JP4474221B2 - Optical displacement meter - Google Patents

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.

  Some optical displacement meters of this type measure the distance or displacement to an object using the principle of triangulation. This optical displacement meter has a laser diode as a light emitting element for irradiating light on an object, and each of a plurality of pixel components receives light from the object and outputs an electrical signal corresponding to the amount of light received And a measurement processing unit that measures the distance to the object or the displacement of the object based on an electrical signal from the image sensor. 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 object 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.

  In the optical displacement meter, the reflectance of light and the amount of light received vary greatly depending on conditions such as the color of the object, the roughness of the surface, and the angle. Therefore, it is common to perform feedback control that adjusts 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 (peak value of the peak) becomes the target value. is there. As a result, the dynamic range can be effectively utilized while avoiding saturation of accumulated charges in each pixel component of the image sensor.

  The optical displacement meter as described above is used for, for example, inspecting the uneven shape on the surface of a printed wiring board on which surface-mounted components are mounted. In other words, it is possible to automatically inspect whether surface-mounted components are correctly mounted or whether the soldered part is lifted by using an optical displacement meter placed above the printed wiring board. Can do. In such an application, the light emitted from the optical displacement meter toward the printed wiring board is reflected by the edge portion of the mounting component, and further follows the optical path that returns to the optical displacement meter after being reflected by another portion. There is a case. In other words, the secondary reflected light reflected twice on the surface of the mounting component on the printed wiring board is optical in addition to the primary reflected light that is reflected directly on the surface of the printed wiring board or the mounting component. Return to the displacement meter. Light reflected three times or more (third-order or more reflected light) may return to the optical displacement meter.

  When such secondary reflected light or tertiary or higher reflected light (multiple reflected light) returns to the optical displacement meter and is received by the image sensor, a plurality of peaks appear in the received light waveform obtained therefrom. . In this case, it is necessary to determine which peak portion is an effective peak portion, obtain the peak position or the center of gravity position, and calculate the distance to the object. For example, there is a method in which a peak having a higher peak is an effective peak, or a method in which a peak that appears first is an effective peak.

  However, these methods are all convenient, and a correct measurement result cannot always be obtained. If the amount of primary reflected light is always greater than the amount of multiple reflected light, the peak with the higher peak may be the effective peak, but the amount of multiple reflected light is greater than the amount of primary reflected light. Sometimes it becomes. In addition, when the peak portion of the received light waveform by the primary reflected light always appears first, the peak portion that appears first may be set as an effective peak portion, but it is difficult to set so as to be the case in all applications.

  In the application of the optical displacement meter as described above, the measurement by the optical displacement meter is executed at a constant sampling period while the object moves in the direction crossing the light (light beam) emitted from the optical displacement meter. The For example, light is irradiated from an optical displacement meter disposed above a target object placed on a belt conveyor moving at a constant speed, and the distance to the target object (surface of the target object) at a constant sampling period. Concavo-convex shape) is measured. Alternatively, the optical displacement meter may be provided with an optical scanning unit that changes the light and scans the surface of the object. In this case, the uneven shape of the surface of the stopped object can be measured. In any case, the distance to the object that relatively moves in the direction crossing the light beam is continuously measured at a constant period.

Therefore, as a method of determining one peak portion that is effective when a plurality of peak portions appear in the received light waveform, it is possible to determine with reference to the information of the previous received light waveform. For example, Patent Document 1 describes a method in which when a plurality of peaks appear in the received light waveform, a peak closest to the peak position (beam spot position) of the previous received light waveform is determined as an effective peak. Has been.
Japanese Patent Publication No.7-117387

  However, in the above-mentioned example, the multiple reflected light returns to the optical displacement meter and is received by the image sensor when the light hits the edge of the printed circuit board mounting component, and measurements before and after that. At the timing, it is considered that light hits the surface (flat part) of the mounted component and only one peak appears in the received light waveform. Also, even if the measurement result when light hits the edge of the mounted component is lost, if the correct measurement result is obtained at the measurement timing before and after that, the uneven shape on the surface of the printed wiring board including the mounted component can be obtained. In most cases, there are no particular problems in the inspection.

  Therefore, the present invention provides an optical displacement meter that outputs measurement results reasonably and appropriately when a plurality of peaks appear in the received light waveform due to the multiple reflected light received on the surface of the object. The purpose is to do.

  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 an electrical signal from the image sensor is processed to detect a peak portion of the received light waveform corresponding to the distribution of the amount of received light. A measurement processing unit that continuously executes a measurement process for measuring a distance or a displacement of an object at a constant period, stores a measurement result, and outputs the measurement result. When is detected, the previous measurement result is output as the current measurement result.

  According to such a configuration, in the optical displacement meter of the present invention, when a plurality of peaks appear in the received light waveform, the previous measurement result is held. Therefore, there is no possibility of outputting an erroneous measurement result based on the peak portion due to the multiple reflected light. As described above, even if the correct measurement result at the current sampling timing is missing, if the correct measurement result is obtained at the next sampling timing, the uneven shape of the surface of the object identified from the time-series measurement result is It will be almost accurate.

  A second configuration of the optical displacement meter according to the present invention is the same as the first configuration described above, except that the amplifier that amplifies the light emission amount of the light emitting element or the electric signal from the image sensor so that the peak value of the peak portion becomes the target value. A control unit capable of switching and executing a first mode for executing feedback control of the amplification factor and a second mode for increasing an appropriate light emission amount or amplification factor obtained by the feedback control by a predetermined multiple And the measurement processing unit executes measurement processing based on the received light waveform obtained in the second mode.

  According to such a configuration, even if the peak value of the peak due to the multiple reflected light is low and is not detected because it is below the threshold in the first mode with feedback control, the light emission amount or the amplification factor In the second mode in which is increased by a predetermined multiple, a peak due to multiple reflected light may be detected. In this case, since a plurality of peaks are detected, the previous measurement result is held as shown in the first configuration. The predetermined multiple is not limited to an integral multiple, and may be a multiple including a decimal part, for example, 5.5.

  A third 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 according 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 an electrical signal from the image sensor is processed to detect a peak portion of the received light waveform corresponding to the distribution of the amount of received light. A measurement processing unit that continuously executes a measurement process for measuring the distance or the displacement of the object at a constant cycle and outputs the measurement result, and a light emission amount of the light emitting element so that the peak value of the peak part becomes a target value Alternatively, the first mode for executing feedback control of the amplification factor of the amplifier that amplifies the electric signal from the image sensor and the appropriate light emission amount or amplification factor obtained as a result of the feedback control are increased by a predetermined multiple. A control unit capable of switching between two modes and executing the measurement processing unit, which appears first or last when a plurality of peaks are detected in the received light waveform obtained in the second mode. It is characterized in that the measurement processing is executed with the mountain portion as an effective mountain portion, and the measurement result is output.

  According to such a configuration, even if the peak value of the peak due to the multiple reflected light is low and is not detected because it is below the threshold in the first mode with feedback control, the light emission amount or the amplification factor In the second mode in which is increased by a predetermined multiple, a peak due to multiple reflected light may be detected. In this case, the measurement processing unit can execute the measurement process with the peak part that appears first or last as an effective peak part, and output an appropriate measurement result.

  A fourth 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 according 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 an electrical signal from the image sensor is processed to detect a peak portion of the received light waveform corresponding to the distribution of the amount of received light. A measurement processing unit that continuously executes a measurement process for measuring a distance or a displacement of an object at a constant period, stores a measurement result, and outputs the measurement result. If the difference between the current measurement result and the previous measurement result is smaller than the predetermined change allowable value, the measurement process is executed with the peak that appears first or last as the effective peak. Valid measurement results And outputs as the measurement result, and, if the difference between the current measurement result and the previous measurement result is predetermined allowable change value or more and outputs a previous measurement result as the current measurement result.

  According to such a configuration, it is possible to rationally eliminate an erroneous measurement result obtained based on the peak portion due to the multiple reflected light. In other words, when a plurality of peaks are detected, the measurement processing unit executes the measurement process for the time being using the first or last peak that is likely to be the correct peak as an effective peak. If the difference between the previous measurement result and the previous measurement result is larger than the allowable change value, it is determined that the measurement result is incorrect, and the previous measurement result is output (held). If it is less than the allowable change value, it is output as an effective measurement result.

  A fifth configuration of the optical displacement meter according to the present invention is the same as the fourth configuration described above in that the amplifier that amplifies the light emission amount of the light emitting element or the electric signal from the image sensor so that the peak value of the peak portion becomes the target value. A control unit capable of switching and executing a first mode for executing feedback control of the amplification factor and a second mode for increasing an appropriate light emission amount or amplification factor obtained by the feedback control by a predetermined multiple And the measurement processing unit executes measurement processing based on the received light waveform obtained in the second mode.

  According to such a configuration, even if the peak value of the peak due to the multiple reflected light is low and is not detected because it is below the threshold in the first mode with feedback control, the light emission amount or the amplification factor In the second mode in which is increased by a predetermined multiple, a peak due to multiple reflected light may be detected. In this case, since a plurality of peaks are detected, the previous or current measurement result is output according to the difference from the previous measurement result as shown in the fourth configuration.

  A sixth 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 according 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 an electrical signal from the image sensor is processed to detect a peak portion of the received light waveform corresponding to the distribution of the amount of received light. A measurement processing unit that continuously executes a measurement process for measuring a distance or a displacement of an object at a constant period, stores a measurement result, and outputs the measurement result. When the first or last peak is detected as an effective peak when the error is detected, the difference between the current measurement result and the previous measurement result is less than the predetermined allowable change Validate this measurement result If the difference between the current measurement result and the previous measurement result is greater than the predetermined allowable change value, the peak adjacent to the first or last peak appears as an effective peak. A measurement process is executed, and the measurement result is output.

  According to such a configuration, it is possible to rationally eliminate an erroneous measurement result obtained based on the peak portion due to the multiple reflected light. In other words, when a plurality of peaks are detected, the measurement processing unit executes the measurement process for the time being using the first or last peak that is likely to be the correct peak as an effective peak. When the difference between the previous measurement result and the previous measurement result is larger than the allowable change value, the adjacent peak part (or the other peak part when two peak parts appear) is used as an effective peak part to perform the measurement process. If it is less than the allowable change value, it is output as an effective measurement result.

  A seventh configuration of the optical displacement meter according to the present invention is the same as that of the sixth configuration described above in that the amplifier that amplifies the light emission amount of the light emitting element or the electric signal from the image sensor so that the peak value of the peak portion becomes the target value. A control unit capable of switching and executing a first mode for executing feedback control of the amplification factor and a second mode for increasing an appropriate light emission amount or amplification factor obtained by the feedback control by a predetermined multiple And the measurement processing unit executes measurement processing based on the received light waveform obtained in the second mode.

  According to such a configuration, even if the peak value of the peak due to the multiple reflected light is low and is not detected because it is below the threshold in the first mode with feedback control, the light emission amount or the amplification factor In the second mode in which is increased by a predetermined multiple, a peak due to multiple reflected light may be detected. In this case, since a plurality of peaks are detected, as shown in the sixth configuration, the current measurement result is output according to the difference from the previous measurement result, or based on another adjacent peak Thus, measurement processing and measurement result output are performed.

  The eighth 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 according 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 an electrical signal from the image sensor is processed to detect a peak portion of the received light waveform corresponding to the distribution of the amount of received light. A measurement processing unit that continuously executes a measurement process for measuring a distance or a displacement of an object at a constant period, stores a measurement result, and outputs the measurement result. Is detected, the measurement process is executed with the first or last peak as an effective peak, and the current measurement result is estimated from the increase or decrease in the previous measurement result with respect to the previous measurement result. Within the forecast range If outputs a current measurement result as a valid measurement results, and, if current measurement result is not within the expected range and outputs a previous measurement result as the current measurement result.

  According to such a configuration, it is possible to rationally eliminate an erroneous measurement result obtained based on the peak portion due to the multiple reflected light. In other words, when a plurality of peaks are detected, the measurement processing unit executes the measurement process with the first or last peak that is likely to be a correct peak as an effective peak. The validity of the measurement result is determined by determining whether or not the measurement result is within the prediction range estimated from the change tendency of the measurement result, and the previous or current measurement result is output according to the determination result .

  A ninth configuration of the optical displacement meter according to the present invention is the same as that of the eighth configuration described above in that the amplifier that amplifies the light emission amount of the light emitting element or the electric signal from the image sensor so that the peak value of the peak portion becomes the target value. A control unit capable of switching and executing a first mode for executing feedback control of the amplification factor and a second mode for increasing an appropriate light emission amount or amplification factor obtained by the feedback control by a predetermined multiple And the measurement processing unit executes measurement processing based on the received light waveform obtained in the second mode.

  According to such a configuration, even if the peak value of the peak due to the multiple reflected light is low and is not detected because it is below the threshold in the first mode with feedback control, the light emission amount or the amplification factor In the second mode in which is increased by a predetermined multiple, a peak due to multiple reflected light may be detected. In this case, since a plurality of peaks are detected, as shown in the eighth configuration, the previous time or the current time depending on the validity of the current measurement result determined from the change tendency of the previous measurement result and the previous measurement result. The measurement result is output.

  A tenth 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 according 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 an electrical signal from the image sensor is processed to detect a peak portion of the received light waveform corresponding to the distribution of the amount of received light. A measurement processing unit that continuously executes a measurement process for measuring a distance or a displacement of an object at a constant period, stores a measurement result, and outputs the measurement result. Is detected, the first or last peak appears as an effective peak, and the current measurement result is estimated from the increase or decrease in the previous measurement result relative to the previous measurement result. Within the predicted range In some cases, the current measurement result is output as an effective measurement result, and if the current measurement result is not within the prediction range, the peak adjacent to the first or last peak is measured as an effective peak. The process is executed, and the measurement result is output.

  According to such a configuration, it is possible to rationally eliminate an erroneous measurement result obtained based on the peak portion due to the multiple reflected light. In other words, when a plurality of peaks are detected, the measurement processing unit executes the measurement process with the first or last peak that is likely to be a correct peak as an effective peak. The validity of the measurement result is determined by determining whether or not the measurement result is within the prediction range estimated from the change tendency of the measurement result. If it is determined to be valid, the measurement result is output. If it is determined not to be valid, the adjacent peak (the other peak when two peaks appear) is the effective peak. The measurement process is executed as follows.

  An eleventh configuration of the optical displacement meter according to the present invention is the same as the tenth configuration in the amplifier that amplifies the light emission amount of the light emitting element or the electric signal from the image sensor so that the peak value of the peak portion becomes the target value. A control unit capable of switching and executing a first mode for executing feedback control of the amplification factor and a second mode for increasing an appropriate light emission amount or amplification factor obtained by the feedback control by a predetermined multiple And the measurement processing unit executes measurement processing based on the received light waveform obtained in the second mode.

  According to such a configuration, even if the peak value of the peak due to the multiple reflected light is low and is not detected because it is below the threshold in the first mode with feedback control, the light emission amount or the amplification factor In the second mode in which is increased by a predetermined multiple, a peak due to multiple reflected light may be detected. In this case, since a plurality of peaks are detected, as shown in the tenth configuration, the current measurement is performed according to the validity of the current measurement result determined from the change tendency of the previous measurement result and the previous measurement result. The result is output, or the measurement process and the output of the measurement result are performed based on another adjacent mountain.

  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 for non-contact measurement of the displacement of an object using the principle of triangulation. The 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 object WK. Part of the laser light reflected by the object 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 object WK is displaced as indicated by a broken line in FIG. 1, the optical path of the laser light reflected by the object WK and reaching the linear image sensor 15 changes as indicated by the 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 object 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 obtains the displacement of the object WK from the signal read from the linear image sensor 15. Built-in electronic circuit. 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 and display of various set values, and can simultaneously display two measurement results or set values 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 object 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 AD converter (A / D) 47, a processing unit (measurement processing unit and control unit) 44, a DA converter (D / A) 45, an amplifier 46, and a reset / control circuit 48. Including. The processing unit 44 includes a memory 44a for temporarily storing measurement results and the like.

  The laser light emitted from the laser diode 12 passes through the light projection lens 13 and irradiates the object WK. Part of the laser light reflected by the object 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 readout circuit 16 is passed to the controller unit 22, and the high frequency component is first removed by the low pass filter 41. This high frequency component includes the frequency component of the pixel selection signal given to the linear image sensor 15.

  When the output signal of the readout circuit 16 passes through the low-pass filter 41, the high frequency component corresponding to the frequency of the pixel selection signal is removed, and only the low frequency component corresponding to the envelope becomes a voltage signal. This voltage signal includes information on the distribution of the amount of received light 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, converted to 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 through the AD converter 47 and obtains the peak position or the center of gravity position. 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.

  In FIG. 3, the intensity (light emission amount) of the laser light emitted from the laser diode 12 is controlled by the processing unit (corresponding to a control 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 object 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 object WK, saturation of accumulated charges in each pixel component of the linear image sensor 15 is avoided. However, 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).

  The 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, the peak value (digital conversion value) of the 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 (the linear image sensor 15, the readout circuit 16, the AD converter 47, etc.) is fed back again to the comparison unit 441 of the processing unit 44, thereby forming a feedback loop. Yes.

  In the optical displacement meter of the present embodiment, the processing unit (control unit) 44 has a first mode in which the feedback control as described above is executed, and a light emission amount or an amplification factor (both may be obtained) obtained as a result of the feedback control. The second mode in which the appropriate value is increased by a predetermined multiple can be switched and executed. As a result, in the first mode where feedback control is applied, the peak portion due to the multiple reflected light which is not detected and becomes lower than the threshold value, and in the second mode where the light emission amount or amplification factor is increased by a predetermined multiple, the peak due to the multiple reflected light. May be detected. In this case, a plurality of peaks are detected in the received light waveform.

  FIG. 5 is a diagram schematically showing a state in which a plurality of peaks appear in the received light waveform when multiple reflected light generated on the surface of the object returns to the optical displacement meter and is received by the linear image sensor. It is. In the illustrated example, the laser light L0 is irradiated downward from an optical displacement meter disposed above the printed wiring board 60 on which the circuit components 61 and 62 are mounted. Part of the laser light reflected by the edge portion of the circuit component 61 returns directly to the optical displacement meter as primary reflected light L1 indicated by a solid line and is received by the linear image sensor 15. As a result, a first peak portion 64 is formed in the light receiving waveform 63. Further, another part of the laser light reflected at the edge portion of the circuit component 61 is further reflected at the edge portion of another adjacent circuit component 62 as shown by a broken line, and then secondary reflected light (multiple reflected light). L2 returns to the optical displacement meter and is received by the linear image sensor 15. As a result, a second peak 65 is formed in the light receiving waveform 63.

  In many cases, the objects 61 and 62 that generate the multiple reflected light L2 on the surface of the printed wiring board 60 are not two circuit components but different portions of one circuit component. For example, the multiple reflected light L2 is often generated between adjacent pins of an integrated circuit where a plurality of pins are protruding or between their soldered portions. Further, in FIG. 5, for easy understanding, the laser light L0 is irradiated obliquely from above toward the printed wiring board 60 on which the circuit components 61 and 62 are mounted, and the reflected lights L1 and L2 are directed obliquely upward. However, in practice, the laser light L0 is irradiated from the upper side to a position substantially directly below, and the reflected lights L1 and L2 are also directed substantially directly above.

  Further, in the light receiving waveform 63 shown in FIG. 5, the second peak 65 generated by the secondary reflected light L2 is smaller than the first peak 64 generated by the primary reflected light L1 (the peak value is low). However, this is not always the case. Depending on the surface shape, material, and other conditions of the circuit components 61 and 62, the second peak 65 generated by the secondary reflected light L2 may be larger than the first peak 64 generated by the primary reflected light L1. possible. On the contrary, there is a case where the second peak 65 is not detected because the amount of received light is smaller than the threshold value although the secondary reflected light L2 is generated.

  FIG. 6 is a diagram illustrating a state in which a peak portion due to multiple reflected light is detected in the second mode in which the light emission amount or the amplification factor is increased by a predetermined multiple. A light reception waveform 63 indicated by a solid line indicates a light reception waveform in the first mode, and the light emission amount or (and) the amplification factor is controlled so that the peak value of the first peak portion 64 becomes a target value. At this time, the second peak 65, which is a peak due to multiple reflected light, is not detected as a peak because its peak value is lower than the threshold value.

  On the other hand, a light reception waveform 63 ′ indicated by a broken line indicates a light reception waveform in the second mode, which is a light reception waveform when an appropriate light emission amount or (and) amplification factor in the first mode is increased by a predetermined multiple. Become. Therefore, the light receiving waveform 63 'in the second mode is the light receiving waveform 63 in the first mode extended in the vertical axis direction by a predetermined multiple. As a result, the peak value of the second peak 65 ′ becomes higher than the threshold value, and is detected as a peak by the processing unit 44. Instead, the peak value of the first peak portion 64 'is clamped at the saturation level, so the accuracy of the calculation result of the center of gravity position of the first peak portion 64' is slightly lowered.

  In the second mode, the light emission amount and / or the rate of increasing the amplification factor (predetermined multiple) is determined to an appropriate value in consideration of the threshold value and the S / N ratio of the signal processing circuit. It is not limited to an integer multiple (for example, 5 times), and may be a multiple including a decimal number (for example, 5.5 times). Several embodiments of the measurement process performed by using both the second mode and the first mode will be described below.

  FIG. 7 is a flowchart showing the flow of measurement processing according to Embodiment 1 of the present invention. In step # 101, the processing unit 44 performs feedback control in the first mode and adjusts the light emission amount or (and) the amplification factor to 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, it is checked whether or not there are a plurality of peaks in the received light waveform. If there are a plurality of peaks, the process proceeds to step # 108. If there is only one peak, in step # 104, the amount of light emission and / or amplification factor in the second mode is increased, and in step # 105, it is checked again whether there are multiple peaks. To do. When there are a plurality of peaks, the previous measurement result (stored in the memory 44a) is output. That is, the previous measurement result is held.

  If there is only one peak in step # 105, a measurement process is performed in step # 106 to calculate the center of gravity of the peak and calculate the distance to the object, and in step # 107, the measurement result is stored in the memory 44a. Memory and output to the outside. As described above, in this embodiment, when only one peak portion exists in the received light waveform even after the light emission amount or (and) the amplification factor is increased in the second mode, the measurement process is executed based on the peak portion. However, when a plurality of peaks are detected, the previous measurement result is output as the current measurement result (the previous measurement result is held).

  Note that the measurement process in step # 106 and the measurement result in step # 107 may be stored immediately before step # 104. That is, the measurement process is performed on the received light waveform in the state where the feedback before the execution of the increase in the light emission amount or (and) the amplification factor in the second mode is performed, the measurement result is stored, and the light emission amount in the second mode or (And) If only one peak exists in the received light waveform even when the amplification factor is increased, the measurement result may be read and output. As described above, the calculation accuracy of the center of gravity of the mountain portion (the calculation accuracy of the distance to the object) is improved.

  Further, as a modification of the present embodiment, the light reception waveform is obtained only when the light emission amount and the amplification factor are adjusted to appropriate values by feedback control without executing the second mode for increasing the light emission amount or (and) the amplification factor. Depending on the determination result of whether or not there are a plurality of peaks, measurement processing may be executed, or the previous measurement result may be held.

  FIG. 8 is a flowchart showing the flow of measurement processing according to Embodiment 2 of the present invention. Similar to the first embodiment, feedback control in the first mode is executed in step # 201, and a peak portion of the received light waveform is detected in step # 202. In the next step # 203, it is checked whether or not there are a plurality of peaks in the received light waveform. If there are a plurality of peaks, the process proceeds to step # 206. If there is only one peak, in the subsequent step # 204, the light emission amount or (and) the amplification factor is increased in the second mode, and in step # 205, it is checked again whether there are multiple peaks. To do. If there are a plurality of peaks, the process proceeds to the subsequent step # 206. If there is only one peak, the process skips step # 206 and proceeds to step # 207.

  In step # 206, the peak that appears first in the received light waveform is adopted as an effective peak. The peak that first appears means, for example, the peak 64 closest to the left end of the time axis (horizontal axis) in the received light waveform 63 shown in FIG. In the subsequent step # 207, a measurement process for calculating the center of gravity of the mountain and calculating the distance to the object is executed, and in step # 208, the measurement result is stored in the memory 44a and output to the outside.

  As described above, in this embodiment, whether or not there are a plurality of peaks in the received light waveform is checked not only in the first mode in which feedback is applied, but also in the second mode in which the light emission amount or (and) the amplification factor is increased. However, when there are a plurality of ridges, the ridge that appears first is adopted as an effective ridge. As a modification, the peak that appears last, that is, the peak closest to the right end of the time axis (horizontal axis) in the received light waveform may be adopted as an effective peak.

  FIG. 9 is a flowchart showing the flow of measurement processing according to the third embodiment of the present invention. Similar to the first embodiment, feedback control in the first mode is executed to detect a peak portion of the received light waveform. These steps are omitted in FIG. In the next step # 303, it is checked whether or not there are a plurality of peaks in the received light waveform. If there are a plurality of peaks, the process proceeds to step # 307. If there is only one peak, in step # 304, the light emission amount or (and) the amplification factor is increased in the second mode, and in step # 305, it is checked again whether there are multiple peaks. To do. If there is still only one peak, a measurement process is performed to calculate the distance to the object by obtaining the center of gravity of the peak (step # 306), and the measurement result is stored and output (step #). 311). If there are a plurality of peaks, the process proceeds to step # 307.

  In step # 307, the peak that appears first in the received light waveform is adopted as an effective peak. The meaning of the mountain that first appears is as described in the second embodiment. Further, the second embodiment is similar to the second embodiment in that a modified example in which the peak that appears last instead of the peak that appears first is possible. In the subsequent step # 308, a measurement process for calculating the center of gravity of the mountain portion and calculating the distance to the object is executed. In step # 309, the previous measurement result (stored in the memory 44a) is compared with the current measurement result. I do. When the difference between the two is equal to or less than the predetermined change allowable value (Yes in Step # 310), the measurement result is stored and output as an effective measurement result (Step # 311). However, if the difference between the two is larger than the allowable change value (No in step # 310), the previous measurement result is output (held) (step # 312).

  As described above, in this embodiment, when only one peak portion exists in the received light waveform even after the light emission amount or (and) the amplification factor is increased in the second mode, the measurement process is executed based on the peak portion. The measurement result is output, but when a plurality of peaks are detected, the measurement processing is executed with the peak that appears first or last as the effective peak. Then, the measurement result is compared with the previous measurement result, and if the difference between the two is less than or equal to a predetermined allowable change value, the measurement result is output as valid. Is output as the current measurement result (the previous measurement result is held).

  As a modification of the present embodiment, instead of outputting the previous measurement result in step # 312, the peak adjacent to the peak that appears first (or last) (or the other peak if there are two peaks) It is also possible to execute the measurement process using as an effective peak and output the measurement result.

  Further, as another modification, the second embodiment is not executed in which the second mode for increasing the light emission amount or (and) the amplification factor is executed, but only in a state where the light emission amount and the amplification factor are adjusted to appropriate values by feedback control. Or you may perform the process of a modification. That is, when there are multiple peaks in the received light waveform, the measurement process is executed based on the peak that appears first (or last), the measurement result is compared with the previous measurement result, and the difference between the two is the allowable change value. If it is below, it is output as a valid measurement result, and if it is larger than the allowable change value, the previous measurement result is held, or the measurement process is executed with another adjacent peak as a valid peak. Output.

  FIG. 10 is a flowchart showing the flow of measurement processing according to the fourth embodiment of the present invention. The measurement process of this embodiment is almost the same as the measurement process of the third embodiment shown in FIG. 9, but the processes after step # 409 are different. In other words, when multiple peaks are detected, the measurement processing is executed with the first or last peak as the effective peak, and instead of comparing the measurement result with the previous measurement result, the following is performed: Perform appropriate processing. In this embodiment, not only the previous measurement result but also the previous measurement result is stored in the memory 44 a of the processing unit 44. The processing unit 44 estimates a range (predicted range) where the current measurement result will exist based on an increase or decrease tendency (change tendency) of the previous measurement result with respect to the measurement result of the previous time. If the current measurement result is within this prediction range (Yes in step # 410), the measurement result is stored and output as an effective measurement result (step # 411). However, if the current measurement result is not within the prediction range (No in step # 410), the previous measurement result is output (held) (step # 412).

  In the case of this embodiment, similarly to the third embodiment, as a modification, instead of outputting the previous measurement result in step # 412, the peak portion adjacent to the first (or last) peak portion (the peak portion is 2). In the case of a single piece, the measurement process may be executed by using the other peak portion as an effective peak portion, and the measurement result may be output.

  Further, as another modification, the second embodiment is not executed in which the second mode for increasing the light emission amount or (and) the amplification factor is executed, but only in a state where the light emission amount and the amplification factor are adjusted to appropriate values by feedback control. Or you may perform the process of a modification. That is, when there are multiple peaks in the received light waveform, the measurement process is executed based on the peaks that appear first (or last), and the measurement results are within the prediction range estimated from the change trend of the previous and previous measurement results. If there is a measurement result, it is output as a valid measurement result, and if there is no measurement result within the predicted range, the previous measurement result is held, or measurement processing is executed with another adjacent peak as a valid peak. Output the result.

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 process part. It is a figure which shows typically a mode that several peak parts appear in a light reception waveform by the multiple reflected light which arose on the surface of the target object. It is a figure which shows a mode that the peak part by multiple reflected light is detected in the 2nd mode in which light emission amount or amplification factor is increased only by predetermined multiple. It is a flowchart which shows the flow of the measurement process which concerns on Example 1 of this invention. It is a flowchart which shows the flow of the measurement process which concerns on Example 2 of this invention. It is a flowchart which shows the flow of the measurement process which concerns on Example 3 of this invention. It is a flowchart which shows the flow of the measurement process which concerns on Example 4 of this invention.

Explanation of symbols

12 Laser diode (light emitting element)
15 linear image sensor 44 processing unit (measurement processing unit and control unit)
63 Light reception waveform 64, 65 Mountain

Claims (8)

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 obtained, or the distance to the target object or the target object A measurement processing unit that continuously executes a measurement process for measuring the displacement of the sensor and stores the measurement result and outputs the measurement result,
When a plurality of peaks are detected in the received light waveform, the measurement processing unit executes the measurement process with the first or last peak as an effective peak, and the current measurement result and the previous measurement result If the difference between the current measurement result and the previous measurement result is less than or equal to a predetermined allowable change value, the current measurement result is output as a valid measurement result, and the difference between the current measurement result and the previous measurement result is greater than the predetermined change allowable value. An optical displacement meter that outputs the previous measurement result as the current measurement result if it is larger. A first mode for performing feedback control of the light emission amount of the light emitting element or the amplification factor of an amplifier for amplifying an electric signal from the image sensor so that the peak value of the peak portion becomes a target value; and a result of the feedback control A control unit capable of switching and executing a second mode in which an appropriate value of the obtained light emission amount or amplification factor is increased by a predetermined multiple;
The measurement processing unit, an optical displacement meter according to claim 1, wherein performing said measurement processing on the basis of the light reception waveform obtained in the second 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 obtained, or the distance to the target object or the target object A measurement processing unit that continuously executes a measurement process for measuring the displacement of the sensor and stores the measurement result and outputs the measurement result,
When a plurality of peaks are detected in the received light waveform, the measurement processing unit executes the measurement process by using the first or last peak as an effective peak, and the current measurement result and the previous measurement are performed. If the difference from the result is less than or equal to the predetermined change allowable value, the current measurement result is output as an effective measurement result, and the difference between the current measurement result and the previous measurement result is the predetermined change allowable value An optical displacement meter characterized in that if it is larger, the measurement processing is executed with the peak adjacent to the peak appearing first or last as an effective peak and the measurement result is output. A first mode for performing feedback control of the light emission amount of the light emitting element or the amplification factor of an amplifier for amplifying an electric signal from the image sensor so that the peak value of the peak portion becomes a target value; and a result of the feedback control A control unit capable of switching and executing a second mode in which an appropriate value of the obtained light emission amount or amplification factor is increased by a predetermined multiple;
The optical displacement meter according to claim 3, wherein the measurement processing unit executes the measurement process based on the received light waveform obtained in the second 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 obtained, or the distance to the target object or the target object A measurement processing unit that continuously executes a measurement process for measuring the displacement of the sensor and stores the measurement result and outputs the measurement result,
When a plurality of peaks are detected in the received light waveform, the measurement processing unit executes the measurement process with the first or last peak as an effective peak, and the current measurement result is If the measurement result is within the predicted range estimated from the increase or decrease tendency of the previous measurement result, the current measurement result is output as an effective measurement result, and the current measurement result is not within the prediction range An optical displacement meter that outputs the previous measurement result as the current measurement result. A first mode for performing feedback control of the light emission amount of the light emitting element or the amplification factor of an amplifier for amplifying an electric signal from the image sensor so that the peak value of the peak portion becomes a target value; and a result of the feedback control A control unit capable of switching and executing a second mode in which an appropriate value of the obtained light emission amount or amplification factor is increased by a predetermined multiple;
The optical displacement meter according to claim 5, wherein the measurement processing unit executes the measurement process based on the received light waveform obtained in the second 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 obtained, or the distance to the target object or the target object A measurement processing unit that continuously executes a measurement process for measuring the displacement of the sensor and stores the measurement result and outputs the measurement result,
When a plurality of peaks are detected in the received light waveform, the measurement processing unit executes the measurement process with the first or last peak as an effective peak, and the current measurement result is When the current measurement result is output as an effective measurement result when it is within the prediction range estimated from the increase or decrease tendency of the previous measurement result with respect to the measurement result, and the current measurement result is not within the prediction range The optical displacement meter is characterized in that the measurement processing is executed with the peak adjacent to the peak appearing first or last as an effective peak and the measurement result is output. A first mode for performing feedback control of the light emission amount of the light emitting element or the amplification factor of an amplifier for amplifying an electric signal from the image sensor so that the peak value of the peak portion becomes a target value; and a result of the feedback control A control unit capable of switching and executing a second mode in which an appropriate value of the obtained light emission amount or amplification factor is increased by a predetermined multiple;
The optical displacement meter according to claim 7, wherein the measurement processing unit executes the measurement process based on the received light waveform obtained in the second mode.

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