JP2015045571A - Device and method for measuring gap/difference in level - Google Patents

Abstract

Provided is a gap step measuring device that accurately measures a gap step without accurately positioning a sensor.
A planar image of a state in which a plurality of slit lights are irradiated in parallel on the surfaces of two plate members forming a measurement target by slit light sources 16A and 16B, and a plurality of slit lights are irradiated by a sensor unit 18. To get. Based on the acquired planar image, each thin line of the plurality of slit lights is extracted, the edge line of each end of each of the two plate materials is extracted, and each thin line of each of the plurality of slit lights and each of the two plate materials are extracted. Each intersection with the edge line at the end of is detected. The dimension of the gap step is calculated based on the detected three-dimensional position of each intersection.
[Selection] Figure 6

Description

  The present invention relates to a gap step measuring apparatus and method, and more particularly, to a gap step measuring apparatus and method for obtaining a gap formed between two objects and the size of the step.

  2. Description of the Related Art Conventionally, dimensional inspections for assuring the quality of finished automobile bodies have been regarded as important due to demands for improving the appearance quality of automobiles.

  For dimensional inspection of automobile bodies, the inspection of each part panel constituting the body, the inspection in the pre-painted body with each panel assembled (referred to as white body), and after the painting and interior / exterior parts are assembled There is an inspection for the body (called post-painting body), and a very thorough inspection is performed in each process.

  An important one of the dimensional inspections for assuring the quality of installation is inspection of installation dimensions (steps and gaps) such as between doors and between engine hoods and fenders. This inspection is performed while the body of the production line is being transported. Currently, the inspection is carried out closely by visual inspection and tactile sense, but there is a demand for automation due to lack of skilled inspectors and labor saving. Very strong. Regarding inspection of a single panel, there is a report of an automobile panel dimension inspection system using a three-dimensional visual sensor (Non-patent Document 1). In this method, a gap and a step between a panel and a reference block providing reference coordinates are inspected by a three-dimensional visual sensor using a slit light and a television camera. Regarding the inspection of the white body, there is a report of measuring the total length and the total width by attaching a spot light sensor to a 6-axis robot (Non-Patent Document 2). In addition, there is an example in which a lot of slit light sensors are mounted on a fixing jig without using a robot and the installation dimensions of the body are inspected (Non-Patent Documents 3 and 4).

  In addition, for dimensional inspection of various parts instead of automobile bodies, the dimensions of the shape inspection system (Non-Patent Documents 5 and 6) that combines spot light and PSD (semiconductor position detector) and ship propellers are used. There is a report of a system inspected by a sensor (Non-Patent Document 7) that scans in a cotton-like manner (Non-Patent Document 8).

  Conventionally, these sensors are mounted on an actuator such as a robot and positioned at a measurement site, and then measure a gap level difference in a portion where light is projected. For this reason, when the measurement light is not projected perpendicularly to the gap, it is impossible to measure the correct gap. For this reason, the actuator is required to have a high positioning accuracy.

  On the other hand, the present inventors have devised a method of measuring a gap step by obtaining a three-dimensional coordinate at two points on an end face by using a three-dimensional visual sensor that projects slit light in a cross shape and approximating the end face linearly. (Non-patent document 9). According to this method, in most cases, accurate measurement can be performed by rough positioning.

Higuchi, Koseki, Yamamoto, "Automotive panel dimension inspection system using a three-dimensional visual sensor", Electrical Engineering C, Vol.112, February 1992 Y. Sakamoto and K. Yamamoto: “Development of Car Body Inspection System”, Proc. SAE / ESD Int. Computer Graphics Conference, p.101 (1987) G. Seliger, W. Felsing, K. D. Lennartz and H. Trilk: “Laser Scanning for Flexibilization of Robotic Assembly Cells”, Proc. Int. Conf. On Robot Vision and SensoryControls, p. 307 (1988) W. S Wilson: “The Role of Vision in a Dimensional Control Strategy”, Proc. Vision '85, p. 7 (1985) Takagi, Kojima, Takasaki, Kurine, Yoshioka, "Laser applied shape measuring device", Hitachi review, Vol.68, No.73, March 1986 Hattori, Kubo, Sakamoto, Watanabe, “Non-contact 3D measurement on free-form surfaces”, Mitsubishi Electric Technical Report, 62,73, (April 1988 M. Rioux, “Laser Range Finder based on Synchronized Scanner” Appl. 0pt., 23, 3837 (1984) R.F. Livingston, A. F. Tural and M. R. Thomas: “Application of 3-D Vision to the Measurement of Marine Propellers”, Proc. Vision '87, p. 10 (1987) Tsukada, Watanabe, Koide, Tadashi, Horie, Yamagishi, “Development of 3D position measurement technology for round holes”, 17th Image Sensing Symposium SSII2011, IS4-01, June 2011

  Since the sensor described in Non-Patent Document 2 is a spot light sensor, there is a problem in that the mechanical movement of the sensor is necessary for the installation dimension inspection, and measurement time is required.

  The sensors described in Non-Patent Documents 5 and 6 are unsuitable for building inspection for the same reason as the sensor described in Non-Patent Document 2 above.

  In the method described in Non-Patent Document 9, when the projection position of the cross-shaped slit light is deviated, the distance between the two points becomes extremely short, and a large error occurs in the linear approximation of the end face. There is a problem that the gap step cannot be obtained accurately (see FIG. 9).

  The present invention has been made to solve the above-described problems, and provides a gap step measuring apparatus and method that can accurately measure a gap step without accurately positioning a sensor. Objective.

  In order to achieve the above object, a gap level difference measuring apparatus according to the present invention is a gap level difference measuring apparatus for measuring a gap and a gap formed between two objects, and obtaining a dimension of the measurement object, Slit light irradiating means for irradiating the surfaces of the two objects forming the measurement object in parallel with a plurality of slit lights, and the plurality of slit lights disposed so as to face the surfaces of the two objects. The measurement object in a state irradiated with at least the plurality of slit lights among the planar image including the measurement object in a state irradiated with the light and the planar image including the measurement object in a state not irradiated with the plurality of slit lights. Sensor means for acquiring a plane image including the image, and extracting each line of the plurality of slit lights irradiated on the surface of the object based on the plane image acquired by the sensor means. Edge lines of each end of the two objects are extracted, and intersections between the lines of the plurality of slit lights and the edge lines of the ends of the two objects are detected. An intersection point detection unit and a dimension measurement unit that calculates a dimension of the measurement target based on a three-dimensional position of each intersection point detected by the intersection point detection unit.

  A gap level difference measuring method according to the present invention is a gap level difference measuring method for measuring a gap and a level difference formed between two objects, and obtaining a dimension of the measurement target, wherein the measurement is performed by slit light irradiation means. A plurality of slit lights are irradiated in parallel on the surfaces of the two objects forming the object, and the plurality of slit lights are irradiated by sensor means arranged to face the surfaces of the two objects. A plane image including the measurement object in a state in which at least the plurality of slit lights are irradiated among a plane image including the measurement object in a state in which the plurality of slit lights are not irradiated. , And the intersection detection means based on the planar image acquired by the sensor means, each laser beam of the plurality of slit lights irradiated on the surface of the object. And an edge line of each end of each of the two objects is extracted, and each intersection of each line of the plurality of slit lights and an edge line of each end of the two objects is extracted. And the dimension of the measurement target is calculated based on the three-dimensional position of each intersection detected by the intersection detection means.

  As described above, according to the gap level difference measuring apparatus and method of the present invention, the surface of two objects is irradiated with a plurality of slit lights in parallel, and a planar image in a state in which the plurality of slit lights are irradiated is obtained. Acquire and detect each intersection of each of the irradiated slit light lines and the edge line of each end of the two objects, and based on the three-dimensional position of each intersection, By calculating the dimensions, it is possible to obtain an effect that the gap step can be measured accurately without accurately positioning the sensor.

It is a figure which shows a mode that two parallel slit lights are irradiated to the surface of two board | plate materials. It is a figure which shows a mode that the slit light was irradiated to the edge part of two board | plate materials. It is a figure for demonstrating the method of calculating | requiring the straight line which shows the end surface of two board | plate materials, and measuring a clearance gap. It is a figure for demonstrating the relationship between the space | interval of slit light, and a level | step difference. It is a figure which shows the structure of the gap level | step difference measuring apparatus which concerns on embodiment of this invention. It is a figure for demonstrating the method which makes the measurement object the clearance gap and level | step difference formed between two board | plate materials, and calculates | requires the dimension. It is a figure which shows the functional structure of the control calculating part of the gap level | step difference measuring apparatus which concerns on embodiment of this invention. It is a flowchart which shows the process routine by the control calculating part of the gap level | step difference measuring apparatus which concerns on embodiment of this invention. It is a figure which shows a mode that the projection position of the cross-shaped slit light in the prior art shifted | deviated. It is a figure which shows the motor vehicle body used as a test object. It is a figure which shows the triangulation by the light cutting method using TV camera and a slit light source. (A) The figure which shows a mode that it projects perpendicularly | vertically with respect to a clearance direction, (B) The figure which shows a mode that it shifts | deviates from perpendicular | vertical with respect to a clearance direction, (C) It is perpendicular | vertical with respect to a measurement object surface. It is a figure which shows a mode that it projects, and (D) is a figure which shows a mode that it shifts | deviates from perpendicular | vertical with respect to a measurement object surface.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Summary of invention>
FIG. 10 shows an automobile body to be inspected. As shown in FIG. 10, the gap and the step are the distance between the end portions of the surface and the step. As shown in FIG. 11, the three-dimensional coordinates are measured by triangulation by a light cutting method using a TV camera and a slit light source. In the measurement by the conventional light cutting method, the sensor can project the measurement light perpendicularly to the gap direction (see FIG. 12A) and perpendicular to the measurement target surface (see FIG. 12C). Was positioned and measured. In addition, there is a drawback in that when it deviates from the vertical direction with respect to the gap direction, the corresponding amount is measured as an error (see FIG. 12B). There is a drawback in that when it deviates from the perpendicular to the surface to be measured, that amount is measured as an error (see FIG. 12D).

  Therefore, in this embodiment, when two slit light beams for measurement are irradiated in parallel as shown in FIG. 1, the irradiation is performed with a deviation from perpendicular to the gap direction as shown in FIG. In addition, the three-dimensional coordinates of two points on the end surface of the measurement target surface are measured, the straight line of the end surface is obtained, and the gap is correctly measured (see FIG. 3). Furthermore, also in the step measurement, as shown in FIG. 4, when the measurement light is not irradiated perpendicularly to the target surface, the interval (D) between the two slit lights projected on the target surface is measured. Thus, the influence of the inclination is corrected. If the irradiation is performed correctly, the value corresponds to the set interval of the slit light, but if the irradiation is performed obliquely, the interval is widely measured according to the angle. At this time, the measured step is also a value including an error corresponding to the tilt angle. At this time, since there is a proportional relationship (A: B = C: D) between the measured slit light interval and the value of the step, correction can be applied by the original slit light interval B and the measured values C and D. .

<System configuration>
As shown in FIG. 6, the gap level difference measuring apparatus according to the embodiment of the present invention uses a gap and a level difference formed between two plates placed on an inspection table (not shown) as a measurement target. This is a device for obtaining the dimensions.

  FIG. 5 shows a configuration of the gap level difference measuring apparatus 10 for realizing the above measuring method. The gap level difference measuring device 10 includes a sensor head 12 and a control calculation unit 14. The sensor head 12 includes two slit light sources 16A and 16B and a sensor unit 18. The control calculation unit 14 controls the ON / OFF of the slit light of the slit light sources 16A and 16B, the light emission time, and the irradiation intensity according to the command for the slit light sources 16A and 16B. As the sensor unit 18, a CCD camera, a two-dimensional sensor, or a CMOS camera can be used.

  The slit light sources 16A and 16B are fixed to the frame member 20. The slit light sources 16A and 16B are arranged so as to face the surfaces of the two plate materials to be measured, and each of the two plate materials crosses the laser slit light with the length direction of the gap between the two plate materials. It is designed to irradiate the surface. In addition, the slit light sources 16A and 16B are installed so that two laser slit lights (slit lights) formed by the slit light sources 16A and 16B are irradiated in parallel on the surfaces of the two plate members.

  The slit light is applied to the surfaces of the two plates, and the irradiation direction of the slit light is not parallel to the imaging direction of the sensor unit 18.

  Further, the slit light sources 16A and 16B are connected to the control calculation unit 14, respectively, and irradiation control can be performed independently by the control calculation unit 14.

  Moreover, in this gap | interval level | step difference measurement apparatus 10, the sensor part 18 is arrange | positioned in the position facing the surface of two board | plate materials. As shown in FIG. 6, at least the end portion of one plate material and the end portion of the other plate material are both acquired as information of one plane image by the sensor unit 18. The inspection table is provided with a non-reflective coating in accordance with the wavelength of the slit light so that the reflected light of the slit light is not imaged by the sensor unit 18.

  The sensor unit 18 is connected to the control calculation unit 14.

  Further, as shown in FIG. 7, the control calculation unit 14 includes an irradiation control unit 30, an image acquisition unit 32, a slit light line extraction unit 34, a feature point extraction unit 36, a three-dimensional coordinate conversion unit 38, a measurement unit 40, and A step correction unit 42 is provided.

  The irradiation control unit 30 performs irradiation control of the slit light sources 16A and 16B so that the slit light sources 16A and 16B irradiate the slit light. In addition, in order to reduce the influence of the vibration of the measurement object, it is possible to control strong light emission in a short time in a pulse shape.

  The image acquisition unit 32 acquires the slit light image captured by the sensor unit 18 in synchronization with the irradiation timing of the slit light. In addition, you may make it the image acquisition part 32 control the imaging by the sensor part 18 so that it may image in synchronization with the irradiation timing of slit light.

  Moreover, the image acquisition part 32 acquires the image imaged by the sensor part 18 in the state which is not irradiating slit light.

  Further, the image acquisition unit 32 performs preprocessing (for example, binarization processing) and feature point extraction processing by image processing on the acquired slit light image. At this time, the accuracy of feature point extraction in the slit light image is also improved by supplementarily referring to the density information of the image captured in the state where the slit light is not irradiated. Since the positional relationship between the two plate materials to be measured and the sensor head 12 is the same, the positions of the slit light image and the image captured without irradiating the slit light correspond to the same pixel value. .

  In addition, the image acquisition unit 32 performs preprocessing (for example, binarization processing) and feature point extraction processing by image processing on an image captured in a state where the slit light is not irradiated.

  For example, the slit light line extraction unit 34 extracts a skeleton line of the slit light line from the slit light image by thinning processing.

  The feature point extraction unit 36 extracts lines indicating the ends of the two plate members from the image captured in a state where the slit light is not irradiated. The feature point extraction unit 36 includes a thin line of two slit lights on the slit light image extracted by the slit light line extraction part 34, and a line indicating ends of two plate members on the extracted slit light image. Each intersection is calculated.

  The three-dimensional coordinate conversion unit 38 obtains each three-dimensional coordinate of each intersection by performing coordinate calculation with reference to a coordinate conversion table obtained in advance for each coordinate of the calculated intersection. Note that the three-dimensional coordinate system is a three-dimensional coordinate system in which one plate material is used as a reference plate material, and the normal vector of the surface of the reference plate material is used as a coordinate axis reference.

  The measuring unit 40 determines a gap between the two plate members based on a straight line indicating the end surface of one plate member in a three-dimensional space obtained based on the three-dimensional coordinates of each intersection and a straight line indicating the end surface of the other plate member. And the size of the step is calculated, and the calculated size of the gap is output.

  The level difference correction unit 42 calculates the interval between the two slit light thin lines on the slit light image extracted by the slit light line extraction unit 34, and calculates the calculated interval and the two slit light lines obtained in advance. Compared with the interval, the dimension of the step measured by the measuring unit 40 is corrected, and the corrected dimension of the step is output.

  For example, as shown in FIG. 4 above, the interval between two slit light lines obtained in advance is B, the interval between two slit light lines on the slit light image is D, and the step measured by the measuring unit 40 is measured. When the dimension is C, the corrected dimension A of the step is calculated by the following equation.

A = BC / D

<Operation of gap level measuring device>
Next, the flow of processing (gap step measurement method) in the gap step measurement apparatus 10 will be described based on the flowchart shown in FIG. In addition, the process in the control calculation part 14 is performed based on a gap level | step difference measurement program.

  First, for example, the whole illumination of white illumination is performed on the surfaces of the two plate materials to be measured by an imaging illumination unit (not shown), and an image including the end portions of the two plate materials is captured by the sensor unit 18. The captured image is acquired by the control calculation unit 14 (step 100 in FIG. 8).

  Next, the slit light sources 16A and 16B are driven by the control calculation unit 14, and the two laser slit lights are irradiated to the surfaces of the two plate materials, respectively, and include the end portions of the two plate materials in the irradiated state. An image is picked up by the sensor unit 18, and the picked-up slit light image is acquired by the control calculation unit 14 (step 102). Here, as described above, since the inspection table is coated without reflection, the reflected light of the slit light from the inspection table under the gap between the end portions of the two plates is not imaged.

  Each image acquired by the sensor unit 18 is binarized by the control calculation unit 14. By this binarization processing, the boundary line between the irradiated part and the non-irradiated part is clarified. Then, in the control calculation unit 14, two laser slit light lines having a predetermined thickness width on the binarized slit light image are thinned (step 104).

  Further, the control calculation unit 14 extracts the edge lines of the end portions of the two plate materials at the pixel level based on an image obtained by binarizing the image captured under the entire illumination (step 106).

  Then, in the control calculation unit 14, one laser slit is obtained by solving a linear equation based on the thin line of one slit light obtained in steps 104 and 106 and the edge line of the end portions of the two plates. Each intersection of the light and the ends of the two plates is determined below the pixel level (step 108).

  In addition, the control calculation unit 14 solves the straight line equation based on the thin line of the other slit light obtained in steps 104 and 106 and the edge line of the end portions of the two plates, thereby obtaining the other laser slit. Each intersection of the light and the ends of the two plates is calculated (step 108).

  Here, the image picked up by the sensor unit 18 is data on a two-dimensional plane. A lookup table indicating the correspondence between the position on the image and the three-dimensional coordinate is recorded in advance in a storage unit (not shown), and the three-dimensional coordinate can be obtained by referring to it.

  Therefore, the control calculation unit 14 converts the intersection point below the pixel level obtained in step 108 into three-dimensional coordinates (step 110).

  Then, the control calculation unit 14 obtains a straight line in the three-dimensional space based on the two intersections between the obtained two laser slit lights and the end of one plate member. Further, a straight line in the three-dimensional space is obtained based on the two intersections between the obtained two laser slit lights and the end of the other plate (step 112).

  Then, the control calculation unit 14 calculates the gap size and the step size of the end portions of the two plate members based on the two obtained straight lines (step 112). Next, the interval between the thin slit light lines is calculated from the two thin slit light lines obtained in step 106 by the control calculation unit 14. The step size obtained in step 112 is corrected based on the calculated interval between the thin lines of slit light and the interval between the slit light lines obtained in advance (step 116).

  As described above, according to the gap level difference measuring apparatus according to the present embodiment, the surface of two plate members is irradiated with two slit lights in parallel, and the plane in a state in which the two slit lights are irradiated. An image and a plane image in a state where two slit lights are not irradiated are obtained, and each intersection of each thin line of the plurality of irradiated slit lights and an edge line at each end of the two plates , And by calculating the dimensions of the gap and the step based on the three-dimensional position of each intersection, the gap step can be measured accurately without accurately positioning the sensor.

  In addition, by irradiating two parallel lines of measurement light, it is possible to always measure two end points of a plate with a constant interval without being affected by the relative positional relationship between the sensor and the plate. It is not necessary to perform the positioning with high accuracy. Thereby, in the measurement of the gap step of the butt plate material, stable measurement of the gap step can be realized without accurately positioning the sensor with respect to the plate material.

  In the above embodiment, the case where two slit lights are irradiated in parallel has been described as an example. However, the present invention is not limited to this, and three or more slit lights are irradiated in parallel. Also good. In that case, it is possible to perform measurement with higher accuracy by obtaining intersections between the center line of each laser slit light and the edge lines at both ends of the workpiece, and obtaining the dimensions of the measurement object based on the respective intersection positions.

  In the above embodiment, the slit light irradiating means is a slit light source and irradiates the laser slit light. However, the light source is not limited to the laser light, and a light source other than the laser (for example, LED) may be used to form and irradiate slit light.

  In the above embodiment, after binarizing each image acquired by the sensor unit, an example in which a thin line of slit light and an edge line at the end of two plate members are extracted at the pixel level is shown. However, the present invention is not limited to this. For example, the thin lines of slit light and the edge lines of the end portions of two plate members may be extracted from each image without binarizing each image acquired by the sensor unit. In this case, for example, it is preferable to extract a thin line by obtaining luminance center-of-gravity pixels in the width direction of the slit light in the planar image and connecting them in the length direction of the slit light.

  Moreover, although the case where the edge line of the edge part of two board | plate materials was extracted at the pixel level from the image which is not irradiated with slit light was demonstrated to the example, it is not limited to this. Instead of using an image that is not irradiated with slit light, the edges of the two plate members may be extracted as feature points in the thinned image of the slit light image, and the edge lines may be extracted at the pixel level.

DESCRIPTION OF SYMBOLS 10 Gap level | step difference measurement apparatus 12 Sensor head 14 Control calculating part 16A, 16B Slit light source 18 Sensor part 30 Irradiation control part 32 Image acquisition part 34 Slit light line extraction part 36 End point detection part 38 End surface interpolation part 40 Measurement part 42 Step correction part

Claims (4)

A gap step measuring device for measuring a gap and a step formed between two objects and measuring a dimension of the measurement target,
Slit light irradiation means for irradiating a plurality of slit lights in parallel on the surfaces of the two objects forming the measurement object;
A plane image including the measurement object in a state of being irradiated with the plurality of slit lights and the measurement object in a state of not being irradiated with the plurality of slit lights, disposed so as to face the surfaces of the two objects. Sensor means for acquiring a planar image including the measurement object in a state irradiated with at least the plurality of slit lights of the image;
Based on the planar image acquired by the sensor means, each line of the plurality of slit lights irradiated on the surface of the object is extracted, and an edge line at each end of the two objects is extracted. Crossing point detecting means for detecting each crossing point between each line of the plurality of slit lights and an edge line at each end of the two objects;
A dimension measuring means for calculating a dimension of the measurement object based on a three-dimensional position of each intersection detected by the intersection detecting means;
Gap level difference measuring device including.   The interval of each line of the extracted slit light is measured, and the interval between each line of the plurality of slit light obtained in advance and the line of each of the measured slit light are measured. The gap level difference measuring apparatus according to claim 1, further comprising a correction unit that corrects the dimension of the level difference measured by the dimension measurement unit based on the interval.   Based on the three-dimensional position of each intersection detected by the intersection detection means, a straight line indicating the edge line of each end of the two objects is obtained, and based on the obtained straight line, the measurement target The gap level difference measuring device according to claim 1 or 2, wherein a dimension is calculated. A gap step measurement method for measuring a gap and a step formed between two objects and measuring a dimension of the measurement object,
A plurality of slit lights are irradiated in parallel to the surfaces of the two objects forming the measurement object by the slit light irradiation means,
A planar image including the measurement object in a state where the plurality of slit lights are irradiated by the sensor means arranged so as to face the surfaces of the two objects, and the measurement in a state where the plurality of slit lights are not irradiated. Obtaining a planar image including the measurement object in a state irradiated with at least the plurality of slit lights of the planar image including the object;
Based on the plane image acquired by the sensor means, the intersection detection means extracts each line of the plurality of slit lights irradiated on the surface of the object, and detects the end of each of the two objects. Extracting each edge line, and detecting each intersection of each line of the plurality of slit lights and the edge line of each end of the two objects,
A gap step measurement method in which a dimension measurement unit calculates a dimension of the measurement target based on a three-dimensional position of each intersection detected by the intersection detection unit.