JP4887057B2 - Photoelectric sensor - Google Patents

Description

  The present invention relates to a photoelectric sensor that detects an object.

  There is a device called a photoelectric sensor that detects an object by irradiating the object with light and receiving reflected light from the object. As a method for detecting an object using a photoelectric sensor, several methods are taken. One method is a method of determining that an object is present when the amount of reflected light received by the light receiving element exceeds a predetermined threshold (received light amount determination type).

  As another method, a displacement of an object is measured based on reflected light, and an object is detected based on the displacement (distance determination type). Specifically, this is a method in which a light receiving element capable of measuring the centroid position of the received light amount distribution is used, the displacement of the centroid position is measured, and when the displacement exceeds a predetermined threshold, it is determined that an object is present.

  The distance determination type will be described with reference to the drawings. FIG. 23 is a diagram illustrating the principle of measuring the displacement by the distance setting type photoelectric sensor 100. The light emitted from the light projecting unit 101 of the photoelectric sensor 100 is reflected by the reflecting surface 110a or the reflecting surface 110b and received by the light receiving unit 102.

  FIG. 24 is a diagram illustrating the light receiving unit 102. The light receiving unit 102 includes a light receiving lens 103 and a light receiving element 104. The reflected light is received by the light receiving element 104 through the light receiving lens 103. The position where the reflected light forms a spot on the light receiving element 104 differs depending on the light reflection position. For example, in FIG. 23, when light is reflected by the reflective surface 110 a on the side close to the photoelectric sensor 100, the reflected light 111 a forms a spot near the position 104 a of the light receiving element 104. On the other hand, the reflected light 111b reflected by the reflecting surface 110b forms a spot at the position 104b.

  FIGS. 25A and 25B show received light amount distributions formed on the light receiving element 104 by the reflected lights 111a and 111b, respectively. As described above, since the spot formation position differs depending on the light reflection position, the displacement (which may be referred to as the light reflection position or the displacement of the reflection surface) can be measured using this. Then, as shown in FIGS. 23 and 25, when the displacement exceeds the threshold value Th0, the control output is turned ON and it is determined that the object exists.

  FIG. 26 shows a state in which the object 120 is detected by the photoelectric sensor 100. As shown in the figure, the photoelectric sensor 100 irradiates an object 120 flowing on the belt conveyor 121 with light 130, receives the reflected light, and measures the displacement using the principle described with reference to FIGS. .

  FIG. 27 shows a change in displacement measured based on the received light amount distribution of the reflected light received by the photoelectric sensor 100. As described above, the displacement may be considered as a distance from the light projection position to the reflection position. The threshold value Th0 is determined in advance, and when the displacement becomes smaller than the threshold value Th0 (when the distance to the reflecting surface approaches), the detection signal is turned ON and the displacement becomes larger than the threshold value Th0 (reflection) When the distance to the surface increases), the detection signal is turned OFF. That is, when the object 120 passes, the reflection position of light approaches the photoelectric sensor 100, and therefore the object 120 is detected based on this displacement.

  For many objects, a certain degree of object detection accuracy can be obtained by any of the above methods (light reception amount determination type, distance determination type). However, it is difficult to detect an object such as a highly glossy object.

  For example, as shown in FIG. 28A, when the surface 140 of the object is in a mirror state, light having passed through a plurality of paths enters the light receiving unit 102. In the drawing, a broken line indicates light that is regularly reflected and incident on the light receiving unit 102. That is, it is a case where the light projecting unit 101 is reflected. For this reason, as shown in FIG. 28B, a small peak p20 is formed at a position different from the original peak p10 in the received light amount distribution. As a result, the center-of-gravity position g10 is misrecognized by shifting to the right from the original position. That is, the displacement is measured erroneously.

  In addition, as shown in FIG. 29A, when the surface 141 of the object is glossy, there is a problem that light is irregularly reflected. FIG. 29 shows a case where reflected light is incident on the light receiving unit 102 without the influence of irregular reflection. In this case, as shown in FIG. 29 (b), only the peak p10 appears, and its barycentric position g20 also coincides. no problem.

  However, as shown in FIG. 30A or 31A, irregular reflection may occur, and light that has passed through a plurality of paths may enter the light receiving unit 102. In this case, as shown in FIG. 30 (b) or FIG. 31 (b), there is a problem that the gravity center positions g30 and g40 are recognized with a deviation from the original peak p10 position. That is, apart from the original peak p10, small peaks p30 and p40 are formed, so that the position of the center of gravity is shifted left and right. As can be seen from FIGS. 30 and 31, the center of gravity position may be shifted to the right or to the left due to diffuse reflection, so that it is difficult to predict and the displacement cannot be measured.

  As a method of solving such a problem, there is a method of analyzing the distribution of the amount of received light, determining the peak position, and obtaining the displacement. In order to use this method, for example, a light receiving element such as a CCD is used. The received light amount distribution is analyzed, the peak position that is considered to be correct is determined, and the displacement amount is obtained from this peak position.

  Patent Document 1 below discloses a method for determining a peak position by analyzing a received light amount distribution. Specifically, a threshold value is provided, and a peak position lower than the threshold value is discarded, thereby eliminating a noise component and determining an original peak position.

JP-A-10-267648

  As described above, if the peak position is correctly calculated by analyzing the received light amount distribution, an accurate displacement can be obtained, so that the object detection accuracy is also increased. However, the method of analyzing the received light amount distribution is not perfect. For example, a paper box or wood will have high detection accuracy, but the objects shown in FIGS. 32 to 38 are difficult to detect. That is, for the objects as shown in FIGS. 32 to 38, the degree of irregular reflection of light is large, and thus the peak with a high maximum value is not necessarily the true peak. Further, when the received light amount distribution becomes very complicated, it is difficult to detect the peak itself.

  FIG. 32 shows an object 150 wrapped in a highly glossy package 151. FIG. 33 shows an object 152 wrapped in a highly transparent packaging 153. FIG. 34 shows a mirror-finished object 154, and FIG. 35 shows a translucent object 155 having a complicated shape. The objects shown in FIGS. 32 to 35 have a large amount of light irregularly reflected on the surface of the object or the package, and it is difficult to determine the true peak by analyzing the received light amount distribution. That is, since multiple reflection occurs on the object surface or the surface of the package, it is difficult to analyze the received light amount distribution itself.

  Further, as shown in FIGS. 36A and 36B, it is difficult to accurately measure the displacement when it is desired to discriminate the front and back of a metal workpiece such as a ball bearing 156. Alternatively, as shown in FIG. 37, when it is desired to determine the presence / absence of the processed portion 157a of the metal-processed object 157, or in the process of detecting the position of the end face of the laminated glass substrate 158 as shown in FIG. However, it was difficult to accurately measure the displacement.

  Therefore, in view of the above problems, the present invention provides a technique for accurately detecting an object for any surface processed object or an object wrapped in any packaging. The purpose is to provide.

  In order to solve the above problems, the invention according to claim 1 is a light receiving means for receiving reflected light of the light emitted from the light projecting means by the light projecting means and a plurality of light receiving elements arranged in at least one direction. And, based on the received light amount distribution obtained from the light receiving means, means for obtaining a displacement equivalent amount of the object reflected by the light irradiated by the light projecting means, and based on the received light amount distribution, And a multi-reflection detector for detecting presence / absence, and an output unit for outputting information indicating at least one of the presence or absence of multi-reflection detected by the multi-reflection detector to the outside.

  According to a second aspect of the present invention, in the photoelectric sensor according to the first aspect, the multiple reflection detection means can obtain a light reception amount that is equal to or greater than a predetermined threshold when a plurality of peaks exist in the light reception amount distribution. It is characterized in that it is determined that multiple reflection has occurred when there is more than a predetermined range.

  According to a third aspect of the present invention, in the photoelectric sensor according to the first or second aspect, the output means is an indicator lamp provided on the photoelectric sensor for displaying the presence or absence of multiple reflection. .

  According to a fourth aspect of the present invention, in the photoelectric sensor according to the first or second aspect, the object discriminating means for discriminating the state of the object by comparing the obtained displacement equivalent amount with a set threshold value. The output means outputs a signal indicating the discrimination result of the object discriminating means when multiple reflection is not detected, and outputs a signal indicating that multiple reflection is detected when multiple reflection is detected. It is characterized by doing.

  According to a fifth aspect of the present invention, in the photoelectric sensor according to the first or second aspect, the object discrimination means for discriminating the state of the object by comparing the obtained displacement equivalent amount with a set threshold value. The output means is an indicator lamp that displays the presence or absence of multiple reflection provided in the photoelectric sensor, and further outputs a signal indicating the determination result of the object determination means when multiple reflection is not detected, When multiple reflection is detected, a signal indicating that multiple reflection is detected is output.

  According to a sixth aspect of the present invention, in the photoelectric sensor according to the fourth or fifth aspect, one of the signals indicating the discrimination result is the same as the signal indicating that multiple reflection is detected. It is characterized by that.

  According to a seventh aspect of the invention, in the photoelectric sensor according to the fourth or fifth aspect, the object discriminating unit discriminates the state of the object by comparing the obtained displacement equivalent amount with the two threshold values. A signal when it is determined that the displacement equivalent amount obtained from the binary signal indicating the determination result is between the two threshold values, and a binary indicating that multiple reflection is detected The signal is different.

  The invention described in claim 8 includes, in the photoelectric sensor according to claim 4 or 5, further including a range that includes the displacement equivalent amount based on an instruction from the outside and includes the acquired displacement equivalent amount. A threshold value setting means for setting the threshold value for discriminating from a non-existing range, and a signal indicating a range including the acquired displacement equivalent amount and multiple reflections are detected among binary signals indicating the discrimination result This is characterized in that the binary signal indicating this is different.

  According to a ninth aspect of the present invention, in the photoelectric sensor according to the fourth or fifth aspect, the object discriminating unit discriminates the state of the object by comparing the obtained displacement equivalent amount with the two threshold values. The photoelectric sensor further acquires a displacement equivalent amount based on an instruction from the outside, and determines the range including and not including the acquired displacement equivalent amount. A threshold setting means for setting a threshold value, and a signal and multiple reflection when it is determined that the obtained displacement equivalent amount among the binary signals indicating the determination result is between the two threshold values; The binary signal shown is different.

  According to a tenth aspect of the present invention, in the photoelectric sensor according to any one of the fourth to ninth aspects, it is determined that an object has been detected even when no peak is detected from the received light amount distribution. .

  The invention described in claim 11 is the photoelectric sensor according to claim 1 or 2, further calculated immediately before detecting multiple reflections in place of the displacement equivalent amount obtained when multiple reflections are detected. Means for outputting a displacement equivalent amount as a current displacement.

  According to a twelfth aspect of the present invention, in the photoelectric sensor according to the first aspect, the output means displays a displacement equivalent when no multiple reflection is detected, and detects multiple reflection when multiple reflection is detected. It is a display part which displays what was done.

  According to a thirteenth aspect of the present invention, in the photoelectric sensor according to the first aspect, the output means displays a displacement equivalent amount when multiple reflection is not detected, and detects multiple reflection when multiple reflection is detected. The display unit displays a displacement equivalent amount calculated immediately before the detection and that multiple reflection has been detected.

  According to a fourteenth aspect of the present invention, in the photoelectric sensor according to the twelfth aspect, when there are a plurality of peaks in the received light amount distribution, a displacement equivalent amount is obtained based on a peak on a short distance side.

  According to a fifteenth aspect of the present invention, in the photoelectric sensor according to the twelfth aspect, when there are a plurality of peaks in the received light amount distribution, the displacement is obtained based on the peak having the maximum maximum value.

  The photoelectric sensor of the present invention detects the presence or absence of multiple reflection based on the received light amount distribution and outputs a signal related to the presence or absence of multiple reflection. Thereby, it is possible to execute control according to the presence or absence of occurrence of multiple reflection.

  The photoelectric sensor of the present invention can detect an object without specifying a true peak in the received light amount distribution. When a true peak is estimated by an incomplete algorithm, an erroneous object detection result may be output using an incorrect displacement. However, in the present invention, a process for identifying the true peak is necessary. Therefore, the accuracy of object detection can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an external view of a photoelectric sensor 1 according to an embodiment of the present invention. The photoelectric sensor 1 includes a sensor head 2 and an amplifier unit 3. The sensor head 2 is connected to the amplifier unit 3 via a cable 4. The amplifier unit 3 is connected with a cable 5 for exchanging data with the outside. For example, the sensor head 2 is installed in a product production line to detect a product to be conveyed or a processed part of the product.

  FIG. 2A is a front view of the sensor head 2, and FIG. 2B is a rear view. In front of the sensor head 2, a light projecting unit 21 that irradiates light to an object and a light receiving unit 23 that receives reflected light are arranged. An indicator lamp 27 is provided on the back surface. The indicator lamp 27 is composed of a plurality of LEDs 27a to 27c. The LED 27a is turned on when the power is turned on, and the LED 27b is turned on when multiple reflection is detected, which will be described in detail later. The LED 27c is composed of a plurality of LEDs and is used for purposes such as representing displacement.

  FIG. 3 is a plan view of the amplifier unit 3. A setting unit 31 and an indicator lamp 35 are provided on the surface of the amplifier unit 3. The setting unit 31 includes a cross cursor, a plurality of buttons, and the like, and can perform a setting operation on the photoelectric sensor 1. The indicator lamp 35 includes a 7-segment LED 35a that displays a numerical value and a plurality of LEDs, and includes an LED 35b that is used for purposes such as representing the amount of displacement.

  FIG. 4 is a functional block diagram of the sensor head 2 and the amplifier unit 3. The sensor head 2 includes a light projecting unit 21, a light projecting processing unit 22, a light receiving unit 23, an amplification unit 24, an A / D conversion unit 25, a main control unit 26, an indicator lamp 27, and a communication unit 28.

  The light projecting unit 21 is, for example, a laser diode, and emits light by being driven and controlled by the light projecting processing unit 22. In the present embodiment, the light receiving unit 23 uses a CCD. The light receiving unit 23 includes a plurality of light receiving elements, and these light receiving elements receive the reflected light of the light emitted from the light projecting unit 21. When receiving the reflected light, the light receiving unit 23 performs photoelectric conversion to output the received light amount as an analog signal. The amplifying unit 24 amplifies the analog signal output from the light receiving unit 23. The A / D converter 25 digitally converts the analog signal output from the amplifier 24 and outputs it to the main controller 26.

  The main control unit 26 is a processing unit that performs overall control of the sensor head 2, and includes a CPU, a memory, software that operates on the CPU, and the like. The main control unit 26 sends an instruction signal to the light projection processing unit 22 to adjust the light projection amount. Further, the main control unit 26 receives the signal output from the light receiving unit 23 and executes various software processes that are the features of the present invention.

  Here, the light receiving unit 23 is a sensor in which a plurality of light receiving elements are arranged in at least one direction. In the present embodiment, a one-dimensional CCD line sensor is used. Thereby, it is possible to obtain light amount distribution information on the straight line of the received reflected light, and the digital signal input from the A / D conversion unit 25 by the main control unit 26 is a signal indicating a one-dimensional received light amount distribution. is there. The main control unit 26 uses this signal to execute object detection processing and the like. Note that a two-dimensional sensor may be used as the light receiving unit 23.

  As shown in FIG. 2, the indicator lamp 27 is a display unit that displays various types of information. The communication unit 28 communicates with the amplifier unit 3 via the cable 4 to transmit / receive data.

  The amplifier unit 3 includes a setting unit 31, an external input / output unit 32, a storage unit 33, a main control unit 34, an indicator lamp 35, and a communication unit 36. The setting unit 31 is for performing various setting operations on the amplifier unit 3, and is configured by a cross cursor or the like as shown in FIG. The external input / output unit 32 is an interface for outputting detection results, measurement results, and the like of the photoelectric sensor 1 to the outside via the cable 5. It is an interface for inputting setting information and the like from the outside. The storage unit 33 stores setting information and the like. The main control unit 34 includes a CPU, a memory, software operating on the CPU, and the like, and performs overall control of the amplifier unit 3. As shown in FIG. 3, the indicator lamp 35 includes a 7-segment LED 35a and an LED 35b. The communication unit 36 communicates with the communication unit 28 of the sensor head 2, receives detection information from the sensor head 2, and transmits a control signal to the sensor head 2.

  Next, a flow of processing related to object detection in the sensor head 2 will be described. FIG. 5 is a flowchart of the setting process. The setting process is a preparation process for accurately detecting an object prior to the object detection process.

  First, the distance of the workpiece (reference) is stored (step S11). FIG. 6A shows a state in which light 10 is emitted from the sensor head 2 and reflected light from the reference surface 11 is received. Then, the distribution of the received light amount is as shown in FIG. 6B, and the peak position p1 appears. Therefore, the peak position p1 is set as the reference position bp. For example, the reference position bp is set by pressing a setting button (setting unit 31) provided on the amplifier unit 3 while fixing the sensor head 2 in the state of FIG. The reference position bp is stored in storage means in the main control unit 26. If the state where there is no object is used as a reference, the reference surface 11 is the road surface of the transport path along which the object is transported. Alternatively, when detecting a concave portion on the object surface, a flat portion (a surface having no concave portion) on the object surface becomes the reference surface 11.

  Further, when performing an operation for setting the reference surface 11, it is confirmed that multiple reflection has not occurred. As described above, the indicator lamp 27 of the sensor head 2 is provided with the LED 27b that notifies the occurrence of multiple reflection. Therefore, the reference plane 11 is set in a state where the LED 27b is not lit.

  Next, threshold values are set above and below the stored reference position bp (step S12). When the peak position deviates from the reference position bp beyond the threshold, it is determined that there is an object. As shown in FIGS. 7A and 7B, threshold values Tha and Thb are set above and below the reference position bp, and are similarly stored in the storage means in the main control unit 26. The threshold value (width) may be set by operating the setting unit 31 in advance, or may be set in advance by data input from the outside via the external input / output unit 32. Or you may make it set, operating the setting part 31 and changing freely.

  Next, the flow of object detection processing will be described with reference to FIG. After the setting process described with reference to FIG. 5 is completed, the object is actually conveyed under the sensor head 2. Similarly, the sensor head 2 emits light from the light projecting unit 21 and receives reflected light at the light receiving unit 23. Thereby, the main control unit 26 obtains light quantity distribution information. FIG. 8 shows a flow of processing performed in the main control unit 26 after obtaining the light quantity distribution information.

  First, a position having a maximum value on the image sensor is searched (step S21). That is, the main control unit 26 searches for the peak position from the light amount distribution information. Next, the main control unit 26 searches for the number of maximum values (step S22). That is, the number of peaks is measured. Then, the main control unit 26 determines whether or not the number of maximum values is one (step S23). If the number of maximum values is not one, that is, whether the number of maximum values is zero. If there are two or more, the process proceeds to step S27, and the control output is turned ON. That is, a control output indicating that an object has been detected is performed.

  The basis for this determination will be described. First, the case where the number of local maximum values is two or more means that the light irradiated from the light projecting unit 21 is irregularly reflected on the object surface, and the reflected light is incident on the light receiving unit 23 through a plurality of paths. . Here, at the time of the setting process described with reference to FIGS. 5 to 7, the reference position bp and the threshold values Tha and Thb are set in an environment where irregular reflection does not occur. That is, the setting is performed in a state where the number of maximum values is 1.

  On the other hand, when the number of local maximum values is 2 or more, it means that multiple reflection occurs, and it can be determined that the state is different from that at the time of setting. Thus, it is immediately determined that there is an object without measuring or analyzing the amount of displacement.

  For example, a case as shown in FIG. 9 is assumed. As shown in FIG. 9A, when an object is wrapped in a package 12a having a high glossiness, multiple reflection occurs. Then, as shown in FIG. 9B, a plurality of maximum values are searched. In this case, together with the determination that multiple reflections are occurring, it is determined that an object has been detected.

  On the other hand, when the number of maximum values is zero, it can be determined that the state has changed. That is, at the time of setting, the number of local maximum values is one, and it is determined that an object has been detected because the state has clearly changed.

  For example, a case as shown in FIG. 10 is assumed. As shown in FIG. 10A, when the object is wrapped in a high gloss packaging 12 a, the light 10 emitted from the light projecting unit 21 is diffusely reflected without returning to the light receiving unit 23. In this case, as shown in FIG. 10B, the maximum value is not searched, so that it is determined that an object has been detected.

  Return to the flowchart again. If the number of maximum values is one, it is next determined whether or not the position of the maximum value is within the set distance range (step S24). That is, it is determined whether or not the peak position falls within the range of the thresholds Tha and Thb set in step S12 of FIG. If it is not within the set range, the process proceeds to step S27 and the control output is turned ON. That is, a control output indicating that an object has been detected is performed.

  This is because the number of local maximum values is one, but it is out of the range of the thresholds Tha and Thb, indicating that the light reflecting surface has moved. For example, if the object has a low glossiness and does not generate multiple reflections, the light reflection surface clearly moves and the presence of the object is clear. On the other hand, as shown in FIG. 11, even if the object is still wrapped in a highly glossy package 12a, some reflected light overlaps and the maximum value happens to be one. There is a case. However, in this case as well, if the position of the maximum value is out of the range of the thresholds Tha and Thb, it is obvious that the state has changed, so it is determined that the object has been detected.

  When the position of the maximum value is within the set distance range, it is determined whether or not the width of the received light waveform is within the specified range (step S25). If the width of the received light waveform is not within the specified range, the process proceeds to step S27 and the control output is turned ON. That is, a control output indicating that an object has been detected is performed on the assumption that multiple reflection has occurred.

  A case where the width of the received light waveform is not within the specified range will be described with reference to FIG. As shown in FIG. 12A, the object is wrapped in a package 12a having a high glossiness, and the light 10 emitted from the light projecting unit 21 is multiple-reflected by the package 12a. Then, the multiple reflected light is incident on the light receiving unit 23 at a relatively similar angle. In this case, the distribution of the amount of received light is as shown in FIG. In other words, a plurality of mountains overlap to form a long distribution. Generally, as shown in FIG. 6 and the like, the shape of the received light amount distribution becomes narrower toward the peak. For example, if the light amount is 50% of the maximum value, the distribution width can be predicted to some extent. Is possible. Therefore, if the predicted width is set, it is possible to determine that the state has changed when a received light amount distribution exceeding the width is obtained. Thus, it is determined that an object has been detected.

  When the width of the received light waveform is within the specified range, the process proceeds to step S26 and the control output is turned OFF. That is, a control output indicating that no object has been detected is performed. That is, the number of maximum values is 1, the position of the maximum value is within the set range, and the width of the received light waveform is within the specified range, multiple reflection does not occur, and the maximum value is from the reference position bp. Since the waveform does not change greatly and the waveform does not change, it is determined that the object is not detected. For example, as shown in FIG. 13A, no object is present under the sensor head 2 during the object detection process. In this case, as shown in FIG. 13B, the received light amount distribution is approximate to the received light amount distribution at the time of the setting process (FIG. 6B), and it is determined that no object is detected. is there.

  Thus, according to the photoelectric sensor 1 of the present embodiment, first, when multiple reflection is detected, it is immediately determined that there is an object. Thereby, when there are a plurality of peaks, a complicated process of selecting which peak to determine the displacement can be eliminated. In addition, the process of determining which peak may be erroneously determined, but according to the present embodiment, in determining the presence or absence of an object, the detection accuracy of the object can be improved by eliminating the determination. Can be high.

  Also, it is determined that there is an object when the number of peaks becomes 0 or when the width of the received light waveform is not within the specified range. This eliminates the need for a complicated process of analyzing a complex received light waveform and obtaining a displacement by estimation, and can immediately determine the presence or absence of an object.

  Conventionally, in a photoelectric sensor that detects an object, an emphasis has been placed on which peak is selected as a true peak from the distribution of received light amount. In other words, even when a complex received light waveform is obtained, various algorithms are used to find the true peak, the displacement is calculated from the estimated true peak, and the displacement is compared with the threshold value. The presence or absence of an object was judged. On the other hand, the photoelectric sensor 1 of the present embodiment determines the presence / absence of an object only by the number of local maximum values without performing complicated waveform analysis. Alternatively, the presence or absence of an object is determined based on the width of the waveform. Thereby, highly accurate object detection is possible without performing complicated processing.

  14 to 19 are examples of detecting the presence or absence of various objects using the photoelectric sensor 1 of the present embodiment.

  FIG. 14 is a diagram illustrating a detection example of the object 12b wrapped in a highly transparent package. In FIG. 14A, it is determined that the number of peaks is one, the peak position is within the set range, the width of the received light waveform is within the specified range, and no object is present. In FIG. 14B, since a plurality of peaks are searched, it is determined that there is an object. In FIG. 14C, there is one peak by chance, but the peak position exceeds the set range, and it is determined that there is an object.

  FIG. 15 is a diagram illustrating a detection example of the mirror-finished object 12c. In FIG. 15A, the number of peaks is one, the peak position is within the set range, the width of the received light waveform is within the specified range, and it is determined that there is no object. In FIG. 15B, since no peak is searched, it is determined that there is an object. In FIG. 15C, there is only one peak by chance, but the peak position exceeds the set range, and it is determined that there is an object.

  FIG. 16 is a diagram illustrating an example of detecting a translucent object 12d having a complicated shape. In FIG. 16A, it is determined that the number of peaks is one, the peak position is within the set range, the width of the received light waveform is within the specified range, and no object is present. In FIG. 16B, since a plurality of peaks are searched, it is determined that there is an object. In FIG. 16C, there is one peak by chance, but the peak position exceeds the set range, and it is determined that there is an object.

  FIG. 17 is a diagram illustrating a detection example of the bearing 12e with the back surface facing upward. In this case, as shown in FIG. 17D, the setting process is performed with the back surface (bottom surface) with the bearing 12e facing the back side as the reference surface 11. In other words, in the setting process described with reference to FIG. 5, as illustrated in FIG. 6, the setting is performed on the conveyance path where no object is placed as the reference plane 11. On the other hand, when detecting the bearing 12e facing backward, the setting process is performed with the back surface as the reference surface 11 in a state where the bearing 12e is placed facing away. Therefore, the thresholds Tha and Thb are set at the upper and lower positions of the back surface.

  In FIG. 17A and FIG. 17B, since a plurality of peaks are searched, it is determined that the bearing 12e is not facing down. In FIG. 17 (c), there is only one peak by chance, but the peak position exceeds the set range, and it is determined that the bearing 12e is not facing backward. In FIG. 17D, it is determined that the number of peaks is one, the peak position is within the set range, the width of the received light waveform is within the specified range, and the bearing 12e is face down.

  FIG. 18 is a diagram illustrating a detection example of the metal processed portion 12g of the metal processed product 12f. In this case, as shown in FIG. 18C, the setting process is performed with the portion without the metal processed portion 12g as the reference plane 11.

  In FIG. 18A, since a plurality of peaks are searched, it is determined that the metal processed portion 12g exists. In FIG. 18B, there is one peak by chance, but the peak position exceeds the set range, and it is determined that the metal processed portion 12g exists. In FIG. 18C, it is determined that the number of peaks is one, the peak position is within the set range, the width of the received light waveform is within the specified range, and the metal processed portion 12g does not exist.

  FIG. 19 is a diagram illustrating a positioning detection example of the glass substrate end face. In this case, as shown in FIG. 19A, the setting process is performed with the end surface of the glass substrate 12h as the reference surface 11.

  In FIG. 19A, it is determined that the number of peaks is one, the peak position is within the set range, the width of the received light waveform is within the specified range, and is the end face of the glass substrate. In FIG. 19B, since a plurality of peaks are searched, it is determined that the peak is not the end face of the glass substrate.

  Thus, according to the photoelectric sensor 1 of the present embodiment, it is possible to accurately detect the presence or absence of an object of any shape or an object wrapped in any package. In addition, it is possible to accurately detect a processed part of a metal processed product or a mirror-finished product.

  Next, an additional function of the photoelectric sensor 1 of the present invention will be described. The additional function is a function related to display. As described with reference to FIGS. 2 and 3, the sensor head 2 and the amplifier unit 3 are provided with indicator lights 27 and 35, respectively. Various information is displayed using the indicator lamps 27 and 35.

  First, in the sensor head 2, when the main control unit 26 detects multiple reflections, the main control unit 26 performs lighting control of the LED 27b. As a result, the user can recognize that multiple reflection has occurred immediately upon seeing lighting of the LED 27b. As described above, when the reference plane 11 is set, the display of the LED 27b may be referred to. Further, the main control unit 26 expresses the calculated displacement amount by the lighting width of the LED 27c. That is, when the amount of displacement increases, the lighting width of the LED 27c is lengthened to provide sensory information on the amount of displacement to the user.

  Further, the main control unit 26 detects the object by the above algorithm, and then transfers information regarding the presence / absence of the object and displacement information to the amplifier unit 3. In the amplifier unit 3, the main control unit 34 performs display control of the indicator lamp 35 based on the information received from the sensor head 2.

  The main controller 34 controls the display of displacement information for the 7-segment LED 35a. That is, distance information from the light projecting unit 21 of the sensor head 2 to the reflecting surface is displayed. The calculated displacement amount is expressed by the lighting width of the LED 35b. That is, when the amount of displacement increases, the lighting width of the LED 35b is lengthened, so that sensory information on the amount of displacement is provided to the user.

  As described above, in order to detect the presence / absence of an object, it is not necessary to estimate a true peak in the present invention. However, in order to display displacement information as reference information for the user, the main control unit 26 measures the displacement. For example, when multiple reflection is not detected, the displacement information is displayed by the LED 35a, and when multiple reflection is detected, the LED 27b may be turned on.

  A displacement measuring method by the main control unit 26 will be described. First, when there is only one peak, the displacement is measured by a normal method based on the peak position. That is, the displacement is measured based on the same principle as described with reference to FIGS.

  Next, when there are a plurality of peaks, the peak on the short distance side is selected as the first method. That is, the peak existing on the side close to the sensor head 2 is estimated as the true peak. However, depending on the nature of the object to be detected, it may be set to select a peak on the far side. As a second method, a peak having the largest maximum value is estimated as a true peak.

  It was the premise of the present invention that these first and second methods are not completely reliable estimates in the first place. However, here, since displacement information is displayed as reference information, these methods are used to estimate the true peak as much as possible. The sensor head 2 displays the presence / absence of detection of an object by the LED 27b. Therefore, the sensor head 2 has a highly convenient configuration by giving the user displacement information as reference information together with this highly accurate information. .

  Next, a modified example of the present invention will be described. In the above embodiment, the photoelectric sensor 1 determines the presence or absence of an object by detecting multiple reflections. This modification is a method for detecting an object based on a conventional displacement measurement while using a detection result of multiple reflections.

  FIG. 20 is a diagram illustrating a method of detecting the metal processed portion 12j in the metal processed product 12i. In FIG. 20A, the sensor head 2 irradiates light 10 to a flat portion without the metal processed portion 12j. Multiple reflection at this time does not occur. Therefore, the displacement can be obtained based on the peak position of the light quantity distribution. In FIG. 21, the portion indicated by the region Ra is the displacement measured in FIG.

  Next, when the metal workpiece 12i moves to the state of FIG. 20 (b), multiple reflection occurs. At this time, since the light 10 is reflected at various angles and received by the light receiving unit 23, the measured displacement varies finely. In FIG. 21, the region Rb shows the displacement measured in a state where multiple reflection occurs.

  And if the metal workpiece 12i moves to the position of FIG.20 (c), multiple reflection will disappear again and the peak in light quantity distribution will also become one. The displacement in this state corresponds to the region Rc in FIG.

  Thus, the displacement measurement result is not reliable during the period in which multiple reflection occurs. Therefore, in this modification, the previous displacement is maintained. Thereby, the displacement output from the sensor head 2 is represented in FIG. That is, for the region Rb, the displacement measured in the region Ra is maintained. Therefore, when the multiple reflection is not detected, the calculated displacement amount is displayed on the LED 35a, and when the multiple reflection is detected, the displacement amount calculated immediately before the multiple reflection is detected is displayed. You can do it. At this time, the LED 27b may be turned on to notify that multiple reflection is detected.

  Then, when detecting multiple reflection, the main control unit 26 determines the presence or absence of an object using the displacement immediately before the occurrence of multiple reflection as the current displacement. Thereby, even in the state where multiple reflection occurs, it is possible to remove the influence of multiple reflection as much as possible and detect an object.

  Alternatively, the displacement immediately before the occurrence of multiple reflection is output to the amplifier unit 3 as the current displacement. Then, the amplifier unit 3 outputs the current displacement to the indicator lamp 35. Further, the amplifier unit 3 may output the displacement to the outside via the external input / output unit 32. Further, as described in the above embodiment, while it is determined that there is an object by detecting multiple reflections, the displacement values before the occurrence of multiple reflections may be maintained and provided to the user.

It is an external view of the photoelectric sensor which concerns on this Embodiment. It is the front view and back view of a sensor head. It is a top view of an amplifier unit. It is a block diagram of a sensor head and an amplifier unit. It is a flowchart of a setting process. It is a figure which shows the light reception state at the time of the setting of a reference plane. It is a figure which shows the positional relationship of the threshold value set with a reference plane. It is a flowchart of an object detection process. It is a figure which shows the light reception state and light reception amount distribution by which two or more local maximum values are searched. It is a figure which shows the light reception state in which a local maximum is not searched, and light reception amount distribution. It is a figure which shows the light reception state and the received light amount distribution whose peak position is not in the setting range. It is a figure which shows the light reception state and light reception amount distribution with which several peaks overlap. It is a figure which shows the light reception state and light reception amount distribution in case an object does not exist. It is a figure which shows the example of a detection of the object wrapped in the packaging with high transparency. It is a figure which shows the example of a detection of a specular object. It is a figure which shows the example of a detection of the translucent object with a complicated shape. It is a figure which shows the example of front / back discrimination of a metal workpiece. It is a figure which shows the example of a detection of a metal processing part. It is a figure which shows the example of a detection of the end surface position of a glass substrate. It is a figure which shows the state of the reflected light from a metal workpiece. It is a figure which shows the change of the displacement amount computed from the reflected light from a metal workpiece. It is a figure which shows the change of the displacement amount at the time of maintaining the displacement before generation | occurrence | production of multiple reflection. It is a figure which shows the displacement measuring method of the photoelectric sensor in a prior art. It is detail drawing of a light-receiving part. It is a figure which shows the relationship between a peak position and a threshold value. It is a system diagram which detects the object which flows on a belt conveyor. It is a figure which shows the relationship between the displacement and threshold value which the photoelectric sensor calculated | required. It is a figure which shows the example which a some peak generate | occur | produces in received light amount distribution by specular reflection. It is a figure which shows the example which one peak generate | occur | produces in received light amount distribution by glossy surface reflection. It is a figure which shows the example which a some peak generate | occur | produces in received light amount distribution by glossy surface reflection. It is a figure which shows the example which a some peak generate | occur | produces in received light amount distribution by glossy surface reflection. It is a figure which shows the object wrapped in the packaging with high glossiness which is difficult to detect. It is a figure which shows the object wrapped in the packaging with high transparency which is difficult to detect. It is a figure which shows the mirror surface object which is difficult to detect. It is a figure which shows the complicated translucent object of the shape where detection is difficult. It is a figure which shows the metal workpiece in which front / back determination is difficult. It is a figure which shows the metal workpiece in which a process part detection is difficult. It is a figure which shows the laminated | stacked glass substrate where it is difficult to detect an end surface position.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoelectric sensor 2 Sensor head 3 Amplifier unit 10 Light (irradiated from a light projection part) 11 Reference surface

Claims (15)

Floodlight means;
A light receiving means for receiving reflected light of the light emitted by the light projecting means by a plurality of light receiving elements arranged in at least one direction;
Based on the received light amount distribution obtained from the light receiving means, means for obtaining a displacement equivalent amount of the object reflected by the light irradiated by the light projecting means;
Multiple reflection detection means for detecting the presence or absence of multiple reflection based on the received light amount distribution;
Output means for outputting information indicating at least one of presence or absence of multiple reflection detected by the multiple reflection detection means to the outside;
A photoelectric sensor comprising: The photoelectric sensor according to claim 1,
The multiple reflection detection means that multiple reflection occurs when a plurality of peaks exist in the received light amount distribution and / or when a region where the received light amount equal to or greater than a predetermined threshold is present exceeds a predetermined range. A photoelectric sensor characterized by determining. The photoelectric sensor according to claim 1 or 2,
The photoelectric sensor according to claim 1, wherein the output means is a display lamp provided on the photoelectric sensor for displaying the presence or absence of multiple reflection. The photoelectric sensor according to claim 1 or 2, further comprising:
Object discriminating means for discriminating the state of the target by comparing the obtained displacement equivalent amount with a set threshold value;
With
The output means outputs a signal indicating the discrimination result of the object discrimination means when multiple reflection is not detected, and outputs a signal indicating that multiple reflection is detected when multiple reflection is detected. A photoelectric sensor. The photoelectric sensor according to claim 1 or 2, further comprising:
Object discriminating means for discriminating the state of the target by comparing the obtained displacement equivalent amount with a set threshold value;
With
The output means is an indicator lamp provided on the photoelectric sensor for displaying the presence or absence of multiple reflection. If multiple reflection is not detected, a signal indicating the discrimination result of the object discrimination means is output, and multiple reflection is detected. If it is, a photoelectric sensor that outputs a signal indicating that multiple reflection has been detected. In the photoelectric sensor according to claim 4 or 5,
One of the signals indicating the discrimination result and the signal indicating that multiple reflection is detected are the same. In the photoelectric sensor according to claim 4 or 5,
The object determining means determines the state of the target by comparing the obtained displacement equivalent amount with the second threshold value,
Among the binary signals indicating the discrimination results, the signal when it is determined that the obtained displacement equivalent amount is between the two threshold values is different from the binary signal indicating that multiple reflection is detected. A characteristic photoelectric sensor. The photoelectric sensor according to claim 4 or 5, further comprising:
Threshold setting means for acquiring a displacement equivalent amount based on an instruction from the outside, and setting the threshold value for determining a range including the acquired displacement equivalent amount and a range not including the displacement equivalent amount,
With
A photoelectric sensor, characterized in that a binary signal indicating that multiple reflection is detected is different from a signal indicating a range including the acquired displacement equivalent amount among binary signals indicating the discrimination result. In the photoelectric sensor according to claim 4 or 5,
The object determining means determines the state of the target by comparing the obtained displacement equivalent amount with the second threshold value,
The photoelectric sensor further acquires a displacement equivalent amount based on an instruction from the outside, and sets a threshold value setting two threshold values for discriminating between a range including the acquired displacement equivalent amount and a range not including the acquired displacement equivalent amount With means,
Of the binary signal indicating the discrimination result, a signal when it is determined that the obtained displacement equivalent amount is between the two threshold values is different from a binary signal indicating that multiple reflection is detected. A photoelectric sensor. The photoelectric sensor according to any one of claims 4 to 9,
It is determined that an object has been detected even when no peak is detected from the received light amount distribution. The photoelectric sensor according to claim 1 or 2, further comprising:
Means for outputting, as the current displacement, the displacement equivalent calculated immediately before detecting the multiple reflection in place of the displacement equivalent obtained when the multiple reflection is detected;
A photoelectric sensor comprising: The photoelectric sensor according to claim 1,
The photoelectric sensor is a display unit that displays a displacement equivalent amount when multiple reflection is not detected and displays that multiple reflection is detected when multiple reflection is detected. The photoelectric sensor according to claim 1,
When the multiple reflection is not detected, the output means displays the displacement equivalent amount, and when the multiple reflection is detected, the displacement equivalent amount calculated immediately before the multiple reflection is detected and the multiple reflection is detected. A photoelectric sensor which is a display unit for displaying. The photoelectric sensor according to claim 12, wherein
A photoelectric sensor characterized in that, when a plurality of peaks exist in the received light amount distribution, a displacement equivalent amount is obtained based on a peak on a short distance side. The photoelectric sensor according to claim 12, wherein
When there are a plurality of peaks in the received light amount distribution, the photoelectric sensor is characterized in that a displacement is obtained based on a peak having a maximum maximum value.

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