JP7066113B2 - Photoelectric sensor - Google Patents

Description

The present invention relates to a photoelectric sensor.

Conventionally, in a transmissive photoelectric sensor, the threshold value used for object detection may be corrected or the received light amount to be displayed may be corrected by using the light receiving average value in the section where the light receiving amount exceeds a predetermined reference value. ..

For example, in Patent Document 1 below, the sampled light-receiving amount is compared with a predetermined reference value higher than the threshold value used for object detection, and the first period in which the light-receiving amount exceeds the reference value and the light-receiving amount refer to the reference value. The threshold value is corrected based on the degree of decrease of each sampling light receiving amount with respect to the target value of the light receiving amount according to the determination of the second period to be lower than the second period and the number of samplings during the first period reaching a predetermined value. A photoelectric sensor is described.

Further, in Patent Document 2 below, a sensitivity adjustment process for determining a reference light receiving amount used as a reference for setting a threshold value based on the light receiving amount and setting the reference light receiving amount to a value suitable for setting the threshold value is provided. Described is a photoelectric sensor that is executed, changes the threshold value according to the degree of change due to the sensitivity adjustment process, and displays a value obtained by correcting the actual amount of received light according to the degree of change.

Japanese Unexamined Patent Publication No. 2014-96715. Patent No. 6007717

According to the techniques described in Patent Documents 1 and 2, even when the light receiving amount gradually changes due to the influence of dust or the like, the threshold value used for object detection is corrected or displayed according to the time change of the light receiving amount. The amount of light received can be corrected.

However, when objects are continuously detected, or depending on the shape of the object to be detected, the light-receiving waveform does not become rectangular, but becomes close to a triangular wave shape, and the light-receiving average value in the section where the light-receiving amount exceeds the reference value. May be low. Therefore, correction based on a low light-receiving average value may be performed.

Therefore, the present invention provides a photoelectric sensor capable of appropriately correcting the threshold value used for object detection.

The photoelectric sensor according to one aspect of the present disclosure includes a light projecting unit that projects light on a detection region, a measuring unit that receives light from the detection region and converts the received light amount into a signal value, and a comparison between a signal value and a threshold value. Based on this, a determination unit that determines whether or not an object exists in the detection area, a timing unit that measures the first hour when it is determined that the object does not exist in the detection area, and the first time elapses. After that, a storage unit that stores the signal value measured by the measurement unit and a correction unit that corrects the threshold value based on the signal value stored in the storage unit are provided.

According to this aspect, the object passes through the detection area by waiting until the first time elapses after it is determined that the object does not exist in the detection area and then correcting the threshold value based on the signal value measured thereafter. Then, it is possible to wait until the signal value stabilizes and correct the threshold value appropriately.

In the above embodiment, the timekeeping unit may reset the timekeeping if the determination unit determines that an object exists in the detection area before the first time elapses after the start of the timekeeping.

According to this aspect, by resetting the timing when the object arrives in the detection area again by the time when the first time elapses after it is determined that the object does not exist in the detection area, the threshold value is set when the signal value is not stable. Correction can be postponed.

In the above embodiment, the storage unit stores the signal value measured by the measurement unit over the second time after the lapse of the first time, and the correction unit stores the statistics of the signal value measured by the measurement unit over the second time. The threshold may be corrected based on the value.

According to this aspect, the influence of ambient light is reduced by measuring the signal value used for correcting the threshold value over the second time and correcting the threshold value based on the statistical value of the measured signal value. , The threshold can be corrected appropriately.

In the above embodiment, if the determination unit determines that an object exists in the detection area before the second time elapses, the storage unit may reset the signal value referred to by the correction unit.

According to this aspect, the signal value stored when the object arrives in the detection area again by the time when the second time elapses from the start of measuring the signal value for correcting the threshold value is reset, and the signal value is not stable. In some cases, the threshold correction can be postponed.

In the above embodiment, a display unit for displaying the signal value and the threshold value may be further provided, and the correction unit may correct the signal value and the threshold value displayed by the display unit.

According to this aspect, it waits until the first time elapses after it is determined that the object does not exist in the detection area, and corrects the signal value and the threshold value displayed on the display unit based on the signal value measured thereafter. Therefore, the displayed value can be appropriately corrected so that the displayed signal value and the threshold value are constant regardless of the actual amount of received light.

In the above aspect, when the correction is performed by the correction unit, the display unit may display at least one of the correction being performed, the ratio of the correction amount, and the change in the correction amount.

According to this aspect, the actual state of the correction can be grasped at a glance, and the state of the photoelectric sensor can be easily grasped.

In the above aspect, the display unit may display at least one of the elapsed time from the previous correction by the correction unit and the time until the correction by the correction unit is performed.

According to this aspect, the schedule for correction can be grasped at a glance, and the state of the photoelectric sensor can be easily grasped.

In the above embodiment, an input unit for receiving input from the user is further provided, and the timekeeping unit may perform timekeeping for the first time when it is determined that no object exists in the detection area and the input unit accepts the input. good.

According to this aspect, it waits until the first time elapses after it is determined that the object does not exist in the detection area, and when there is a user input, the threshold value is corrected based on the signal value measured thereafter. Therefore, the threshold value can be corrected at a timing desired by the user.

According to the present invention, it is possible to provide a photoelectric sensor capable of appropriately correcting a threshold value used for object detection.

It is a figure which shows the outline of the photoelectric sensor which concerns on embodiment of this invention. It is a figure which shows the functional block of the photoelectric sensor which concerns on this embodiment. It is a figure which shows the signal value and the threshold value displayed by the photoelectric sensor which concerns on this embodiment. It is a flowchart of 1st example of the correction process executed by the photoelectric sensor which concerns on this embodiment. It is a flowchart of the 2nd example of the correction process executed by the photoelectric sensor which concerns on this embodiment. It is a figure which shows the signal value and the threshold value displayed by the conventional photoelectric sensor.

Embodiments of the present invention will be described with reference to the accompanying drawings. In each figure, those with the same reference numerals have the same or similar configurations.

FIG. 1 is a diagram showing an outline of a photoelectric sensor 10 according to an embodiment of the present invention. The photoelectric sensor 10 according to the present embodiment detects the work 100 transported by the transport device 50 and transmits a signal value to the controller 20.

The photoelectric sensor 10 according to the present embodiment is a transmissive photoelectric sensor. The photoelectric sensor 10 projects light onto the detection region 10a, and detects the work 100 depending on whether the light is shielded by the work 100 and is not received or is received without being shielded. However, the photoelectric sensor 10 may be a regression reflection type. That is, the photoelectric sensor 10 projects light on the detection region 10a and detects the work 100 depending on whether the light is shielded by the work 100 and not received, or is reflected back and received without being shielded. There may be.

The photoelectric sensor 10 according to the present embodiment includes a first optical fiber 101 and a second optical fiber 102 arranged so as to detect the work 100 in a transmissive type. When the photoelectric sensor 10 is composed of a transmission type or a regression reflection type, when the work 100 reaches the detection region 10a of the photoelectric sensor 10, the amount of detected light decreases.

The work 100 is an object to be detected by the photoelectric sensor 10, and may be, for example, a finished product of a product to be produced or an unfinished product such as a part.

The controller 20 controls the transport device 50. The controller 20 may be configured by, for example, a PLC (Programmable Logic Controller). The controller 20 may detect that the work 100 has arrived by the output from the photoelectric sensor 10 and control other devices.

The transport device 50 transports the work 100 under the control of the controller 20. The transport device 50 may be, for example, a belt conveyor, and may transport the work 100 at a speed set by the controller 20.

FIG. 2 is a diagram showing a functional block of the photoelectric sensor 10 according to the present embodiment. The photoelectric sensor 10 includes a light projecting unit 11, a measuring unit 12, a processing unit 13, an input unit 14, and a display unit 15.

<Light projector>
The light projecting unit 11 projects light on the detection region 10a where the work 100 arrives. The light projecting unit 11 includes a light projecting element 11a and a drive circuit 11b. The light emitting element 11a may be composed of an LED (Light Emitting Diode) or a laser diode, and the drive circuit 11b controls a current for causing the light emitting element 11a to emit light. The drive circuit 11b may intermittently cause the light projecting element 11a to emit light in a pulsed manner. The light emitted from the light projecting element 11a may be applied to the detection region 10a via a lens (not shown) or the first optical fiber 101 of FIG.

<Measurement unit>
The measuring unit 12 receives the light from the detection region 10a and converts the received light amount into a signal value. The measuring unit 12 includes a light receiving element 12a, an amplifier 12b, a sample / hold circuit 12c, and an A / D converter 12d. The light receiving element 12a may be composed of a photodiode, and converts a light receiving amount into an electrical signal. The measuring unit 12 may make the light reflected or transmitted in the detection region 10a incident on the light receiving element 12a via a lens (not shown) or the second optical fiber 102 of FIG. The amplifier 12b amplifies the output signal of the light receiving element 12a. The sample / hold circuit 12c holds the output signal of the light receiving element 12a amplified by the amplifier 12b in synchronization with the timing of the pulse emission by the light projecting unit 11. This reduces the influence of ambient light. The A / D converter 12d converts the analog signal value held by the sample / hold circuit 12c into a signal value of a light receiving amount which is a digital value.

<Processing unit>
The processing unit 13 includes a determination unit 13a, a timing unit 13b, a storage unit 13c, and a correction unit 13d. The processing unit 13 may be composed of a computer, and the computer may be composed of, for example, a microprocessor, a memory, a program stored in the memory, and the like.

The determination unit 13a determines whether or not an object exists in the detection region 10a based on the comparison between the signal value and the threshold value. When the photoelectric sensor 10 is a transmission type or a retroreflective type, the determination unit 13a determines that an object does not exist in the detection region 10a if the signal value is larger than the threshold value, and if the signal value is smaller than the threshold value, the object is in the detection region 10a. Determined to exist. The work 100 is an example of an object in the present invention.

When it is determined that the object does not exist in the detection area 10a, the timekeeping unit 13b performs the timekeeping for the first time. The first time can be arbitrarily set, but may be, for example, about 3 seconds. Further, if the determination unit 13a determines that an object exists in the detection region 10a before the first time elapses after the start of the time measurement, the time measurement unit 13b may reset the time measurement. That is, if it is determined that the object does not exist in the detection region 10a and then it is determined that the object exists in the detection region 10a again before the first time elapses, the timing unit 13b may reset the timing. In this way, by resetting the timing when an object arrives in the detection area 10a again by the time when the first time elapses after it is determined that the object does not exist in the detection area 10a, the threshold value is set when the signal value is not stable. Correction can be postponed.

The storage unit 13c stores the signal value measured by the measurement unit 12 after the first time has elapsed. The storage unit 13c may store the signal value measured by the measurement unit 12 for the second time after the lapse of the first time. The second time can be set arbitrarily, but may be, for example, about 3 seconds.

The correction unit 13d corrects the threshold value based on the signal value stored in the storage unit 13c. When the photoelectric sensor 10 is a transmission type or a regression reflection type, the correction unit 13d calculates the corrected threshold value by multiplying the signal value stored in the storage unit 13c by a predetermined value that is greater than 0 and less than 1. good. According to the photoelectric sensor 10 according to the present embodiment, the threshold value is corrected based on the signal value measured after waiting until the first time elapses after it is determined that the object does not exist in the detection region 10a. The threshold value can be appropriately corrected by waiting until the object passes through the detection region 10a and the signal value stabilizes. As a result, even if the light projecting element 11a or the light receiving element 12a is contaminated by dust or the like, or the optical axes of the first optical fiber 101 and the second optical fiber 102 are displaced, an object that reaches the detection region 10a. Can be detected properly.

The correction unit 13d may correct the threshold value based on the statistical value of the signal value measured by the measurement unit 12 over the second time. The correction unit 13d may correct the threshold value using, for example, the average, variance, and median of the signal values measured by the measurement unit 12. Here, the average may be an average regarding the number of samplings corresponding to the second time. In this way, the signal value used to correct the threshold value is measured over the second hour, and the threshold value is corrected based on the statistical value of the measured signal value to reduce the influence of ambient light and reduce the threshold value. Can be corrected appropriately.

If the determination unit 13a determines that an object exists in the detection area 10a before the second time elapses, the storage unit 13c may reset the signal value referred to by the correction unit 13d. That is, when it is determined that the object exists in the detection region 10a again by the time when the second time elapses from the start of measuring the signal value for correcting the threshold value, the storage unit 13c may reset the stored signal value. .. In this way, when the signal value stored when the object arrives at the detection area 10a again by the time when the second time elapses from the start of measuring the signal value for correcting the threshold value is reset and the signal value is not stable. The threshold correction can be postponed.

<Input section>
The input unit 14 receives an input from a user who operates the photoelectric sensor 10. The input unit 14 may include a physical operation switch, a touch panel, or the like.

When it is determined that the object does not exist in the detection area 10a and the input unit 14 accepts the input, the timekeeping unit 13b may perform the timekeeping for the first time. In this way, by waiting until the first time elapses after it is determined that the object does not exist in the detection area 10a, and when there is further user input, the threshold value is corrected based on the signal value measured thereafter. , The threshold can be corrected at the user's desired timing.

<Display unit>
The display unit 15 displays the signal value and the threshold value. The display unit 15 may display various data including the determination result by the determination unit 13a. The display unit 15 may display, for example, a signal value being measured, a threshold value used for determination by the determination unit 13a, and a binary output of a determination result by the determination unit 13a.

The correction unit 13d may correct the signal value and the threshold value displayed by the display unit 15. In this case, the correction unit 13d is a display unit even when the light projecting element 11a and the light receiving element 12a are contaminated by dust or the like, or when the optical axes of the first optical fiber 101 and the second optical fiber 102 are misaligned. The displayed signal value and threshold value may be corrected so that the signal value and threshold value displayed by 15 are constant. In this way, after waiting until the first time elapses after it is determined that the object does not exist in the detection region 10a, the signal value and the threshold value displayed on the display unit 15 are corrected based on the signal values measured thereafter. Therefore, the displayed value can be appropriately corrected so that the displayed signal value and the threshold value are constant regardless of the actual amount of received light.

When the correction is performed by the correction unit 13d, the display unit 15 may display that the correction is being performed. The display unit 15 may indicate, for example, that the correction has been performed by lighting an LED or by an indicator. As a result, it becomes possible to grasp at a glance whether or not the correction is performed by the correction unit 13d, and it becomes easy to grasp the state of the photoelectric sensor 10.

The display unit 15 may display the ratio of the correction amount when the correction is performed by the correction unit 13d. The display unit 15 may display, for example, the percentage of correction. As a result, it is possible to grasp at a glance whether or not the maintenance time is near, and it becomes easy to grasp the state of the photoelectric sensor 10.

The display unit 15 may display a change in the correction amount when the correction is performed by the correction unit 13d. For example, when the correction is applied because the first optical fiber 101 and the second optical fiber 102 are dirty, the change in the correction amount is relatively small. On the other hand, when the correction is made because the optical axes of the first optical fiber 101 and the second optical fiber 102 are misaligned, the change in the correction amount is relatively large. In this way, the cause of the correction can be identified from the amount of change in the correction, and the state of the photoelectric sensor 10 can be easily grasped.

The display unit 15 may display the elapsed time since the previous correction by the correction unit 13d was performed. Further, the display unit 15 may display the time until the correction by the correction unit 13d is performed. Neither time may be accurate and may be a rough guide. As a result, the schedule for correction can be grasped at a glance, and the state of the photoelectric sensor can be easily grasped. If the elapsed time from the previous correction by the correction unit 13d is longer than a predetermined time, the correction unit 13d may display an error on the display unit 15 or forcibly correct the correction. good.

The photoelectric sensor 10 may output the display contents to the controller 20 or another external device instead of or displaying various displays by the display unit 15.

FIG. 3 is a diagram showing a signal value and a threshold value displayed by the photoelectric sensor 10 according to the present embodiment. In the figure, the magnitude of the signal value displayed on the vertical axis is shown, and the time is shown on the horizontal axis.

In this example, after the work 100 arrives at the detection region 10a and the signal value decreases and falls below the threshold value Th, the work 100 passes through and the signal value increases, but the next work is reached until the reference value Rf is reached. The case where 100 arrives, the signal value decreases, and the threshold value falls below Th again is shown.

The photoelectric sensor 10 starts the time counting of the first time T1 when the second work 100 passes and the signal value exceeds the threshold value. By waiting for the passage of the first time T1, the signal value stabilizes at the reference value Rf.

The photoelectric sensor 10 stores the signal value measured by the measuring unit 12 over the second time T2 after the first time T1 has elapsed. The photoelectric sensor 10 stores the signal value as many times as the number of samplings corresponding to the second time T2. In the case of this example, the stored signal value is almost the same as the reference value Rf.

The photoelectric sensor 10 calculates the corrected threshold value by averaging the signal values measured over the second time T2 by the number of samplings and multiplying by a predetermined magnification.

As long as the object does not arrive at the detection region 10a again, the photoelectric sensor 10 may store the signal value measured by the measuring unit 12 over the second time T2 and repeat the correction of the threshold value. In this way, the threshold value can be appropriately corrected by waiting until the object passes through the detection region 10a and the signal value stabilizes.

FIG. 4 is a flowchart of a first example of the correction process executed by the photoelectric sensor 10 according to the present embodiment. The photoelectric sensor 10 projects light onto the detection region 10a (S10), receives light from the detection region 10a, and converts the amount of light received into a signal value (S11). Then, the photoelectric sensor 10 compares the signal value with the threshold value to determine whether or not an object exists in the detection region 10a (S12).

When there is no object in the detection region 10a (S12: NO), the photoelectric sensor 10 measures the time for the first time (S13). Then, when the first time has not elapsed (S14: NO), the photoelectric sensor 10 projects light onto the detection region 10a (S10), receives light from the detection region 10a, and converts the amount of received light into a signal value. Then, a series of processes of comparing the signal value and the threshold value to determine whether or not an object exists in the detection region 10a (S12) is repeated.

Here, if it is determined that an object exists in the detection region 10a after the time counting of the first time is started and before the first time elapses (S12: YES), the photoelectric sensor 10 resets the time counting. (S15), the object detection is repeated again.

On the other hand, when the first time elapses (S14: YES), the photoelectric sensor 10 projects light onto the detection area 10a (S16), receives light from the detection area 10a, converts the amount of received light into a signal value, and converts the light received. The signal value is stored (S17), and the signal value and the threshold value are compared to determine whether or not an object exists in the detection region 10a (S18). When there is no object in the detection region 10a (S18: NO), the photoelectric sensor 10 determines whether or not the signal value has been measured over the second time (S19). When the second time has not elapsed (S19: NO), the photoelectric sensor 10 projects light onto the detection area 10a (S16), receives light from the detection area 10a, converts the amount of received light into a signal value, and converts the light received. A series of processes of storing the signal value (S17), comparing the signal value with the threshold value, and determining whether or not an object exists in the detection region 10a (S18) are repeated.

Here, when it is determined that an object exists in the detection region 10a after the time counting of the second time is started and before the second time elapses (S18: YES), the photoelectric sensor 10 stores the stored signal value. Is reset (S20), the time is reset (S21), and then the object detection is repeated again.

On the other hand, when the second time has elapsed (S19: YES), the photoelectric sensor 10 corrects the threshold value based on the statistical value of the signal value measured over the second time (S22). Finally, the photoelectric sensor 10 corrects the displayed signal value and the threshold value (S23). This completes the first example of the correction process.

FIG. 5 is a flowchart of a second example of the correction process executed by the photoelectric sensor 10 according to the present embodiment. The photoelectric sensor 10 projects light onto the detection region 10a (S30), receives light from the detection region 10a, and converts the amount of light received into a signal value (S31). Then, the photoelectric sensor 10 compares the signal value with the threshold value to determine whether or not an object exists in the detection region 10a (S32).

When there is no object in the detection region 10a (S32: NO), the photoelectric sensor 10 determines whether there is an input for starting the time counting of the first time (S33). When there is no input for starting the time counting in the first time (S33: NO), the photoelectric sensor 10 projects light on the detection area 10a (S30), receives the light from the detection area 10a, and converts the received light amount into a signal value. A series of processes of conversion (S31), comparison of the signal value and the threshold value, and determination of whether or not an object exists in the detection region 10a (S32) are repeated.

On the other hand, when there is no object in the detection region 10a (S32: NO) and there is an input for starting the time counting in the first time (S33: YES), the photoelectric sensor 10 performs the time counting in the first time (S34). .. Then, when the first time has not elapsed (S35: NO), the photoelectric sensor 10 projects light onto the detection region 10a (S30), receives light from the detection region 10a, and converts the amount of received light into a signal value. Then, a series of processes of comparing the signal value and the threshold value to determine whether or not an object exists in the detection region 10a (S32) are repeated.

Here, if it is determined that an object exists in the detection region 10a after the time counting of the first time is started and before the first time elapses (S32: YES), the photoelectric sensor 10 resets the time counting. (S36), the object detection is repeated again.

On the other hand, when the first time has elapsed (S35: YES), the photoelectric sensor 10 projects light onto the detection area 10a (S37), receives light from the detection area 10a, converts the amount of received light into a signal value, and converts the light received. The signal value is stored (S38), and the signal value and the threshold value are compared to determine whether or not an object exists in the detection region 10a (S39). When there is no object in the detection region 10a (S39: NO), the photoelectric sensor 10 determines whether or not the signal value has been measured over the second time (S40). When the second time has not elapsed (S40: NO), the photoelectric sensor 10 projects light onto the detection area 10a (S37), receives light from the detection area 10a, converts the amount of received light into a signal value, and converts the light received. A series of processes of storing the signal value (S38), comparing the signal value with the threshold value, and determining whether or not an object exists in the detection region 10a (S39) are repeated.

Here, when it is determined that an object exists in the detection area 10a after the time counting of the second time is started and before the second time elapses (S39: YES), the photoelectric sensor 10 stores the stored signal value. Is reset (S41), the time is reset (S42), and then the object detection is repeated again.

On the other hand, when the second time has elapsed (S40: YES), the photoelectric sensor 10 corrects the threshold value based on the statistical value of the signal value measured over the second time (S43). Finally, the photoelectric sensor 10 corrects the displayed signal value and the threshold value (S44). This completes the second example of the correction process.

FIG. 6 is a diagram showing a signal value and a threshold value displayed by a conventional photoelectric sensor. In the figure, the magnitude of the signal value displayed on the vertical axis is shown, and the time is shown on the horizontal axis.

In this example, after the work 100 arrives at the detection region 10a and the signal value decreases and falls below the threshold value Th, the work 100 passes through and the signal value increases, but the next work is reached until the reference value Rf is reached. The case where 100 arrives, the signal value decreases, and the threshold value falls below Th again is shown.

The conventional photoelectric sensor may sample a signal value having a threshold value Th or more over the third time T3 and correct the threshold value based on the average value. In the case of this example, the period in which the signal value is equal to or greater than the threshold value in the third time T3 is the first period T3a, the second period T3b, and the third period T3c. In FIG. 6, the integral of the sampled signal values is shown by hatching.

In the conventional photoelectric sensor, the integral (total) of the signal values measured in the first period T3a, the second period T3b, and the third period T3c in which the signal value is equal to or higher than the threshold Th in the third time T3 is obtained, and the number of samplings is obtained. The average value is calculated by dividing by. Then, the corrected threshold value is calculated by multiplying the calculated average value by a predetermined magnification.

In the case of this example, the sampled signal value has a triangular wave shape, and the average value is smaller than the case where the signal value is constant at the reference value Rf. Therefore, the correction corresponding to the case where the light receiving amount is small is performed, and the threshold value is corrected to be inappropriately small.

Further, the conventional photoelectric sensor may be corrected so that the displayed signal value becomes constant. In the case of this example, since the calculated average value is small, the signal value to be displayed is corrected to be large. Therefore, in the conventional photoelectric sensor, the displayed signal value is inappropriately displayed in a large size.

After that, the conventional photoelectric sensor can return to the correct threshold value by sampling the signal value of the threshold value Th or more over the third time T3 and correcting the threshold value based on the average value. Moreover, it is possible to return to the correct display by correcting the signal value to be displayed.

On the other hand, the photoelectric sensor 10 according to the present embodiment waits until the first time elapses after it is determined that the object does not exist in the detection region 10a, and corrects the threshold value based on the signal value measured thereafter. The threshold value can be appropriately corrected by waiting until the object passes through the detection region 10a and the signal value stabilizes.

The embodiments described above are for facilitating the understanding of the present invention, and are not for limiting the interpretation of the present invention. Each element included in the embodiment and its arrangement, material, condition, shape, size, and the like are not limited to those exemplified, and can be appropriately changed. Further, it is possible to partially replace or combine the configurations shown in different embodiments.

[Appendix 1]
A light projecting unit (11) that projects light on the detection area (10a),
A measuring unit (12) that receives light from the detection region (10a) and converts the amount of received light into a signal value.
A determination unit (13a) for determining whether or not an object exists in the detection region (10a) based on the comparison between the signal value and the threshold value.
When it is determined that the object does not exist in the detection area (10a), the timekeeping unit (13b) that performs the timekeeping for the first time and the timekeeping unit (13b)
After the lapse of the first time, the storage unit (13c) for storing the signal value measured by the measurement unit (12) and the storage unit (13c)
A correction unit (13d) that corrects the threshold value based on the signal value stored in the storage unit (13c), and a correction unit (13d).
A photoelectric sensor (10).

10 ... Photoelectric sensor, 10a ... Detection area, 11 ... Light projector, 11a ... Light projector, 11b ... Drive circuit, 12 ... Measurement unit, 12a ... Light receiving element, 12b ... Amplifier, 12c ... Sample / hold circuit, 12d ... A / D converter, 13 ... Processing unit, 13a ... Judgment unit, 13b ... Measuring unit, 13c ... Storage unit, 13d ... Correction unit, 14 ... Input unit, 15 ... Display unit, 20 ... Controller, 50 ... Conveyor device, 100 ... Work, 101 ... First optical fiber, 102 ... Second optical fiber

Claims (7)

A light projecting unit that casts light on the detection area,
A measuring unit that receives light from the detection area and converts the amount of received light into a signal value.
A determination unit that determines whether or not an object exists in the detection region based on a comparison between the signal value and the threshold value.
When it is determined that the object does not exist in the detection area, a timekeeping unit that performs timekeeping for the first time and a timekeeping unit.
After the lapse of the first time, a storage unit that stores the signal value measured by the measuring unit for the second time, and a storage unit.
A correction unit that corrects the threshold value by multiplying the statistical value of the signal value measured by the measurement unit over the second time stored in the storage unit by a predetermined magnification.
A display unit that displays at least one of the ratio of the correction amount of the threshold value and the change of the correction amount when the threshold value for determining whether or not an object exists in the detection area is corrected by the correction unit. ,
A photoelectric sensor equipped with. The timekeeping unit resets the timekeeping when the determination unit determines that the object exists in the detection area before the first time elapses after the start of the timekeeping.
The photoelectric sensor according to claim 1. If the determination unit determines that the object is present in the detection region before the second time elapses, the storage unit resets the signal value referred to by the correction unit.
The photoelectric sensor according to claim 1 or 2. The correction unit corrects the signal value and the threshold value displayed by the display unit.
The photoelectric sensor according to any one of claims 1 to 3. When the correction by the correction unit is performed, the display unit displays that the correction has been performed.
The photoelectric sensor according to claim 4. The display unit displays at least one of the elapsed time from the previous correction by the correction unit and the time until the correction by the correction unit is performed.
The photoelectric sensor according to claim 4 or 5. It also has an input unit that accepts input from the user.
When it is determined that the object does not exist in the detection area and the input is received by the input unit, the timekeeping unit performs the timekeeping for the first time.
The photoelectric sensor according to any one of claims 1 to 6.

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