JP2008116214A - Displacement sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a displacement sensor capable of improving noise by reducing the phenomena that the peak position of the light receiving signal deviates from the focus of the image sensor and performing the smoothing process to the wave form. <P>SOLUTION: The display sensor comprises: a CPU built in a controller 10 of the displacement sensor for calculating the moving average of the light receiving amount averaged with a plurality of pixels for every pixel; and a sensor head 20a which discriminates the pixel position becoming the peak of the receiving light amount and also connected to the controller 10 for detecting the displacement of the work W based on the result of the discrimination. Therein, the CPU is characteristically constituted so that it calculates the moving averages based on the number of references previously set for every pixel position. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a displacement sensor.

  A displacement sensor using light includes a controller and a head having a light projecting element and a line sensor or a two-dimensional sensor. The light projected from the light projecting element provided in the head irradiates the detected object. And the sensor used as a light receiving element receives the reflected light from this to-be-detected body. The head outputs the amount of light received by each pixel of the sensor, and the controller detects the displacement of the reflecting surface of the measurement object based on the amount of light received by each pixel. A personal computer having a display device is connected to the controller in order to confirm the setting and the sensor output of the head. The personal computer receives the amount of light received by the head sensor from the controller and displays the waveform. Therefore, the surface state of the detected object can be confirmed by looking at the display screen (see, for example, Patent Document 1).

Depending on the reflectance of the light to be detected, the intensity of light received by the light receiving element changes, and if the amount of received light is small, the peak position may be erroneously detected due to noise. In order to remove this noise, signal processing such as moving average using a plurality of data is performed.
Japanese Patent No. 3797422

  By the way, when the reflected light is irradiated in the vicinity of the center of the detection region of the light projecting element, the light is received at the focused position of the image sensor, and the diameter of the light receiving spot is reduced. On the other hand, in the detection area of the light projecting element, when the reflected light hitting the object to be detected is received at a location where the image sensor is not focused, the size of the diameter of the light receiving spot at the image sensor that has received the reflected light Occurs. When the diameter of the light receiving spot is increased, the amount of incident light on one pixel is reduced, so that it is easily affected by noise. For this reason, in the conventional moving average process, the moving average value is calculated with a fixed number of data set according to a large light receiving spot. Accordingly, in the vicinity of the center where the diameter of the light receiving spot is small, the moving average value including the data other than the actual light receiving spot is calculated, so that the moving average value moves like the waveform of the light receiving signal S and the signal Se after the moving average processing in FIG. There is a possibility that the peak position after the average processing shifts, or that the waveform becomes a gentle waveform and the peak position is difficult to judge.

  The present invention has been made to solve the above-mentioned problems, and its purpose is to reduce the phenomenon that the peak position of the received light signal deviates from the focus of the image sensor, and to reduce noise by applying a smoothing process to the waveform. It is to provide an improved displacement sensor.

  In order to solve the above-mentioned problem, the invention described in claim 1 includes a light projecting means for projecting a spot light toward the object to be detected, and a reflected light reflected by the object to be detected, comprising a plurality of pixels. A plurality of pixels are arranged in at least one column along the direction of change of the position of the light receiving spot according to the distance to the object to be detected, and according to the amount of light received by the plurality of pixels An image sensor that sequentially outputs the received light signal; a signal processing unit that calculates a moving average value based on the received light signal; and a pixel position at which the amount of received light peaks from the moving average value, and based on the determination result Detecting means for detecting the displacement of the object to be detected, wherein the signal processing means calculates a moving average value based on a reference number set in advance for each pixel position. And features.

  Since the number of data for moving average processing can be set for each area, the number of data for moving average processing can be set for each area according to the size of the light receiving spot, and the peak position can be correctly identified can do. As a result, it is possible to provide a displacement sensor that reduces the phenomenon in which the peak position of the received light signal deviates from the focus of the image sensor and improves noise by performing a smoothing process on the waveform.

  According to a second aspect of the present invention, in the displacement sensor according to the first aspect, the signal processing unit is configured to measure a plurality of pixels of the image sensor along the direction of change of the position of the light receiving spot. The reference number set for each of the plurality of regions divided according to the number is stored, and the moving average value is calculated based on the light reception signals of the reference number of pixels.

  Since the central area is set to the smallest number of data, the difference in the number of data from the two end areas having the largest number of data is reduced, so that it is not necessary to set the number of data used for the moving average excessively. In addition, since it is not necessary to use excessive storage capacity during the moving average process, the operation load on the storage area can be reduced.

  According to a third aspect of the present invention, in the displacement sensor according to the second aspect, a setting mode for setting the reference number and a signal processing for calculating a moving average value by the processing means based on the set reference number. A switching means capable of switching between modes, and the received light signal level based on each received light signal output from the image sensor when the detected object is disposed in advance in a plurality of different locations in the detection area in the setting mode. The reference number of pixels in which is equal to or greater than a predetermined value is set by the number of pixels greater than or equal to the predetermined value, and the reference number of pixels in which the light reception signal level does not exceed the predetermined value Setting means for setting based on the reference number set for a pixel that is equal to or greater than the value, and storing the reference number set by the setting means in association with the detection area of the image sensor That storage means comprises, in the signal processing mode, the processing means performs signal processing using the data stored in the storage means for each of the predetermined region. Thereby, the characteristic for each different image sensor can be immediately reflected as the reference number of the process such as the moving average process.

  According to a fourth aspect of the present invention, in the displacement sensor according to the third aspect, the plurality of locations include at least the center of the detection region and both ends. For this reason, the reference number of all pixels can be set with a small number of measurements.

  Therefore, according to the above-described invention, it is possible to provide a displacement sensor that reduces the phenomenon that the peak position of the received light signal deviates from the focus of the image sensor and improves noise by performing a smoothing process on the waveform.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing a displacement sensor of the present embodiment.
The displacement sensor controller 10 is provided with a plurality of cable connection terminals 10a to 10d, and a cable C1a of a sensor head 20a as a head portion is connected to the cable connection terminal 10a. The sensor head 20a is disposed above the measurement table T by a fixture (not shown), and irradiates the workpiece W as a detection object placed on the measurement table T under the control of the controller 10 with a laser beam. A signal corresponding to the reflected light is output.

  A console 30 as a display screen is connected to the cable connection terminal 10c of the controller 10 via a cable C2. The console 30 has an input circuit and a display screen that can be displayed in a dot matrix such as an LCD, and can display characters and line drawings. Further, the console 30 is smaller than the personal computer, and can be brought into a place where the personal computer cannot be carried. The controller 10 outputs display data to the console 30 based on the signal input from the sensor head 20a, and the console 30 displays a numerical value of the received light amount and a waveform of the received light amount based on the display data.

Next, the electrical configurations of the controller 10 and the sensor head 20a will be described.
As shown in FIG. 2, the controller 10 includes a signal processing means, a display control means, a detection means, a setting means corresponding to button operation, a switching means for controlling switching, and a CPU 11 as a setting means. The head communication circuit 12 is connected. The head communication circuit 12 is connected to the cable connection terminals 10a and 10b. A sensor head 20a is connected to the cable connection terminal 10a. Moreover, the sensor head 20b shown with a broken line can be connected to the cable connection terminal 10b via the cable C1b. That is, two sensor heads 20 a and 20 b can be connected to the controller 10, and the CPU 11 can communicate with each sensor head 20 a and 20 b via the head communication circuit 12. The CPU 11 outputs a control signal to the head communication circuit 12, and the head communication circuit 12 transmits a control signal to each of the sensor heads 20a and 20b. The CPU 11 inputs received light amount data received from the sensor heads 20 a and 20 b by the head communication circuit 12.

  The CPU 11 is connected to a first storage circuit 13 (displayed as memory 1) and a second storage circuit 14 (displayed as memory 2) as storage means. The CPU 11 stores received light amount data received from the sensor head 20 a via the head communication circuit 12, set values related to the sensor head 20 a, and the like in the first storage circuit 13. Further, the CPU 11 stores the received light amount data received from the sensor head 20 b via the head communication circuit 12, the set value related to the sensor head 20 b, and the like in the second storage circuit 14.

  Further, a console communication circuit 15 and a personal computer communication circuit 16 are connected to the CPU 11. The console communication circuit 15 is connected to a cable connection terminal 10c, and a console (CS) 30 is connected to the cable connection terminal 10c. The CPU 11 communicates with the console 30 via the console communication circuit 15. The personal computer communication circuit 16 is connected to a cable connection terminal 10d, and a personal computer (PC) 40 indicated by a broken line is connected to the cable connection terminal 10d via a cable C3.

  The sensor head 20 a includes a communication circuit 21 for communicating with the controller 10, and the communication circuit 21 is connected to the CPU 22. The CPU 22 inputs a control signal received by the communication circuit 21, and controls the sensor head 20a based on the control signal. The CPU 22 is connected to a display circuit 23 and a laser diode (LD) 24 as light projecting means. The display circuit 23 is composed of an LED or the like provided so as to be visible from the outside of the sensor head 20a. The CPU 22 outputs a signal to the display circuit 23 and causes the display circuit 23 to display an operation state. The CPU 22 controls the laser diode 24 to irradiate the workpiece W with laser light.

  Reflected light from the workpiece W or the like enters an image sensor (IS) 25. The image sensor 25 is, for example, a two-dimensional CCD, and outputs a light reception signal having a voltage corresponding to the amount of light received at each pixel to an analog / digital (A / D) converter 26. The A / D converter 26 analog-digital converts the received light signal into received light amount data, and outputs the received light amount data (pixel data for each pixel) to the CPU 22. The CPU 22 outputs the received light amount data to the communication circuit 21, and the communication circuit 21 transmits the received light amount data to the controller 10.

  As described above, the CPU 11 of the controller 10 stores the received light amount data received from the sensor head 20 a via the head communication circuit 12 in the first storage circuit 13. Then, the CPU 11 measures the displacement of the reflecting surface based on the received light amount data stored in the first storage circuit 13.

  More specifically, the laser light emitted from the sensor head 20a is reflected by a reflective surface (for example, the surface of the workpiece W), and the reflected light is incident on the image sensor 25. The incident position is from the sensor head 20a to the reflective surface. Varies according to the distance. The CPU 11 of the controller 10 detects the peak value in the received light amount data stored in the first storage circuit 13, and the displacement of the reflecting surface is detected by the change in the position (peak position) of the pixel that outputs the received light amount data of the peak value. Measure. In the case of a transparent body such as glass, the distance between the reflecting surfaces (the thickness of the glass) is measured based on a plurality of peak positions due to reflected light from a plurality of reflecting surfaces (the front surface and the back surface of the glass). .

  In response to the request signal from the console 30, the controller 10 transmits the detected peak value, the variation amount of the reflection surface, the received light amount data stored in the storage circuits 13 and 14, the detection condition, and the like to the console 30. Further, the controller 10 performs various settings based on the setting data output from the console 30.

Next, the optical system of the displacement sensor 20a will be described with reference to FIG.
The optical system element of the displacement sensor 20a includes a laser diode 24 that is a light projecting element, an image sensor 25 that is a light receiving element, a lens 51 that makes light emitted from the laser diode 24 go straight in parallel, and a reflected light that goes straight in parallel. A lens 52 is provided.

  The CPU 22 emits light from the laser diode 24, and the emitted light passes through the lens 51 and strikes the workpiece W. The light reflected from the workpiece W passes through the lens 52 and is received by the image sensor 25. By this operation, the presence / absence and shape of the workpiece W in the detection area can be expressed as a light reception signal.

  By the way, the light projected from the laser diode 24 has a small irradiation light diameter at a specific point (the center, the end, etc. of the irradiation light) in the manufacturing process of the laser diode 24. This occurs because, as the distance from the center increases, the light received by the image sensor becomes out of focus, resulting in the appearance of an optical system with a wider spot diameter. The spot diameter when the irradiated light hits the workpiece W and becomes reflected light and is received by the image sensor 25 is also the characteristics of the irradiated light and any part of the detection area (far / near from the sensor head 20a). A change occurs depending on whether the light is reflected at. When the reflected light from the detection area close to the head and the detection area far from the head strikes the image sensor 25, the spot diameter of the reflected light slightly spreads because the light strikes diagonally. On the other hand, when the reflected light from the center of the detection region hits the light receiving element, the spot diameter of the reflected light becomes the smallest.

  Furthermore, the lens characteristics of the lens used in the image sensor 25 are also formed around a specific point determined in the manufacturing process, and the lens center can be formed anywhere on the lens. Therefore, for example, the focal point is most reduced at the center of the lens, and the focal point is most reduced at the lens end point. In the present embodiment, the lens characteristics of the image sensor 25 are designed so as to focus on the center of the lens.

  In the present embodiment, it is set so that light is collected at the center of the irradiation light of the laser diode 24. The image sensor 25 is also designed to have the smallest spot diameter at the center. In the case where the laser diode 24 and the image sensor 25 designed so that the spot diameter is reduced in the peripheral portion, similar characteristics are generated around the position where the spot diameter is the smallest.

  Due to the characteristics of the laser diode 24 and the image sensor 25, the light reflected from the workpiece W is applied to the image sensor 25 at the spot diameter shown in FIG. 3B according to the reflection position of the detection region in FIG. Received light. The spot diameter becomes the smallest at the center K1 of the detection area of the sensor head 20a, and as it goes to the outer edge K3 from the center K1 and the outer edge K3 from the center K1 of the detection area, the spot diameter increases. The spot diameter increases. If the spot diameter is too close or too far from the sensor head 20a, the spot diameter will be increased.

  The light received by the image sensor 25 is stored in the storage circuit 13 as a light reception signal under the control of the CPU 11. The stored light reception signal is largely affected by noise (due to variations in surface accuracy or noise) as it is, and therefore the noise is suppressed by performing a moving average process.

  The calculation method of the moving average process is a method in which a reference number (natural number) is set and an average value of light reception amount data continuous from a specific light reception amount by the number of the reference number is calculated. When the reference number is set to a large value, the CPU 11 performs the moving average process using the value, and therefore the waveform is smoothed. When the reference number is set to a small value, the CPU 11 performs a moving average process using the value of the reference number, so that a sharpening process is performed on the waveform.

  When smoothing is performed, the received light waveform is smoothed in a specific section, so that noise is suppressed. In addition, when sharpening is performed, a feature of the received light waveform is obtained in a specific section, so that a peak waveform can be easily obtained. The number of references having such different effects is set for each detection region (center part K1, peripheral part K2, end part K3) shown in FIG. 3B, and the received light data is obtained after the CPU 11 performs the moving average process. And the received light data is stored in the storage circuit 13.

  In order to separate the noise and the peak by using the number of points according to the spot diameter, for example, the reference number is set to 2 in the central portion K1 of the detection region. As the distance from the central portion K1, the reference number is set to 4 at the peripheral portion K2, and the reference number is set to 8 at the end K3 further outside the peripheral portion K2.

  As shown in FIG. 4, when the reference number at the center is small, the received light signal S sharply detects the vicinity of the peak value of the signal Sa after the moving average process when the moving average process is performed using the reference number. can do. In addition, since the value of the reference number increases from the periphery where the focal point is formed toward the end, variation in the signal Sa after moving average processing due to noise generated at the end is suppressed, and a gentle waveform can be obtained. Therefore, noise can be removed.

  Since the numerical value of the reference number can be changed as appropriate, the CPU 11 determines which position in the detection region the position where the spot diameter is the smallest is, and assigns an appropriate reference number. The reference number can be changed by the operator.

  This processing is different from the prior art in that the number of references used in the moving average is changed in consideration of the detection area corresponding to the spot diameter, instead of performing the moving average processing uniformly on the entire signal. Further, since the detection area is different for each sensor head, the CPU 11 stores the characteristics of the sensor head 20a to be used in the storage circuit 13 in advance. If there are multiple sensor heads, they are stored in a storage circuit corresponding to the sensor head. By storing the characteristics in a different storage circuit for each sensor head, the CPU 11 can easily detect a peak even when a plurality of sensor heads are used, and can perform a moving average process that further suppresses noise.

Next, characteristic actions and effects of the present embodiment will be described.
(1) A CPU 11 that calculates a moving average value based on the light reception signal S, and a sensor head that determines a pixel position where the amount of received light peaks from the moving average value, and detects the displacement of the workpiece W based on the determination result. 20a. In the displacement sensor, the CPU 11 calculates a moving average value based on a reference number set in advance for each pixel position.

  In the image sensor 25, the diameter of the light receiving spot is different between the area near the center of all pixels and the area near both ends. In the present application, since the number of data at the time of moving average processing can be set for each region, the number of data at the time of moving average processing can be set by the reference number preset for each pixel position, and the peak position can be set. It can be determined correctly.

  As a result, it is possible to provide a displacement sensor that can reduce the phenomenon that the peak position of the received light signal deviates from the focus of the image sensor and can improve noise by performing a smoothing process on the waveform. This also makes it possible to correctly determine the peak position.

  (2) The CPU 11 sets the reference number set for each of the plurality of regions obtained by dividing the plurality of pixels of the image sensor 25 according to the size of the diameter of the light receiving spot along the change direction of the position of the light receiving spot. And the moving average value is calculated based on the light reception signals of the reference number of pixels.

  Since the central area is set to the smallest number of data, the difference in the number of data from the two end areas having the largest number of data is reduced, so that it is not necessary to set the number of data used for the moving average excessively. In addition, since it is not necessary to use excessive storage capacity during the moving average process, the operation load on the storage area can be reduced.

The embodiment of the present invention may be modified as follows.
The reference numbers such as the focal positions and distances of the laser diode 24 and the image sensor 25 are determined at the manufacturing stage, and a combination of these can produce displacement sensors in many modes. All used in this embodiment had a characteristic of focusing on the center, but a displacement sensor may be configured by changing this to a laser diode and an image sensor having other characteristics.

  In the setting mode, the CPU 11 is based on the respective light reception signals output from the image sensor 25 when the workpieces W are previously arranged at a plurality of different locations in the detection area, and the reference number in the pixel at which the light reception signal level is a predetermined value or more. Is set according to the number of pixels equal to or greater than a predetermined value. Further, the reference number of pixels whose light reception signal level does not become a predetermined value or more is set based on the reference number set for the pixels whose light reception signal level becomes a predetermined value or more. And a storage circuit 13 for storing the reference number set in the CPU 11 in association with the detection area of the image sensor 25. In the signal processing mode, the CPU 11 stores the data stored in the storage circuit 13 for each predetermined area. Signal processing may be performed using Thereby, the characteristic for each different image sensor can be immediately reflected as the reference number of the process such as the moving average process.

  -By including at least the center of the detection region and both ends at a plurality of different locations in the detection region, the reference number of all pixels can be set with a small number of measurements. Further, when setting the number of references for different locations in the detection area, weighting may be performed using an arbitrary function such as a linear expression, a quadratic expression, and a cycloid curve.

  This embodiment uses a displacement sensor as one mode of use of the displacement sensor, such as displaying a received light waveform and a peak value on a display device such as a display and a console to inform the operator of the detection status of the detected object. You may incorporate in a detection apparatus.

The front view of a displacement sensor. The block diagram which shows the electric constitution of a displacement sensor. (A) (b) is explanatory drawing which shows the engineering structure of a displacement sensor. The wave form diagram which shows a received light signal and the waveform after a moving average process. The wave form diagram which shows the conventional light reception signal and the waveform after a moving average process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Controller, 11 ... CPU of controller, 13 ... 1st memory circuit, 14 ... 2nd memory circuit, 20a, 20b ... Sensor head, 22 ... CPU of sensor head, 24 ... Laser diode, 25 ... Image sensor, 30 ... console, S ... light reception signal, Sa, Se ... signal after moving average processing, W ... detected object (work).

Claims (4)

A light projecting means for projecting spot light toward the object to be detected;
A plurality of pixels are formed, and a light receiving spot is formed by reflected light reflected by the detection object, and the plurality of pixels are arranged along a change direction of the position of the light reception spot according to a distance to the detection object. An image sensor that is arranged in at least one column and sequentially outputs a light reception signal corresponding to a light reception amount in the plurality of pixels;
Signal processing means for calculating a moving average value based on the received light signal;
A detection unit that determines a pixel position where the amount of received light reaches a peak from the moving average value, and detects a displacement of the detected object based on the determination result
In a displacement sensor comprising:
The signal processing means calculates a moving average value based on a reference number set in advance for each pixel position;
A displacement sensor characterized by that. The displacement sensor according to claim 1,
The signal processing means stores a reference number set for each of a plurality of regions obtained by dividing the plurality of pixels of the image sensor according to the size of the light receiving spot along the change direction of the position of the light receiving spot. Calculating the moving average value based on the light reception signals of the reference number of pixels;
A displacement sensor characterized by that. The displacement sensor according to claim 2, wherein
Switching means capable of switching between a setting mode for setting the reference number and a signal processing mode for calculating a moving average value by the processing means according to the set reference number;
In the setting mode, based on each light reception signal output from the image sensor when the object to be detected is previously arranged at a plurality of different positions in the detection region, the reference in the pixel in which the light reception signal level is a predetermined value or more The number is set according to the number of pixels that are equal to or greater than the predetermined value, and the reference number of the pixels whose light reception signal level is not equal to or greater than the predetermined value is set to the pixel whose light reception signal level is equal to or greater than the predetermined value. Setting means for setting based on the number;
Storage means for storing the reference number set by the setting means in association with the detection area of the image sensor;
With
In the signal processing mode, the processing means performs signal processing using data stored in the storage means for each predetermined area. The displacement sensor according to claim 3,
The plurality of locations include at least the center of the detection region and both ends.

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