JP7483205B2 - Photoelectric Sensor - Google Patents

Description

The present invention relates to a photoelectric sensor that detects a bottle-shaped transparent object.

Conventionally, photoelectric sensors have been used as sensors for detecting the presence or absence of an object, which irradiate the object with light and detect the light that passes through the object, detect the light being blocked by the object, or detect the light reflected by the object. Here, the object may be a transparent body.

Regarding photoelectric sensors for detecting transparent objects, for example, the following Patent Document 1 describes a photoelectric sensor that projects linearly polarized light onto a transparent object, receives two or more polarized components of the light that passes through the transparent object separately, and detects the presence or absence of a transparent object based on changes in the amount of light received for each polarized component.

Furthermore, the following Patent Document 2 describes a photoelectric sensor that projects light into an object detection area, receives an instruction for the timing or period for acquiring the amount of received light from the object detection area, and determines a display reference amount that serves as a reference for displaying the amount of received light based on the amount of received light acquired at the timing or period corresponding to the instruction. The photoelectric sensor further calculates a threshold value for determining the presence or absence of an object based on the acquired amount of received light as a value smaller than the display reference amount, converts the amount of received light to a display amount of received light that is zero if the amount of received light is equal to or greater than the display reference amount, and converts the amount of received light to a display amount that increases as the amount of received light decreases if the amount of received light is smaller than the display reference amount, and displays the converted display amount of received light.

JP 2010-107475 A JP 2009-152813 A

In order to detect transparent objects using photoelectric sensors, hardware that is not required when detecting opaque objects may be added, as in the technology described in Patent Document 1, for example. Such photoelectric sensors essentially become dedicated machines for detecting transparent objects, and must be installed separately from photoelectric sensors that detect opaque objects.

In addition, when detecting a transparent object by comparing the amount of received light with a threshold, even if the display is devised as in the technology described in Patent Document 2, for example, setting the threshold can still be difficult.

Therefore, the present invention provides a photoelectric sensor that does not require the setting of a threshold value and can detect a bottle-shaped transparent object with a simple configuration.

A photoelectric sensor according to one aspect of the present disclosure is a photoelectric sensor used to detect a plurality of bottle-shaped transparent objects passing through a detection area in sequence, and includes a light-projecting unit that emits light toward the detection area, a light-receiving unit that is disposed opposite the light-projecting unit across the detection area and acquires a time-series signal value corresponding to the amount of received light, and a determination unit that alternately repeats a process of determining whether the time-series signal value satisfies an arrival condition until the arrival condition is satisfied, and a process of determining whether the time-series signal value satisfies a reset condition until the reset condition is satisfied, where the arrival condition is a condition for identifying that a bottle-shaped transparent object has arrived at the detection area, and the reset condition is a condition for identifying that a bottle-shaped transparent object has left the detection area.

According to this aspect, by alternately repeating a determination of whether the time-series signal value satisfies the arrival condition and a determination of whether the time-series signal value satisfies the reset condition, it is possible to detect a bottle-shaped transparent object with a simple configuration without the need to set a threshold value.

In the above aspect, the arrival condition may be a condition for identifying that the signal value falls below a light-shielded reference value that is smaller than a non-light-shielded reference value that represents a signal value acquired when there is no bottle-shaped transparent object in the detection area, and the reset condition may be a condition for identifying that the magnitude of the time-series signal value is substantially equal to the non-light-shielded reference value over a predetermined period of time.

In the above embodiment, the non-light-shielded reference value may be the average value of the time series signal values acquired when there is no bottle-shaped transparent object in the detection area.

In the above aspect, the reset condition that the magnitude of the time series signal value is substantially equal to the non-shading reference value may be that the absolute value of the difference between the time series signal value and the non-shading reference value is smaller than a predetermined allowable value.

In the above aspect, the arrival condition is a condition for identifying that the time-series signal value exceeds a light-collecting reference value that is greater than a non-light-blocking reference value that represents a signal value acquired when there is no bottle-shaped transparent object in the detection area, and the reset condition may be a condition for identifying that a predetermined dead period has elapsed since it was determined that the arrival condition is satisfied.

In the above aspect, the insensitive period may be longer than the representative value of the first period, which is one continuous period during which all time series signal values greater than the light concentration reference value appear during the period during which the bottle-shaped transparent object is assumed to be passing through the detection area, and shorter than the representative value of the second period from when the arrival condition is satisfied to when the arrival condition is satisfied again after the reset condition is satisfied.

In the above embodiment, the representative value for the first period may be the longest value for the first period, and the representative value for the second period may be the shortest value for the second period.

The present invention provides a photoelectric sensor that does not require a threshold value to be set and can detect a bottle-shaped transparent object with a simple configuration.

1 is a diagram showing an overview of a detection system including a photoelectric sensor according to a first embodiment of the present invention. 1 is a diagram showing a configuration of a photoelectric sensor according to an embodiment of the present invention; FIG. 2 is a diagram illustrating an example of the configuration of a processing unit of the photoelectric sensor according to the embodiment. 1A and 1B are diagrams illustrating a state in which a bottle-shaped transparent object approaches the photoelectric sensor according to the embodiment. 1 is a diagram showing a state in which a part of light emitted from the photoelectric sensor according to the embodiment is reflected and received by a bottle-shaped transparent body. FIG. 1 is a diagram showing a state in which a part of the light emitted from the photoelectric sensor according to the embodiment is reflected by a bottle-shaped transparent body and not received. FIG. 1 is a diagram showing how light emitted from a photoelectric sensor according to the embodiment is collected by a bottle-shaped transparent body. FIG. 5A and 5B are diagrams illustrating an example of the amount of received light measured by the photoelectric sensor according to the embodiment. 5 is a flowchart of a process for detecting a bottle-shaped transparent object, which is executed by a photoelectric sensor according to the present embodiment. 5 is a flowchart of an automatic adjustment process executed by the photoelectric sensor according to the present embodiment. 6 is a flowchart showing details of a process for detecting a bottle-shaped transparent object executed by a photoelectric sensor according to the present embodiment. 11 is a diagram showing an example of the amount of received light measured by a photoelectric sensor according to a second embodiment of the present invention; FIG. 5 is a flowchart of an automatic adjustment process executed by the photoelectric sensor according to the present embodiment. 6 is a flowchart showing details of a process for detecting a bottle-shaped transparent object executed by a photoelectric sensor according to the present embodiment.

Below, an embodiment of one aspect of the present invention (hereinafter, referred to as "this embodiment") will be described with reference to the drawings. Note that in each drawing, parts with the same reference numerals have the same or similar configurations.

[First embodiment]
[Configuration example]
An example of the configuration of a photoelectric sensor 10 according to a first embodiment of the present invention will be described with reference to Figures 1 and 2. Figure 1 is a diagram showing an overview of a detection system 1 including the photoelectric sensor 10 according to the first embodiment. The detection system 1 includes the photoelectric sensor 10, a controller 20, a computer 30, a robot 40, and a transport device 50.

The photoelectric sensor 10 is a device that detects the arrival of the bottle-shaped transparent body 100 in the detection area 10a based on a signal value corresponding to a physical quantity whose value changes depending on whether the bottle-shaped transparent body 100 has arrived in the detection area 10a. The photoelectric sensor 10 may be a transmission type photoelectric sensor. In FIG. 1, the photoelectric sensor 10 includes a light-projecting optical fiber 101 and a light-receiving optical fiber 102 arranged for transmission type detection. When the bottle-shaped transparent body 100 arrives in the detection area 10a of the photoelectric sensor 10, the amount of light detected by the photoelectric sensor 10 changes.

The bottle-shaped transparent body 100 is an object to be detected by the photoelectric sensor 10, and is a transparent body having an approximately cylindrical or prismatic shape. The bottle-shaped transparent body 100 may be, for example, a finished product being manufactured, or an unfinished product such as a part.

The controller 20 controls the robot 40 and the transport device 50. The controller 20 may be configured, for example, as a PLC (Programmable Logic Controller). The controller 20 detects the arrival of the bottle-shaped transparent object 100 based on the output from the photoelectric sensor 10, and controls the robot 40.

The computer 30 configures the photoelectric sensor 10, the controller 20, and the robot 40. The computer 30 also obtains from the controller 20 the results of the control performed by the controller 20.

The robot 40 operates and processes the bottle-shaped transparent body 100 according to the control of the controller 20. For example, the robot 40 may pick up the bottle-shaped transparent body 100 and move it to another location, or cut or assemble the bottle-shaped transparent body 100.

The conveying device 50 is a device that conveys the bottle-shaped transparent body 100 according to the control of the controller 20. The conveying device 50 may be, for example, a belt conveyor, and may convey the bottle-shaped transparent body 100 at a speed set by the controller 20.

Figure 2 is a diagram showing the configuration of the photoelectric sensor 10 according to this embodiment. The photoelectric sensor 10 includes a light-emitting unit 11, a light-receiving unit 12, a processing unit 13, an operation unit 14, and an output unit 15.

<Light projection section>
The light-projecting unit 11 emits light toward the detection area 10a where the bottle-shaped transparent body 100 arrives. The light-projecting unit 11 may include a light-projecting element 11a and a driving circuit 11b. The light-projecting element 11a may be composed of an LED (Light Emitting Diode) or a laser diode, and the driving circuit 11b controls a current for causing the light-projecting element 11a to emit light. The driving circuit 11b may cause the light-projecting element 11a to emit pulses intermittently, for example, at a period of 0.1 ms. The light emitted from the light-projecting element 11a may be irradiated onto the detection area 10a via a lens (not shown) or the light-projecting optical fiber 101 of FIG. 1.

<Light receiving section>
The light receiving unit 12 is disposed opposite the light projecting unit 11 across the detection area 10a, and acquires a time series signal value corresponding to the amount of light received. The light receiving unit 12 may include 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 configured with a photodiode, and converts the amount of light received into an electrical output signal. The light receiving unit 12 may cause light reflected or transmitted through the detection area 10a to enter the light receiving element 12a through a lens (not shown) or the light receiving optical fiber 102 of FIG. 1. 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 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 the amount of light received, which is a digital value. The light receiving section 12 is an example of a measurement section that receives light from the detection region 10a and sequentially converts the amount of received light into a signal value.

<Processing section>
The processing unit 13 includes an operation control unit 13a, a memory 13b, and a determination unit 13c. The processing unit 13 may be configured as a computer including, for example, a microprocessor, a memory, and a program stored in the memory.

The operation control unit 13a may control the overall operation of the photoelectric sensor 10 in addition to the determination process described below.

The memory 13b stores time-series signal values corresponding to the amount of received light acquired by the light receiving unit 12. The memory 13b may be composed of any storage medium, for example, a FIFO (First In First Out) memory.

The determination unit 13c alternately repeats a process of determining whether the time-series signal value satisfies the arrival condition until the arrival condition is satisfied, and a process of determining whether the time-series signal value satisfies the reset condition until the reset condition is satisfied. Here, the arrival condition is a condition for identifying that the bottle-shaped transparent body 100 has arrived at the detection area 10a. Also, the reset condition is a condition for identifying that the bottle-shaped transparent body 100 has left the detection area 10a.

<Operation section>
The operation unit 14 is for operating the photoelectric sensor 10 and may include an operation switch, a display, etc.

<Output section>
The output unit 15 outputs various data including the judgment result by the judgment unit 13c. The output unit 15 may most simply output the binary result of the judgment by the judgment unit 13c. When the judgment unit 13c judges that the arrival condition is satisfied, the output unit 15 may output a signal indicating that the bottle-shaped transparent body 100 has arrived at the detection area 10a. When the judgment unit 13c judges that the reset condition is satisfied, the output unit 15 may output a signal indicating that the bottle-shaped transparent body 100 has escaped from the detection area 10a. The output unit 15 may have a communication function capable of outputting a large amount of data.

Figure 3 is a diagram explaining the operation of the photoelectric sensor 10 according to the first embodiment. In the first period, the processing unit 13 updates the signal value stored in the memory 13b and stores the digital value of the amount of received light output from the A/D converter 12d.

The first period for updating the memory 13b may be the same as the period (referred to as the second period) of the pulse emission of the light projector 11 and the conversion by the A/D converter 12d, or may be different, such as an integer multiple of the second period. For example, the second period may be fixed to a value (e.g., 0.1 ms) specific to the photoelectric sensor 10. The first period may be set from the computer 30 shown in FIG. 1 via the controller 20. The first period must be determined so that the range of signal value waveforms to be processed simultaneously fits within the memory 13b. The first period is often longer than the second period, and may be, for example, 1 ms.

The determination unit 13c determines whether the signal value stored in the memory 13b satisfies the arrival condition or the reset condition in the first period, and outputs the determination result to the operation control unit 13a in the first period.

The arrival condition may be a condition for identifying that the signal value falls below a light-shielding reference value that is smaller than a non-light-shielding reference value that represents a signal value acquired when the bottle-shaped transparent body 100 is not present in the detection area 10a. Specifically, as a "light-shielding reference value smaller than the non-light-shielding reference value", for example, a light-shielding reference value that is 50% or less of the non-light-shielding reference value, a light-shielding reference value that is 20% or less of the non-light-shielding reference value, or a light-shielding reference value that is 10% or less of the non-light-shielding reference value may be appropriately adopted.

The non-light-shielding reference value may be the average value of the time-series signal values acquired when there is no bottle-shaped transparent body 100 in the detection area 10a. However, the non-light-shielding reference value may also be any statistical value of the time-series signal values acquired when there is no bottle-shaped transparent body in the detection area 10a.

The reset condition may be a condition for identifying whether the magnitude of the time series signal value is substantially equal to the non-shaded reference value over a specified period of time. Here, "the magnitude of the time series signal value is substantially equal to the non-shaded reference value over a specified period of time" means that the magnitude of the time series signal value is equal to the non-shaded reference value over the specified period of time, except for the degree of difference caused by fluctuations in the signal value due to the effects of optical and electrical disturbances and internal noise.

In the reset condition, the magnitude of the time series signal value is substantially equal to the non-shading reference value, which may mean that the absolute value of the difference between the time series signal value and the non-shading reference value is smaller than a predetermined tolerance. Here, the predetermined tolerance may be, for example, a value obtained by multiplying the standard deviation of the time series signal value acquired when there is no bottle-shaped transparent body 100 in the detection area 10a by a predetermined number.

Figure 4a is a diagram showing a bottle-shaped transparent body 100 approaching the photoelectric sensor 10 according to this embodiment. As shown in the figure, when the bottle-shaped transparent body 100 is not in the detection area 10a, part of the light emitted from the light-emitting unit 11 is received by the light-receiving unit 12.

Figure 4b is a diagram showing how part of the light emitted from the photoelectric sensor 10 according to this embodiment is reflected and received by the bottle-shaped transparent body 100. As shown in the figure, when the bottle-shaped transparent body 100 approaches the area between the light-emitting unit 11 and the light-receiving unit 12, part of the light emitted from the light-emitting unit 11 is reflected by the bottle-shaped transparent body 100, and the amount of light received temporarily increases compared to when the bottle-shaped transparent body 100 is not present in the detection area 10a.

Figure 4c is a diagram showing how part of the light emitted from the photoelectric sensor 10 according to this embodiment is reflected by the bottle-shaped transparent body 100 and not received. As shown in the figure, when the bottle-shaped transparent body 100 approaches further into the area between the light-projecting unit 11 and the light-receiving unit 12, most of the light emitted from the light-projecting unit 11 is reflected by the bottle-shaped transparent body 100, and almost no light is incident on the light-receiving unit 12. At this time, the amount of received light is significantly lower than when the bottle-shaped transparent body 100 is not present in the detection area 10a.

Figure 4d is a diagram showing how light emitted from the photoelectric sensor 10 according to this embodiment is collected by the bottle-shaped transparent body 100. As shown in the figure, when the bottle-shaped transparent body 100 enters the area between the light-emitting unit 11 and the light-receiving unit 12, the light emitted from the light-emitting unit 11 is collected by the bottle-shaped transparent body 100, and the light enters the light-receiving unit 12. At this time, the amount of light received is greater than when the bottle-shaped transparent body 100 is not present in the detection area 10a.

Figure 5 is a diagram showing an example of the amount of received light (time-series signal value) measured by the photoelectric sensor 10 according to this embodiment. The figure includes a first region A showing the amount of received light when the bottle-shaped transparent body 100 is not present in the detection area 10a, a second region B showing the timing when the amount of received light falls below the light-blocking reference value Z, a third region C showing the timing when the amount of received light fluctuates and falls below the light-blocking reference value Z again, and a fourth region D showing the amount of received light after the bottle-shaped transparent body 100 escapes from the detection area 10a.

When there is no bottle-shaped transparent body 100 in the detection area 10a, as in the first area A, the amount of received light is substantially equal to the non-light-shielded reference value over a predetermined period of time. Here, the non-light-shielded reference value is the average value of the time series signal values acquired when there is no bottle-shaped transparent body 100 in the detection area 10a.

When the bottle-shaped transparent body 100 approaches the detection area 10a and the light emitted from the light-projecting unit 11 is reflected, the amount of received light drops sharply and falls below the light-blocking reference value Z. The photoelectric sensor 10 determines that the arrival condition is met at the timing of area B when the amount of received light falls below the light-blocking reference value Z.

Then, the light emitted from the light-projecting unit 11 is concentrated by the bottle-shaped transparent body 100, causing the amount of received light to temporarily exceed the non-light-shielding reference value. However, the amount of received light fluctuates wildly, and falls below the light-shielding reference value Z again at the timing of the third region C. For this reason, if an attempt is made to detect the arrival of the bottle-shaped transparent body 100 based only on the arrival conditions, there is a risk that multiple detections will be performed on one bottle-shaped transparent body 100.

The photoelectric sensor 10 according to this embodiment determines that the arrival condition is met at the timing of the second region B, and then performs a process of determining whether or not the reset condition is met until the reset condition is met. Here, the reset condition is that the magnitude of the time series signal value is substantially equal to the non-light-blocking reference value for a predetermined period of time, and the reset condition is met at the timing of the fourth region D.

In this way, the photoelectric sensor 10 according to this embodiment can detect the bottle-shaped transparent body 100 with a simple configuration without the need to set a threshold value by alternately repeating whether the time-series signal value satisfies the arrival condition and whether it satisfies the reset condition. In addition, by alternately repeating whether the time-series signal value satisfies the arrival condition and whether it satisfies the reset condition, erroneous detection of the bottle-shaped transparent body 100 can be prevented.

Figure 6 is a flowchart of the process of detecting the bottle-shaped transparent body 100 executed by the photoelectric sensor 10 according to this embodiment. First, the photoelectric sensor 10 performs an automatic adjustment operation (S10). The details of the automatic adjustment operation will be explained in detail using the next figure. Note that the automatic adjustment operation only needs to be performed once the first time the power to the photoelectric sensor 10 is turned on, and if the process is interrupted and then resumed, the automatic adjustment operation may be omitted.

Next, the photoelectric sensor 10 performs a process of waiting for detection of the arrival condition (S11). For example, the photoelectric sensor 10 waits until a condition is met for identifying that the signal value falls below a light-shielded reference value that is smaller than a non-light-shielded reference value that represents a signal value acquired when the bottle-shaped transparent body 100 is not present in the detection area 10a.

When the arrival condition is detected, the photoelectric sensor 10 outputs the detection (S12). The detection may be output in any manner, for example, by turning on an indicator light or outputting a detection signal to the outside.

Thereafter, the photoelectric sensor 10 performs a process of waiting for detection of a reset condition (S13). For example, the photoelectric sensor 10 waits for a condition to be satisfied for identifying that the magnitude of the time-series signal value is substantially equal to the non-shaded reference value for a predetermined period of time.

If the reset condition is detected and the power is not turned off (S14: NO), the photoelectric sensor 10 executes steps S11 to S13 again. On the other hand, if the power is turned off (S14: YES), the process of detecting the bottle-shaped transparent body 100 ends.

Figure 7 is a flowchart of the automatic adjustment process executed by the photoelectric sensor 10 according to this embodiment. This figure shows the details of the automatic adjustment operation (S10) in Figure 6. The automatic adjustment operation (S10) is performed in a state where the bottle-shaped transparent body 100 is not present in the detection area 10a.

First, the photoelectric sensor 10 adjusts the amount of light emitted and the gain of the light receiving amplifier (S101). Then, the photoelectric sensor 10 acquires a plurality of signal values (S102) and calculates the average value of the plurality of signal values (S103). The photoelectric sensor 10 also calculates the standard deviation of the plurality of signal values (S104).

Finally, the photoelectric sensor 10 sets a non-shading reference value and a tolerance value based on the average value and the standard deviation (S105). For example, the photoelectric sensor 10 may set the non-shading reference value to the average value, and set the tolerance value for determining whether the magnitude of the time series signal value under the reset condition is substantially equal to the non-shading reference value to a constant multiple of the standard deviation.

Figure 8 is a flowchart showing the details of the process of detecting the bottle-shaped transparent body 100 executed by the photoelectric sensor 10 according to this embodiment. This figure shows the details of processes S11 to S13 among the processes shown in Figure 6. The process of waiting for arrival condition detection (S11) includes a process of acquiring a signal value and storing it in memory 13b (S111) and a process of determining whether the signal value has fallen below the light-blocking reference value (S112). If the photoelectric sensor 10 determines that the latest signal value has fallen below the light-blocking reference value (S112: YES), it outputs the fact of detection (S12). On the other hand, if the signal value is not below the light-blocking reference value (S112: NO), it acquires a new signal value and stores it in memory 13b (S111).

The process of waiting for detection of the reset condition (S13) includes a process of acquiring a signal value and storing it in memory 13b (S131) and a process of determining whether the signal value is substantially equal to the non-shaded reference value over a predetermined period (S132). Whether the signal value is substantially equal to the non-shaded reference value over a predetermined period may be determined by whether the absolute value of the difference between the signal value and the non-shaded reference value over the predetermined period is smaller than a tolerance value. When the photoelectric sensor 10 determines that the signal value is substantially equal to the non-shaded reference value over the predetermined period (S132: YES), it determines that the reset condition is satisfied and waits for detection of the arrival condition again (see FIG. 6). On the other hand, when it is not determined that the signal value is substantially equal to the non-shaded reference value over the predetermined period (S132: NO), it acquires a new signal value and stores it in memory 13b (S131).

[Second embodiment]
9 is a diagram showing an example of the amount of received light measured by the photoelectric sensor 10 according to the second embodiment of the present invention. The physical configuration of the photoelectric sensor 10 according to this embodiment may be the same as the physical configuration of the photoelectric sensor 10 according to the first embodiment, but the arrival condition and reset condition used by the determination unit 13c of the photoelectric sensor 10 according to this embodiment are different from the arrival condition and reset condition used by the determination unit 13c of the photoelectric sensor 10 according to the first embodiment.

The arrival condition used by the determination unit 13c of the photoelectric sensor 10 according to this embodiment is a condition for identifying that the time series signal value exceeds a light collection reference value that is greater than a non-light blocking reference value that represents a signal value acquired when the bottle-shaped transparent body 100 is not present in the detection area 10a. The reset condition used by the determination unit 13c of the photoelectric sensor 10 according to this embodiment is a condition for identifying that a predetermined insensitive period has elapsed since it was determined that the arrival condition is satisfied.

Here, the non-light-shielding reference value representing the signal values acquired when there is no bottle-shaped transparent body 100 in the detection area 10a may be the average value of the signal values acquired when there is no bottle-shaped transparent body 100 in the detection area 10a. The light-gathering reference value may be the average value of the signal values acquired when there is no bottle-shaped transparent body 100 in the detection area 10a plus a constant multiple of the standard deviation. In FIG. 9, μ+3σ is exemplified as the light-gathering reference value. Here, μ is the average value of the signal values acquired when there is no bottle-shaped transparent body 100 in the detection area 10a, and σ is the standard deviation of the signal values acquired when there is no bottle-shaped transparent body 100 in the detection area 10a.

The dead period may be longer than the representative value of the first period, which is a continuous period during which all time series signal values greater than the light collection reference value appear during the period during which the bottle-shaped transparent body 100 is assumed to be passing through the detection area 10a, and shorter than the representative value of the second period from when the arrival condition is satisfied, when the reset condition is satisfied, until when the arrival condition is satisfied again. In FIG. 9, T1 is shown as the representative value of the first period, which is a continuous period during which all time series signal values greater than the light collection reference value appear. Also, T2 is shown as the representative value of the second period from when the arrival condition is satisfied, when the reset condition is satisfied, until when the arrival condition is satisfied again. Then, the dead period T is shown. The dead period T is a period longer than T1 and shorter than T2.

The period during which the bottle-shaped transparent body 100 is assumed to be passing through the detection area 10a may specifically be, for example, the period between the period during which the time-series signal value continues to be substantially equal to the non-light-shielded reference value and the next same period.

The representative value of the first period may be the longest value of the first period, and the representative value of the second period may be the shortest value of the second period. The photoelectric sensor 10 may store the first period and the second period when multiple bottle-shaped transparent bodies 100 are detected, and may use the longest value of the first period measured multiple times as the representative value of the first period, and the shortest value of the second period measured multiple times as the representative value of the second period.

The photoelectric sensor 10 according to this embodiment determines that the arrival condition is met at the timing of the fifth region E when the signal value exceeds the light collection reference value (μ+3σ). After that, the photoelectric sensor 10 determines that the reset condition is met if a predetermined dead period T has elapsed since it was determined that the arrival condition was met, and again determines whether the arrival condition is met.

Figure 10 is a flowchart of the automatic adjustment process executed by the photoelectric sensor 10 according to this embodiment. The automatic adjustment process is executed before the process of detecting the bottle-shaped transparent body 100 is executed by the photoelectric sensor 10, and it is sufficient to execute it once when the power is turned on. The automatic adjustment process is performed by detecting multiple bottle-shaped transparent bodies 100 on a trial basis.

First, the photoelectric sensor 10 adjusts the amount of light emitted and the gain of the light receiving amplifier (S101). Then, the photoelectric sensor 10 acquires a plurality of signal values (S102) and calculates the average value of the plurality of signal values (S103). The photoelectric sensor 10 also calculates the standard deviation of the plurality of signal values (S104). After that, the photoelectric sensor 10 sets the light concentration reference value to the average value plus a predetermined number times the standard deviation (S105).

The photoelectric sensor 10 also calculates a representative value for a first period, which is one continuous period during which all time series signal values greater than the light concentration reference value appear (S106). Furthermore, the photoelectric sensor 10 calculates a representative value for a second period from when the arrival condition is satisfied, to when the reset condition is satisfied, and then until the arrival condition is satisfied again (S107). Finally, the photoelectric sensor 10 sets the dead period to be longer than the representative value for the first period and shorter than the representative value for the second period (S108).

Figure 11 is a flowchart showing the details of the process of detecting the bottle-shaped transparent body 100 executed by the photoelectric sensor 10 according to this embodiment. The photoelectric sensor 10 first performs a process of waiting for the arrival condition to be detected (S11). The process of waiting for the arrival condition to be detected (S11) includes a process of acquiring a signal value and storing it in the memory 13b (S115) and a process of determining whether the signal value has exceeded the light concentration reference value (S116). If the photoelectric sensor 10 determines that the latest signal value has exceeded the light concentration reference value (S116: YES), it outputs the fact of detection (S12). On the other hand, if the signal value does not exceed the light concentration reference value (S116: NO), it acquires a new signal value and stores it in the memory 13b (S115).

Then, the photoelectric sensor 10 performs a process of waiting for detection of the reset condition (S13). The process of waiting for detection of the reset condition (S13) includes a process of determining whether or not a predetermined insensitive period has elapsed (S133). If the predetermined insensitive period has elapsed (S133: YES), the photoelectric sensor 10 determines that the reset condition has been satisfied, and again waits for detection of the arrival condition. On the other hand, if the predetermined insensitive period has not elapsed (S133: NO), the photoelectric sensor 10 waits for the insensitive period to elapse.

The above-described embodiments are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The elements of the embodiments, as well as their arrangement, materials, conditions, shapes, sizes, etc., are not limited to those exemplified, and may be modified as appropriate. In addition, configurations shown in different embodiments may be partially substituted or combined.

[Appendix 1]
A photoelectric sensor (10) used to detect a plurality of bottle-shaped transparent objects (100) passing through a detection area (10a) in sequence,
A light projecting unit (11) that emits light toward the detection area (10a);
a light receiving unit (12) disposed opposite the light projecting unit (11) across the detection area (10a) and configured to acquire a time-series signal value corresponding to the amount of received light;
a determination unit (13c) that alternately repeats a process of determining whether or not the time-series signal value satisfies an arrival condition until the arrival condition is satisfied, and a process of determining whether or not the time-series signal value satisfies a reset condition until the reset condition is satisfied,
The arrival condition is a condition for identifying that the bottle-shaped transparent object (100) has arrived at the detection area (10a),
The reset condition is a condition for identifying that the bottle-shaped transparent body (100) has escaped from the detection area (10a).
A photoelectric sensor (10).

[Appendix 2]
The arrival condition is a condition for identifying that the signal value falls below a light-shielded reference value that is smaller than a non-light-shielded reference value that represents a signal value acquired in a state in which the bottle-shaped transparent body (100) is not present in the detection area (10a),
the reset condition is a condition for identifying whether the magnitude of the time series signal value is substantially equal to the non-shaded reference value over a predetermined period of time;
2. The photoelectric sensor (10) of claim 1.

[Appendix 3]
The non-light-shielded reference value is an average value of the time-series signal values acquired when the bottle-shaped transparent body (100) is not present in the detection area (10a).
3. The photoelectric sensor (10) of claim 2.

[Appendix 4]
In the reset condition, the magnitude of the time-series signal value being substantially equal to the non-light-shielded reference value means that the absolute value of the difference between the time-series signal value and the non-light-shielded reference value is smaller than a predetermined allowable value.
4. The photoelectric sensor (10) according to claim 2 or 3.

[Appendix 5]
The arrival condition is a condition for identifying that the time-series signal value exceeds a light-collecting reference value that is greater than a non-light-shielded reference value that represents a signal value acquired in a state in which the bottle-shaped transparent body (100) is not present in the detection area (10a),
The reset condition is a condition for identifying that a predetermined insensitive period has elapsed since it was determined that the arrival condition is satisfied.
2. The photoelectric sensor (10) of claim 1.

[Appendix 6]
the insensitive period is longer than a representative value of a first period, which is one continuous period during which all of the signal values in the time series that are greater than the light concentration reference value appear during a period during which the bottle-shaped transparent body (100) is assumed to be passing through the detection area (10a), and is shorter than a representative value of a second period from when the arrival condition is satisfied to when the arrival condition is satisfied again after the reset condition is satisfied.
6. The photoelectric sensor (10) according to claim 5.

[Appendix 7]
the representative value of the first period is the longest value of the first period, and the representative value of the second period is the shortest value of the second period;
7. The photoelectric sensor (10) according to claim 6.

1...detection system, 10...photoelectric sensor, 10a...detection area, 11...light projecting section, 11a...light projecting element, 11b...drive circuit, 12...light receiving section, 12a...light receiving element, 12b...amplifier, 12c...sample/hold circuit, 12d...A/D converter, 13...processing section, 13a...operation control section, 13b...FIFO memory, 13c...determination section, 14...operation section, 15...output section, 20...controller, 30...computer, 40...robot, 50...transport device, 100...bottle-shaped transparent body, 101...light projecting optical fiber, 102...light receiving optical fiber

Claims (7)

A photoelectric sensor used to detect a plurality of bottle-shaped transparent objects passing through a detection area in sequence,
a light projecting unit that projects light toward the detection area;
a light receiving unit disposed opposite the light projecting unit across the detection area and configured to obtain a time-series signal value corresponding to the amount of received light;
a determination unit that alternately repeats a process of determining whether or not the time-series signal value satisfies an arrival condition until the arrival condition is satisfied, and a process of determining whether or not the time-series signal value satisfies a reset condition until the reset condition is satisfied;
the arrival condition is a condition for identifying that the bottle-shaped transparent object has arrived in the detection area,
the reset condition is a condition for identifying that the bottle-shaped transparent object has escaped from the detection area and a condition for identifying that the magnitude of the time-series signal value is substantially equal to a non-shaded reference value representing a signal value acquired in a state in which the bottle-shaped transparent object is not present in the detection area for a predetermined period of time;
Photoelectric sensor. The arrival condition is a condition for identifying whether the light intensity falls below a shaded reference value that is smaller than the non- shaded reference value.
The photoelectric sensor according to claim 1 . The non-light-shielded reference value is an average value of the time-series signal values acquired in a state in which the bottle-shaped transparent object is not present in the detection area.
The photoelectric sensor according to claim 2. In the reset condition, the magnitude of the time-series signal value being substantially equal to the non-light-shielded reference value means that the absolute value of the difference between the time-series signal value and the non-light-shielded reference value is smaller than a predetermined allowable value.
The photoelectric sensor according to claim 2 or 3. the arrival condition is a condition for identifying whether the time-series signal value exceeds a light-collected reference value that is greater than the non -light-shaded reference value;
The reset condition is a condition for identifying that a predetermined insensitive period has elapsed since it was determined that the arrival condition is satisfied.
The photoelectric sensor according to claim 1 . the insensitive period is longer than a representative value of a first period, which is one continuous period during which all of the signal values in the time series that are greater than the light concentration reference value appear during a period during which the bottle-shaped transparent object is assumed to be passing through the detection area, and is shorter than a representative value of a second period from when the arrival condition is satisfied to when the arrival condition is satisfied again after the reset condition is satisfied.
The photoelectric sensor according to claim 5 . the representative value of the first period is the longest value of the first period, and the representative value of the second period is the shortest value of the second period;
The photoelectric sensor according to claim 6.