Displacement Sensor

Abstract

To provide a displacement sensor that can reduce adjustment time.SOLUTION: A displacement sensor 10 comprises: a light projection unit 11 that includes a light projection element 11a; a light reception unit 12 that includes an image sensor 12a; a control unit 13; and a storage unit 14. The light reception unit outputs an image signal S12 corresponding to reflected light L2 that is reflected from a detected object W and received by the image sensor 12a. The control unit 13 executes feedback control for adjusting an operation amount including at least one of a light projection amount of the light projection element 11a and a reception amount of the image sensor 12a, on the basis of the light reception level of the image signal S12 outputted by the light reception unit. The control unit 13 executes the feedback control when the light reception level is within a first range. The control unit 13 adjusts the operation amount by a first or second adjustment value stored in the storage unit 14 when the light reception level is equal to or more than a specified value X1 that is above the first range, or the light reception level is equal or less than a specified value X2 that is below the first range.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to displacement sensors. [Background technology]

[0002] Conventionally, as this type of displacement sensor, there is known one that measures the displacement, surface shape, etc. of an object to be measured using the principle of triangulation (see, for example, Patent Document 1). In this type of displacement sensor, a light projecting unit irradiates light onto the object, and a light receiving unit such as an image sensor receives the reflected light from the object, and outputs a measurement value signal obtained from the received light signal to measure the displacement, surface shape, etc. of the object. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-011566 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in cases where the reflectance changes suddenly at each measurement site on the object, the amount of received light finally stabilizes after multiple feedback adjustments, and therefore measurements must be performed 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 will not be obtained during this transitional period. [Means for solving the problem]

[0005] A displacement sensor according to one aspect of the present disclosure comprises 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, and is equipped with a light-receiving unit that outputs an image signal corresponding to the reflected light received by the image sensor, a control unit that performs feedback control to adjust at least one of operation 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, and a memory unit that stores an adjustment value for the operation variable, wherein the control unit performs the feedback control when the light-receiving level is within a first range, and adjusts the operation variable using the adjustment value stored in the memory unit when the light-receiving 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. [Effects of the Invention]

[0006] According to one aspect of the present disclosure, it is possible to provide a displacement sensor that can reduce the adjustment time. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a block diagram showing the electrical configuration of the displacement sensor. [Figure 2] FIG. 2 is a flowchart of the feedback control of the amount of emitted and received light. [Figure 3] FIG. 3 is a flowchart of the tuning process for the amount of emitted and received light. [Figure 4] FIG. 4 is an explanatory diagram showing the operation of the displacement sensor. [Figure 5] FIG. 5 is an explanatory diagram showing the operation of the displacement sensor. [Figure 6] FIG. 6 is an explanatory diagram showing the processing of the displacement sensor. [Figure 7] FIG. 7 is an explanatory diagram showing the processing of the displacement sensor. [Figure 8] FIG. 8 is an explanatory diagram showing the processing of the displacement sensor. [Figure 9]FIG. 9 is an explanatory diagram showing the processing of the displacement sensor. [Figure 10] FIG. 10 is an explanatory diagram showing the processing of the displacement sensor. [Figure 11] FIG. 11 is an explanatory diagram showing the processing of the displacement sensor. DETAILED DESCRIPTION OF THE INVENTION

[0008] 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.

[0009] 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.

[0010] As shown in Figures 4 and 5, the image sensor 12a has a plurality of light-receiving cells 12s. The image sensor 12a of this embodiment is a CMOS image sensor. Note that the image sensor 12a may be a device having a plurality of light-receiving cells 12s, such as a CCD image sensor or a 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 the reflected light L2 received, and outputs the electrical signal.

[0011] 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.

[0012] The control unit 13 detects the light-receiving center position of the reflected light L2 in the image sensor 12a based on the image signal S12 from the light-receiving unit 12. Then, the control unit 13 measures the displacement of the object W from the light-receiving center position.

[0013] 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 to be detected W. Reflected light L2 reflected by the object to be detected W passes through the light-receiving lens 22 and is incident on the image sensor 12a. The image sensor 12a has a plurality of light-receiving cells 12s.

[0014] The control unit 13 detects the light-receiving center position O1 of the reflected light L2 from the object W, which is indicated by a solid line. For example, the control unit 13 detects the position of the light-receiving cell 12s having the maximum light-receiving level (amount of received light) in the image signal S12 as the light-receiving center position O1. Furthermore, when the amount of received light of the plurality of light-receiving cells 12s is a saturated value in the image signal S12, the control unit 13 detects the position of the plurality of light-receiving cells 12s at the saturated value as the light-receiving center position O1.

[0015] Next, when the object W is displaced to the position indicated by the dashed line, the reflected light L2 from the object W is incident on the image sensor 12a at a different position from 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 the presence or absence of the object W, the surface shape of the object W, etc. can also be detected by moving the object W relative to the displacement sensor 10 in a direction perpendicular to the optical axis of the detection light L1.

[0016] The input / output unit 15 is configured to be able to communicate with an external device 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.

[0017] The storage unit 14 stores various information when various processing operations of the control unit 13 are performed. The information stored in the storage unit 14 includes set values ​​and change values ​​in the displacement sensor 10. The set values ​​and change values ​​are used to adjust the amount of light emitted by the light-emitting element 11a and the amount of light received by the image sensor 12a. of The values ​​for adjusting the amount of light emitted include, for example, the light-emitting time for driving the light-emitting element 11a, the drive voltage supplied to the light-emitting element 11a, etc. The values ​​for adjusting the amount of light received include, for example, the exposure time in the light-receiving unit 12, the amplification factor for amplifying the signal output from the light-receiving unit 12, etc. Furthermore, the set values ​​and changed values ​​include initial values, values ​​received from external devices, values ​​set by teaching processing, etc.

[0018] The control unit 13 has a function of performing feedback control of the amount of light emitted and received, which adjusts the amount of light emitted (light-emitting time) of the light-emitting element 11a and the amount of light received (exposure time) of the image sensor 12a based on the image signal S12 from the image sensor 12a. The amount of reflected light L2 received by the image sensor 12a changes depending on the state of reflection on the surface of the object W to be detected. As described above, the control unit 13 detects the light-receiving center position at which the reflected light L2 is received by the image sensor 12a. If the amount of light received by the image sensor 12a is large or small, 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).

[0019] The amount of light emitted can be adjusted by the light-emitting time during 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 make the detection light L1 pulse-like. The longer the time during 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.

[0020] The amount of received light can be adjusted by adjusting the exposure time for which the image sensor 12a receives the reflected light L2. The light-receiving control circuit 12b controls the image sensor 12a to be exposed intermittently. Image sensor 12a If the exposure time is increased, the time that the reflected light L2 is incident on the image sensor 12a becomes longer, that is, the amount of light received becomes larger. The control unit 13 sets the exposure time in the light-receiving control circuit 12b.

[0021] The control unit 13 also has a function of executing tuning processing. The tuning processing is, for example, processing for storing an adjustment value for the object W2 to be detected shown in FIG. 5. The object W2 to be detected has a plurality of portions with different reflectances, and has non-uniform reflectance. Specifically, the object W2 to be detected has a portion WA made of a material with high reflectance (for example, a metal such as aluminum) and a portion WB made of a material with low reflectance (for example, a black resin).

[0022] In the first measurement of such an object W2 after the measurement portion is changed from the high-reflectivity region WA to the low-reflectivity region WB, the received light level may be excessive. In the tuning process for such an object W2, the control unit 13 stores in the memory unit 14 as a first 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 becomes excessive, 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 emitted light and the amount of received light, using the first adjustment value stored in the memory unit 14.

[0023] In addition, for the object W2, the measurement area is changed from the low reflectance area WB to the high reflectance area WA. was In the initial measurement, the received light level may be too low. For such an object W2 to be detected, in the tuning process, the control unit 13 stores in the memory unit 14 as a second adjustment value a value set so as to bring the amount of received light in the image sensor 12a closer to the optimum 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 emitted light and the amount of received light, using the second adjustment value stored in the memory unit 14.

[0024] [Tuning process] FIG. 3 shows the tuning process for the amount of light emitted and received. First, in step 51, the first workpiece is set. The first workpiece is a workpiece with high reflectivity. For example, the portion WA of the object to be detected W2 shown in FIG. 5 is set as the first workpiece.

[0025] Next, in step 52, the control unit 13 performs feedback control on the first amount of workpiece light reception. Next, in step 53, the control unit 13 determines whether the amount of received light is an optimum value based on the received light level. That is, the control unit 13 determines whether the amount of received light adjusted by the feedback control in step 52 is an optimum value. If the amount of received light is an optimum value (determination: YES), the process proceeds to step 54.

[0026] In step 54, the control unit 13 saves the light receiving level corresponding to the adjusted amount of light receiving as the adjustment value (first adjustment value) for the first work. For example, the control unit 13 stores the first adjustment value in the memory unit 14 of FIG. 1.

[0027] Next, in step 55, a second workpiece is set. The second workpiece has low reflectivity. For example, the portion WB of the object W2 shown in FIG. 5 is set as the second workpiece.

[0028] Next, in step 56, the control unit 13 performs feedback control on the second amount of workpiece light reception. Next, in step 57, the control unit 13 determines whether the amount of received light is an optimum value based on the received light level. That is, the control unit 13 determines whether the amount of received light adjusted by the feedback control in step 56 is an optimum value. If the amount of received light is an optimum value (determination: YES), the process proceeds to step 58.

[0029] In step 58, the control unit 13 stores the light receiving level corresponding to the adjusted amount of light receiving as the adjustment value for the second work (second adjustment value). For example, the control unit 13 stores the second adjustment value in the memory unit 14 of FIG.

[0030] Then, the control unit 13 ends the tuning process. If the amount of received light is not the optimum value in step 53 (determination: NO), the control unit 13 proceeds to step 59. In step 59, the control unit 13 determines whether or not 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).

[0031] Furthermore, if the amount of received light is not the optimum value in step 57 (determination: NO), the control unit 13 proceeds to step 61. In step 61, the control unit 13 determines whether or not 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 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 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).

[0032] [Feedback control of light emission and reception] FIG. 2 shows feedback control of the amount of emitted and received light. First, in step 31, the control unit 13 acquires the light reception level.

[0033] Next, in step 32, the control unit 13 determines whether the amount of received light is within the optimum range based on the received light level. If the amount of received light is within the optimum 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 optimum range (determination: NO), the control unit 13 proceeds to step 33.

[0034] 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 (flag) 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."

[0035] In step 34, the control unit 13 determines whether the light reception level is equal to or greater than a predetermined value X1. The predetermined value X1 is a first level that is greater than the optimum value range. This first level is the saturation level or a level close to the saturation level. If the light reception level is equal to or greater than the predetermined value X1 (determination: YES), the process proceeds to step 35.

[0036] 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 operation amount. The control unit 13 adjusts the amount of light emitted and received using the first adjustment value.

[0037] After adjusting the amount of emitted and received light, the control unit 13 proceeds to step 31. In step , if the received light level is less than the predetermined value X1 (determination: NO), the control unit 13 proceeds to step .

[0038] 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 optimum 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.

[0039] In step 37, the control unit 13 adjusts the amount of light emitted and received. At this time, the control unit 13 uses a setting value for no amount of 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 light emitted by the light emitter 11 and the amount of light received by the light receiver 12. The second 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 operation amount. The control unit 13 adjusts the amount of light emitted and received using the second adjustment value.

[0040] After adjusting the amount of emitted and received light, the control unit 13 proceeds to step 31. In step , if the received light level is not equal to or less than the predetermined value X2 (determination: NO), the control unit 13 proceeds to step .

[0041] In step 38, the control unit 13 determines whether the received light level is greater than the optimum value range. If the received light level is greater than the optimum value range (determination: YES), the control unit 13 proceeds to step 39.

[0042] In step 39, the control unit 13 reduces the amount of light projected and received. For example, the control unit 13 subtracts a predetermined change value from the current setting values ​​(light projection time, exposure time) for the light projecting unit 11 and the light receiving unit 12, and sets the result as new setting values ​​for the light projecting unit 11 and the light receiving unit 12. The change value may be a fixed value or a variable value.

[0043] 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, and sets the resulting value as a new set value to adjust 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 as the difference between the received light level and the optimal value range increases. After reducing the amount of emitted and received light, the control unit 13 proceeds to step 31.

[0044] 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 emitter 11 and the light receiver 12, and sets the result as new setting values ​​for the light emitter 11 and the light receiver 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.

[0045] The control unit 13 also multiplies the current amount of emitted and received light by a coefficient (increase coefficient) for increasing 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.

[0046] (action) Next, the operation of the displacement sensor 10 of this embodiment will be described. 6 and 7 show the waveform of light received by the image sensor 12a. In FIGS. 6 and 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 receiving level). In FIG. 6, the hatched area H1 represents the optimum value range for the object W to be detected, which has a large amount of reflection. In FIG. 7, the hatched area H2 represents the optimum value range for the object W, which has a large amount of reflection. few The optimum value range is shown for the object W. The optimum value range may be the same for the amount of received light.

[0047] 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 indicate when the amount of received light (received light level) is lower than the optimal value range. In this case, the manipulated variable (amount of emitted light, amount of received light) is increased so that it approaches the received light waveforms F11 and F21. The received light waveforms F13 and F23 shown by dashed dotted lines indicate when the amount of received light (received light level) is higher than the optimal value range. In this case, the manipulated variable (amount of emitted light, amount of received light) is decreased so that it approaches 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.

[0048] 8 and 9 show the relationship between the reflectance of the object W to be detected and the adjustment value. Note that Figs. 8 and 9 show the case where adjustment of the light projection time is used as the adjustment value. In Figs. 8 and 9, region H21 indicates the optimum range of the amount of received light, region H22 indicates the saturated state range, and region H23 indicates the range of insufficient amount of received light. The range from region H22 to region H23 corresponds to the first range.

[0049] 8 and 9, point P11 indicates the light projection time when measuring area WB of object W2 shown in FIG. 5. Point P12 indicates the optimal light projection time for area WA. In this adjusted state, area WA of object W2 shown in FIG. 5 is next measured. In this case, area WA has high reflectivity, so the amount of received light becomes saturated, as shown at point P21.

[0050] When only feedback control is performed, the amount of received light is gradually reduced to within the optimum value range by repeating feedback control, as shown at points P21, P22, and P23 in Fig. 9. On the other hand, in the displacement sensor 10 of this embodiment, the amount of received light (light reception level) at point P21 in Fig. 8 is saturated, so the light projection time is adjusted in one adjustment using the first adjustment value.

[0051] The control unit 13 obtains the light-receiving level from the image signal S12, for example, by 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 corresponding 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 received light in a stepwise manner. For example, if the maximum value (peak value) of the amount of received light slightly exceeds the saturation level, several light-receiving cells 12s will become saturated cells. In this case, the light-receiving level (amount of received light) can be reduced below the saturation value by several rounds of feedback control, bringing it within or close to the optimal value range.

[0052] On the other hand, as shown in the light reception waveform F13 indicated by the dashed line in Figure 6, when the number of saturated cells is large, the maximum value (peak value) of the light reception level is much larger than the saturated value, and even if feedback control is repeated, it may not even be possible to make it fall below the saturated value.

[0053] As shown in FIG. 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 also 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.

[0054] In the displacement sensor 10 of this embodiment, when the number of saturated cells is equal to or greater than a predetermined number N, the first adjustment value stored in the memory unit 14 is used to easily bring the manipulated variables (amount of projected light, amount of received light) within or close to the optimum value range. Furthermore, because the manipulated variables (amount of projected light, amount of received light) can be adjusted with a single adjustment, the adjustment time can be shortened. As a result, stable measurement results can be obtained in a short time.

[0055] FIG. 10 shows the measurement state and the received light waveform when a plurality of objects W2 to be detected are transported. 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.

[0056] When the area WA is measured at time T11, the amount of light is insufficient when measuring the area WB at time T12. Therefore, the control unit 13 increases the amount of light received in the received light waveform using the second adjustment value, as shown at time T12+1. This received light waveform enables the control unit 13 to measure the area WB.

[0057] 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 to be detected is measured. At this time, the amount of received light is 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 causes the control unit 13 to WA can be measured.

[0058] The control unit 13 sets the first adjustment value and the second adjustment value through tuning processing of the amount of emitted and received light, and stores them in the storage unit 14. Therefore, in the tuning processing, the first adjustment value and the second adjustment value can be easily set by setting the object W2 to be detected.

[0059] In the tuning process for the amount of emitted and received light, the control unit 13 stores the adjustment values ​​adjusted by feedback control as first and second adjustment values ​​in the storage unit 14. Therefore, the first and second adjustment values ​​suitable for the workpiece when performing feedback control can be easily set and stored.

[0060] As described above, this embodiment provides the following advantages. (1) Displacement sensor 10 includes light-projecting unit 11 including light-projecting element 11a, light-receiving unit 12 including image sensor 12a, control unit 13, and memory unit 14. Light-receiving unit 12 outputs image signal S12 corresponding to reflected light L2 from object W to be detected and received by image sensor 12a. Control unit 13 performs feedback control to adjust at least one of manipulated variables including the amount of light projected by light-projecting element 11a and the amount of light received by image sensor 12a, based on the light-receiving level of image signal S12 output from light-receiving unit 12. 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 that is greater than the first range or equal to or less than a predetermined value X2 that is smaller than the first range, control unit 13 adjusts the manipulated variable using a first adjustment value and a second adjustment value stored in memory 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 amount of light emitted and the amount of light received, using the first adjustment value and the second adjustment value stored in the memory unit 14.

[0061] (2) The control unit 13 sets the first adjustment value and the second adjustment value through the tuning process of the amount of emitted and received light, and stores them in the storage 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.

[0062] (3) In the tuning process for the amount of emitted and received light, the control unit 13 stores the adjustment values ​​adjusted by feedback control as first and second adjustment values ​​in the storage unit 14. Therefore, the first and second adjustment values ​​suitable for the workpiece when performing feedback control can be easily set and stored.

[0063] (4) The control unit 13 adjusts the set light projection time for the light projecting unit 11. This makes it possible to easily adjust the amount of light projected by the light projecting 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.

[0064] [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.

[0065] In the above embodiment, as shown in Figure 5, the object to be detected W2 has the areas WA and WB. However, the object to be detected may have only one of the areas 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, as in the above embodiment.

[0066] 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 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 manipulated variables including the amount of light emitted by the light-emitting element and the amount of light received by the image sensor based on the 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, the received light level is determined to be 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. 10. The displacement sensor of 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; The 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 relative 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 by an exposure time of the image sensor. [Explanation of symbols]

[0067] 10 Displacement Sensor 11 Light projector 11a Light-emitting element 11b Light projection control circuit 12 Light receiving part 12a image sensor 12b Light receiving control circuit 12s photodetector cell 12s12s Photodetector cell 13 Control Unit 14 Storage section 15 Input / output section S12 image signal W, W2 Object to be detected WA part WB part

Claims

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 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. 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.

3. The reference range includes a first reference range for a detected object having a large amount of reflection and a second reference range for a detected 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.

4. 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.

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; The displacement sensor according to claim 4 .

6. 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.

7. 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.

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