JP2011252892A - Measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring instrument that automatically corrects a measured value by discriminating a change of receiving light quantity caused by approach of a work-piece and a change of receiving light quantity caused by influence of adhesion of dust or the like.SOLUTION: The measuring instrument is composed of a reference receiving light quantity storage unit 32 for retaining a reference receiving light quantity A that shows a receiving light quantity when a work-piece W does not enter a measuring area 2, a measurement value calculation unit 33 for calculating a measurement value y showing an advancement amount of the work-piece W into the measuring area 2 based on a ratio of the reference receiving light quantity A and a receiving light quantity X, a reference receiving light quantity correction unit 38 for correcting the reference receiving light quantity A so that the ratio of the reference receiving light quantity A and the receiving light quantity X becomes closer to a predetermined value, and a change rate calculation unit 35 for obtaining a change rate of the receiving light quantity X corresponding to an advancing speed V of the work-piece W into the measuring area 2. The reference receiving light quantity correction unit 38 corrects the reference receiving light quantity A when the change rate is smaller than a predetermined threshold Th1 and the receiving light quantity X is larger than a threshold Th2 determined based on the reference receiving light quantity A.

Description

  The present invention relates to a measuring instrument. More specifically, the present invention relates to a light projecting element that irradiates detection light to a measurement region through which a workpiece passes, and the detection light received through the measurement region, in accordance with the amount of work entering the measurement region. The present invention relates to an improvement of a measuring instrument including a light receiving element that detects the amount of received light.

  In an FA (Factory Automation) system, a dimension measuring instrument is used as a detection device that detects a workpiece being conveyed. The dimension measuring device receives the detection light from the light projecting element that irradiates the measurement light to the measurement area through which the work passes, and the amount of light received according to the amount of the work entering the measurement area. (For example, patent document 1). In general, the amount of light received detected by the light receiving element varies due to the influence of dirt on the lens due to the adhesion of dust. Therefore, in the conventional dimension measuring device, when obtaining a measurement value indicating the amount of work entering the measurement region, the reference value is corrected based on the received light amount acquired at the timing operated by the operator, and the corrected reference value The measured value was calculated using. In other words, when the workpiece has not entered the measurement area, the operator can operate the dimension measuring device to correct the reference value, thereby obtaining a correct measurement value in which the influence of lens contamination is compensated.

JP 2000-35310 A

  However, in the dimension measuring instrument as described above, it is difficult for the operator to instruct the timing when the workpiece has not yet entered the measurement area, so that it is difficult to automate the reference value correction process.

  This invention is made | formed in view of the said situation, and it aims at providing the measuring device which can obtain a correct measured value, even if there exists adhesion of dust. In particular, it is an object of the present invention to provide a measuring device that can discriminate between a change in the amount of received light due to the entry of a workpiece and a change in the amount of received light due to the influence of dust adhesion and the like, and can automatically correct the measurement value.

  A measuring instrument according to a first aspect of the present invention receives a light projecting unit that irradiates parallel light to a measurement region through which a work passes, and receives the parallel light through the measurement region, and according to the amount of work entering the measurement region. A reference light receiving unit for detecting a received light amount, and a reference received light amount storage means for holding a reference received light amount indicating a received light amount when the workpiece does not enter the measurement area, and the reference Based on the ratio of the amount of received light and the amount of received light detected by the light receiving unit, a measurement value calculating means for calculating a measured value indicating the amount of work entering the measurement area, and the light receiving amount detected by the reference received light amount and the light receiving unit Reference light amount correction means for correcting the reference light reception amount so that the ratio of the amounts approaches a predetermined value, and a change rate calculation for obtaining a change rate of the light reception amount according to the approach speed of the workpiece into the measurement area Means and The quasi-received light amount correcting means has the rate of change smaller than a predetermined first threshold value, and the received light amount detected by the light receiving unit is smaller than a second threshold value determined based on the reference received light amount. When it is larger, it is configured to correct the reference received light amount.

  In this measuring instrument, the reference light reception amount is automatically set so that the measurement value calculated by the measurement value calculation means approaches the measurement value when the workpiece has not entered the measurement area, that is, when the workpiece is not yet entered. It is corrected to. At that time, when the rate of change in the amount of received light is smaller than a predetermined first threshold value, the reference amount of received light is corrected. Therefore, a sharp change in the amount of received light due to the entry of a workpiece whose approach speed is a certain value or more. And a gradual (relatively slow) change in received light amount due to the influence of dust adhesion or the like can be identified to correct the reference received light amount. In addition, when the received light amount is larger than the second threshold obtained from the reference received light amount, the reference received light amount is corrected, so the change in the received light amount due to the entry of a workpiece of a certain size or more and the influence of dust adhesion, etc. It is possible to correct the reference received light amount by discriminating the change in the received light amount due to. Accordingly, it is possible to identify the change in the amount of received light due to the entry of the workpiece and the change in the amount of received light due to the influence of dust adhesion, etc., and automatically correct the measurement value.

  The measuring device according to the second aspect of the present invention, in addition to the above-described configuration, may be configured such that the reference received light amount correction means corrects the reference received light amount so that the correction amount does not exceed a predetermined upper limit correction amount. It is configured to correct the amount of received light.

  According to such a configuration, the correction amount when correcting the reference light reception amount is limited to a range that does not exceed a predetermined upper limit correction amount. Less is enough.

  In addition to the above-described configuration, the measuring device according to a third aspect of the present invention is configured so that the reference received light amount correction unit includes the reference received light amount when the received light amount detected by the light receiving unit is smaller than a predetermined correction limit received light amount. The correction is not performed. According to such a configuration, when the change in the amount of received light is small, it is possible to prevent the reference received light amount from being corrected indefinitely following the decrease in the received light amount. In other words, when the amount of received light is greater than or equal to a predetermined correction limit amount of received light, the reference amount of received light is corrected.

  A measuring instrument according to a fourth aspect of the present invention is configured such that, in addition to the above configuration, the reference light reception amount correction unit corrects the reference light reception amount when the rate of change in a certain period is less than a first threshold value. Configured. According to such a configuration, even when the amount of received light fluctuates greatly due to the influence of noise or temperature change, the change in the amount of received light due to the entry of a workpiece and the change in the amount of received light due to the influence of dust adhesion etc. It is possible to correct the reference received light amount by identifying. In addition, it is possible to stabilize the determination of whether or not to correct the reference light reception amount.

  A measuring instrument according to a fifth aspect of the present invention includes a threshold value calculation means for calculating a second threshold value by multiplying the reference received light amount by a certain ratio in addition to the above configuration. According to such a configuration, the second threshold value can be appropriately set by following the reference received light amount.

  A measuring instrument according to a sixth aspect of the present invention comprises an operation input means for inputting a parameter relating to the constant ratio in addition to the configuration described above, and the threshold value calculation means is configured to output a second value based on the reference received light amount and the parameter. The threshold is calculated. According to such a configuration, the user can appropriately set the second threshold according to the amount of received light (measured value) determined as noise.

  In the measuring device according to the seventh aspect of the present invention, in addition to the above configuration, the reference light reception amount correction means compares the absolute value of the change rate with a first threshold value, and based on the comparison result, the reference light reception amount It is configured to make corrections. According to such a configuration, the threshold when the amount of received light decreases and the threshold when the amount of light received increase are made common, so that the configuration can be simplified.

  A measuring instrument according to an eighth aspect of the present invention includes a measurement value display unit that displays the measurement value calculated by the measurement value calculation unit in addition to the above configuration.

  According to the measuring instrument according to the present invention, when the rate of change in the amount of received light is smaller than a predetermined first threshold, the reference amount of received light is corrected. The reference received light amount can be corrected by discriminating the change in the received light amount and the change in the received light amount due to the influence of dust adhesion or the like. In addition, when the received light amount is larger than the second threshold obtained from the reference received light amount, the reference received light amount is corrected, so the change in the received light amount due to the entry of a workpiece of a certain size or more and the influence of dust adhesion, etc. It is possible to correct the reference received light amount by discriminating the change in the received light amount due to. Therefore, it is possible to realize a measuring instrument that can obtain a correct measurement value even if dust adheres.

It is the perspective view which showed one structural example of the workpiece | work detection system containing the measuring device by embodiment of this invention, and the dimension measuring device 10 is shown as an example of a measuring device. FIG. 2 is an explanatory diagram schematically showing an example of the operation of the dimension measuring instrument 10 in the workpiece detection system of FIG. 1, and shows a state when the workpiece W enters the measurement region 2. It is explanatory drawing which showed typically an example of operation | movement of the dimension measuring device 10 of FIG. 1, and the mode that the correction | amendment of the reference | standard light reception amount A is automatically performed based on the detected light reception amount is shown. FIG. 2 is a block diagram illustrating a configuration example of the dimension measuring instrument 10 in FIG. 1, illustrating an example of a functional configuration in the controller 13. It is the figure which showed an example of operation | movement of the dimension measuring device 10 of FIG. 1, and the mode of the light reception amount X and the measured value y when the workpiece | work W more than fixed size approached is shown. It is the figure which showed an example of operation | movement of the dimension measuring device 10 of FIG. 1, and the mode of change of the light reception amount X and the measured value y when the dust of less than a fixed size adheres is shown. It is the figure which showed an example of operation | movement of the dimension measuring device 10 of FIG. 1, and the mode of the light reception amount X and the measured value y when the workpiece | work W approachs with the approach speed V more than a fixed value is shown. It is the figure which showed an example of operation | movement of the dimension measuring device 10 of FIG. 1, and the mode of the light reception amount X and the measured value y when the workpiece | work W approachs with the approach speed V below a fixed value is shown. It is the figure which showed the other structural example of the dimension measuring device 10 of FIG.

<Work detection system>
FIG. 1 is a perspective view showing one configuration example of a workpiece detection system including a measuring instrument according to an embodiment of the present invention, and a dimension measuring instrument 10 is shown as an example of the measuring instrument. In this workpiece detection system, the workpiece measuring machine 10 is detected by the dimension measuring device 10 by a conveyor such as the belt conveyor B. The workpiece W is a measurement object and passes through the measurement region 2 at a substantially constant approach speed V.

  The dimension measuring device 10 is a measuring device including a light projecting unit 11, a light receiving unit 12, and a controller 13, and irradiates the measurement light 2 to the measurement region 2 through which the workpiece W passes, and the amount of the workpiece W entering the measurement region 2. The amount of received light is detected. The light projecting unit 11 is a light source unit having a light projecting element for irradiating the measurement region 2 with the detection light 1 and an optical lens for making the detection light 1 parallel light. As the light projecting element, a light emitting element such as an LED (light emitting diode) or an LD (laser diode) is used.

  The light receiving unit 12 receives the detection light 1 from the light projecting unit 11 through the measurement region 2, and includes a light receiving element and a condenser lens for detecting the amount of light received according to the amount of work W entering the measurement region 2. A received light amount detection unit. As the light receiving element, for example, a single PD (photodiode) is used. A plurality of PDs or CCDs may be used, but a single system can simplify the system.

  The detection light 1 is composed of parallel light, and a measurement region 2 is formed as an arbitrary cross section thereof. The detection light 1 emitted from the light projecting unit 11 enters the condensing lens of the light receiving unit 12 through the measurement region, and is collected on the light receiving element. That is, when the workpiece W has not yet entered the measurement area 2, the detection light 1 emitted from the light projecting unit 11 toward the light receiving unit 12 is substantially entirely incident on the light receiving unit 12.

  In this example, a rectangular region having a width in the traveling direction of the workpiece W is formed as the measurement region 2. In addition, the light projecting unit 11 and the light receiving unit 12 are disposed as a head unit near the conveyance path of the workpiece W. Specifically, the light projecting unit 11 and the light receiving unit 12 are arranged to face each other with the workpiece W interposed therebetween, and the detection light 1 transmitted through the measurement region 2 is received by the light receiving unit 12.

  The controller 13 is a main unit that drives and controls the light projecting unit 11 and calculates a measurement value indicating the amount of work W entering the measurement region 2 based on the amount of light received detected by the light receiving unit 12. A unit 21 and an operation input unit 22 are provided. The measurement value display unit 21 is a display device for displaying the calculated measurement value. The operation input unit 22 is an input device for inputting parameters and the like. The calculated measurement value is output to a control device such as a PLC (programmable logic controller).

  FIGS. 2A and 2B are explanatory views schematically showing an example of the operation of the dimension measuring instrument 10 in the workpiece detection system of FIG. 1, and how the workpiece W enters the measurement region 2. It is shown. FIG. 2A shows a state where the workpiece W enters from the outside of the measurement area 2 into the measurement area 2 at a constant approach speed V. FIG. 2B shows the change in the amount of received light at that time. It is shown.

  The amount of received light detected by the light receiving unit 12 is substantially constant in a state where the workpiece W has not entered the measurement region 2, and the workpiece W is in the middle of entering the measurement region 2 at a constant entry speed V. In state, it decreases with a constant slope. If the length of the measurement region 2 is longer than the workpiece W with respect to the entry direction of the workpiece W, the amount of received light is substantially constant when the workpiece W is moving in the measurement region 2.

In this example, the light reception amount x ₁ is constant from time 0 to time t ₁ when the workpiece W does not enter the measurement region 2. Further, during the middle of the time _{t 1 at} which the workpiece W is entered the measuring area 2 at approach speed V until time _{t 2, the} amount of light received from _{x 1} to _x 2 _(x 2 _{<x 1),} It decreases with a certain slope. Then, after the time t ₂ when the workpiece W is moving in the measurement region 2, the light reception amount x ₂ is constant.

  The measurement value y calculated by the controller 13 is based on the amount of light received when the workpiece W has not entered the measurement region 2, and the ratio (x / A) between this reference amount of light received A and the amount of light received x detected. It is requested from.

  For example, the measured value y is determined to be 100% (or 1) if the received light amount x matches the reference received light amount A, and the detection light 1 is completely blocked by the work W, and the received light amount x is 0. If there is, 0% (or 0) is obtained. Alternatively, in the case of a head unit in which the length of the measurement region 2 is 30 mm, the measured value y is obtained as 30 mm if the received light amount x matches the reference received light amount A. If the received light amount x is 0, 0 mm is obtained. The shielding state may be 100%.

<Auto adjustment>
FIG. 3 is an explanatory diagram schematically showing an example of the operation of the dimension measuring instrument 10 of FIG. 1, and the reference light receiving amount A is automatically corrected based on the detected light receiving amount x. It is shown. The light receiving unit 12 repeatedly detects the received light amount x at a constant time interval T1. That is, the detection point 3 of the received light amount x is generated at a constant time interval T1, for example, T1 = 160 μs.

  In order to reduce the influence of noise and temperature change, the dimension measuring instrument 10 obtains an average received light amount X as a time average of a plurality of received light amounts x detected within a predetermined time T2, and this average received light amount X The measured value y is calculated based on For example, the average received light amount X is obtained from 128 detection points 3. That is, the average received light amount X is repeatedly detected at a constant time interval T2 = 20.48 ms, and the detection point 4 is generated every T2.

  The measured value y is obtained from the ratio between the average received light amount X and the reference received light amount A. On the other hand, the reference received light amount A is corrected so that the calculated measurement value y approaches the measurement value when the workpiece W has not entered the measurement region 2. The correction amount for correcting the reference light reception amount A is determined based on the difference between the average light reception amount X and the reference light reception amount A.

Here, such correction with respect to the reference received light amount A is referred to as adjustment, and the following (1) to (5) are required as adjustment execution conditions for executing automatic adjustment for automatic correction.
(1) The rate of change of the average amount of received light X is equal to or less than a predetermined threshold Th1.
(2) The average amount of received light X is equal to or greater than the threshold Th2 obtained from the reference amount of received light A.
(3) The average received light amount X is equal to or greater than a predetermined correction limit received light amount Th3.
(4) Conditions (1) to (3) are satisfied continuously for a certain number of times.
(5) The correction amount of the reference light reception amount A does not exceed a predetermined upper limit correction amount Th5.

  The change rate of the average received light amount X changes according to the approach speed V of the workpiece W to the measurement region 2 and is obtained from the difference between the current average received light amount X and the average received light amount X detected in the past. For example, the rate of change is obtained from {(current average received light amount X) − (average received light amount X detected in the past)} / (current reference received light amount A). In the condition (1), such a change rate is compared with a threshold Th1, for example, Th1 = 0.3%.

  When the rate of change is positive, the rate of change is compared with a positive threshold Th1 (+), and when the rate of change is negative, the rate of change is compared with a negative threshold Th1 (−). The condition (1) may be that the rate of change is greater than or equal to Th1 (−) and less than or equal to Th1 (+). Here, in order to simplify the configuration, the absolute value of the rate of change is compared with the positive threshold value Th1. The condition (1) is that the absolute value of the change rate is equal to or less than the threshold value Th1.

  The threshold value Th2 is determined based on the parameter specified by the user and the reference light reception amount A, and changes according to the value of the reference light reception amount A. For example, when it is determined that the change in the received light amount up to 3% of the reference received light amount A is due to dust adhesion, the threshold Th2 is 97% of the current reference received light amount A. The correction limit light reception amount Th3 is determined to be 80% of the initial reference light reception amount A, for example. The auto adjustment is executed when all of the conditions (1) to (4) are satisfied.

  In this example, the rate of change is obtained from the difference between the current average received light amount X and the average received light amount X detected four times before, that is, 81.92 ms before. When the conditions (1) to (3) are continuously satisfied three times or more, the correction of the reference received light amount A is executed.

  When correcting the reference light reception amount A, if the rate of change of the average light reception amount X is greater than a predetermined threshold Th4, the correction of the reference light reception amount A is performed so that the correction amount does not exceed the predetermined upper limit correction amount Th5. Is done. That is, the adjustment execution condition (5) is that the correction amount when correcting the reference light reception amount A is limited to a predetermined upper limit correction amount Th5 or less. For example, when Th4 = Th5 = 0.02% of the initial reference received light amount A and the rate of change is larger than the threshold Th4, the reference received light amount A is corrected within a range not exceeding the upper limit correction amount Th5. On the other hand, when the change rate of the average received light amount X is equal to or less than the threshold Th4, correction is performed with a correction amount corresponding to the difference between the average received light amount X and the reference received light amount A.

  Here, the cycle for updating the measurement value y, the rate of change, and the threshold Th2 and the cycle for determining whether or not to correct the reference received light amount A are synchronized with the cycle for updating the average received light amount X. Shall. That is, every time the average received light amount X is updated, the measurement value y and the rate of change are updated, and processing for determining whether or not the adjustment execution condition is satisfied is performed.

<Controller>
FIG. 4 is a block diagram showing a configuration example of the dimension measuring instrument 10 of FIG. 1, and shows an example of a functional configuration in the controller 13. The controller 13 includes a measurement value display unit 21, an operation input unit 22, an average received light amount calculation unit 31, a reference received light amount storage unit 32, a measured value calculation unit 33, a received light amount storage unit 34, a change rate calculation unit 35, and a parameter storage. A unit 36, a threshold value calculation unit 37, a reference light reception amount correction unit 38, and a measurement area information storage unit 39.

  The average received light amount calculation unit 31 calculates an average received light amount X based on the received light amount x detected by the light receiving unit 12, and outputs the average received light amount X to the measured value calculation unit 33, the change rate calculation unit 35, and the reference received light amount correction unit 38. At the same time, the received light amount is stored in the storage unit 34. The reference received light amount storage unit 32 stores a reference received light amount A indicating the received light amount when the workpiece W has not entered the measurement region 2.

  The measurement value calculation unit 33 calculates a measurement value y indicating the amount of work W entering the measurement region 2 based on the ratio between the average light reception amount X and the reference light reception amount A, and outputs the measurement value y to the measurement value display unit 21. The measurement value y is calculated based on information about the measurement region 2, for example, the width of the measurement region 2 or the area of the measurement region 2. Information regarding the measurement region 2 is held in the measurement region information storage unit 39.

  The change rate calculation unit 35 calculates the change rate of the average received light amount X according to the entry speed V of the workpiece W into the measurement region 2 and outputs the change rate to the reference received light amount correction unit 38. The change rate of the average received light amount X is calculated based on the difference between the current average received light amount X and the past average received light amount X held in the received light amount storage unit 34.

  The parameter storage unit 36 holds parameters input by the operation input unit 22 and determined based on the workpiece W. The threshold value calculation unit 37 calculates the threshold value Th2 based on the reference light reception amount A and the above parameters, and outputs the threshold value Th2 to the reference light reception amount correction unit 38. Specifically, the threshold Th <b> 2 is obtained by multiplying the reference light reception amount A by a certain ratio obtained from the parameters stored in the parameter storage unit 36. Alternatively, the threshold value Th2 is obtained by subtracting a certain value from the reference received light amount A. As a method for obtaining the threshold value Th2 from the reference received light amount A, a method other than the method described above may be used.

  The threshold value Th2 is a threshold value for determining whether or not the reference received light amount A is to be corrected, and includes the received light amount that the user determines to be noise. The threshold Th2 is a parameter that follows the reference light reception amount A because it is calculated based on the reference light reception amount A.

  The reference light reception amount correction unit 38 corrects the reference light reception amount A so that the measurement value y calculated by the measurement value calculation unit 33 approaches the measurement value when the workpiece W does not enter the measurement region 2. The reference received light amount A in the reference received light amount storage unit 32 is updated. Specifically, the correction of the reference light reception amount A so that the ratio between the reference light reception amount A and the average light reception amount X calculated by the average light reception amount calculation unit 31 approaches a predetermined value, for example, approximately 1. Is done. That is, the reference received light amount A is automatically corrected so as to substantially match the current received light amount (see FIG. 6 described later).

  The correction of the reference light reception amount A is executed when the adjustment execution condition is satisfied. That is, the correction of the reference light reception amount A is executed when the rate of change of the average light reception amount X is smaller than a predetermined threshold value Th1 and the average light reception amount X is larger than the threshold value Th2. However, when the average received light amount X is smaller than a predetermined correction limit received light amount Th3, the reference received light amount A is not corrected.

  When correcting the reference light reception amount A, if the rate of change is greater than a predetermined threshold Th4, the correction of the reference light reception amount A is performed so that the correction amount does not exceed the predetermined upper limit correction amount Th5. Is performed (see FIG. 8 described later).

  FIG. 5 is a diagram showing an example of the operation of the dimension measuring instrument 10 of FIG. 1, and shows how the received light amount X and the measured value y change when a workpiece W of a certain size or more enters. In FIG. 5 to FIG. 8, the average received light amount X is simply referred to as received light amount X, the initial values (default values) of the reference received light amount A and the threshold Th2 are described as A1 and A2, respectively, and the corrected limit received light amount Th3 is indicated. It is described as A3. In addition, a graph representing the received light amount X is described as B1, a graph representing the reference received light amount A is represented as B2, a graph representing the threshold value Th2 is represented as B3, and a graph representing the corrected limit received light amount Th3 is represented as B4.

The lower limit of the amount of received light that the user determines to be noise, that is, a workpiece W of a certain size or more corresponding to the threshold Th2, for example, a workpiece W having a diameter of 1 mm, enters the measurement region 2 and is represented by a graph B1. The amount of received light X decreases from A1 to A4. Received light amount X = A4 is smaller than the initial value A2 of the threshold Th2, also the rate of change of the received light amount X at time _{t 11} is beyond the threshold value Th1.

That is, the received light amount X represented by the graph B1 is in the interval from time 0 to the workpiece W enters to the time _{t 11,} a constant value X = A1, at time _{t 11} after a constant value X = A4. Interval from time 0 to time t ₁₁ is filled in the adjustment execution conditions (1) to (4), the correction of the reference received light amount A is executed, and the received light amount X and the reference received light amount A from the beginning Since they match, the correction amount is zero. At time _{t 11,} the adjust execution condition (1), no longer satisfied (2) and (4), also at time _{t 11} after, since the adjust execution condition (2) is not satisfied, the reference amount of light received A correction is not performed.

  For this reason, the graphs B2 and B3 are straight lines parallel to the time axis. The graph B4 is a straight line that is always parallel to the time axis because the correction limit light reception amount Th3 is a fixed value determined from the initial value A1 of the reference light reception amount A.

Measurements y obtained from the ratio of the received light quantity X and the reference received light amount A is represented by a graph similar to the graph B1, is constant in the interval from time 0 to time _{t 11 (y = a 1)} , the time in t ₁₁ or _later, it has become _{a 11 (a 11 <a 1} ). With this configuration, it is possible to identify a change in the amount of received light X due to the entry of a workpiece W having a certain size or more. That is, when a work W of a certain size or more enters and the work W remains in the measurement area 2 as it is, a correct measurement value can be obtained by not performing auto-adjustment.

FIG. 6 is a diagram showing an example of the operation of the dimension measuring instrument 10 of FIG. 1, and shows how the received light amount X and the measured value y change when dust less than a certain size adheres. When dust of less than a certain size, for example, dust with a diameter of 0.5 mm adheres, the amount of received light X decreases from A1 to A5. Received light amount X = A5 is greater than the initial value A2 of the threshold Th2, also the rate of change of the received light amount X at time _{t 21} is beyond the threshold value Th1.

That is, at time t _21, the rate of change of the received light amount X is larger than the threshold value Th1, not satisfied in the adjustment execution conditions (1), correction of the reference received light amount A is no longer being executed. Then, while even after the time t _21, since the adjust execution condition (4) is not satisfied, the correction is not executed, the condition (4) to become time t ₂₂ after meet the, the reference received light amount A Correction has been performed. Thus, in a section from time t ₂₂ to time t _23, the execution of the correction of the reference received light amount A, graph B2 and B3 have decreased with a constant gradient. Reference received light amount A at time t ₂₂ instead of matching the subsequent immediately received light amount X, the are you gradually decreased, by (5) of the adjustment execution conditions described above, when correcting the reference received light amount A This is because the correction amount is limited.

The measured value y is a ₂₁ (a ₂₁ <a ₁ ) in the section from time t ₂₁ to time t ₂₂ , whereas in the section from time t ₂₂ to time t ₂₃ , the measurement value y is reduced. Increasing with a certain slope. After time t ₂₃ is a light receiving amount X and the reference received light amount A match. With this configuration, it is possible to automatically change the reference received light amount A so that the reference received light amount A substantially matches the current received light amount X by identifying a change in the received light amount X due to adhesion of dust less than a certain size.

FIG. 7 is a diagram showing an example of the operation of the dimension measuring instrument 10 of FIG. 1, and shows how the received light amount X and the measured value y change when the workpiece W enters at an approach speed V equal to or higher than a certain value. Has been. In this figure, there is a case where the workpiece W enters the measurement region 2 at an entry speed V equal to or higher than a certain value corresponding to the threshold value Th1 for determining whether or not to correct the reference received light amount A, for example, 5 mm / s. It is shown. Received light amount X represented by the graph B1 is a section from time 0 to the workpiece W does not enter the measurement region 2 to the time _{t 31,} at time _{t 38} after a constant (X = A1). Interval from time t ₃₁ to time t ₃₄ is on the way the work W is entered the measuring area 2 at approach speed V state, the light receiving amount X is reduced with a constant gradient.

The received light amount X is constant (X = A6) in the section from time t ₃₄ to time t _{35 in} which the workpiece W is moving in the measurement region 2, and the workpiece W is at the approach speed V and the measurement region 2. in the interval from time t ₃₅ in the middle of the state where the exit to the time t ₃₈ from increasing at a constant gradient.

In the interval from time 0 to time t ₃₁ , the adjustment execution conditions (1) to (4) are satisfied and the correction of the reference light reception amount A is executed. As a result, the correction amount is zero. On the other hand, the interval from time t ₃₁ to time t _38, since the adjustment execution conditions are not met, the correction of the reference received light amount A is not executed.

Specifically, from the time _{t 31,} in the section from time _{t 32} where the light receiving amount X coincides with the threshold value Th2, the condition (1) is not satisfied, from the time _{t 32,} the time t of received light amount X coincides with A3 _In the section up to ₃₃ , the conditions (1) and (2) are not satisfied. In addition, since at least the conditions (2) and (3) are not satisfied in the section from time t ₃₃ through time t ₃₄ , t ₃₅ to time t ₃₆ when the received light amount X again coincides with A3, time t ₃₆ from the section up to the time _{t 37} where the light receiving amount X coincides again with the threshold value Th2, the condition (1) and (2) is not satisfied.

Then, from the time _{t 37,} in the section from time _{t 38} where the light receiving amount X coincides with A1, the condition (1) is not satisfied, since a while even the time _{t 38} after does not satisfy the condition (4), the correction Is not executed. For this reason, the graphs B2 and B3 are straight lines parallel to the time axis.

Further, the measured value y is represented by a graph similar to the graph B1. That is, the measurement value y is constant (y = a ₁ ) in the section from time 0 to time t ₃₁ and after time t ₃₈ . Interval from time t ₃₁ to time t _34, the measured value y is decreased with a constant gradient. Then, the measured value y is in the interval from time _{t 34} to time _{t 35,} a constant (y _{= a 31),} in the section from time _{t 35} to time _{t 38,} has increased with a constant gradient.

  With this configuration, for the workpiece W that enters the measurement region 2 at an approach speed V that is equal to or greater than a certain value, the change in the received light amount X due to the entry of the workpiece W is identified and the reference received light amount A is corrected. be able to.

FIG. 8 is a diagram showing an example of the operation of the dimension measuring instrument 10 of FIG. 1, and shows how the received light amount X and the measured value y change when the workpiece W enters at an approach speed V less than a certain value. Has been. When the workpiece W enters the measurement region 2 at an entry speed V less than a certain value, for example, 4 mm / s, the received light amount X represented by the graph B1 is from time 0 when the workpiece W does not enter the measurement region 2. and the section from time _{t 41,} at time _{t 48} after a constant (X = A1).

Section from time t ₄₁ to time t ₄₃ is on the way the work W is entered the measuring area 2 at approach speed V state, the light receiving amount X is reduced with a constant gradient. The amount of received light X is constant in the section from time t ₄₃ to time t ₄₄ when the workpiece W is moving in the measurement region 2 (X = A6). in the interval from time t ₄₄ in the middle of the state where the exit to the time t ₄₈ from increasing at a constant gradient.

In the section from time 0 to time t ₄₁ and after time t ₄₉ , the adjustment execution conditions (1) to (4) are satisfied and the correction of the reference light reception amount A is executed. Since the amount A coincides with the amount A, the correction amount is zero. In this interval, the measurement value y is a _1.

On the other hand, from the time _{t 41,} the interval up to time _{t 42} where the light receiving amount X coincides with the threshold value Th2, the adjustment execution conditions (1) to (4) is satisfied, correction of the reference received light amount A is executed. Therefore, in this section, the reference received light amount A represented by the graph B2 decreases with a constant slope by executing the correction. However, since the correction amount is limited to the upper limit correction amount Th5 or less by the adjustment execution condition (5), the slopes of the graphs B2 and B3 are smaller in absolute value than the slope of the graph B1. Measurements y has a _{a 41 (a 41 <a 1} ) at time _{t 42.}

In the interval from time t ₄₂ to time t _45, the received light amount X is less than the threshold Th2, since the adjust execution condition (2) is not satisfied, correction of the reference received light amount A is not executed. Then, the received light amount X after time _{t 45} becomes the threshold Th2 or more, even when the meet the conditions (1) to (3), the interval up to time _{t 46} to become the condition (4) is satisfied, The correction of the reference received light amount A is not executed. Thus, in a section from time t ₄₂ to time t _46, becomes a straight line parallel to the axis graphs B2 and B3 is the time, measured value y is changed in proportion to the amount of light received X. The measured value y is a ₄₂ (a ₄₂ <a ₄₁ ) from time t ₄₃ to time t ₄₄ .

Section from time _{t 46} to time _{t 49,} the adjustment execution conditions (1) to (4) is satisfied, correction of the reference received light amount A is executed. Therefore, in this section, the reference received light amount A increases with a constant slope by performing correction. However, since the correction amount is limited to the upper limit correction amount Th5 or less by the adjustment execution condition (5), the slopes of the graphs B2 and B3 are smaller in absolute value than the slope of the graph B1. Further, in the section from time t ₄₇ to time t ₄₉ , the light reception amount X exceeds the reference light reception amount A, so the measured value y is larger than a ₁ .

  By configuring in this way, the correction amount when correcting the reference light reception amount A does not exceed a predetermined upper limit correction amount Th5. An excessive correction amount can be suppressed. That is, even when the reference light reception amount A is corrected by mistake, the correction amount when correcting the reference light reception amount A is limited to the upper limit correction amount Th5 or less, so the reference light reception amount A is an appropriate value. Can be prevented from greatly deviating.

More specifically, since FIG. 8 shows a case where the workpiece W enters, the graph B2 is preferably a constant value as shown in FIG. However, when the adjustment execution condition (1) is satisfied (when the workpiece W enters at 4 mm / s or less, the adjustment execution condition (1) is satisfied), the graph B2 is downwardly sloping. For this reason, an error is included in the measurement value a ₄₂ when the workpiece W has completely entered. In order to reduce this error, an adjustment execution condition (5) is provided. If this condition (5) exists, when the graph B2 falls to the right, the slope becomes small. As a result, the graph B3 that follows the graph B2 also has a gentle slope and a downward-sloping graph, and the timing at which auto-adjustment is not performed (time t ₄₂ ) can be advanced, so the error included in the measured value a ₄₂ Can be reduced.

Note that the threshold value Th1 in the adjustment execution condition (1) is preferably 0 in an ideal environment. At this time, the graph B2 in FIG. 8 becomes a straight line parallel to the time axis like the graph B2 in FIG. 7, and no error is included in the measured value a ₄₂ (the measured value a ₃₁ in FIG. Not included). However, the threshold value Th1 must have a finite value larger than 0 due to the influence of circuit characteristics, disturbance light, and the like.

  More specifically, the graph B1 in FIG. 8 is not actually a straight line, but has a shape of a wavy line that fluctuates due to the influence of circuit characteristics, disturbance light, or the like. And when the approach speed of the workpiece W is slow, the measuring instrument side distinguishes whether the graph B1 is fluctuating because the workpiece W has entered, or whether the graph B1 is fluctuating due to the influence of ambient light or the like. Is not attached. For this reason, the threshold value Th1 must have a finite value in order to execute auto-adjustment even if the graph B1 fluctuates due to ambient light or the like.

<Other configuration examples of dimension measuring instrument>
In FIG. 1, the example in which the dimension measuring instrument 10 includes the light projecting unit 11 and the light receiving unit 12 arranged to face each other with the workpiece W interposed therebetween has been described, but the present invention is not limited to this. For example, the head unit 14 includes a light projecting unit 11, a light receiving unit 12, and a half mirror 5, and the dimension measuring device 10 in which the light projecting unit 11, the light receiving unit 12, and the half mirror 5 are arranged in a common housing is also provided. It is included in the invention.

  FIG. 9 is a diagram showing another configuration example of the dimension measuring instrument 10 of FIG. The dimension measuring device 10 includes a head unit 14 including a light projecting unit 11, a light receiving unit 12, and a half mirror 5, a mirror 6, and a controller 13. The light projecting unit 11 and the mirror 6 are arranged to face each other, and the detection light emitted from the light projecting unit 11 passes through the half mirror 5 and is reflected by the mirror 6.

  The detection light reflected by the mirror 6 is reflected by the half mirror 5 and enters the light receiving unit 12. The measurement area 2 is formed between the head unit 14 and the mirror 6, and a workpiece W entering at a constant entry speed V is detected.

  According to the present embodiment, since the reference received light amount A is corrected when the rate of change of the received light amount X is smaller than a predetermined threshold Th1, the entry of the work W whose approach speed V is equal to or greater than a certain value. The reference light reception amount A can be corrected by discriminating between the light reception amount change due to and the light reception amount change due to the influence of dust adhesion and the like. Further, when the received light amount X is larger than the threshold Th2, the correction of the reference received light amount A is performed, so that the received light amount change due to the entry of the work W of a certain size or more and the received light amount change due to the influence of dust adhesion etc. The reference received light amount A can be corrected by identification. Therefore, it is possible to identify the change in the amount of received light due to the entry of the workpiece W and the change in the amount of received light due to the influence of dust adhesion, etc., and automatically correct the measurement value y.

  Further, when the received light amount X is smaller than the predetermined correction limit received light amount Th3, the correction of the reference received light amount A is not performed, so that when the change in the received light amount X is small, the decrease in the received light amount X is followed. Thus, it is possible to prevent the reference received light amount A from being corrected indefinitely.

  In this embodiment, each time the average received light amount X is updated, the measurement value y and the rate of change are updated, and an example in which processing for determining whether or not the adjustment execution condition is satisfied is described. However, the present invention is not limited to this. The cycle for updating the measurement value y and the rate of change and the cycle for determining whether to correct the reference light reception amount A may be different from the cycle for updating the average light reception amount.

  Further, in the present embodiment, an example of a transmission type dimension measuring device that receives the detection light 1 transmitted through the measurement region 2 has been described, but the present invention is not limited to this. For example, the present invention can also be applied to a reflective dimension measuring device that receives detection light reflected by the workpiece W.

  In the present embodiment, an example in which the reference received light amount A is corrected based on the received light amount detected by the light receiving unit 12 during the period during which the light projecting unit 11 emits light has been described. The zero point of the amount A is adjusted based on the amount of received light detected by the light receiving unit 12 during the extinguishing period of the light projecting unit 11, for example. If it demonstrates more concretely, the light projection part 11 will repeat alternately the light emission period which radiate | emits the detection light 1, and the light extinction period when the detection light 1 is not radiate | emitted. The repetition interval of the light emission period is T1 = 160 μs. The correction of the reference light reception amount A is performed based on the light reception amount x detected during this light emission period. On the other hand, the zero point of the reference light reception amount A is adjusted based on the light reception amount x detected during the extinguishing period, and is adjusted so that the reference light reception amount A matches the light reception amount x. Such zero point adjustment of the reference received light amount A is executed at the timing when auto adjustment is executed.

DESCRIPTION OF SYMBOLS 1 Detection light 2 Measurement area | region 3, 4 Detection point 5 Half mirror 6 Mirror 10 Dimension measuring device 11 Light projection part 12 Light reception part 13 Controller 14 Head unit 21 Measurement value display part 22 Operation input part 31 Average received light quantity calculation part 32 Reference light reception Amount storage unit 33 Measurement value calculation unit 34 Light reception amount storage unit 35 Change rate calculation unit 36 Parameter storage unit 37 Threshold calculation unit 38 Reference light reception amount correction unit 39 Measurement region information storage unit B1 Graph B2 indicating the light reception amount X Reference light reception amount A A graph B3 representing a threshold value Th2 A graph representing a correction limit light reception amount Th3

Claims (8)

A light projecting unit that emits parallel light to a measurement region through which a workpiece passes, and a light receiving unit that receives the parallel light through the measurement region and detects the amount of received light that changes according to the amount of work entering the measurement region. A measuring instrument comprising:
A reference light reception amount storage means for holding a reference light reception amount indicating a light reception amount when the workpiece does not enter the measurement area;
Measurement value calculation means for calculating a measurement value indicating the amount of work entering the measurement region based on a ratio between the reference light reception amount and the light reception amount detected by the light receiving unit;
A reference light reception amount correcting means for correcting the reference light reception amount so that a ratio between the reference light reception amount and the light reception amount detected by the light receiving unit approaches a predetermined value;
A rate-of-change calculating means for obtaining a rate of change of the amount of received light according to the speed of entry of the workpiece into the measurement area,
The reference received light amount correcting means has a rate of change smaller than a predetermined first threshold value, and the received light amount detected by the light receiving unit is higher than a second threshold value determined based on the reference received light amount. A measuring instrument that corrects the reference amount of received light when the value is larger.   2. The reference light reception amount correction unit corrects the reference light reception amount so that the correction amount does not exceed a predetermined upper limit correction amount when correcting the reference light reception amount. The measuring instrument described.   The reference light reception amount correction unit does not correct the reference light reception amount when the light reception amount detected by the light receiving unit is smaller than a predetermined correction limit light reception amount. Measuring instrument.   The measuring device according to claim 1, wherein the reference light reception amount correction unit corrects the reference light reception amount when the rate of change in a certain period is less than a first threshold value.   2. The measuring instrument according to claim 1, further comprising a threshold value calculation means for calculating a second threshold value by multiplying the reference received light amount by a certain ratio. Comprising an operation input means for inputting parameters relating to the fixed ratio,
6. The measuring device according to claim 5, wherein the threshold value calculation means calculates a second threshold value based on the reference received light amount and the parameter.   2. The measurement according to claim 1, wherein the reference received light amount correction unit compares the absolute value of the change rate with a first threshold value, and corrects the reference received light amount based on the comparison result. vessel.   2. The measuring instrument according to claim 1, further comprising measurement value display means for displaying the measurement value calculated by the measurement value calculation means.

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