JP7734348B2 - Displacement Sensor - Google Patents

Description

This disclosure relates to a displacement sensor.

Conventionally, a known displacement sensor of this type uses the principle of triangulation to measure the displacement, surface shape, etc. of an object being measured (see, for example, Patent Document 1). This type of displacement sensor irradiates the object with light from a light-emitting unit, receives the light reflected from the object with a light-receiving unit such as an image sensor, and outputs a measurement value signal obtained from the received light signal to measure the displacement, surface shape, etc. of the object.

JP 2013-011566 A

However, when the reflectance of an object changes suddenly at each measurement location, the amount of received light finally stabilizes after multiple feedback adjustments, making it necessary to perform measurements after multiple feedback adjustments. However, simply performing multiple feedback adjustments takes time until the amount of received light stabilizes, and there is a risk that accurate measurement results may not be obtained during this transitional period.

A displacement sensor according to one aspect of the present disclosure includes a light-projecting unit including a light-projecting element that projects light onto an object to be detected and a light-projection control circuit that controls the light-projecting element; an image sensor that receives light reflected from the object to be detected; and a light-receiving control circuit that controls the image sensor. The light-receiving unit outputs an image signal corresponding to the reflected light received by the image sensor. A control unit performs feedback control to adjust at least one of manipulated variables including the amount of light projected by the light-projecting element and the amount of light received by the image sensor based on the light-receiving level of the image signal. A memory unit stores an adjustment value for the manipulated variable. The control unit performs the feedback control when the light-receiving level is within a first range, and adjusts the manipulated variable using the adjustment value stored in the memory unit when the light-receiving level is equal to or greater than a first level greater than the first range or equal to or less than a second level less than the first range.

One aspect of the present disclosure provides a displacement sensor that can shorten adjustment time.

FIG. 1 is a block diagram showing the electrical configuration of a displacement sensor. FIG. 2 is a flowchart of the feedback control of the amount of projected and received light. FIG. 3 is a flowchart of the tuning process for the amount of projected and received light. FIG. 4 is an explanatory diagram showing the operation of the displacement sensor. FIG. 5 is an explanatory diagram showing the operation of the displacement sensor. FIG. 6 is an explanatory diagram showing the processing of the displacement sensor. FIG. 7 is an explanatory diagram showing the processing of the displacement sensor. FIG. 8 is an explanatory diagram showing the processing of the displacement sensor. FIG. 9 is an explanatory diagram showing the processing of the displacement sensor. FIG. 10 is an explanatory diagram showing the processing of the displacement sensor. FIG. 11 is an explanatory diagram showing the processing of the displacement sensor.

An embodiment will be described below with reference to the accompanying drawings.
The displacement sensor 10 shown in FIG. 1 projects a detection light L1 onto an object W to be detected, and detects the displacement, shape, etc. of the object W to be detected.

As shown in FIG. 1, the displacement sensor 10 includes a light projecting unit 11, a light receiving unit 12, a control unit 13, a storage unit 14, and an input/output unit 15.
The light-projecting unit 11 includes a light-projecting element 11a and a light-projection control circuit 11b. The light-receiving unit 12 includes an image sensor 12a and a light-receiving control circuit 12b. The light-projecting element 11a projects detection light L1 toward the object to be detected W. The light-projecting element 11a is, for example, a laser diode. The light-projection control circuit 11b controls the light-projecting element 11a. The detection light L1 projected from the light-projecting element 11a is reflected by the object to be detected W. The reflected light L2 is incident on the image sensor 12a of the light-receiving unit 12.

As shown in Figures 4 and 5, the image sensor 12a has multiple light-receiving cells 12s. In this embodiment, the image sensor 12a is a CMOS image sensor. Note that the image sensor 12a can be a device with multiple light-receiving cells 12s, such as a CCD image sensor or PSD. The image sensor 12a converts the reflected light L2 received by each light-receiving cell 12s into an electrical signal with a voltage level corresponding to the amount of reflected light L2 received, and outputs the electrical signal.

The light-receiving control circuit 12b controls the image sensor 12a. The light-receiving control circuit 12b generates an electrical signal output from the image sensor 12a, i.e., an image signal S12 corresponding to the amount of reflected light L2 received by the image sensor 12a. The light-receiving unit 12 outputs the image signal S12. The image signal S12 includes the light-receiving level of each light-receiving cell 12s of the image sensor 12a. The light-receiving level is a value proportional to the amount of light received by each light-receiving cell 12s. In other words, the image signal S12 is a time-series signal (light-receiving waveform) corresponding to the distribution of the amount of light received on the light-receiving surface of the image sensor 12a.

The control unit 13 detects the light-receiving center position of the reflected light L2 at the image sensor 12a based on the image signal S12 from the light-receiving unit 12. The control unit 13 then measures the displacement of the detected object W from that light-receiving center position.

As shown in FIG. 4, the displacement sensor 10 has a light-projecting lens 21 and a light-receiving lens 22. Detection light L1 projected from the light-projecting element 11a passes through the light-projecting lens 21 and is irradiated onto the object W to be detected. Reflected light L2 reflected by the object W passes through the light-receiving lens 22 and is incident on the image sensor 12a. The image sensor 12a has multiple light-receiving cells 12s.

The control unit 13 detects the light receiving center position O1 of the reflected light L2 from the object W to be detected, shown by the solid line. For example, the control unit 13 detects the position of the light receiving cell 12s with the maximum light receiving level (amount of received light) in the image signal S12 as the light receiving center position O1. Furthermore, if the amount of received light of multiple light receiving cells 12s is a saturated value in the image signal S12, the control unit 13 detects the position of the multiple light receiving cells 12s with the saturated value as the light receiving center position O1.

Next, if the object W is displaced to the position indicated by the dashed line, the reflected light L2 from the object W enters the image sensor 12a at a different position than the reflected light L2 indicated by the solid line. In other words, the light-receiving center position O2 changes depending on the distance from the displacement sensor 10 to the surface of the object W. The control unit 13 detects the light-receiving center position O2 of this reflected light L2. The difference between these light-receiving center positions O1 and O2 corresponds to the amount of displacement of the object W. Note that by moving the object W relative to the displacement sensor 10 in a direction perpendicular to the optical axis of the detection light L1, it is also possible to detect the presence or absence of the object W, the surface shape of the object W, etc.

The input/output unit 15 is configured to be able to communicate with external devices connected to the displacement sensor 10. The communication may be wired or wireless. The input/output unit 15 transmits, for example, the detection results of the control unit 13 to the external device. The input/output unit 15 also receives control signals, setting values, etc. for the displacement sensor 10.

The memory unit 14 stores various information when various processing operations of the control unit 13 are performed. The information stored in the memory unit 14 includes set values and changed values for the displacement sensor 10. The set values and changed values are values for adjusting the amount of light emitted by the light-emitting element 11a and the amount of light received by the image sensor 12a. Values for adjusting the amount of light emitted include, for example, the light-emitting time for driving the light-emitting element 11a and the drive voltage supplied to the light-emitting element 11a. Values for adjusting the amount of received light include, for example, the exposure time for the light-receiving unit 12 and the amplification factor for amplifying the signal output from the light-receiving unit 12. The set values and changed values also include initial values, values received from external devices, values set by teaching processing, etc.

The control unit 13 has the function of performing feedback control of the amount of light emitted and received, adjusting the amount of light emitted (light emission time) of the light-emitting element 11a and the amount of light received (exposure time) of image sensor 12a based on the image signal S12 from image sensor 12a. The amount of reflected light L2 received by image sensor 12a changes depending on the state of reflection on the surface of the object W. As described above, the control unit 13 detects the light-receiving center position at which reflected light L2 is received by image sensor 12a. If the amount of light received by image sensor 12a is high or low, an error may occur in the detected light-receiving center position. For this reason, the control unit 13 adjusts the amount of light emitted and received so that the amount of light received falls within an optimal value range (reference range).

The amount of light emitted can be adjusted by the light-emitting time for which the light-emitting element 11a emits the detection light L1. The light-emitting control circuit 11b intermittently drives the light-emitting element 11a to pulse the detection light L1. The longer the time for which the detection light L1 is emitted, the greater the amount of light emitted. The control unit 13 sets the light-emitting time for the light-emitting control circuit 11b.

The amount of received light can be adjusted by adjusting the exposure time during which the image sensor 12a receives reflected light L2. The light-receiving control circuit 12b controls the image sensor 12a so that the image sensor 12a is exposed intermittently. Increasing the exposure time increases the time during which reflected light L2 is incident on the image sensor 12a, i.e., increases the amount of received light. The control unit 13 sets the exposure time for the light-receiving control circuit 12b.

The control unit 13 also has the function of executing tuning processing. The tuning processing is, for example, processing for storing adjustment values for the object to be detected W2 shown in Figure 5. The object to be detected W2 has multiple parts with different reflectivities, and has non-uniform reflectivities. Specifically, the object to be detected W2 has a portion WA made of a material with high reflectivity (e.g., a metal such as aluminum) and a portion WB made of a material with low reflectivity (e.g., black resin).

For such an object W2, the initial measurement after changing the measurement area from the high-reflectivity area WA to the low-reflectivity area WB may result in an excessively high light reception level. For such an object W2, during tuning processing, the control unit 13 stores in the memory unit 14 as a first adjustment value a value set to bring the amount of light received by the image sensor 12a closer to the optimal range. Therefore, if the light reception level becomes excessive, the time required to adjust the amount of light reception can be shortened by adjusting the manipulated variable, i.e., at least one of the amount of light emitted and the amount of light received, using the first adjustment value stored in the memory unit 14.

Furthermore, in the first measurement of the object W2 after the measurement portion is changed from the low-reflectivity region WB to the high-reflectivity region WA, the received light level may be too low. For such an object W2, in the tuning process, the control unit 13 stores in the memory unit 14 as the second adjustment value a value set to bring the amount of received light in the image sensor 12a closer to the optimal value range. Therefore, if the received light level is too low, the time required to adjust the amount of received light can be shortened by adjusting the manipulated variable, i.e., at least one of the amount of light emitted and the amount of light received, using the second adjustment value stored in the memory unit 14.

[Tuning process]
FIG. 3 shows the tuning process for the amount of projected and received light.
First, in step 51, a first workpiece is set. The first workpiece is a workpiece with high reflectivity. For example, a portion WA of the object W2 shown in FIG. 5 is set as the first workpiece.

Next, in step 52, the control unit 13 performs feedback control on the first amount of light received by the workpiece.
Next, in step 53, the control unit 13 determines whether the amount of received light is optimal based on the light reception level. That is, the control unit 13 determines whether the amount of received light adjusted by the feedback control in step 52 is optimal. If the amount of received light is optimal (determination: YES), the process proceeds to step 54.

In step 54, the control unit 13 saves the light reception level corresponding to the adjusted amount of light reception as the adjustment value for the first workpiece (first adjustment value). For example, the control unit 13 stores the first adjustment value in the memory unit 14 of FIG. 1.

Next, in step 55, a second workpiece is set. The second workpiece has low reflectivity. For example, portion WB of object W2 shown in Figure 5 is set as the second workpiece.

Next, in step 56, the control unit 13 performs feedback control on the second amount of light received by the workpiece.
Next, in step 57, the control unit 13 determines whether the amount of received light is optimal based on the light reception level. That is, the control unit 13 determines whether the amount of received light adjusted by the feedback control in step 56 is optimal. If the amount of received light is optimal (determination: YES), the process proceeds to step 58.

In step 58, the control unit 13 saves the light reception level corresponding to the adjusted amount of light reception as the adjustment value for the second workpiece (second adjustment value). For example, the control unit 13 stores the second adjustment value in the memory unit 14 of FIG. 1.

Then, the control unit 13 ends the tuning process.
If the amount of received light is not the optimal value in step 53 (determination: NO), the control unit 13 proceeds to step 59. In step 59, the control unit 13 determines whether adjustment is possible. If the amount of received light is adjustable (determination: YES), the control unit 13 proceeds to step 52 and performs feedback control. On the other hand, if the amount of received light is not adjustable (determination: NO), the control unit 13 proceeds to step 60, executes error processing, and ends the processing. For example, in the error termination processing, the control unit 13 notifies the user via the input/output unit 15 in FIG. 1 that adjustment of the amount of received light is impossible, that the first adjustment value could not be stored, etc. Note that in the error termination processing, an error may be displayed on a display unit (not shown).

Furthermore, if the amount of received light is not the optimal value in step 57 (determination: NO), the control unit 13 proceeds to step 61. In step 61, the control unit 13 determines whether adjustment is possible. If the amount of received light is adjustable (determination: YES), the control unit 13 proceeds to step 56 and performs feedback control. On the other hand, if the amount of received light is not adjustable (determination: NO), the control unit 13 proceeds to step 62, executes error processing, and terminates processing. For example, in the error termination processing, the control unit 13 notifies the user via the input/output unit 15 in FIG. 1 that adjustment of the amount of received light is impossible, that the second adjustment value could not be stored, etc. Note that in the error termination processing, an error may be displayed on a display unit (not shown).

[Feedback control of light emission and reception]
FIG. 2 shows feedback control of the amount of projected and received light.
First, in step 31, the control unit 13 acquires the light reception level.

Next, in step 32, the control unit 13 determines whether the amount of received light is within the optimal range based on the light reception level. If the amount of received light is within the optimal range (determination: YES), the control unit 13 proceeds to step 31. On the other hand, if the amount of received light is not within the optimal range (determination: NO), the control unit 13 proceeds to step 33.

In step 33, the control unit 13 determines whether tuning is enabled. For example, mode information is stored in the memory unit 14 shown in FIG. 1. The mode information includes information (flags) indicating whether tuning is enabled or disabled. The control unit 13 determines whether tuning is enabled or disabled based on the mode information. If tuning is enabled (determination: YES), the control unit 13 proceeds to step 34, and if tuning is not enabled (determination: NO), the control unit 13 proceeds to step 38. Note that the control unit 13 may determine that tuning is disabled when at least one of the first adjustment value and the second adjustment value is a predetermined value in the memory unit 14 shown in FIG. 1. The predetermined value may be, for example, a value that cannot be set as the first adjustment value or the second adjustment value, such as "0."

In step 34, the control unit 13 determines whether the received light level is equal to or greater than a predetermined value X1. The predetermined value X1 is a first level that is greater than the optimal value range. This first level is the saturation level or a level close to the saturation level. If the received light level is equal to or greater than the predetermined value X1 (determination: YES), the process proceeds to step 35.

In step 35, the control unit 13 adjusts the amount of light emitted and received. At this time, the control unit 13 uses the saturated setting value, i.e., the first adjustment value set using a workpiece with high reflectivity. The control unit 13 reads the first adjustment value from the memory unit 14 shown in FIG. 1, and adjusts the amount of light emitted by the light emitter 11 and the amount of light received by the light receiver 12. The first adjustment value includes an adjustment value that adjusts at least one of the amount of light emitted and the amount of light received as an operating variable. The control unit 13 adjusts the amount of light emitted and received using the first adjustment value.

After adjusting the amount of emitted and received light, the control unit 13 proceeds to step 31.
In step 34, if the light reception level is less than the predetermined value X1 (determination: NO), the control unit 13 proceeds to step 36.

In step 36, the control unit 13 determines whether the received light level is equal to or less than a predetermined value X2. The predetermined value X2 is a second level that is smaller than the optimal value range. This second level is a level close to the zero level. If the received light level is equal to or less than the predetermined value X2 (determination: YES), the process proceeds to step 37.

In step 37, the control unit 13 adjusts the amount of emitted and received light. At this time, the control unit 13 uses a setting value for no received light, i.e., a second adjustment value set using a workpiece with low reflectivity. The control unit 13 reads the second adjustment value from the memory unit 14 shown in FIG. 1, and adjusts the amount of emitted light for the light projector 11 and the amount of received light for the light receiver 12. The second adjustment value includes an adjustment value that adjusts at least one of the amount of emitted light and the amount of received light as an operating variable. The control unit 13 adjusts the amount of emitted and received light using the second adjustment value.

After adjusting the amount of emitted and received light, the control unit 13 proceeds to step 31.
In step 36, if the light reception level is not equal to or less than the predetermined value X2 (determination: NO), the control unit 13 proceeds to step 38.

In step 38, the control unit 13 determines whether the received light level is greater than the optimal value range. If the received light level is greater than the optimal value range (determination: YES), the control unit 13 proceeds to step 39.

In step 39, the control unit 13 reduces the amount of light emitted and received. For example, the control unit 13 subtracts a predetermined change value from the current settings (light emission time, exposure time) for the light emitter 11 and the light receiver 12, and sets the results as new settings for the light emitter 11 and the light receiver 12. The change value may be a fixed value or a variable value.

The control unit 13 also multiplies the current amount of emitted and received light by a coefficient (reduction coefficient) for reducing the amount of emitted and received light, sets the resulting value as a new setting value, and adjusts the amount of emitted and received light. The reduction coefficient is a value less than 1, such as 0.8. The reduction coefficient can also be changed depending on the received light level and the optimal value range. For example, the reduction coefficient is set smaller the greater the difference between the received light level and the optimal value range. After reducing the amount of emitted and received light, the control unit 13 proceeds to step 31.

On the other hand, if the light reception level is equal to or lower than the optimum value range in step 38 (determination: NO), the control unit 13 proceeds to step 40 .
In step 40, the control unit 13 increases the amount of light emitted and received. For example, the control unit 13 adds a predetermined change value to the current settings (light emission time, exposure time) for the light projecting unit 11 and the light receiving unit 12, and sets the result as new settings for the light projecting unit 11 and the light receiving unit 12. The change value may be a fixed value or a variable value. Note that the change value when decreasing the amount of light emitted and received and the change value when increasing the amount of light emitted and received may be the same value or may be different values.

The control unit 13 also multiplies the current amount of emitted and received light by a coefficient (increase coefficient) that increases the amount of emitted and received light, and sets the resulting value as the new amount of emitted and received light. The increase coefficient is a value greater than "1," such as "1.2." The increase coefficient can also be changed depending on the light reception level and the optimal value range. For example, the increase coefficient is increased as the difference between the light reception level and the optimal value range increases. After increasing the amount of emitted and received light, the control unit 13 proceeds to step 31.

(effect)
Next, the operation of the displacement sensor 10 of this embodiment will be described.
6 and 7 show the light reception waveforms in the image sensor 12a. In Fig. 6 and Fig. 7, the horizontal axis represents the cell position of the light receiving cell 12s, and the vertical axis represents the amount of light received (light reception level). In Fig. 6, the hatched area H1 indicates the optimum value range for an object W with a large amount of reflection. In Fig. 7, the hatched area H2 indicates the optimum value range for an object W with a small amount of reflection. Note that the optimum value range may be the same for the amount of light received.

In Figures 6 and 7, the received light waveforms F11 and F21, shown by solid lines, are waveforms suitable for detecting peak positions. The received light waveforms F12 and F22, shown by dashed dotted lines, represent a case where the amount of received light (received light level) is lower than the optimal value range. In this case, the control variables (amount of emitted light, amount of received light) are increased to approach the received light waveforms F11 and F21. The received light waveforms F13 and F23, shown by dashed dotted lines, represent a case where the amount of received light (received light level) is higher than the optimal value range. In this case, the control variables (amount of emitted light, amount of received light) are decreased to approach the received light waveforms F11 and F21. In the received light waveform F13 shown in Figure 6, the straight line portion indicates that the amount of received light is saturated in many of the light-receiving cells 12s.

Figures 8 and 9 show the relationship between the reflectance of the object W to be detected and the adjustment value. Note that Figures 8 and 9 show the case where adjustment of the light projection time is used as the adjustment value. In Figures 8 and 9, region H21 indicates the optimal range of the amount of received light, region H22 indicates the saturated state range, and region H23 indicates the range of insufficient received light. The range from region H22 to region H23 corresponds to the first range.

In Figures 8 and 9, point P11 indicates the light projection time when measuring area WB of object W2 shown in Figure 5. Point P12 indicates the optimal light projection time for area WA. In this adjusted state, area WA of object W2 shown in Figure 5 is next measured. In this case, because area WA has high reflectivity, the amount of received light becomes saturated, as shown at point P21.

When only feedback control is performed, the amount of received light is gradually reduced by repeating feedback control, as shown at points P21, P22, and P23 in Figure 9, until it is within the optimal value range. In contrast, in the displacement sensor 10 of this embodiment, the amount of received light (light reception level) at point P21 in Figure 8 is saturated, so the light projection time is adjusted in one adjustment using the first adjustment value.

The control unit 13 obtains the light receiving level from the image signal S12, for example, through A/D conversion (analog-to-digital conversion). If this light receiving level is the maximum value of the input range (maximum value of A/D conversion), that light receiving cell 12s is a saturated cell. The control unit 13 counts the number of saturated cells and determines whether the count value (number of saturated cells) is equal to or greater than a predetermined value N. The predetermined value N is set to correspond to a light receiving level that can be brought close to the optimal value range in a short period of time using feedback control that increases and decreases the amount of light receiving in steps. For example, if the maximum value (peak value) of the amount of light receiving slightly exceeds the saturation level, several light receiving cells 12s will become saturated cells. In this case, the light receiving level (amount of light receiving) can be reduced below the saturation value through several rounds of feedback control, bringing it within or close to the optimal value range.

On the other hand, as shown in the light reception waveform F13 indicated by the two-dot chain line in Figure 6, when the number of saturated cells is large, the maximum light reception level (peak value) is much higher than the saturation value, and even repeated feedback control may not even be able to reduce it below the saturation value.

As shown in Figure 11, the amount of received light is saturated at time T21. Time T22 shows the received light waveform after several rounds of feedback control. In this case, the received light level is saturated. Time T23 shows the received light waveform after several more rounds of feedback control. In this received light waveform, the peak value is still higher than the optimal value range. However, because the peak value is known, it is possible to bring the peak of the received light waveform within the optimal value range, as in the received light waveform shown at time T24. In this way, it takes time for the received light amount (received light level) to approach the optimal value range.

When the number of saturated cells is equal to or greater than a predetermined number N, the displacement sensor 10 of this embodiment can easily bring the manipulated variables (amount of emitted light, amount of received light) within or close to the optimal value range by using the first adjustment value stored in the memory unit 14. Furthermore, because the manipulated variables (amount of emitted light, amount of received light) can be adjusted with a single adjustment, the adjustment time can be shortened. This makes it possible to obtain stable measurement results in a short time.

FIG. 10 shows the measurement state and the received light waveform when a plurality of objects W2 to be detected are conveyed.
At times T11, T12, T13, T14, and T15, the area WA, the area WB, the transport path, the area WA, and the area WB are measured.

When area WA is measured at time T11, the amount of light is insufficient when area WB is measured at time T12. Therefore, the control unit 13 uses the second adjustment value to increase the amount of light received in the light received waveform, as shown at time T12+1. This light received waveform enables the control unit 13 to measure area WB.

Next, at time T13, there is no object W2 to be detected, and light reflected by the transport path is received.
Next, at time T14, the area WA of the object W2 is measured. At this time, the amount of received light has been increased by the second adjustment value, so the received light waveform at the area WA is saturated. Therefore, the control unit 13 reduces the amount of received light of the received light waveform using the first adjustment value, as shown at time T14+1. This received light waveform allows the control unit 13 to measure the area WA .

The control unit 13 sets the first and second adjustment values through a tuning process for the amount of emitted and received light, and stores them in the memory unit 14. Therefore, in the tuning process, the first and second adjustment values can be easily set by setting the object W2 to be detected.

The control unit 13 stores the adjustment values obtained by feedback control during the tuning process for the amount of emitted and received light in the memory unit 14 as first and second adjustment values. This makes it easy to set and store first and second adjustment values that are appropriate for the workpiece when performing feedback control.

As described above, this embodiment provides the following advantages.
(1) The displacement sensor 10 includes a light-projecting unit 11 including a light-projecting element 11a, a light-receiving unit 12 including an image sensor 12a, a control unit 13, and a storage unit 14. The light-receiving unit 12 outputs an image signal S12 corresponding to reflected light L2 from an object W to be detected and received by the image sensor 12a. The control unit 13 performs feedback control to adjust at least one of the manipulated variables, including the amount of light projected by the light-projecting element 11a and the amount of light received by the image sensor 12a, based on the light-receiving level of the image signal S12 output from the light-receiving unit 12. The control unit 13 performs feedback control when the light-receiving level is within a first range. When the light-receiving level is equal to or greater than a predetermined value X1 greater than the first range or equal to or less than a predetermined value X2 smaller than the first range, the control unit 13 adjusts the manipulated variable using a first adjustment value and a second adjustment value stored in the storage unit 14. If the light reception level becomes too high or too low, the time required to adjust the amount of light reception can be shortened by adjusting the operation amount, i.e., at least one of the light emission amount and the light reception amount, using the first adjustment value and the second adjustment value stored in the memory unit 14.

(2) The control unit 13 sets the first adjustment value and the second adjustment value through the tuning process for the amount of emitted and received light, and stores them in the memory unit 14. Therefore, in the tuning process, the first adjustment value and the second adjustment value can be easily set by setting the object W2 to be detected.

(3) In the tuning process for the amount of emitted and received light, the control unit 13 stores the adjustment values obtained by feedback control as first and second adjustment values in the memory unit 14. This makes it possible to easily set and store first and second adjustment values that are suitable for the workpiece when performing feedback control.

(4) The control unit 13 adjusts the set light projection time for the light projection unit 11. This makes it possible to easily adjust the amount of light projected by the light projection element 11a.
(5) The control unit 13 adjusts the exposure time set for the light receiving unit 12. This makes it possible to easily adjust the amount of light received by the image sensor 12a.

[Example of change]
The description of the embodiments is merely an example of possible forms of the displacement sensor according to the present disclosure, and is not intended to limit the forms. In addition to the embodiments, the present disclosure may also take forms such as modified examples of the embodiments shown below, and combinations of at least two mutually consistent modified examples.

- In the above embodiment, as shown in Figure 5, the object to be detected W2 has portions WA and WB. However, the object to be detected may have only one of portions WA and WB. For example, the object to be detected may be made of a low-reflectivity material, and the conveying line that conveys the object or the tape that holds the object may be made of a high-reflectivity material. Even in such a case, the time required to adjust the amount of received light can be shortened, just as in the above embodiment.

In the above embodiment, the object to be detected may include a plurality of at least one of the regions WA and WB. Also, the object to be detected may include at least one region having a reflectance different from that of the regions WA and WB.
(Appendix 1)
a light-projecting unit including a light-projecting element that projects light onto the object to be detected and a light-projection control circuit that controls the light-projecting element;
a light receiving unit including an image sensor that receives light reflected from the object to be detected and a light receiving control circuit that controls the image sensor, and that outputs an image signal corresponding to the reflected light received by the image sensor;
a control unit that executes feedback control to adjust at least one of an amount of light emitted by the light-emitting element and an amount of light received by the image sensor based on a light-receiving level of the image signal;
a storage unit that stores an adjustment value for the manipulated variable;
Equipped with
The control unit
When the received light level is within a first range, the feedback control is performed;
When the light receiving level is equal to or higher than a first level that is higher than the first range or equal to or lower than a second level that is lower than the first range, the manipulated variable is adjusted based on the adjustment value stored in the storage unit.
Displacement sensor.
(Appendix 2)
2. The displacement sensor according to claim 1, wherein the control unit controls the manipulated variable in the feedback control so that the light reception level falls within a reference range, and the first range is set to be larger than the reference range.
(Appendix 3)
the adjustment value includes a first adjustment value when the image signal is saturated and a second adjustment value when the reflected light is not received,
When the number of saturated cells in the image signal is equal to or greater than a predetermined number, it is determined that the received light level is equal to or greater than the first level, and the first adjustment value is set as the manipulated variable;
When the light reception level is equal to or lower than a predetermined value, the light reception level is determined to be equal to or lower than the second level, and the second adjustment value is set as the manipulated variable.
3. The displacement sensor according to claim 1 or 2.
(Appendix 4)
4. The displacement sensor according to claim 3, wherein the control unit executes a tuning process to store the first adjustment value and the second adjustment value in the storage unit.
(Appendix 5)
In the tuning process, the control unit
an adjustment value obtained when the feedback control is performed based on the light receiving level for the first workpiece is stored in the storage unit as the first adjustment value;
an adjustment value obtained when the feedback control is performed based on the light receiving level for the second workpiece is stored in the storage unit as the second adjustment value;
5. The displacement sensor of claim 4.
(Appendix 6)
the light-projection control circuit controls a light-projection time of the light-projecting element so as to project pulsed light;
6. The displacement sensor according to claim 1, wherein the control unit adjusts a light projection time of the light projection element with respect to the light projection control circuit.
(Appendix 7)
the light-receiving control circuit controls an exposure time of the image sensor,
7. The displacement sensor according to claim 1, wherein the control unit adjusts the amount of received light based on an exposure time of the image sensor.

REFERENCE SIGNS LIST 10 Displacement sensor 11 Light-emitting section 11a Light-emitting element 11b Light-emitting control circuit 12 Light-receiving section 12a Image sensor 12b Light-receiving control circuit 12s Light-receiving cell 12s12s Light-receiving cell 13 Control section 14 Storage section 15 Input/output section S12 Image signal W, W2 Detected object WA part WB part

Claims (7)

a light-projecting unit including a light-projecting element that projects light onto the object to be detected and a light-projection control circuit that controls the light-projecting element;
a light receiving unit including an image sensor that receives light reflected from the object to be detected and a light receiving control circuit that controls the image sensor, and that outputs an image signal corresponding to the reflected light received by the image sensor;
a control unit that executes feedback control to adjust at least one of an amount of light emitted by the light-emitting element and an amount of light received by the image sensor based on a light-receiving level of the image signal;
a storage unit that stores an adjustment value for the manipulated variable;
Equipped with
The control unit
When the maximum value of the received light level is within a first range, the feedback control is performed;
adjusting the manipulated variable using the adjustment value stored in the storage unit when the maximum value of the received light level is equal to or greater than a first level that is greater than the first range or equal to or less than a second level that is smaller than the first range ;
the adjustment value includes a first adjustment value that brings the maximum value of the light reception level in a saturated state range closer to a reference range or that brings the maximum value of the light reception level in a range of insufficient light reception closer to the reference range or that brings the maximum value of the light reception level within the reference range,
When the number of saturated cells in the image signal is equal to or greater than a predetermined number, it is determined that the maximum value of the received light level is equal to or greater than the first level, and the first adjustment value is set as the manipulated variable;
When the maximum value of the light reception level is equal to or less than a predetermined value, it is determined that the maximum value of the light reception level is equal to or less than the second level, and the second adjustment value is set as the manipulated variable .
Displacement sensor. 2. The displacement sensor according to claim 1, wherein the control unit controls the manipulated variable in the feedback control so that the maximum value of the light reception level falls within the reference range, and the first range is set to be larger than the reference range. the reference range includes a first reference range for an object having a large amount of reflection and a second reference range for an object having a small amount of reflection,
the first adjustment value is a value that brings the maximum value of the received light level in the saturated state range closer to the first reference range or brings the maximum value of the received light level in the saturated state range within the first reference range,
3. The displacement sensor according to claim 1, wherein the second adjustment value is a value that brings the maximum value of the light reception level that is in the range of insufficient light reception closer to the second reference range or brings the maximum value of the light reception level within the second reference range. The displacement sensor according to claim 1 , wherein the control unit executes a tuning process to store the first adjustment value and the second adjustment value in the storage unit. In the tuning process, the control unit
an adjustment value obtained when the feedback control is performed based on the light receiving level for the first workpiece is stored in the storage unit as the first adjustment value;
an adjustment value obtained when the feedback control is performed based on the light receiving level for the second workpiece is stored in the storage unit as the second adjustment value;
The displacement sensor according to claim 4 . the light-projection control circuit controls a light-projection time of the light-projecting element so as to project pulsed light;
The displacement sensor according to claim 1 , wherein the control unit adjusts a light projection time of the light projection element relative to the light projection control circuit. the light-receiving control circuit controls an exposure time of the image sensor,
The displacement sensor according to claim 1 , wherein the control unit adjusts the amount of received light by adjusting an exposure time of the image sensor.