JP2006038571A - Optical displacement gauge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical displacement gauge capable of maintaining a high measurement accuracy by choosing suitable measurement algorithm according to a kind of object etc., while reducing the judgment of user and burden of operation as much as possible. <P>SOLUTION: The optical displacement gauge comprises: a light emitting device for irradiating a workpiece with light; an image sensor for outputting an electric signal corresponding to amount of light reception received from the workpiece by each of a plurality of pixel constitutional part; and a process unit for performing measurement process for measuring the distance to the object or displacement of the object by the peak position or position of the center of gravity of the peak part of the light reception wave form corresponding to distribution of the light reception by operating the electric signal from the image sensor. The measurement process part is provided with a plurality of measurement mode with different calculation methods for calculating the peak position or position of the center of gravity and extracts (#103) feature amount such as width of the peak part and selects an appropriate measurement mode (#104-#108) corresponding to the feature amount. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical displacement meter that measures the distance to an object or the displacement of the object from an electrical signal obtained by irradiating the object with light and receiving light from the object with an image sensor.

  As this type of optical displacement meter, there is one that measures the distance or displacement to an object (hereinafter also referred to as a workpiece) using the principle of triangulation. This optical displacement meter has an image in which a laser diode as a light emitting element for irradiating light to a work and each of a plurality of pixel components receives light from the work and outputs an electrical signal corresponding to the amount of light received. A sensor and a measurement processing unit that measures a distance to the workpiece or a displacement of the workpiece based on an electrical signal from the image sensor are provided. An electric signal from the image sensor is converted into a digital value by an AD converter and input to a measurement processing unit.

  The measurement processing unit detects the peak portion of the received light waveform corresponding to the distribution of the received light amount, and calculates the distance to the workpiece using the principle of triangulation by obtaining the peak position or the center of gravity position of the peak portion. The peak portion in the received light waveform is a portion where an electric signal (for example, voltage) corresponding to the amount of received light once increases and then decreases. Strictly speaking, a portion whose height and width exceed a predetermined value is a peak portion. Detected.

  The workpieces to be measured by the optical displacement meter as described above include printed wiring boards, semiconductor substrates, metal products, resin products, and other various types. For example, the reflectivity of light, and hence the amount of received light, varies greatly depending on the state of the surface of the workpiece. When the surface of the work is a surface having a high light reflectance such as a mirror surface, a great amount of reflected light returns to the optical displacement meter, and the amount of light received by the image sensor becomes very large. On the other hand, when the surface of the workpiece is rough and light reflection is likely to occur, the amount of light received by the image sensor of the optical displacement meter becomes very small.

  As described above, when the amount of received light varies greatly due to the difference in the material and surface state of the workpiece, it becomes difficult to effectively use the dynamic range while avoiding saturation of the accumulated charge of the image sensor. Therefore, feedback control is generally performed to adjust the light emission amount of the light emitting element and the amplification factor of the amplifier that amplifies the electric signal from the image sensor so that the light reception amount (for example, the peak value of the peak) becomes a target value. (For example, see Patent Document 1).

  The difference in workpiece material and surface condition affects not only fluctuations in the amount of received light typified by the peak value of the peak of the received light waveform, but also the shape of the peak of the received light waveform. In a typical workpiece, light causes moderate diffuse reflection on the surface, and a relatively clean peak appears in the received light waveform. For example, a workpiece having a surface with high light reflectance such as a mirror surface has a narrow base. A steep mountain appears. On the other hand, in a workpiece having a large unevenness on the surface, irregularly reflected light called diving light is generated, so that the shape of the mountain portion is often disordered or becomes gentle. Thus, when the shape of the peak changes greatly, it is difficult to maintain high measurement accuracy with a uniform algorithm for measuring the distance to the workpiece by obtaining the peak position or the center of gravity of the peak.

Therefore, it is conceivable to change the algorithm for measuring the distance to the workpiece by obtaining the peak position or the center of gravity position of the peak according to the type of the workpiece, such as a mirror workpiece or a workpiece with a lot of irregular reflections. A plurality of modes having different measurement algorithms may be prepared in advance, and the mode used by the user may be set according to the type of workpiece.
JP 2001-159516 A

  However, setting one of a plurality of modes with different measurement algorithms in accordance with the type of workpiece or the like is considered difficult for an unfamiliar user. In addition, there may be a user who feels such a setting operation troublesome.

  Accordingly, the present invention provides an optical displacement meter that can maintain high measurement accuracy by selecting an appropriate measurement algorithm according to the type of object while reducing the burden of user judgment and operation as much as possible. The purpose is to provide.

  The first configuration of the optical displacement meter according to the present invention includes a light emitting element for irradiating light on an object, and an electric power corresponding to the amount of light received by each of a plurality of pixel components by receiving light from the object. An image sensor that outputs a signal, and processes the electrical signal from the image sensor to detect the peak of the received light waveform corresponding to the distribution of the amount of received light, and calculates the peak position or centroid position of the peak to the target A measurement processing unit that executes a measurement process for measuring a distance or a displacement of an object, and the measurement processing unit changes a calculation method of a peak position or a gravity center position according to a feature amount extracted from a received light waveform. And

  According to such a configuration, the measurement processing unit executes the measurement process by automatically changing the calculation method of the peak position or the barycentric position according to the feature amount extracted from the received light waveform. Therefore, an appropriate measurement algorithm is selected according to the type of the object and the like, and high measurement accuracy can be maintained without imposing a burden on the user regarding the type of the object or the like. Note that “change the calculation method of the peak position or centroid position” refers to whether to change the calculation method of the peak position, to change the calculation method of the centroid position, and to calculate either the peak position or the centroid position ( This includes the case of changing which one is adopted as the value corresponding to the distance to the object.

  The second configuration of the optical displacement meter according to the present invention is a preferred embodiment of the first configuration, and the feature amount extracted from the received light waveform is the width of the peak portion of the received light waveform. To do. Here, the “peak width” means, for example, the distance between two points where a straight line of a certain level set near the base of the peak and the peak of the received light waveform intersect. In general, when the surface of an object is a surface having a high light reflectance such as a mirror surface, the width of the peak is narrow, and conversely, when the object is rough and subject to light irregular reflection, the width of the peak is small. Become wider. As the “feature amount extracted from the received light waveform”, various parameters that change in accordance with the type of the object can be adopted in addition to the width of the peak portion. For example, the number of ridges appearing in the received light waveform, the symmetry of the ridge shape with respect to a vertical line passing through the peak of the ridge, the ratio of the area above and below a certain level of the ridge, etc. can be considered.

  The third configuration of the optical displacement meter according to the present invention shows a preferred embodiment in any one of the above configurations, and the measurement processing unit has a plurality of modes with different calculation methods of the peak position or the gravity center position. Further, one of a plurality of modes is selected according to the feature amount extracted from the received light waveform. With such a configuration, assembly of the measurement algorithm is facilitated. Further, coupled with the fourth configuration, the user can easily understand the measurement algorithm.

  A fourth configuration of the optical displacement meter according to the present invention is characterized in that in the third configuration described above, the optical displacement meter further includes a display for displaying information indicating one selected mode. According to such a configuration, since the mode of the measurement algorithm automatically selected and executed by the measurement processing unit is displayed on the display, the user can know the mode being executed from the display, The relationship between the object and mode can be confirmed. The “information indicating the mode” may be any information as long as the user can specify the mode being executed, such as a character string including a mode number and a symbol. Therefore, a 7-segment display capable of displaying at least a number is sufficient.

  A fifth configuration of the optical displacement meter according to the present invention includes a light emitting element for irradiating light on an object, and an electric light corresponding to the amount of light received by each of a plurality of pixel components by receiving light from the object. An image sensor that outputs a signal, and processes the electrical signal from the image sensor to detect the peak of the received light waveform corresponding to the distribution of the amount of received light, and calculates the peak position or centroid position of the peak to the target A measurement processing unit that executes a measurement process that measures the distance of the object or a displacement of the object, and a display that displays a feature amount extracted from the received light waveform, and the measurement processing unit uses a calculation method of the peak position or the center of gravity position. A plurality of types are stored in advance, and one of a plurality of types of peak position or barycentric position calculation methods is selected according to a selection input, and measurement processing is executed.

  According to such a configuration, the feature amount extracted from the received light waveform that changes in accordance with the type of the object is displayed on the display, and the user can display an appropriate peak position or centroid position from the feature amount display. A calculation method (measurement mode) can be selected. For example, according to a correspondence table described in a manual or the like, the user may select a calculation method (measurement mode) corresponding to the feature amount displayed on the display. Therefore, the burden on the determination for the user's selection is reduced as compared with the case where the calculation method (measurement mode) is selected according to the type of the object. Since the feature amount is displayed as a numerical value, a 7-segment display capable of displaying at least a number is sufficient for the display used for the display.

  A sixth configuration of the optical displacement meter according to the present invention is characterized in that, in the fifth configuration, the feature amount extracted from the received light waveform is a width of a peak portion of the received light waveform. Here, the “peak width” means, for example, the distance between two points where a straight line of a certain level set near the base of the peak and the peak of the received light waveform intersect. In general, when the surface of an object is a surface having a high light reflectance such as a mirror surface, the width of the peak is narrow, and conversely, when the object is rough and subject to light irregular reflection, the width of the peak is small. Narrow. As the “feature amount extracted from the received light waveform”, various parameters that change in accordance with the type of the object can be adopted in addition to the width of the peak portion. For example, the number of ridges appearing in the received light waveform, the symmetry of the ridge shape with respect to a vertical line passing through the peak of the ridge, the ratio of the area above and below a certain level of the ridge, etc. can be considered.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram illustrating the measurement principle of an optical displacement meter according to an embodiment of the present invention. This optical displacement meter is also called a laser displacement meter, and is used to measure the displacement of an object (hereinafter referred to as a workpiece) in a non-contact manner using the principle of triangulation. Laser light emitted from the laser diode 12 under the control of the LD driver 11 passes through the light projecting lens 13 and irradiates the work WK. Part of the laser light reflected by the workpiece WK passes through the light receiving lens 14 and is received by the linear image sensor 15. The linear image sensor 15 is a CCD or CMOS image sensor in which a plurality of pixel components are arranged in a line, and a charge corresponding to the amount of received light is accumulated and extracted for each pixel component.

  When the workpiece WK is displaced as shown by a broken line in FIG. 1, the optical path of the laser beam that is reflected by the workpiece WK and reaches the linear image sensor 15 changes as shown by a broken line. As a result, the position of the light receiving spot on the light receiving surface of the linear image sensor 15 moves, and the light receiving waveform, that is, the peak position or the gravity center position of the received light amount changes. Accumulated charges corresponding to the amount of received light in each pixel component of the linear image sensor 15 are read out by the readout circuit 16 and a received light waveform that is a one-dimensional received light amount distribution is obtained by signal processing. The displacement of the workpiece WK is obtained from the peak position or the center of gravity position of the received light waveform.

  2A and 2B show the appearance of the optical displacement meter, FIG. 2A is a plan view, and FIG. 2B is a side view. The optical displacement meter includes a sensor head unit 21 and a controller unit 22. The sensor head unit 21 incorporates the LD driver 11, the laser diode 12, the light projecting lens 13, the light receiving lens 14, the linear image sensor 15, and the readout circuit 16.

  The controller unit 22 controls the output (light emission amount) of the laser diode 12 via the LD driver 11 of the sensor head unit 21 and calculates the displacement of the workpiece WK from the signal read from the linear image sensor 15. Built-in electronic circuit to execute. Further, on the upper surface of the controller unit 22, a display 221 using a 7 segment LED, an increase / decrease key 222 which is a seesaw type push button switch used for setting a target value, and the like are provided. The display 221 is used for numerical display of measurement results, display of a measurement mode described later, or display of information for selection thereof, and can display them simultaneously in two upper and lower stages.

  The sensor head unit 21 and the controller unit 22 are connected by an electric cable 23 to exchange electric signals with each other, and a power supply voltage is supplied from the controller unit 22 to the sensor head unit 21. The sensor head unit 21 is fixed to a predetermined mounting base 25 using two bolts 24. Two mounting holes through which the bolts 24 are inserted are provided along the reference surface 26 of the sensor head portion 21. The reference surface 26 is a surface on which the measurement laser light is emitted and the reflected light from the workpiece WK is incident.

  FIG. 3 is a block diagram showing a main circuit configuration of the optical displacement meter. The sensor head unit 21 includes a laser diode 12 and its drive circuit (LD driver) 11, a linear image sensor 15 and its readout circuit 16, a light projecting lens 13 and a light receiving lens 14. The controller unit 22 includes a low-pass filter (LPF) 41, an amplifier 46, an AD converter 47, a processing unit (measurement processing unit) 44, a DA converter 45, and a reset / control circuit 48. The processing unit 44 is an integrated circuit (LSI) in which a microprocessor, its peripheral circuits, a dedicated circuit for image signal processing, and the like are integrated.

  Laser light emitted from the laser diode 12 passes through the light projecting lens 13 and irradiates the work WK. Part of the laser light reflected by the work WK passes through the light receiving lens 14 and enters the linear image sensor 15. The charge accumulated in each pixel component of the linear image sensor 15 is read out by the readout circuit 16. The readout circuit 16 obtains a time-series voltage signal corresponding to a one-dimensional received light amount distribution by applying a pixel selection signal that is a readout pulse signal to the linear image sensor 15 and sequentially scanning each pixel component.

  For example, when the linear image sensor 15 is composed of 256 pixels and the transfer rate for each pixel is 1 microsecond, the accumulated charge of all the pixel components is read out in 256 microseconds, and the time series voltage is read from the readout circuit 16. Output as a signal. The time required to read the accumulated charges of all the pixels is the sampling period. The output signal of the reading circuit 16 is passed to the controller unit 22.

  The voltage signal from the readout circuit 16 includes information on the distribution of received light amount regarding the pixel position in the linear image sensor 15. The higher the voltage value, the greater the amount of light received at that pixel position. The waveform of this voltage signal is the above-described received light waveform, and the received light waveform includes a peak portion that increases and then decreases. The peak position of this peak corresponds to the pixel position having the largest amount of received light corresponding to the distance to the workpiece WK.

  As shown in FIG. 3, the voltage signal output from the low-pass filter 41 is amplified by the amplifier 46 and then converted into a digital value by the AD converter 47, and the digital value is sequentially given to the processing unit 44. The processing unit 44 detects the peak portion of the received light waveform from the sequential data input via the AD converter 47 and obtains the peak position or (and) the center of gravity position. When the received light waveform has a relatively clean and steep peak, the peak position corresponds to the distance to the work WK as described above. Therefore, if the peak position is obtained, the distance to the work WK can be accurately determined. It can be measured.

  However, since it is often difficult to calculate the peak position of the peak with high accuracy, usually the center of gravity of the peak is often calculated. When the peak position or the gravity center position of the mountain portion is calculated, the distance or displacement to the workpiece WK is measured from the above-described triangulation principle. The measurement result is displayed on the display 221 and is given from the processing unit 44 to the DA converter 45, converted into an analog voltage, and output to an external device. The optical displacement meter of the present embodiment extracts the feature amount of the received light waveform that changes according to the type of the workpiece WK and displays it on the display 221, or the peak position or the center of gravity position of the mountain portion is displayed. It has a function to automatically switch the calculation method (measurement mode). This function will be described later.

  In FIG. 3, the intensity (light emission amount) of the laser light emitted from the laser diode 12 is controlled by the processing unit 44 via the LD driver 11. If the intensity of the laser light changes, the amount of light (the amount of received light) reflected by the workpiece WK and incident on the linear image sensor 15 also changes. Therefore, by adjusting the intensity of the laser light emitted from the laser diode 12 according to the light reflectance (brightness) of the work WK, it is possible to avoid saturation of accumulated charges in each pixel component of the linear image sensor 15. , So that the dynamic range can be fully utilized. Specifically, the intensity of the laser beam is adjusted by changing the pulse width or duty ratio of a pulse for driving the laser diode 12. Of course, the intensity of the laser beam may be adjusted by changing the pulse voltage (peak value).

  Control of the light emission amount (laser light intensity) by the processing unit 44 as described above is performed as a kind of feedback control. That is, feedback control of the light emission amount (laser light intensity) is performed so that a value (for example, peak value) corresponding to the light reception amount becomes a predetermined target value. Instead of the feedback control of the light emission amount, feedback control of the gain (amplification factor) of the amplifier 46 may be performed as shown by a broken line in FIG. Alternatively, the feedback control of the light emission amount and the feedback control of the amplification factor of the amplifier 46 may be used in combination. For example, the feedback control of the amplification factor of the amplifier 46 is performed while the error of the feedback amount with respect to the target value is within a predetermined range, and the feedback control of the light emission amount is performed when the error of the feedback amount exceeds the predetermined range. It can be configured as follows.

  FIG. 4 is a block diagram showing a configuration of feedback control by the processing unit 44. The processing unit 44 includes a comparison unit 441, an operation amount calculation unit 442, and an output unit 443. Further, the LD driver 11 and the laser diode 12 in FIG. 3 correspond to the control target 51, and the linear image sensor 15, the readout circuit 16, the AD converter 47, and the like correspond to the feedback circuit (FB circuit) 52. In this example, a peak value (digital conversion value) of a voltage signal corresponding to the received light amount is input to the comparison unit 441 of the processing unit 44 as a feedback amount (FB amount).

  The comparison unit 441 compares a predetermined target value with the feedback amount and outputs the error. Based on this error, the operation amount calculation unit 442 calculates the operation amount and provides it to the output unit 443. This operation amount corresponds to the above-described light emission amount or (and) amplification factor. The operation amount is given to the control target 51 as a control signal from the output unit 443 of the processing unit 44. That is, a control signal is given to the LD driver 11 or (and) the amplifier 46, and the light emission amount of the laser diode 12 or (and) the amplification factor of the amplifier 46 is controlled. Then, the peak value of the received light amount obtained by the feedback circuit 52 (linear image sensor 15, readout circuit 16, AD converter 47, etc.) is fed back to the comparison unit 441 of the processing unit 44, thereby forming a feedback loop. Yes.

  Next, several embodiments of the measurement algorithm provided in the optical displacement meter of the present embodiment will be described. The optical displacement meter of the present embodiment extracts the feature quantity of the received light waveform that changes according to the type of the workpiece WK and displays it on the display 221 or the measurement algorithm (peak position or centroid position of the mountain) The function of automatically switching the calculation method). This makes it possible to maintain high measurement accuracy even if the type of the workpiece WK changes while reducing the burden on the user's judgment and operation as much as possible. The measurement algorithm, that is, the peak peak position or the center of gravity position calculation method is configured by a microprocessor program included in the processing unit 44.

  FIG. 5 is a flowchart showing the flow of measurement processing according to the first embodiment of the present invention. In step # 101, the processing unit 44 executes the above-described feedback control and adjusts the light emission amount or (and) the amplification factor to be an appropriate value. In subsequent step # 102, a peak portion of the received light waveform obtained from the output signal of the linear image sensor 15 is detected. Among the portions where the electrical signal (voltage) corresponding to the amount of received light once increases and then decreases, those whose peak value is equal to or greater than the threshold and whose width exceeds a predetermined value are detected as peaks.

  In the next step # 103, the width D of the peak is extracted as the feature amount of the received light waveform. As illustrated in FIG. 6, the received light waveform 63 has a peak portion 64, and a distance D between two points where a straight line of a certain level (threshold value) set near the peak portion 64 intersects the peak portion 64 is a peak portion. It corresponds to the width of. FIG. 6 shows a state where the peak value of the peak portion 64 is adjusted to the target value by the feedback control described above.

  In subsequent step # 104, the width D of the peak is determined. That is, the reference values d1 and d2 (d1 <d2) are compared with the width D of the peak portion to branch in three ways. If the crest width D is smaller than the reference value d1, mode 1 is selected in step # 105. If the crest width D is not less than the reference value d1 and not more than d2, mode 2 is selected in step # 106. If the part width D is greater than the reference value d2, mode 3 is selected in step # 107.

  The width D of the peak portion can be represented by, for example, the number of pixels occupying 256 pixels corresponding to the maximum width of the linear image sensor 15. For example, in a standard work, the peak width D corresponds to 5 to 10 pixels. Therefore, when the reference values d1 and d2 are set to 5 and 10, mode 1 corresponds to a workpiece measurement mode having a high surface light reflectance, and mode 2 corresponds to a standard workpiece measurement mode. 3 corresponds to a workpiece measurement mode in which light is easily diffusely reflected on the surface.

  FIG. 7 is a diagram illustrating a method for calculating the center of gravity in the three measurement modes according to the first embodiment. (A) shows the mode 1 executed when the crest width D is smaller than the reference value d1, and (b) shows the mode 2 executed when the crest width D is not less than the reference value d1 and not more than d2. (C) shows the mode 3 executed when the width D of the peak is larger than the reference value d2. When calculating the position of the center of gravity of the mountain portion 64 in each mode, the center of gravity is calculated for the portion above the straight line (center of gravity calculation line) L1, L2 or L3 parallel to the horizontal axis. In the example shown in the drawing, this barycentric calculation line becomes higher in the order of mode 1, mode 2, and mode 3. Note that the center-of-gravity calculation line L1 in mode 1 coincides with the straight line of the threshold when the width D of the peak is obtained, but it is not always necessary to coincide.

  The reason for changing the vertical position of the gravity center calculation line L1 according to the width D of the peak as described above is as follows. That is, in mode 1 in the case of measuring a workpiece having a narrow peak width D compared to mode 2 in the case of measuring a standard workpiece, the center of gravity calculation line L1 is used to calculate the center of gravity by lowering it from L2. Increase the number of data to be saved. Otherwise, since the peak width D is small, the number of data used for centroid calculation is small, and the accuracy of the calculation result may not be sufficiently ensured. On the other hand, in the mode 3 in the case of measuring a workpiece having a wide ridge width D, the number of data used for centroid calculation is reduced by raising the centroid calculation line L3 above L2. By doing so, the adverse effect (displacement) that the parasitic mountain portion (65 in FIG. 7C) generated in the vicinity of the base due to the diffusely reflected light and the multiple reflected light has on the centroid calculation is suppressed, and the true distance corresponding to the distance to the workpiece is achieved. The position of the center of gravity can be calculated with high accuracy. Further, when the width D of the mountain portion is wide, the number of data used for the centroid calculation is sufficiently large. Therefore, there is no problem even if the number of data used for the centroid calculation is reduced by increasing the centroid calculation line L3.

Returning to the flowchart of FIG. 5, in the three modes from Step # 105 to Step # 107, the center of gravity position of the mountain portion 64 is calculated by the center of gravity calculation as described above (Step # 108). Then, the distance to the workpiece is obtained from the calculation result, and the measurement result is displayed on the display 221 as described above, and is output to the external device (step # 109).
(Modification of Example 1)

  As a modified example of the first embodiment, instead of calculating the center of gravity position of the mountain portion 64, the distance to the workpiece may be obtained by calculating the peak position. The peak position can be easily obtained by a known peak detection process. Alternatively, a method is also known in which a quadratic curve passing through three points sampled before and after the peak position of the peak portion 64 is estimated and the peak position is obtained. For peak positions, if there is a certain regularity in the tendency to shift depending on the type of workpiece, etc., prepare multiple measurement modes with different correction directions and correction amounts, It is possible to configure the processing unit 44 to select and execute an appropriate measurement mode according to the feature amount.

  Moreover, you may make it switch according to measurement mode whether the gravity center position of the peak part 64 or a peak position is calculated as an amount corresponding to the distance to a workpiece | work. For example, the center of gravity position may be calculated in the case of the received light waveform as shown in FIGS. 7A and 7B, and the peak position may be calculated in the case of the received light waveform as shown in FIG. 7C. That is, in the first embodiment, in the case of the received light waveform of FIG. 7C, the adverse effect of the parasitic mountain portion 65 generated in the vicinity of the skirt is eliminated by raising the center of gravity calculation line L3, but only in the case of (c). If the peak position is calculated instead of the centroid position of the peak portion 64, the adverse effect of the parasitic peak portion 65 can be eliminated.

  Further, as the feature quantity of the received light waveform, it is possible to extract not only the width of the peak portion but also various feature quantities and use them for switching the measurement mode. For example, the objectivity related to the vertical line passing through the peak of the mountain portion 64 may be extracted as a feature amount and used for switching the measurement mode. FIG. 8 illustrates a case where the objectivity related to the vertical line passing through the peak of the peak portion 64 is broken. FIG. 8A is the same as the received light waveform shown in FIG. 7C, and the objectivity related to the vertical line 66 passing through the peak is broken due to the formation of the parasitic mountain 65. FIG. In FIG. 8B, the parasitic mountain portion is not generated, but the objectivity regarding the vertical line 66 passing through the peak is broken due to the influence of irregular reflection and multiple reflected light on the surface of the workpiece.

  As shown in FIG. 8, the collapse of the objectivity related to the vertical line 66 passing through the peak of the peak portion 64 is obtained by dividing the distance D between the two points where the threshold line 67 and the peak portion 64 intersect with each other with the vertical line 66 as D1 and D2. Can be determined by obtaining the difference between D1 and D2. Alternatively, the area of the peak 64 above the threshold line 67 may be divided by the vertical line 66 and obtained separately, and the collapse of the objectivity may be determined by comparing the two.

  As an example of switching the measurement mode according to the objectivity extracted as the feature quantity, the center of gravity position is calculated or the peak position is determined according to the presence or absence of objectivity collapse (whether the difference between the left and right is greater than a predetermined value). It is possible to switch whether to calculate. Alternatively, when there is a collapse of the target property, it is possible to add a positive or negative correction amount to the calculation result of the peak position or the center of gravity position according to the direction (whether the left or right is swollen).

  As another example of the feature amount of the received light waveform, the area of the peak portion 64 above the threshold line 67 is divided vertically by an appropriate level line between the peak value level and the threshold value, and the upper and lower areas are individually divided. The ratio between the two may be calculated as the feature amount. Also, depending on the type of workpiece, a plurality of peaks may appear in the received light waveform, so the measurement mode may be switched using the number of detected peaks as the feature quantity of the received light waveform.

  As another modification of the first embodiment, information indicating the measurement mode selected by the processing unit 44 based on the feature amount extracted from the received light waveform as described above may be displayed on the display 221. As a result, the user can know the measurement mode being executed from the display, and can confirm the relationship between the workpiece being measured and the measurement mode. As the information indicating the measurement mode, for example, display “A-1” indicating mode 1, display “A-2” indicating mode 2, or display “A-3” indicating mode 3 is displayed on the upper stage of the display 221. Alternatively, it is possible to display using 3 digits × 7 segments in the lower row (see FIG. 2).

  FIG. 9 is a flowchart showing the flow of measurement processing according to the second embodiment of the present invention. In step # 201, the processing unit 44 performs the above-described feedback control, and adjusts the light emission amount or (and) the amplification factor to an appropriate value. In subsequent step # 202, a peak portion of the received light waveform obtained from the output signal of the linear image sensor 15 is detected. Among the portions where the electrical signal (voltage) corresponding to the amount of received light once increases and then decreases, those whose peak value is equal to or greater than the threshold and whose width exceeds a predetermined value are detected as peaks.

  In the next step # 203, the peak width D is extracted as the feature amount of the received light waveform. As illustrated in FIG. 6 in the description of the first embodiment, the light receiving waveform 63 has a peak portion 64, and between two points where a straight line of a certain level (threshold value) set near the peak portion 64 and the peak portion 64 intersect. The distance D corresponds to the width of the peak. The value of the ridge width D extracted as the feature amount is displayed on the display 221 in the next step # 204. The width D of the peak portion can be represented by, for example, the number of pixels occupying 256 pixels corresponding to the maximum width of the linear image sensor 15. For example, in a standard work, the peak width D corresponds to 5 to 10 pixels. Therefore, the number of pixels corresponding to the width D of the peak portion is numerically displayed using the three-digit × 7-segment display in the upper or lower stage of the display 221 (see FIG. 2).

  The user looks at the feature quantity of the received light waveform displayed on the display 221, that is, the number of pixels corresponding to the width D of the peak portion, and performs selection input of an appropriate measurement mode. For example, measurement mode selection input is performed using the setting increase / decrease key 222 shown in FIG. In the first embodiment, the processing unit 44 automatically selects an appropriate measurement mode based on the feature amount of the received light waveform. However, in this embodiment, the feature amount of the received light waveform is only displayed and the user can Look at the display and select the measurement mode. In this case, the user can determine the measurement mode to be executed in consideration of other factors, if necessary, while checking the relationship between the type of workpiece and the like and the feature quantity of the received light waveform. Note that the standard relationship between the feature quantity of the received light waveform and the measurement mode can be known in advance by the user if it is described in a manual or the like as a correspondence table. A correspondence table may be printed in a space such as a side surface of the optical displacement meter, or a print sticker may be attached.

In the example of the flowchart shown in FIG. 9, three measurement modes are prepared, as in the case of the first embodiment shown in FIG. In step # 205, whether or not there is a selection input is checked. If there is a selection input, the selected measurement mode is determined in the next step # 206, and the process branches to each measurement mode (steps # 207 to # 209). The difference in the calculation method of the gravity center position (or peak position) of the peak portion in each measurement mode is as described in the first embodiment and its modification. When the gravity center position (or peak position) of the mountain portion is calculated in step # 210, the distance to the workpiece is obtained from the calculation result, and is displayed on the display 221 as the measurement result as described above. It is output to the device (step # 211).
(Modification of Example 2)

  Each of the above-described configurations described as modifications of the first embodiment can be similarly applied to the second embodiment, except that the processing unit 44 automatically selects and executes an appropriate measurement mode. is there. In other words, the second embodiment is characterized in that the feature quantity of the received light waveform extracted by the processing unit 44 is displayed on the display 221 to assist the judgment when the user performs selection input of the measurement mode. The above description regarding the example of the feature amount other than the peak width D and the other example of the calculation method of the gravity center position (or peak position) of the peak executed in a plurality of measurement modes also applies to the second embodiment. be able to.

  As mentioned above, although the Example of this invention and its modification were demonstrated, this invention is not limited to these Examples and modification, It is also possible to implement with another form. For example, in the above-described embodiments and modifications, a plurality of measurement modes are prepared in advance, and one processing unit 44 is provided according to the feature amount extracted from the received light waveform or according to the user's selection input viewed in the feature amount display. Select and execute the measurement mode. However, without preparing such a plurality of measurement modes, in one measurement mode, the processing unit 44 calculates the center of gravity (or peak position) of the mountain according to the feature amount (for example, a center of gravity calculation line). (Variable parameters) may be changed.

It is a figure which shows the measurement principle of the optical displacement meter which concerns on the Example of this invention. It is the top view and side view which show the external appearance of an optical displacement meter. It is a block diagram which shows the main circuit structures of an optical displacement meter. It is a block diagram which shows the structure of the feedback control by a processing unit. It is a flowchart which shows the flow of the measurement process which concerns on Example 1 of this invention. It is a figure which illustrates the width | variety of the peak part extracted as a feature-value of a received light waveform. It is a figure which illustrates the calculation method of the gravity center position in three kinds of measurement modes which concern on Example 1. FIG. It is a figure which illustrates the case where the objectivity about the perpendicular line which passes the peak of the peak part of a received light waveform has collapsed. It is a flowchart which shows the flow of the measurement process which concerns on Example 2 of this invention.

Explanation of symbols

12 Laser diode (light emitting element)
15 Linear Image Sensor 44 Processing Unit (Measurement Processing Unit)
63 Light reception waveform 64 Peak 221 Display D Width of peak

Claims (6)

A light emitting device for irradiating the object with light;
An image sensor that receives light from the object and outputs an electrical signal corresponding to the amount of light received by each of the plurality of pixel components,
The electrical signal from the image sensor is processed to detect the peak portion of the received light waveform corresponding to the distribution of the amount of received light, and the peak position or the center of gravity position of the peak portion is calculated to calculate the distance to the object or the target A measurement processing unit that executes a measurement process for measuring the displacement of an object,
The optical displacement meter, wherein the measurement processing unit changes a calculation method of the peak position or the center of gravity position according to a feature amount extracted from the received light waveform. The optical displacement meter according to claim 1, wherein the feature amount extracted from the light reception waveform is a width of a peak portion of the light reception waveform. The measurement processing unit has a plurality of modes with different calculation methods of the peak position or the center of gravity position, and is configured to select one of the plurality of modes according to a feature amount extracted from the received light waveform. The optical displacement meter according to claim 1 or 2. The optical displacement meter according to claim 3, further comprising a display for displaying information indicating the selected one mode. A light emitting device for irradiating the object with light;
An image sensor that receives light from the object and outputs an electrical signal corresponding to the amount of light received by each of the plurality of pixel components,
The electrical signal from the image sensor is processed to detect the peak portion of the received light waveform corresponding to the distribution of the amount of received light, and the peak position or the center of gravity position of the peak portion is calculated to calculate the distance to the object or the target A measurement processing unit for executing a measurement process for measuring the displacement of an object;
A display for displaying the feature amount extracted from the received light waveform;
The measurement processing unit stores a plurality of types of calculation methods for the peak position or the center of gravity position in advance, selects one of the plurality of types of calculation methods for the peak position or the center of gravity position according to a selection input, and performs the measurement processing. An optical displacement meter characterized by being executed. The optical displacement meter according to claim 4, wherein the feature amount extracted from the light reception waveform is a width of a peak portion of the light reception waveform.

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