plurality of received light amount information corresponding to a plurality of wavelengths of light generated by the information generating means when the detection region is in the first state, and the detection region When one of the plurality of light sources is in the second state, one or a plurality of light sources are selected from the plurality of light sources based on the magnitude relationship with the plurality of received light amount information corresponding to the light of the plurality of wavelengths generated by the information generating unit. Is selected. During the second teaching, the setting means automatically sets a threshold value for detecting an object based on one or more received light amount information corresponding to one or more light sources selected by the selection means. Is done. During the object detection operation, the detection state of the object is determined based on one or more received light amount information corresponding to one or more light sources selected by the selection means and a threshold set by the setting means. Determined by means.

  As described above, one or more light sources are selected based on the magnitude relationship between the plurality of light reception amount information in the first state and the plurality of light reception amount information in the second state, and the selected light source is used. Since the threshold value is set and the detection state of the object is determined, an object having a predetermined color can be easily detected with high accuracy.

  In addition, since one or a plurality of light sources that make the difference between the plurality of received light amount information in the first state and the plurality of received light amount information in the second state clear can be selected, more accurate detection can be performed. Can be realized.

  The selection unit generates a plurality of received light amount information corresponding to light of a plurality of wavelengths generated by the information generation unit when the detection region is in the first state, and generates information when the detection region is in the second state. The difference between the received light amount information corresponding to the light of the plurality of wavelengths generated by the means is calculated as the received light amount information difference, and the total received light amount information difference having a positive value and the received light amount having a negative value One or a plurality of light sources corresponding to a large sum among the sums of information differences may be selected.

  In this case, the received light amount information difference having a positive value that is the difference between the plurality of received light amount information when the detection region is in the first state and the plurality of received light amount information when the detection region is in the second state. And one or a plurality of light sources are selected based on the sum of the received light amount information differences having a negative value. Thereby, since one or a plurality of light sources in which the difference between the plurality of received light amount information corresponding to the first state and the plurality of received light amount information corresponding to the second state becomes clear can be selected. It is possible to realize highly accurate detection of an object.

  The photoelectric switch may further include a first display unit that displays one or more received light amount information corresponding to one or more light sources selected by the selection unit. In this case, the operator can easily recognize one or a plurality of received light amount information corresponding to the one or a plurality of light sources selected by the selection unit by the first display unit.

  The photoelectric switch may further include a second display unit indicating one or more light sources selected by the selection unit. In this case, the operator can easily recognize one or a plurality of light sources selected by the selection unit by the second display unit.

  Each of the plurality of received light amount information may be a received light amount of light of each wavelength. In this case, an object having a desired color can be detected with high accuracy even when the ratio of the amounts of received light of a plurality of wavelengths becomes the same value.

  Each of the plurality of received light amount information may be a ratio of the received light amount of each wavelength with respect to the sum of the received light amounts of light of a plurality of wavelengths. In this case, the detection range can be accurately set regardless of the distance from the light source to the object.

  The determining means determines the detection state of the object based on a sum of one or more received light amount information corresponding to one or more light sources selected by the selecting means and a threshold set by the setting means. May be.

  In this case, the process for detecting an object having a predetermined color can be simplified, and the object can be detected with high accuracy.

  The first state of the detection area is a state where an object having a color to be detected exists in the detection area, and the second state of the detection area is an object having a color to be detected in the detection area. It may be in a nonexistent state.

  In this case, a plurality of received light amount information corresponding to the color to be detected when the detection region is in the first state is obtained, and a plurality of light amounts corresponding to the background color is obtained when the detection region is in the second state. Received light amount information is obtained.

  According to the present invention, an object having a predetermined color can be easily detected with high accuracy.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic diagram of a photoelectric switch according to the present embodiment.

  The photoelectric switch 100 according to the present embodiment includes a sensor head portion 10, an optical fiber cable 20, an electric cable 30, a main body portion 40, and an output cable 50. The main body unit 40 includes a setting input unit 45 and a main body side display unit 46.

  As shown in FIG. 1, the optical fiber cable 20 and the electric cable 30 extending from the sensor head portion 10 are connected to the main body portion 40. The output cable 50 extending from the main body 40 is connected to another external device (not shown).

  The sensor head portion 10 is provided with a light projecting optical system 11 and a light receiving optical system 12. The light L emitted from the light projecting optical system 11 is reflected by the object W and enters the light receiving optical system 12.

  The setting input unit 45 includes a mode key 4d, a setting key 4e, an up key 4f, and a down key 4g. The main body side display unit 46 includes an output indicator lamp 4a, a selected light source indicator lamp 4h, and 7-segment LEDs 4b and 4c.

  The mode key 4d is used by the user to change the operation mode. The setting key 4e is used when teaching processing described later is performed. Details will be described later. The upper key 4f and the lower key 4g are used for manual adjustment of a threshold value, for example.

  The output indicator lamp 4a displays the detection state (detection and non-detection) of the object W by lighting and non-lighting. In the present embodiment, four detection states corresponding to four types of color setting values are displayed.

  The 7-segment LED 4b displays, for example, the sum of received light amounts described later. The 7-segment LED 4c has, for example, red light, green light, and blue light (hereinafter referred to as three colors) corresponding to a detection threshold described later or one or a plurality of detection light projecting elements described later. Are called in the order of light. The current amount of received light is the amount of reflected light received based on the current three colors of light emission. The selected light source indicator lamp 4h displays a detection light projecting element selected by a teaching process described later by lighting and non-lighting.

  FIG. 2 is a block diagram showing an internal configuration of the photoelectric switch 100 according to the present embodiment.

  The sensor head portion 10 of the photoelectric switch 100 includes a light projecting optical system 11, a light receiving optical system 12, a light receiving element 13, and a light receiving circuit 14. The main body 40 of the photoelectric switch 100 includes a light projecting control unit 41, a plurality of light projecting elements 42a, 42b, 42c, a signal processing control unit 43, an output circuit 44, a setting input unit 45, a main body side display unit 46, and a storage unit 47. Is provided.

  The light projection control unit 41 controls the light emission operation of the plurality of light projecting elements 42a, 42b, and 42c. Specifically, a light projection timing signal ST indicating the light emission timing of each of the plurality of light projecting elements 42 a, 42 b, 42 c is output to the plurality of light projecting elements 42 a, 42 b, 42 c and the signal processing control unit 43.

  The plurality of light projecting elements 42a, 42b, 42c are, for example, LEDs (light emitting diodes). The light L generated by the plurality of light projecting elements 42 a, 42 b, 42 c is guided to the light projecting optical system 11 of the sensor head 10 through the optical fiber cable 20. The fiber optic cable 20 includes a single optical fiber. The light emitting colors of the light projecting elements 42a, 42b, and 42c are different. In the present embodiment, the light projecting element 42a emits green light, the light projecting element 42b emits blue light, and the light projecting element 42c emits red light.

  The light projecting optical system 11 and the light receiving optical system 12 are composed of, for example, lenses. The light L generated by the plurality of light projecting elements 42 a, 42 b, 42 c is emitted to the outside through the light projecting optical system 11 through the optical fiber cable 20. In the light receiving optical system 12, the light L reflected by the object W out of the light L emitted to the outside by the light projecting optical system 11 is incident.

  The light L incident on the light receiving optical system 12 is guided to the light receiving element 13. The light receiving element 13 generates a light receiving signal S1 corresponding to the amount of received light.

  The light receiving circuit 14 amplifies the light reception signal S <b> 1 generated by the light receiving element 13 and transmits the amplified light reception signal S <b> 1 to the signal processing control unit 43 of the main body 40 through the electric wire cable 30.

  The signal processing control unit 43 performs predetermined signal processing on the light reception signal S <b> 1 and outputs a detection signal S <b> 2 indicating detection and non-detection of the object W to the outside via the output circuit 44. The signal processing control unit 43 performs teaching processing and detection processing described later as the predetermined signal processing.

  Further, the signal processing control unit 43 causes the main body side display unit 46 to display predetermined information based on the received light reception signal S1 and the operation of the setting input unit 45 by the user.

  The storage unit 47 stores a threshold value and the like calculated by teaching processing.

  Next, the light projecting elements 42a, 42b, and 42c provided in the photoelectric switch 100 will be described.

  FIG. 3 is a schematic cross-sectional view showing the arrangement of the plurality of light projecting elements 42a, 42b, 42c inside the sensor head unit 10. As shown in FIG.

  In FIG. 3, the holder 9 is provided with light projecting elements 42a, 42b, 42c, a light projecting lens 3, and two dichroic mirrors 5a, 5b. An optical fiber cable 20 is attached in front of the light projecting lens 3.

  The light projecting element 42c is arranged such that its optical axis Lc is parallel to the optical axis Lx of the light projecting lens 3 and is slightly shifted in consideration of light refraction by the dichroic mirrors 5a and 5b. The light projecting element 42 b is arranged so that its optical axis Lb intersects the optical axis Lx of the light projecting lens 3 substantially perpendicularly. The light projecting element 42a is arranged so that its optical axis La intersects the optical axis Lx of the light projecting lens 3 at an angle (acute angle) greater than 0 degree and smaller than 90 degrees. The optical axes La, Lb, and Lc of the light projecting elements 42a, 42b, and 42c are arranged on the same plane. Thereby, the sensor head portion 10 itself can be thinned.

  The dichroic mirrors 5a and 5b each reflect light in a specific wavelength range and transmit light of other wavelengths. In the present embodiment, the dichroic mirror 5a reflects light having the emission wavelength of the light projecting element 42a and transmits light having other wavelengths. The dichroic mirror 5b reflects light having the emission wavelength of the light projecting element 42b and transmits light having other wavelengths.

  The dichroic mirror 5b is arranged so as to transmit the light emitted from the light projecting element 42c and guide it to the light projecting lens 3, and to reflect the light emitted from the light projecting element 42b and guide it to the light projecting lens 3. Yes. The dichroic mirror 5a transmits the light from the light projecting element 42c transmitted through the dichroic mirror 5b and the light from the light projecting element 42b reflected by the dichroic mirror 5b to guide it to the light projecting lens 3, and the light projecting element. It arrange | positions so that the light radiate | emitted from 42a may be reflected and it may guide to the light projection lens 3. FIG.

  The total of the optical path length from the light projecting element 42a to the dichroic mirror 5a and the optical path length from the dichroic mirror 5a to the light projecting lens 3, the optical path length from the light projecting element 42b to the dichroic mirror 5b, and the light projecting lens 3 from the dichroic mirror 5b. The total optical path length up to and the optical path length from the light projecting element 42c to the light projecting lens 3 are set to be approximately equal in consideration of the wavelength of light.

  The light projecting lens 3 is disposed so as to condense light from the light projecting elements 42 a, 42 b, 42 c on one end of the optical fiber cable 20. The optical fiber cable 20 guides the light L collected by the light projecting lens 3 to the light projecting optical system 11 of the sensor head 10 in FIG. Thereby, the light L condensed by the light projecting lens 3 is emitted from the light projecting optical system 11 of the sensor head 10 to the object W.

  The light projecting elements 42a, 42b, and 42c are sequentially turned on in a time-sharing manner according to the light emission timing controlled by the light projecting control unit 41 in FIG.

  When the light projecting element 42a is turned on, the green light emitted from the light projecting element 42a is reflected by the dichroic mirror 5a, and the sensor head 10 is reflected by the light projecting lens 3 and the optical fiber cable 20 in FIG. Are projected to the detection area.

  When the light projecting element 42b is turned on, the blue light emitted from the light projecting element 42b is reflected by the dichroic mirror 5b, and the reflected light is transmitted through the dichroic mirror 5a, so that the light projecting lens 3 and FIG. The optical fiber cable 20 guides the light to the light projecting optical system 11 of the sensor head 10 and projects it onto the detection area.

  When the light projecting element 42c is turned on, red light emitted from the light projecting element 42c passes through the dichroic mirror 5b and the dichroic mirror 5a, and is sent to the sensor by the light projecting lens 3 and the optical fiber cable 20 in FIG. The light is guided to the light projecting optical system 11 of the head unit 10 and projected onto the detection area.

  When the object W exists in the detection region, the light L reflected from the object W is guided to the light receiving element 13 via the light receiving optical system 12. The color of the object W is detected based on the amount of red light received, the amount of green light received, and the amount of blue light received by the light receiving element 13.

  Here, the signal processing by the signal processing control unit 43 in FIG. 2 will be described.

  The predetermined signal processing by the signal processing control unit 43 is performed based on the light projection timing signal ST provided from the light projection control unit 41.

  For example, the light projection control unit 41 first causes the light projecting element 42a to emit light. In this case, the other light projecting elements 42b and 42c do not emit light. At this time, the green light L is incident on the light receiving element 13. The light receiving element 13 detects the incident green light L and generates a light receiving signal S1.

  Here, the light projection timing signal ST for causing the light projecting element 42 a to emit light is input from the light projecting control unit 41 to the signal processing control unit 43, and the light receiving signal S 1 generated by the light receiving element 13 is received from the light receiving circuit 14. Entered. Thereby, the light projection control part 41 can obtain the received light amount of the reflected light when the green light L is projected onto the object W.

  Subsequently, the light projecting control unit 41 causes the light projecting element 42b to emit light. In this case, the other light projecting elements 42a and 42c do not emit light. At this time, the blue light L is incident on the light receiving element 13. The light receiving element 13 detects the incident blue light L and generates a light receiving signal S1.

  Similarly to the above, the light projection timing signal ST for causing the light projecting element 42b to emit light is input from the light projecting control unit 41 to the signal processing control unit 43, and the light receiving signal S1 generated by the light receiving element 13 is received by the light receiving circuit. 14 is input. Thereby, the light projection control part 41 can obtain the received light amount of the reflected light when the blue light L is projected onto the object W.

  Furthermore, the light projection control unit 41 causes the light projecting element 42c to emit light. In this case, the other light projecting elements 42a and 42b do not emit light. At this time, the red light L is incident on the light receiving element 13. The light receiving element 13 detects the incident red light L and generates a light receiving signal S1.

  Similarly to the above, the light processing timing signal ST for causing the light projecting element 42c to emit light is input from the light projecting control unit 41 to the signal processing control unit 43, and the light receiving signal S1 generated by the light receiving element 13 is received by the light receiving circuit. 14 is input. Thereby, the light projection control part 41 can obtain the received light amount of the reflected light when the red light L is projected onto the object W.

  When the received light amounts of the three colors of reflected light obtained by reflection from the object W are compared, the color of the object W can be determined. This is because when the wavelength of the light L incident on the object W is different, the amount of the light L reflected from the object W is different.

  Hereinafter, the object W used for the teaching process is referred to as a reference object, and the object W actually detected in the detection process is referred to as a detection object.

  Next, teaching processing and detection processing by the signal processing control unit 43 will be described with reference to flowcharts.

  FIG. 4 is a flowchart showing teaching processing by the signal processing control unit 43. The teaching process is started when the setting key 4e of the setting input unit 45 is pressed.

  First, the worker places a reference object having a color to be detected in the detection area. As shown in FIG. 4, the signal processing control unit 43 reads the received light amounts of the three colors from the reference object as first received light amounts R1, G1, and B1 (step S1). For example, R1 = 5, G1 = 2, and B1 = 10.

  Next, the operator removes the reference object having the color to be detected from the detection area. The signal processing control unit 43 determines whether or not the setting key 4e of the setting input unit 45 has been pressed again (step S2). When the setting key 4e is pressed again, the signal processing control unit 43 reads the received light amounts of the three colors from the background as the second received light amounts R2, G2, and B2 (step S3). For example, R2 = 3, G2 = 6, and B2 = 5. When the setting key 4e is not pressed, the signal processing control unit 43 stands by until the setting key 4e is pressed.

  Next, the signal processing control unit 43 calculates the difference between the first received light amount and the second received light amount as received light amount differences ΔR, ΔG, ΔB for the three colors of light (step S4). The received light amount difference ΔR is calculated by subtracting the received light amount R2 from the received light amount R1, the received light amount difference ΔG is calculated by subtracting the received light amount G2 from the received light amount G1, and the received light amount difference ΔB is the received light amount. It is calculated by subtracting the received light amount B2 from B1. In this case, ΔR = 2, ΔG = −4, and ΔB = 5.

  Next, the signal processing control unit 43 divides the calculated received light amount difference ΔR, ΔG, ΔB into a received light amount difference having a positive value and a received light amount difference having a negative value, and receives a received light amount having a positive value. The sum of the differences and the sum of the difference in received light amount having a negative value are respectively calculated (step S5). In this case, the sum of the received light amount differences having a positive value is 7 in absolute value, and the sum of the received light amount differences having a negative value is 4 in absolute value.

  Subsequently, the signal processing control unit 43 detects a light projecting element corresponding to the larger sum of the calculated sum of received light amount differences having a positive value and the sum of received light amount differences having a negative value. It selects as an optical element (step S6). In this case, the light projecting element 42c that emits red light and the light projecting element 42b that emits blue light corresponding to the sum of received light amount differences having positive values are selected as the light projecting elements for detection.

  Next, the signal processing control unit 43 calculates a detection threshold value from the total sum of the first received light amounts and the total sum of the second received light amounts of the selected detection light projecting elements (step S7). In this case, the total sum of the first received light amounts of the selected detection light projecting elements is 15 calculated by 5 + 10, and the total sum of the second received light amounts of the selected detection light projecting elements is calculated by 3 + 5. Will be 8. Therefore, the detection threshold value is 11.5 calculated by (15 + 8) / 2. Thereafter, the teaching process ends.

  Note that, in the above step S5, when the calculated difference in received light amount of each of the three colors of light has a positive value or a negative value, all of the three colors of light projecting elements are detected light projecting elements. Used as

  FIG. 5 is a flowchart showing detection processing by the signal processing control unit 43. In the initial setting, the detection signal S2 is not detected.

  First, the detection light projecting element selected by the teaching process is turned on. As shown in FIG. 5, the signal processing control unit 43 reads the received light amount based on the light by the detection light projecting element selected by the teaching process (step S <b> 51).

  Next, the signal processing control unit 43 calculates the total of the calculated received light amounts (step S52). When there is one detection light projecting element, the calculated received light amount itself corresponds to the total received light amount.

  Next, the signal processing control unit 43 determines whether or not the calculated sum of received light amounts is equal to or greater than a detection threshold value set in advance by teaching processing (step S53).

  When the calculated total amount of received light is equal to or greater than the detection threshold value, the signal processing control unit 43 sets the detection signal S2 to a detection state (step S54). Thereafter, the detection process ends.

  In step S53, when the calculated sum of received light amounts is not equal to or greater than the detection threshold value, the signal processing control unit 43 ends the detection process.

  In the present embodiment, it is possible to automatically set a detection threshold for detecting a detection object by performing a teaching process. In this case, the threshold value setting process and the detection process are performed using the larger sum of the sum of the received light amount differences having a positive value and the sum of the received light amount differences having a negative value. It is possible to set a detection threshold value for detecting a high accuracy and to easily detect a detection target.

  Further, in the present embodiment, it is not necessary to use a non-selected light projecting element by selecting a light projecting element for detection for detecting a detection target object with high accuracy by teaching processing. Thereby, the lifetime of the light projecting element for detection is extended.

  In the present embodiment, the light projecting elements 42a, 42b, and 42c correspond to light sources, the amount of received light and the ratio of received light amount correspond to received light amount information, and the signal processing control unit 43 includes information generation means, setting means, and determination means. , The received light amount difference corresponds to the received light amount information difference, the detection threshold value corresponds to the threshold value, the 7 segment LED 4c corresponds to the first display section, and the selected light source indicator lamp 4h corresponds to the second. It corresponds to the display part.

  In the present embodiment, the state in which the object is arranged in the detection area corresponds to the first state of the detection area, and the state in which the object is not arranged in the detection area is the second state of the detection area. Correspondingly, the teaching process for selecting the detection light projecting element corresponds to the first teaching, and the teaching process for setting the detection threshold corresponds to the second teaching.

  The present invention capable of automatically selecting a light projecting element for detecting a detection object with high accuracy includes, for example, a teaching process called full auto teaching and a teaching process called positioning teaching shown below. It can also be applied to various teaching processes.

  In full auto teaching, the signal processing control unit stores the maximum value and the minimum value of the amount of received light during the sampling period in the storage unit. Further, the signal processing control unit determines whether or not the object has passed based on whether or not the ratio between the maximum value and the minimum value stored in the storage unit is larger than a predetermined value. When there is no passage of the object, the signal processing control unit sets a threshold value for detection so as not to detect the background and stores it in the storage unit. When there is passage of the object, the signal processing control unit The unit sets a detection threshold value between the maximum value and the minimum value, and stores it in the storage unit. In this case, the first state of the detection region corresponds to a state in which the object is arranged in the detection region, and the second state of the detection region corresponds to a state in which the object is not arranged in the detection region.

  In this way, with full auto teaching, the presence or absence of a change in the amount of received light is automatically recognized, and if there is no change in the amount of received light, the amount of received light is regarded as the amount of received light in the background and detection is performed so that the background is not detected. The threshold value for detection can be set to a stable level, and if the change in the amount of received light exceeds a predetermined value, the threshold value for detection can be set to an appropriate level between the maximum and minimum values of the received light amount. it can.

  In the positioning teaching, the operator inputs a setting control signal when the object reaches the positioning point and at the positioning point. Accordingly, the signal processing control unit performs the first half sampling and the second half sampling, and stores the received light amounts obtained by the first half sampling and the second half sampling as first and second received light amounts V1 and V2, respectively. Remember me. The signal processing control unit stores the magnitude relationship between the first received light amount V1 and the second received light amount V2 and the value of the second received light amount V2 in the storage unit. The signal processing control unit sets the detection threshold to V2 and V2−hysteresis when V1 <V2, and sets the detection threshold to V2 + hysteresis and V2 when V1 ≧ V2. In this case, the first state of the detection area corresponds to a state where the object has reached just before the positioning point, and the second state of the detection area corresponds to a state where the object has reached the positioning point. .

  In this way, in positioning teaching, even when the amount of received light changes from “dark” to “bright” or when the amount of received light changes from “bright” to “dark”, The detection threshold can be set so that the state of the detection signal changes.

  In the teaching process, the received light amount of the three colors of the reference object is read as the first received light amount, and the received light amount of the background three colors of light is read as the second received light amount. The received light amount of the three colors of light of the predetermined object may be read as the second received light amount.

  In the teaching process, the detection threshold value setting process and the detection process are performed based on the difference between the first received light quantity and the second received light quantity. However, the present invention is not limited to this. The detection threshold value setting process and the detection process may be performed based on the ratio of the second received light amount with respect to.

  Further, although three light projecting elements 42a, 42b, and 42c are used as the light projecting elements, the present invention is not limited to this, and two light projecting elements or four or more light projecting elements may be used.

  In addition, although light is emitted using the three light projecting elements 42a, 42b, and 42c, the present invention is not limited to this, and a light projecting element that emits white light including a plurality of wavelengths is used. The wavelength spectrum of reflected light or transmitted light from the detection object may be divided into a plurality of colors (for example, three colors of red, green, and blue) and received.

  The teaching process setting is not limited to the operation of each key of the setting input unit 45 but may be performed by an external signal.

  Three light projecting elements 42 a, 42 b and 42 c may be provided in the sensor head unit 10. In this case, it is not necessary to provide the optical fiber cable 20, and the electric cable 30 can be used in common.

  Further, the present invention is applied to the separation type photoelectric switch 100 in which the sensor head portion 10 and the main body portion 40 are separated. However, the present invention is not limited to this, and the present invention is not limited to this. The present invention can also be applied to an integrated photoelectric switch in which is integrated.

  In the present embodiment, an example in which the first teaching process for selecting the detection light projecting element and the second teaching process for setting the detection threshold value are performed together is shown. However, the present invention is not limited to this. However, the first teaching process and the second teaching process may be performed separately, or the first teaching process and the second teaching process can be performed collectively. It is also possible to set the modes that can be performed in step 1, and select these modes.

  Further, in the present embodiment, one or a plurality of light projecting elements are selected from the light projecting elements 42a, 42b, and 42c by the signal processing control unit 43, and the total received light amount corresponding to the selected light projecting element for detection. However, the present invention is not limited to this, and all of the light projecting elements 42a, 42b, and 42c are used as the light projecting elements for detection, and 1 or 3 of the three received light amounts corresponding to these are used. A plurality of received light amounts may be selected by the signal processing control unit 43, and the sum of the selected received light amounts may be calculated.

  In particular, in the case of a photoelectric switch that outputs a plurality of detection signals with one unit, all of the light projecting elements 42a, 42b, and 42c are used as the light projecting elements for detection, and one or more of the three received light amounts corresponding thereto are used. It is preferable to select the amount of received light by the signal processing control unit 43 and calculate the sum of the selected amounts of received light.

  For example, the detection result of the object based on the sum of the received light amounts is output as the first detection signal, and the detection result of the object based on the received light amount ratio is output as the second detection signal. In this case, if only the amount of received light corresponding to the selected light projecting element for detection exists, the result of detection based on the ratio of received light amount cannot be obtained. Therefore, it is preferable to use all of the light projecting elements 42a, 42b, and 42c as the light projecting elements for detection and to select one or a plurality of received light amounts by the signal processing control unit 43. In this case, it is preferable that the display unit displays the light projecting element corresponding to the amount of received light selected by the signal processing control unit 43.

  The photoelectric switch according to the present invention can be used for detecting an object based on information on the amount of received light.

It is a schematic diagram of the photoelectric switch which concerns on this Embodiment. It is a block diagram which shows the internal structure of the photoelectric switch which concerns on this Embodiment. It is a typical sectional view showing arrangement of a plurality of light projecting elements inside a sensor head part. It is a flowchart which shows the teaching process by a signal processing control part. It is a flowchart which shows the detection process by a signal processing control part.

Explanation of symbols

4a Output indicator 4b, 4c 7 segment LED
4e setting key 4h selection light source indicator lamp 10 sensor head unit 11 light projecting optical system 13 light receiving element 40 body unit 41 light projecting control unit 42a, 42b, 42c light projecting element 43 signal processing control unit 45 setting input unit 100 photoelectric switch W target object

Claims (8)

A photoelectric switch that projects light onto a detection region and receives return light, and detects an object based on a threshold value and an amount of light received for detecting the object,
A plurality of light sources that project light having a plurality of different wavelengths;
A light receiving element that receives feedback light based on light of each wavelength;
Information generating means for generating received light amount information based on the received light amount obtained by the light receiving element for each wavelength of light;
During the first teaching, when the detection area is in the first state, a plurality of received light amount information corresponding to light of a plurality of wavelengths generated by the information generation means, and the detection area in the second state A selection unit that selects one or a plurality of light sources among the plurality of light sources based on a magnitude relationship with a plurality of received light amount information corresponding to light of a plurality of wavelengths generated by the information generation unit in a certain case;
Setting means for setting a threshold value based on one or a plurality of received light amount information corresponding to one or a plurality of light sources selected by the selection means during the second teaching;
The object detection state based on one or more received light quantity information corresponding to one or more light sources selected by the selection means and a threshold set by the setting means during the object detection operation A photoelectric switch comprising: a determination unit that determines The selection means includes a plurality of received light amount information corresponding to light of a plurality of wavelengths generated by the information generation means when the detection area is in the first state, and the detection area is in the second state. In this case, the difference between the received light amount information corresponding to the light of the plurality of wavelengths generated by the information generating means is calculated as the received light amount information difference, and the sum of the received light amount information difference having a positive value and the negative 2. The photoelectric switch according to claim 1, wherein one or a plurality of light sources corresponding to a large sum among the sums of received light amount information differences having values are selected. 3. The photoelectric switch according to claim 1, further comprising a first display unit that displays one or a plurality of received light amount information corresponding to one or a plurality of light sources selected by the selection unit. . The photoelectric switch according to claim 1, further comprising a second display unit indicating one or a plurality of light sources selected by the selection unit. 5. The photoelectric switch according to claim 1, wherein each of the plurality of light reception amount information is a light reception amount of light of each wavelength. 6. The photoelectric according to claim 1, wherein each of the plurality of received light amount information is a ratio of a received light amount of each wavelength with respect to a sum of received light amounts of the plurality of wavelengths. switch. The determination means includes
Determining a detection state of an object based on a sum of one or a plurality of received light amount information corresponding to one or a plurality of light sources selected by the selection unit and a threshold set by the setting unit; The photoelectric switch according to any one of claims 1 to 6, wherein The first state of the detection region is a state in which an object having a color to be detected exists in the detection region, and the second state of the detection region is a color to be detected in the detection region. The photoelectric switch according to claim 1, wherein there is no object to be present.

Images