JP2848520B2 - Abnormal inspection method for object surface shape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting an abnormal state of a surface of an object for measuring and evaluating an abnormal state such as minute irregularities or undulations partially occurring on a smooth surface of a plastic molded product, and more particularly to a moving image. The present invention relates to an inspection method for continuously and efficiently inspecting an abnormal state over the entire surface of an object using a measurement processing technique.

[0002]

2. Description of the Related Art Various abnormalities in shape are inevitably generated during molding of industrial plastic products. Particularly typical surface irregularities include minute irregularities, undulations, weld lines,
The sink, the sled, the flow mark and the like are known. Conventionally,
These surface shape abnormalities have been identified by the human eye, and the extent has been determined. However, with the improvement of inspection techniques and development of inspection automation techniques, image processing techniques have recently been applied to the inspection field. As a method of evaluating surface shape abnormality by conventional image processing, for example,
In Japanese Patent Application Laid-Open No. 2-285208, a plurality of slit light images are projected onto an object to be inspected, and images are input through a video camera to analyze the distortion (distortion) of the edge line of each slit light image. There is disclosed a technique for evaluating the smoothness of the surface of an object by using the technique. In this case, the edge lines obtained from a plurality of slit light images are at most about 20 lines, and the object surface originally has a two-dimensional spread, and a large number of measurements are required to evaluate the smoothness of the entire surface. Required. Calculating the distortion of a single edge line using the Fourier transform method requires tens of thousands of numerical operations, making it difficult to measure the shape of the entire surface in a short time with a small computer. It is.

[0003]

However, in such a conventional method, still image processing is performed on a reflection image projected by a light source of a grid pattern or a grid pattern, and a portion where the grid pattern or the grid pattern exists is processed. Only distortion was detectable. In addition, since the entire target area is captured as a still image, the spatial resolution of the image has its own limit. That is, there is a problem that the entire object surface cannot be viewed at the same time, and the scanning is one-dimensional, which is inappropriate for grasping the correlation with the adjacent area, and it takes much time and labor to verify the entire surface. Was required.

[0004]

[Means for Solving the Problems] By solving the above problems,
In order to efficiently verify the entire surface of an object in a short time, in the present invention, in a device that projects a point light source or a slit light source on the surface of the object, captures the reflected image with a camera, and processes the image, While moving relative to the light source and the camera, the reflected image obtained during the relative movement is continuously input to the image processing device to perform moving image processing, and the reflected image is caused by unevenness and undulation existing on the surface of the object. The abnormal state that occurs is captured as a deviation from the normal value of the reflection angle of the incident light on the object surface. In the second invention,
Further, a two-dimensional image obtained by imaging the reflected light is set as a collection of minute rectangles previously partitioned in a grid, and the reflection angle is calculated and output for each minute rectangle region. According to a third aspect of the present invention, there is further provided an apparatus for projecting a point light source or a slit light source on the surface of an object, photographing a reflected image of the object with a camera, and performing image processing, wherein the object is positioned relative to the light source or the camera. While moving, the surface of the object is set in advance as a set of small rectangular regions partitioned in a grid shape, and the position of the reflection image of the light illuminated on the surface of the object during the relative movement and the object surface are in an ideal plane. The deviation from the imaging position of the reflection image when it is assumed is sequentially measured for each of the small rectangular areas, and the inclination angle with respect to each ideal plane of the small rectangular area is calculated from each of the deviations. The configuration was such that an abnormal state caused by existing irregularities and undulations was evaluated.

[0005]

According to the present invention, light from a slit light source or a point light source is applied to the surface of an object, and for each minute area divided in advance, the position of the reflected light image as an ideal plane of the reflected light image is defined. After measuring the deviation, calculate the distribution of the inclination angle of each minute area of the object surface converted from the deviation, create and display the distribution map of the object surface inclination angle and the undulation diagram of the object surface by processing the information Inspect the surface for abnormal conditions.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below in detail with reference to the drawings. 1 to 9 relate to an embodiment of the present invention,
FIG. 1 is a schematic configuration diagram of a measuring device in an abnormality inspection method of an object surface shape, FIG. 2 is an explanatory diagram showing a principle of abnormal state detection,
3 is a flowchart of the abnormality inspection method, FIG. 4 is an image diagram showing a normal measurement result, FIGS. 5 to 7 are image diagrams showing various abnormal state measurement results, and FIG. 8 is data showing integrated measurement results. FIG. 9 is a diagram showing an uneven surface of the object.

In FIG. 1, 1 is a light source, 2 is a slit plate, 3 is an object for measuring an abnormality on the surface of an object, and 4 (4a,
4f) is an optical image, 5 is a camera, 6 is a monitor television, 7 is an image processing device, and 8 is a computer. The light from the light source 1 is applied to the surface of the subject 3 through the slit plate 2, and the reflected light image 4 is converted into a camera (CCD camera) 5.
Then, the photographed two-dimensional image P is input to the image processing device 7. The two-dimensional image P is, for example, equally divided into 512 in the vertical direction (longitudinal direction of the slit), and equally in the horizontal direction (moving direction of the subject 3). It is configured as a part of an aggregate of divided fine rectangular (rectangular or square) pixels. The image processing device 7 digitizes the grayscale data of each pixel of the input two-dimensional image P into a numerical value of 256 gradations. Subject 3
Are much brighter than the peripheral portions, and can be extracted by applying an image processing method such as a binarization process. If the surface of the subject 3 is a perfect horizontal plane, the slit light images 4a,... Become perfect rectangles (or squares) at predetermined positions as shown in FIG. 4, and the slit light images 4a,. Present. However, the normal object surface is not completely a mirror-finished plane, but has some irregularities and undulations. Therefore, for example, a slit light image as shown in FIGS. Will be presented. That is, the slit light image is not in the straight state as shown in FIG. 4 but is observed at a position slightly shifted from the original straight position according to the degree.

Next, a measurement principle for quantitatively grasping such an abnormal state will be described. In the present invention, the deviation of the reflection angle is used to quantify the abnormal state. As described above, the surface of a general object including a plastic molded product is not a perfect horizontal surface due to the presence of small irregularities and undulations in each of the plurality of divided small regions described above, even if the surface is manufactured in a plane. It is slightly inclined with respect to the ideal plane. That is, as shown in FIG.
Are sequentially obtained, the distribution of the inclination angle β of the minute region can be measured over the entire surface of the object.

More specifically, the light source 1 is located on the normal plane 3a.
The emitted light passes through the slit plate 2 and passes through the normal plane 3
The light is reflected at the reflection angle α at a to form an image on the camera 5. On the other hand, in the inclined plane 3b inclined at an inclination angle β with respect to the normal plane 3a, the light is reflected at a reflection angle α ′ different from the reflection angle α. Image. On the other hand, the deviation δ and the inclination angle β are

Δ ≒ f · β

Is given by Here, f is a constant determined by the focal length 5a of the camera 5, the distance between the camera 5 and the subject 3, and the distance between the light source 1 and the subject 3, and can be set in advance. By sequentially moving the slit light images 4a, 4b,... By the subject 3 by an amount corresponding to the slit width using the measurement principle as described above, the deviation δ of the reflected image is measured. If the inclination angle β of the area is calculated and calculated according to the above equation, the distribution of the inclination angle β of the minute area can be obtained over the entire surface of the object. FIG.
Shows the distribution change of the inclination angle β for each slit light image 4a,... FIG. 9 shows the state converted into the unevenness of the surface.

Next, an operation procedure of the method for measuring and evaluating an abnormality in the surface shape of an object according to the present invention will be described. FIG. 3 shows a flowchart of the operation procedure. First, object information such as the vertical and horizontal dimensions of the object 3 and information such as a measurement distance (light source to object, object to camera distance and focal length) and After setting and inputting the moving speed of the subject 3 and the like in advance, the light source is set, the mirror surface is placed at the slit light image position, the slit light image is reflected, and a shadow image when the object plane becomes an ideal plane is photographed by the camera 5. Then, the reference image position is stored in the computer 8 via the image processing device 7 (these operations are referred to as “reference image position input” and “initial image”). next,
After setting the subject 3 as a sample, for example, so that the slit light image 4a at the end in FIG. 1 is reflected at the measurement start position (“image input start position”), the movement of the subject 3 is set. Move laterally at speed. While the subject 3 is moving, the camera 5, the image processing device 7, and the computer 8 operate at high speed and sequentially execute the processes in the two loops shown in FIG. First, the slit light image 4a is photographed by the camera 5 and input to the computer via the image processing device (“light image photographing”), and for each of the minute regions (for example, 512 equally divided) divided in the slit longitudinal direction described above. The coordinate position (the coordinate position in the x direction and the y direction in FIG. 1) of the center of the minute rectangular section showing the maximum luminance among the minute rectangular sections divided in the slit width direction is detected, and each coordinate in the y direction is detected. And sequentially stored in the computer 8 (“detection of the center position in the slit width direction”). In order to determine the luminance, the above-mentioned digital density data classified into 256 gradations are used.
The data is easily processed in the computer 8 by comparing the data sizes. The “detection of the center position in the slit width direction” includes, in addition to the above-described method of detecting the minute rectangular section showing the maximum luminance, digitizing the 256-gradation density data into a minute rectangular section of a predetermined value or more. There is also a method of selecting a figure area (by performing a so-called binarization process) and detecting a small rectangular section at the center of the figure area that is continuous in the horizontal direction. Next, the image based on the reflection angle α of the ideal plane 3a and the reflection angle α ^{′ at} the obtained series of designated coordinate positions are obtained.
The inclination angle β of the abnormal plane 3b is calculated by the computer 8 from the deviation δ from the image formed at the focal length 5a by the abnormal plane 3b having the above (the inclination angle is calculated) by the above-mentioned arithmetic expression, and the maximum in the y direction is calculated. The measurement is completed by completing the loop of the processing up to the lower end and the loop of the slit light image 4b which is the next image and the slit light image below it, and creates the data shown in FIGS. It is printed out and output by the monitor television 6 or a printer (not shown). In this embodiment, an example using a slit light source has been described. However, light from a point light source may be scanned on the surface of an object at a high speed in the y direction, and image processing may be performed in the same manner as described above.
In this embodiment, the light source 1 and the camera 5 are
However, the measurement can also be performed by stopping the subject 3 and moving the light source 1 and the camera 5 individually or simultaneously. In the present embodiment, the position of the reflected image obtained when the ideal mirror surface is set as the subject is set as the reference image position. However, the processing of inputting the reference image position is not performed. After detecting the center position in the slit width direction by the method described above, calculate the average value of the center position in the slit width direction in the range from the upper end to the lower end in the y direction, and use this average value as the reference image position in the input image. Can also.

As described above, in the present invention, the center point of the width of the slit light image or the light image by the point light source is selected, and the coordinate position of this center point and the rectangular section of the minute area are the horizontal plane (ideal plane). The amount of lateral blur from the position where the light image should be located, that is, the deviation δ, is obtained, and the inclination angle β of the minute area is obtained (the inclination angle β is 0 on the normal plane 3a). Then, these calculation results can be enlarged and edited over the entire surface of the object, and the undulation state of the entire surface of the object can be grasped as a distribution of the measurement results.

[0014]

As described above, in the method of the present invention, for example, the measurement of the surface shape of a plastic molded product can be automated, and can be accurately performed within a short time. The equipment required for this evaluation method is a normal light source,
It is composed of a slit, a CCD camera, an object moving device and a personal computer for image processing, and can be easily installed and operated on the side of a molding machine. Therefore, continuous automatic measurement and quantified evaluation are performed, and after manufacturing a molded product, the surface shape is measured immediately, and the results are fed back to the manufacturing process to stabilize and improve the quality of the molded product. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a measuring device in a method for inspecting an abnormality of an object surface shape according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing the principle of a method for inspecting an abnormality of an object surface shape according to an embodiment of the present invention.

FIG. 3 is a flowchart of a method for inspecting an abnormality of an object surface shape according to an embodiment of the present invention.

FIG. 4 is an image diagram showing a normal measurement result according to the example of the present invention.

FIG. 5 is an image diagram showing an example of an abnormal state according to the embodiment of the present invention.

FIG. 6 is an image diagram showing an example of an abnormal state according to the embodiment of the present invention.

FIG. 7 is an image diagram showing an example of an abnormal state according to the embodiment of the present invention.

FIG. 8 is a data diagram showing measurement results of integrated tilt angles according to the embodiment of the present invention.

FIG. 9 is a concavo-convex diagram of an object surface according to the example of the present invention.

[Explanation of symbols]

 Reference Signs List 1 light source 2 slit plate 3 subject 3a normal plane (ideal plane) 3b abnormal plane (inclined plane) 4 optical image 4a, 4b, 4c,..., 4f slit optical image 5 camera (CCD camera) 5a focal length 6 monitor television 7 Image processing device (image input board) 8 Computer (PC) α Reflection angle α 'Reflection angle β Tilt angle δ Deviation P Two-dimensional image Q pixel

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-220808 (JP, A) JP-A-59-203906 (JP, A) JP-A-8-21711 (JP, A) JP-A-4- 15505 (JP, A) JP-A-4-50606 (JP, A) JP-A-2-285208 (JP, A) JP-A-62-277508 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01B 11/00-11/30 102 G01N 21/84-21/91 G06T 1/00-7/00

Claims (3)

(57) [Claims] 1. An apparatus for projecting a point light source or a slit light source on the surface of an object, photographing a reflected image of the object with a camera, and processing the image, wherein the object is relatively moved with respect to the light source or the camera. The reflected image obtained during the relative motion is continuously input to the image processing device and subjected to moving image processing, and an abnormal state caused by unevenness or undulation existing on the surface of the object is represented by the reflection angle of incident light on the surface of the object. An abnormality inspection method for an object surface shape characterized by capturing as a deviation from a normal value. 2. The method according to claim 1, wherein a two-dimensional image obtained by photographing the reflected light is set in advance as a set of minute rectangles partitioned in a grid, and the reflection angle is calculated and output for each minute rectangle area. Inspection method for the surface shape of an object. 3. An apparatus for projecting a point light source or a slit light source on the surface of an object, taking a reflected image of the object with a camera, and performing image processing, wherein the object is moved relative to the light source or the camera, and When the surface of the object is set in advance as a set of small rectangular areas partitioned in a grid, the position of the reflected image of light illuminated on the surface of the object during the relative movement and the object surface are assumed to be an ideal plane The deviation from the image forming position of the reflection image is sequentially measured for each of the small rectangular areas, and the inclination angle of each of the small rectangular areas with respect to the ideal plane is calculated from each of the deviations. An abnormality inspection method for an object surface shape, characterized by evaluating an abnormal state caused by an object.