JP2009300111A - Photoelectric sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric sensor which follows environmental factors and automatically adjusts a threshold as a criterion of the amount of light and the amount of light emitted to an objected to be detected, wherein high precision is achieved by improving the reliability of the automatic adjustment of the threshold and the amount of light emitted. <P>SOLUTION: As the current value data of the amount of light received, a fluctuation profile for the amount of light received during a predetermined period after light entry determination by the photoelectric sensor (step S20). Whether or not a period during which the amount of light received keeps constant at a maximum value (peak value) exists is determined (step S25). The current value data of the amount of light received measured when the period during which it keeps constant exists is assumed to be valid, and in automatic adjustment processing, the current value data of the amount of light received is used. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  A sensor that detects the presence or absence of a detection target by detecting a physical quantity of the detection target, and in particular detects the presence or absence of the detection target by receiving reflected or transmitted light of light projected on the detection target. The present invention relates to a photoelectric sensor to be detected.

  The photoelectric sensor projects light such as visible light and infrared light as signal light from the light projecting unit, detects light reflected by the detection target object or light transmitted through the detection target by the light receiving unit, and detects the detection target object. An output signal indicating the presence or absence is obtained. In this respect, the photoelectric sensor is used in various fields because it can detect an object in a non-contact manner and can also determine a color. In recent years, fiber type photoelectric sensors capable of detecting an object with a minute spot are known.

  FIG. 15 is a diagram illustrating a reflection type and a transmission type photoelectric sensor. Here, the detection object is described as a plastic bottle. Here, a PET bottle that is a detection target viewed from above is shown.

FIG. 15A is an example of a reflective photoelectric sensor.
A light projector / receiver is provided on one side of the object to be detected, and light is emitted from the light projector / receiver, and the reflected light reflected by the reflector provided on the other side of the object to be detected is received.

FIG. 15B is an example of a transmissive photoelectric sensor.
A projector is provided on one side of the detection object, and light is emitted from the projector, and light transmitted through the detection object is received by a light receiver provided on the other side of the detection object.

  In any type of photoelectric sensor, a detection area is formed by the projected light, and the presence or absence of a detection target is detected based on a change in the amount of light received as it passes through the detection area.

FIG. 16 is a diagram illustrating the operation of the photoelectric sensor that detects the presence or absence of a detection target.
FIG. 16A is a diagram illustrating a case where the detection target object flows continuously to the detection area. Here, the figure which looked at the plastic bottle which is a detection target from the side is shown.

FIG. 16B is a diagram for explaining a change in the amount of received light in the detection area.
As shown in FIG. 16B, when the detection object passes through the detection area, the light incident state and the light shielding state are repeated. Then, by providing a threshold value between the received light amount in the light incident state and the received light amount in the light blocked state, it is possible to detect the presence or absence of the detection target based on the threshold value. In this example, if the amount of light is greater than or equal to the threshold, the incident light state is set, and if the amount of light is less than the threshold, the light is blocked.

  FIG. 16 (c) shows a case where it is determined that there is a detection object, ON as a sensor output, and when it is determined that there is no detection object, OFF is output as a sensor output. .

  As described above, since the photoelectric sensor projects light and determines the presence / absence of the detection target based on the amount of the reflected light from the detection target or the transmitted light due to the absence of the detection target, various environmental factors are used. There is a problem that it is easily affected by fluctuations in the amount of light. For example, environmental factors such as fluctuations in the optical axis due to vibration, contamination of the light projecting part and light receiving part, ambient temperature fluctuations due to seasonal fluctuations, and aged deterioration of the light projecting elements (mainly LEDs) can be mentioned.

  On the other hand, the light quantity criterion for the photoelectric sensor must be very strict when the change in the light quantity due to the detection object is small. For example, when detecting an object that is close to transparency, there is only about 10% variation in the amount of light when there is no detection object and when there is a detection object. In such a case, it is necessary to set a threshold value as a criterion for determining the presence or absence of the detection target as a light quantity fluctuation of several percent, and the light quantity deterioration due to the environmental factors described above becomes a malfunction factor and cannot be ignored.

  In general, fluctuations in the amount of light due to environmental factors occur very slowly compared to fluctuations in the amount of light caused by the detection object.Therefore, the photoelectric sensor follows the environmental factors and gradually sets a threshold value that is a criterion for determining the amount of light. There has been proposed a method for determining the presence or absence of a detection target in a stable manner even in a long-term operation state by adjusting or automatically adjusting the amount of light emitted to the detection target.

  For example, Japanese Patent Application Laid-Open No. 2007-139494 proposes a method of correcting a threshold value after measuring the amount of received light with respect to a change in the amount of received light over time.

Japanese Patent No. 3684573 proposes a method in which a new threshold value is calculated after calculating a series of received light amount sequences periodically acquired, and the threshold value gradually follows a variation in received light amount. Has been.
JP 2007-139494 A Japanese Patent No. 3684573

  However, in the threshold adjustment method based on the above document, based on the acquired light reception amount current value data on the assumption that the light reception amount current value data is always acquired in ideal data, that is, in an ideal complete light incident state. A method for adjusting the threshold value is proposed, but the acquired received light amount current value data is not always ideal data.

  When the acquired light reception amount current value data is not ideal, an erroneous threshold value is generated, which may cause a malfunction.

  Here, the received light amount current value data refers to a received light amount measured for generating a threshold value and referred to as a value measured and stored in advance when the sensor is operated.

  The most representative received light amount current value data is the amount of received light in the state where there is no detection target in the transmission type photoelectric sensor, and it is not affected by the detection target and is a value that should always be constant if there are no environmental factors. is there.

  On the other hand, the acquired received light amount current value data is not ideal indicates a state in which the received light amount current value data acquired in order to grasp environmental factors is affected by the detection target. For example, in a light incident state in a transmissive photoelectric sensor (a state in which it is originally determined that there is no detection target), the detection target shields a part of the detection area, and there is no detection target at all. When the light amount is slightly attenuated as compared with the case, it indicates the time.

  The present invention has been made in order to solve the above-described problems, and is a photoelectric sensor that automatically adjusts a threshold value that is a criterion for determining a light amount or a light projection amount with respect to a detection target, following environmental factors. An object of the present invention is to provide a highly accurate photoelectric sensor by improving the reliability of automatic adjustment of a threshold value or light projection amount.

  The photoelectric sensor according to the present invention is a photoelectric sensor that detects the presence or absence of an object to be detected, and includes a light projecting unit, a light receiving unit that receives light projected from the light projecting unit, and reception of light received by the light receiving unit. A detection unit that detects the amount of light, a determination unit that compares the predetermined threshold value with the amount of received light to determine the presence or absence of the detection target, and a detection target based on the current value of the received light amount to prevent malfunction due to environmental factors An adjustment unit that adjusts a threshold value for detecting the presence or absence of light or a light projection amount projected from the light projecting unit according to a predetermined method. The adjustment unit monitors the received light amount fluctuation history for a certain period of the received light amount detected by the detecting unit, and only the received light amount when the peak value of the received light amount of the received light amount fluctuation history continues for a certain time is regarded as an effective received light amount. Get the current value of received light.

  Preferably, the adjustment unit compares the current received light amount current value with the current received light amount current value, and if the predetermined condition is not satisfied, the current received light amount current value is adjusted. The current value is invalid.

  Another photoelectric sensor according to the present invention is a photoelectric sensor that detects the presence or absence of an object to be detected, and includes a light projecting unit, a light receiving unit that receives light projected from the light projecting unit, and light received by the light receiving unit. A detection unit that detects the amount of received light, a determination unit that compares the predetermined threshold value with the amount of received light to determine the presence or absence of an object to be detected, and detection based on the current value of the received light amount to prevent malfunction due to environmental factors An adjustment unit that adjusts a threshold for detecting the presence or absence of an object or a light projection amount projected from the light projection unit according to a predetermined method. The adjusting unit monitors the received light amount fluctuation history for a certain period of the received light amount detected by the detecting unit, and the light receiving / light-shielding operation is performed once or more so that the determination unit determines that the detection target is once and then determines that there is no detection object. Adjust only if there is.

  Preferably, the adjustment unit obtains the current received light amount as an effective received light amount only when the peak value of the received light amount in the received light amount fluctuation history continues for a certain period of time.

  The photoelectric sensor according to the present invention monitors the received light amount fluctuation history for a certain period of the detected received light amount, and only the received light amount when the peak value of the received light amount of the received light amount fluctuation history continues for a certain time is an effective received light amount. As shown in FIG. With this method, it is possible to eliminate the measured received light amount when the received light amount is attenuated such that the peak value does not last for a certain period of time, and it is possible to prevent erroneous adjustment of the threshold value or the projected light amount. That is, it is possible to provide a highly accurate photoelectric sensor by improving the reliability of automatic adjustment of the threshold value or the light projection amount.

  Embodiments of the present invention will be described in detail with reference to the drawings. Note that the same or corresponding parts in the drawings are denoted by the same reference numerals and description thereof will not be repeated.

FIG. 1 is a schematic block diagram of a photoelectric sensor 1 according to an embodiment of the present invention.
Referring to FIG. 1, photoelectric sensor 1 according to the embodiment of the present invention includes a light projecting unit 11, a light receiving unit 12, an operation input unit 13, an output unit 14, a display unit 15, and a memory unit 16. CPU (Central Processing Unit) 17. This circuit is configured around the CPU 17.

  The memory unit 16 includes a working RAM necessary for program execution, an EEPROM for storing various setting data, and the like. The CPU 17 reads out a program necessary for executing various functions from the memory unit 16. A predetermined operation is executed.

  The light projecting unit 11 includes a light emitting diode (hereinafter referred to as an LED) 111 which is a light emitting element for detection, and an LED driving unit 112 for driving the LED 111.

  On the other hand, the light receiving unit 12 includes a photodiode (hereinafter referred to as PD) 121 which is a light receiving element for detection, and an amplifier unit 122 for amplifying the output of the PD 121.

  The pulsed light generated from the LED 111 that is a light emitting element for detection by the action of the LED driving unit 112 is guided to the detection area. The pulsed light resulting from transmission or reflection in the detection area arrives at the PD 121 that is a light receiving element for detection. The PD 121 that is a light receiving element for detection performs photoelectric conversion.

  An output signal generated by photoelectric conversion by the PD 121 is amplified by the amplifier unit 122 and then taken into the CPU 17 via an A / D converter (not shown). Note that the basic configuration of these light projections and receptions is well known in various documents, and thus detailed description thereof will be omitted. In the present embodiment, the light projecting unit and the light receiving unit constitute a detection unit that detects the amount of light that is a physical quantity transmitted or reflected by the detection target.

  The display unit 15 is configured by a display for displaying data generated by various calculations in the CPU 17.

  The operation input unit 13 is for inputting various information to the CPU 17. This input unit includes a key input unit and a signal input unit. The key input unit is for an operator to input various data by manual operation, and the signal input unit is for inputting a remote input signal using, for example, a core wire of an electric cord, although not shown. Yes, a control signal input from the outside coming from a core wire or the like via this signal input unit is taken into the CPU 17.

  The output unit 14 is for outputting various output signals generated by the CPU 17, for example, a binary signal based on the presence / absence of a detection target, to an external device such as a PLC.

Next, a case where the acquired received light amount present value data is not ideal will be described.
The case where the received light amount current value data is not ideal is a phenomenon that is recognized by the photoelectric sensor as attenuation of the received light amount as if there was an environmental factor even if there is no environmental factor as described above.

  Here, typically two applications can be considered as applications in which the detection object flows continuously.

FIG. 2 is a diagram illustrating an application in which a detection target object flows continuously.
FIG. 2A is an application for detecting the “number” of detection objects, and is characterized in that there is always a gap between the detection objects and the detection object. In the typical application of FIG. 2A, the width of the detection object is often narrow with respect to the gap, and the light receiving state of the photoelectric sensor is longer in the light incident state than in the light blocking state.

  FIG. 2B is an application that detects “stagnation” of an object to be detected. For example, it is an application that detects whether or not a product to be packed is prepared at the entrance of the packing device. In an application for detecting stagnation, a gap is not necessarily required between the detection object and the detection object. In this case, the light receiving state of the photoelectric sensor is longer in the light shielding state than in the light incident state.

  In the case of the application for detecting stay shown in FIG. 2B, when the gap between the detection objects is narrower than the detection area, the light receiving state of the photoelectric sensor is the light incident state between the detection objects. However, the light incident state is always accompanied by an attenuation of the amount of received light as compared to a complete light incident state (a state in which no detection target exists).

FIG. 3 is a diagram for explaining a malfunction in the case of an application for detecting stay.
FIG. 3A is a diagram illustrating a case where the detection target object flows continuously to the detection area. Here, the figure which looked at the plastic bottle which is a detection target from the side is shown.

FIG. 3B is a diagram for explaining a change in the amount of received light in the detection area.
As shown in FIG. 3B, when the detection object passes through the detection area, the light is almost shielded, but the gap between the detection objects is not completely light incident but is slightly attenuated. Amount.

  In particular, when the gap between detection objects is always narrow, the attenuation of the received light amount always occurs when acquiring the received light amount current value data. This attenuation is caused by environmental factors. I can't tell if it is.

  For example, when automatic adjustment of the threshold value is executed based on the received light amount current value data acquired in a state where the received light amount is attenuated, that is, not the received light amount current value data in the completely incident state but the attenuated received light amount current value data. When the threshold value is adjusted based on the above, it is determined that the amount of light received by the photoelectric sensor is attenuated due to environmental factors, and an adjustment for gradually decreasing the threshold value is executed.

  When it is determined by the adjustment that there is an object to be detected at the beginning, the sensor output is turned ON. When it is determined that there is no object to be detected, the sensor output is output as OFF. It is determined that the amount of received light is attenuated, the threshold is adjusted low, and the detection target cannot be detected correctly. That is, FIG. 3C shows a case where an erroneous operation determined to be absent occurs in a situation where it is originally determined that there is a detection target.

  In particular, for detection objects with high transparency, there is little fluctuation in the amount of light when there is a detection object and when there is no detection object, as described above, and when the automatic adjustment of an inappropriate threshold is performed, a malfunction immediately occurs. There is a possibility.

  Although it is conceivable to closely contact the detection objects so as not to detect the attenuation of the amount of received light, the structure of the PET bottle as an example of the detection object has a constricted shape as shown in FIG. In some cases, it is difficult to completely prevent a gap depending on the product, and a light incident state occurs in the gap.

  On the other hand, in the case of the application that detects the number of detection objects described in FIG. 2A, the light receiving state of the photoelectric sensor is longer than the light blocking state, so the amount of received light is larger. It is unlikely that a problem due to, for example, automatic adjustment of the threshold value occurs based on the received light amount current value data acquired in the attenuated state.

  However, a malfunction may occur even in the case of the application.

  FIG. 5 is a diagram for explaining a malfunction in the case of an application for detecting the number of detection objects.

  FIG. 5A is a diagram illustrating a case where a detection target flows to the detection area. Here, the figure which looked at the plastic bottle which is a detection target from the side is shown.

  Then, consider the case where the flow of the detection object stops in a state where the detection areas partially overlap as shown in the right diagram due to the specification of the device or device trouble. This state is also referred to as “equipment stop state” for convenience in this description.

  FIG. 5B is a diagram for explaining a change in the amount of received light when the flow of the detection object stops in a state in which the detection areas partially overlap.

  As shown in FIG. 5 (b), when the detection object passes through the detection area, the detection object is blocked when the detection object flows while the detection area is partially overlapped. During the period when the flow of the object is stopped, the state where the amount of received light is attenuated is maintained.

  It is unclear how long the flow of the detection object has been stopped for balance of equipment maintenance and the like.

  In particular, when the period of stoppage is long, the above-mentioned attenuation of the received light amount always occurs when acquiring the received light amount current value data, so is this attenuation caused by environmental factors? I can't tell the difference.

  For example, when automatic adjustment of the threshold value is executed based on the received light amount current value data acquired in a state where the received light amount is attenuated, that is, not the received light amount current value data in the completely incident state but the attenuated received light amount current value data. When the threshold value is adjusted based on the above, it is determined that the amount of light received by the photoelectric sensor is attenuated due to environmental factors, and an adjustment for gradually decreasing the threshold value is executed.

  When it is determined by the adjustment that there is an object to be detected at the beginning, the sensor output is turned ON. When it is determined that there is no object to be detected, the sensor output is output as OFF. It is determined that the amount of received light is attenuated, and the threshold value is adjusted low. In this state, even if the equipment stop state is resolved, the detection target cannot be detected correctly because the threshold value is lowered. That is, FIG. 5C shows a case where an erroneous operation determined to be absent occurs in a situation where it is originally determined that there is a detection target.

  In this example, as an example, it has been described as a malfunction that occurs in an application that detects the number of objects to be detected. However, a similar malfunction may also occur in an application that detects stay.

  In this embodiment, the threshold value is automatically adjusted erroneously by correctly recognizing the above state as a “non-ideal” state and excluding the received light amount current value data acquired in the non-ideal state. It is possible to prevent malfunction due to the operation.

  FIG. 6 is a diagram illustrating a main flow for automatically adjusting a threshold value and the like periodically according to the embodiment of the present invention. In this flow, the CPU 17 reads a program from the memory unit 16 and executes it.

  Referring to FIG. 6, first, a check process for a condition for generating a regular adjustment event is executed (step S10). If the condition is satisfied in step S10, next, the received light amount current value data acquisition process is executed (step S20).

  Then, automatic adjustment processing is executed (step S40). And it returns to step S10 again. These processes are repeated.

Hereafter, each of these processes is demonstrated concretely.
FIG. 7 is a flowchart for explaining the check process for the occurrence condition of the periodic adjustment event.

  Referring to FIG. 7, it is first determined whether an incoming / outgoing light shielding event has occurred (step S11). The incident light shielding event is a state in which the photoelectric sensor transitions from the light incident state to the light shielding state, and then transitions to the light incident state again. Alternatively, a transition is made from the light shielding state to the light incident state, and then a transition to the light shielding state is made again. Specifically, as an example, it means an incident light shielding operation in which it is determined that the detection target is once present after it is determined that the target is present.

In step S11, the process waits until the incident / light shielding event occurs one or more times.
In step S11, if an incoming / outgoing light shielding event has occurred once or more, then an automatic adjustment interval (delay process) is executed (step S12). The automatic adjustment interval (delay process) is a process of waiting for a predetermined period when it is determined that an incoming / outgoing light shielding event has occurred. Then, after waiting for a predetermined period (step S12), it is determined that the regular adjustment event occurrence condition check process is completed, and the process proceeds to the next received light amount current value acquisition process.

  Note that by adjusting a predetermined period in the automatic adjustment interval (delay processing), it is possible to adjust the interval for automatically adjusting the threshold value periodically.

  In addition, in this example, although the case where the process which waits for the predetermined period in step S12 was performed after the process of step S11 was demonstrated, it is not restricted to this in particular, It is also possible to perform before step S11, It is also possible to execute step S12 after executing an automatic adjustment process in step S40 described later.

FIG. 8 is a diagram illustrating a case where the amount of light changes due to environmental factors.
Referring to FIG. 8, here, it is shown that the amount of light received in the complete light incident state is generated very slowly compared to the amount of light fluctuation caused by the incident light shielding event by the detection object. In this example, the photoelectric sensor follows environmental factors and the threshold value that is a criterion for determining the amount of light is gradually adjusted.

  FIG. 9 is a diagram for explaining a case where the light amount changes when the detection areas partially overlap in the equipment stop state as described with reference to FIG. 5.

  Referring to FIG. 9, when a part of the detection area overlaps in the equipment stop state, the incident light shielding event is repeated before the equipment stop, but the detection target does not flow after the equipment stop. Therefore, the incoming / outgoing light shielding event is not repeated, and a constant state in which the light amount is attenuated is maintained.

  In the equipment stoppage state, it is not known how long it will be stopped due to equipment maintenance. However, in the equipment stop state, as described above, there is no incident / light shielding event of the photoelectric sensor, and the same state continues.

  Therefore, as an automatic adjustment method according to the embodiment of the present invention, in step S11, as a condition for shifting to the received light amount current value acquisition process for acquiring the received light amount current value data, has an incoming / outgoing light shielding event occurred one or more times? Judge whether.

  By providing the condition, if the equipment is stopped while a part of the detection area of the photoelectric sensor overlaps the detection target, the current light reception amount value data is not acquired because the condition is not satisfied. It is possible to prevent malfunction caused by erroneously automatically adjusting the threshold value based on inappropriate received light amount current value data.

FIG. 10 is a diagram illustrating the details of the received light amount current value acquisition process described with reference to FIG.
With reference to FIG. 10, as the start of the process of acquiring the received light amount current value, it is first determined whether or not it is in a light incident state (step S <b> 21).

  The reason why it is desired to acquire the received light amount current value data is the received light amount when there is no detection target.

  If it is determined in step S21 that the light is not incident, that is, if it is determined that the amount of received light is less than the threshold, the process proceeds to step S29.

  Then, it is determined whether or not it is within the light incident waiting time (step S29). It is assumed that the incoming light waiting time is set to a predetermined time. If it is within the light reception waiting time, the process proceeds to step S21 again to confirm whether it is in the light incident state. That is, it is confirmed whether or not the object to be detected is in a light shielding state.

  If it is determined again in step S21 that it is not in the light incident state, the process proceeds to step S29, and the above-described processing is repeated for a light incident waiting time, that is, a predetermined time. If not, it is determined that the received light amount current value acquisition has failed (step S27). Then, the process for obtaining the received light amount current value is terminated.

  On the other hand, if it is determined in step S21 that the light is incident, that is, if it is determined that the amount of received light is greater than or equal to the threshold value, the process proceeds to step S22.

  In step S22, the amount of received light is measured. Next, peak determination processing is executed (step S30).

FIG. 11 is a flowchart illustrating the peak determination process.
Referring to FIG. 11, the peak determination is started, and first, the measured received light amount is compared with the value set to the maximum value, and whether the received light amount is larger than the value set as the maximum value. It is determined whether or not (step S31). If the measured amount of received light is larger than the value set as the maximum value in step S31, the process proceeds to step S32.

  In step S32, the received light amount is compared with a value obtained by adding a predetermined value to the maximum value, and it is determined whether or not the received light amount is greater than a value obtained by adding the predetermined value to the maximum value.

  In step S32, the received light amount is compared with a value obtained by adding a predetermined value to the maximum value. If the received light amount is greater than the value obtained by adding the predetermined value to the maximum value, the number of peaks is reset (step S35).

  On the other hand, in step S32, the received light amount is compared with a value obtained by adding a predetermined value to the maximum value. If the received light amount is equal to or smaller than the value obtained by adding the predetermined value to the maximum value, 1 is added to the peak number (step S33).

  Then, the measured amount of received light is set to the maximum value (step S34), and the peak determination process ends.

  On the other hand, if it is determined in step S31 that the amount of received light is equal to or less than the maximum value, the process proceeds to step S36.

  In step S36, the received light amount is compared with a value obtained by subtracting a predetermined value from the maximum value. If the received light amount is equal to or greater than a value obtained by subtracting the predetermined value from the maximum value, 1 is added to the peak number.

  On the other hand, in step S36, the received light amount is compared with the value obtained by subtracting the predetermined value from the maximum value. If the received light amount is not equal to or greater than the value obtained by subtracting the predetermined value from the maximum value, the peak determination process is terminated.

In this example, it is assumed that the initial value of the maximum value is set as a threshold value as an example.
This peak determination process compares the amount of light received continuously measured with the maximum value, near the maximum value, specifically, a value obtained by adding a predetermined value from the maximum value and a value obtained by subtracting the predetermined value from the maximum value. In the case of transition within the range, that is, in the case of sticking at the upper limit of the amount of received light as in the complete light incident state, the flow is to add the number of peaks. If not, specifically, if the value of the amount of received light does not maintain the maximum value and increases continuously, the maximum value is updated and the number of peaks is reset. . Also, the number of peaks is not counted up when the amount of light received decreases continuously.

  Again referring to FIG. 10, it is next determined whether or not the measurement conditions are met (step S25).

  Specifically, it is determined whether or not the number of peaks is greater than or equal to a predetermined value. In step S25, if the number of peaks is equal to or greater than a predetermined value, it is determined that the light is completely incident, it is determined that the received light amount current value has been successfully acquired (step S28), and the received light amount value stored as the maximum value is determined. The received light amount current value data. Then, the process for obtaining the received light amount current value is terminated.

  On the other hand, if the measurement conditions are not met in step S25, specifically, if it is determined that the number of peaks is not equal to or greater than the predetermined value, the process proceeds to step S26.

  In step S26, it is determined whether or not the received light amount measurement has been executed a specified number of times. If the received light amount measurement has not been performed the specified number of times, the process proceeds again to step S22, and the above processing is repeated.

  On the other hand, when the received light amount measurement is executed a predetermined number of times in step S26, it is determined that the received light amount current value acquisition has failed (step S27). Then, the process for obtaining the received light amount current value is terminated.

  FIG. 12 is a diagram illustrating a case where the received light amount current value acquisition process is executed in a completely incident state in a gap between detection objects.

FIG. 12A shows a case where the gap between the detection objects is larger than the detection area.
FIG. 12B is a diagram for explaining a change in the amount of received light in the detection area.

  As shown in FIG. 12B, when the received light amount current value acquisition process is executed in the complete light incident state, there is a time when the received light amount is constant. Specifically, there is a certain period of maximum value (peak value).

  Therefore, by executing the peak determination process described with reference to FIG. 11, the peak number continues to be counted up for a certain period when the light is completely incident.

  Therefore, in step S25 of FIG. 10, it is determined that the number of peaks is equal to or greater than the predetermined value, that is, the measurement conditions are met, and then it is determined that the received light amount current value has been successfully acquired (step S28).

  FIG. 13 is a diagram illustrating a case where the received light amount current value acquisition process is executed in a state where the light is not completely incident (a non-ideal state) in the gap between the detection objects.

FIG. 13A shows a case where the gap between the detection objects is narrower than the detection area.
FIG. 13B is a diagram for explaining a change in the amount of received light in the detection area.

  As shown in FIG. 13B, when the received light amount current value acquisition process is executed when the light reception state is not complete, the light reception amount does not exist for a certain time or is short even if it exists. Therefore, there is no fixed period of maximum value (peak value).

  Therefore, when the peak determination process described with reference to FIG. 11 is executed, the peak number does not continue to be counted up because there is no fixed period for the maximum value.

  Therefore, in step S25 of FIG. 10, it is determined that the number of peaks is less than a predetermined value, that is, the measurement conditions do not match. Next, in step S26, the received light amount measurement number is executed a specified number of times. It is determined that the current value acquisition has failed (step S27).

  The received light amount current value acquisition process according to the embodiment of the present invention is a period in which the received light amount fluctuation profile is measured for a certain period after the photoelectric sensor determines the incident light, and the received light amount is constant at the maximum value (peak value). It is determined whether or not the measured received light amount is a valid value as the received light amount current value data.

  In addition, the said fixed period shall be set to an appropriate value from the response speed of a photoelectric sensor, the moving speed of a detection target object, the width of a detection area, etc. supposing the situation where a photoelectric sensor is used.

FIG. 14 is a diagram for explaining the details of the automatic adjustment processing described with reference to FIG.
Referring to FIG. 14, as the start of the automatic adjustment process, first, it is determined whether or not the acquisition of the received light amount current value is successful (step S41).

  In step S41, if acquisition of the received light amount current value is successful, next, received light amount current value calculation processing is executed (step S42).

  Specifically, a moving average process of the received light amount current value data that has been successfully acquired a plurality of times in the past is executed, and the received light amount current value data that has been subjected to the moving average process is acquired.

  Note that the received light amount current value data that has been successfully acquired at the time of sampling may be acquired without executing the moving average process, and the received light amount current value data is a representative symbolically showing a temporal change in the received light amount. It is also possible to use a value, for example, an average value of received light amount per predetermined time, a maximum value of received light amount, a minimum value of received light amount, or the like.

Next, a light projection amount or threshold adjustment value calculation process is executed (step S43).
Specifically, as an example, the threshold value is calculated by multiplying a predetermined coefficient based on the above-described calculated received light amount current value data.

  Alternatively, an adjustment value of the light projection amount of the LED 111 in the light projecting unit 11 is calculated based on the calculated received light amount current value data.

  Next, the threshold value is adjusted based on the threshold value calculated in step S43 (step S44).

  Alternatively, the light projection amount of the LED 111 is adjusted based on the calculated adjustment value of the light projection amount of the LED 111.

Then, the automatic adjustment process ends.
Referring to FIG. 6 again, when the automatic adjustment process is completed, the process returns to step S10 again as described above and the above-described process is repeated.

  The method of automatically adjusting the threshold value or the like according to the embodiment of the present invention obtains a received light amount fluctuation profile for a certain period after the photoelectric sensor determines light incident as the received light amount current value data, and the received light amount is the maximum value ( It is determined whether or not there is a period in which the peak value is constant, and the received light amount current value data is used in the automatic adjustment processing by making the received light amount measured when there is a constant period effective. Therefore, for example, in the situation where the attenuation of the received light amount described above is not ideal, when the received light amount current value data acquisition process is executed, the acquired received light amount current value data is invalid. Since the data is not used in the automatic adjustment process, it is possible to prevent malfunction due to erroneous automatic adjustment of the threshold value based on the inappropriate received light amount current value data.

  In addition, when the equipment stop state continues intermittently, it is unlikely to be probable to stop at the same half light incident state (the state of FIG. 9) every time, but even in such a case, In the case where the acquired received light amount current value data is attenuated beyond the range predicted as an environmental factor, it is determined that the fluctuation is caused by the above-described cause, and the received light amount current value data is It is also possible to add a judgment process that is not used.

  Specifically, as an example, the previous received light amount current value data is compared with the current received light amount current value data, and the current received light amount current value data is greater than or equal to a predetermined value than the previous received light amount current value data. In the case of attenuation, it is possible to add to FIG. 14 a determination that the current received light amount current value data is invalid as the received light amount current value data.

  In this embodiment, a reflective photoelectric sensor, that is, a photoelectric sensor that receives reflected light reflected by a detection target in a detection area and detects the presence or absence of the detection target has been described. However, the present invention is not limited to a reflective photoelectric sensor. However, the present invention can also be applied to a transmissive photoelectric sensor, that is, a photoelectric sensor that receives transmitted light that has passed through a detection target and detects the presence or absence of the detection target. That is, in this case, the light guided to the detection light receiving element is not reflected light but transmitted light, and the other systems are the same.

  In the above description, the photoelectric sensor that detects the amount of light received and detects the presence or absence of the detection target has been described as an example. However, the detection of the presence or absence of the detection target is detected by detecting another physical medium instead of the amount of light reception. The same can be applied to the sensor. For example, a proximity sensor that detects the position of the detection target based on a magnetic action or the like that changes according to the distance to the detection target, or an ultrasonic wave that is reflected with respect to the ultrasonic wave transmitted from the sensor head, The present invention is similarly applicable to an ultrasonic sensor or the like that detects the position of a detection target object by measuring the time from transmission to reception of the sound wave.

  It is also possible to provide a program that causes a computer to function and execute control as described in the above flow. Such a program is stored in a computer-readable recording medium such as a flexible disk attached to the computer, a CD-ROM (Compact Disk-Read Only Memory), a ROM (Read Only Memory), a RAM (Random Access Memory), and a memory card. And can be provided as a program product. Alternatively, the program can be provided by being recorded on a recording medium such as a hard disk built in the computer.

  The program according to the present invention is a program module that is provided as a part of a computer operating system (OS) and calls necessary modules in a predetermined arrangement at a predetermined timing to execute processing. Also good. In that case, the program itself does not include the module, and the process is executed in cooperation with the OS. A program that does not include such a module can also be included in the program according to the present invention.

  The program according to the present invention may be provided by being incorporated in a part of another program. Even in this case, the program itself does not include the module included in the other program, and the process is executed in cooperation with the other program. Such a program incorporated in another program can also be included in the program according to the present invention.

The provided program product is installed in a program storage unit such as a hard disk and executed. The program product includes the program itself and a recording medium on which the program is recorded.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a schematic block diagram of a photoelectric sensor according to an embodiment of the present invention. It is a figure explaining the application from which a detection target flows continuously. It is a figure explaining the malfunctioning in the case of the application which detects a stay. It is a figure explaining the structure of the PET bottle which has a constriction shape which is an example of a detection target. It is a figure explaining the malfunctioning in the case of the application which detects the number of detection target objects. It is a figure explaining the main flow which adjusts a threshold value etc. automatically regularly according to an embodiment of the invention. It is a flowchart explaining the check process of the generation | occurrence | production condition of a regular adjustment event. It is a figure explaining the case where a light quantity changes with an environmental factor. It is a figure explaining the case where the light quantity when a part of detection area overlaps in an equipment stop state. It is a figure explaining the detail of light reception amount present value acquisition processing. It is a flowchart explaining a peak determination process. It is a figure explaining the case where the received light quantity present value acquisition process is performed in the gap between detection objects in a complete light incident state. It is a figure explaining the case where the received light quantity present value acquisition process is performed in the state which is not a perfect light-incidence state in the clearance gap between detection objects. It is a figure explaining the detail of an automatic adjustment process. It is a figure explaining a reflection type and a transmission type photoelectric sensor. It is a figure explaining operation | movement of the photoelectric sensor which detects the presence or absence of a detection target object.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Photoelectric sensor, 11 Light emission part, 12 Light reception part, 13 Operation input part, 14 Output part, 15 Display part, 16 Memory part, 17 CPU, 111 LED, 112 LED drive part, 121 PD, 122 Amplifier part

Claims (4)

A photoelectric sensor for detecting the presence or absence of a detection object,
A light projecting unit;
A light receiving unit that receives light projected from the light projecting unit;
A detection unit for detecting the amount of light received by the light receiving unit;
A determination unit that compares a predetermined threshold value with the amount of received light to determine the presence or absence of the detection target;
Adjustment for adjusting the threshold value for detecting the presence or absence of the detection object based on the received light amount current value or the amount of light projected from the light projecting unit according to a predetermined method in order to prevent malfunction due to environmental factors With
The adjustment unit monitors the light reception amount fluctuation history for a certain period of the light reception amount detected by the detection unit, and only the light reception amount when the peak value of the light reception amount of the light reception amount fluctuation history continues for a certain time is effective. Photoelectric sensor that acquires the current value of received light amount as the received light amount.   The adjustment unit compares the current received light amount current value with the current received light amount current value, and if the predetermined condition is not satisfied, the current received light amount present value is adjusted to the current received light amount current for the adjustment. The photoelectric sensor according to claim 1, wherein the photoelectric sensor is invalid as a value. A photoelectric sensor for detecting the presence or absence of a detection object,
A light projecting unit;
A light receiving unit that receives light projected from the light projecting unit;
A detection unit for detecting the amount of light received by the light receiving unit;
A determination unit that compares a predetermined threshold value with the amount of received light to determine the presence or absence of the detection target;
Adjustment for adjusting the threshold value for detecting the presence or absence of the detection object based on the received light amount current value or the amount of light projected from the light projecting unit according to a predetermined method in order to prevent malfunction due to environmental factors With
The adjustment unit monitors the light reception amount fluctuation history of the light reception amount detected by the detection unit over a certain period, and the determination unit determines that the detection target is once present and then determines that the detection target is absent. A photoelectric sensor that adjusts only when there is at least once.   4. The photoelectric sensor according to claim 3, wherein the adjustment unit obtains a current received light amount as an effective received light amount only when the peak value of the received light amount in the received light amount fluctuation history continues for a predetermined time.

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