JPH10300446A - Surface defect inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface defect inspection device capable of surely detecting defects in the surface of work of low surface gloss without depending on manual power. SOLUTION: A surface defect inspecting device has: a projecting device 11 projecting an image of stripes on the surface of work 50; an image pickup camera 12 photographing the surface of the work 50 on which the image of stripes were projected; support 30 which enables the projection angle of the stripes projected by the projecting device 11 to be varied in an inspection device inspecting the surface state of the work 50; and a computing unit calculating the amount of changes in the pitch of the image of stripes obtained by the image pickup camera 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface defect inspection apparatus for inspecting defects such as distortion of a work surface.

[0002]

2. Description of the Related Art In recent years, resin molded products have been frequently used as interior, exterior and body parts of automobiles, for example, front panels, dashboards, bumpers, door moldings, and the like. Depending on the conditions at the time of manufacture, such resin-formed products
Wavy defects may be formed on the surface of the component, or partial distortion may occur. Since such defects deteriorate the appearance of a product, a defective part must be removed by an inspection process.

Conventionally, for such a surface defect of a resin-formed product, an operator such as a fluorescent lamp illuminates the resin-formed product, and an operator looks at the surface of the component to inspect for defects such as distortion of the component surface.

[0004]

However, since such inspections rely on human judgment, the frequency of detecting defects in products may vary depending on the skill level of the operator. Become. In particular, in the case of resin-formed products, at the stage before painting (usually inspecting surface defects at this stage), the surface of the component is not glossy, and the distortion of the component surface due to reflected light is very difficult to see. This is a process that requires skill.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a surface defect inspection apparatus capable of reliably detecting a surface defect of a resin-formed product, particularly a work having a low surface gloss, without manual operation.

[0006]

According to a first aspect of the present invention, there is provided a projection apparatus for projecting a stripe image on a work surface, and an imaging apparatus for imaging the work surface on which the stripe image is projected. A surface defect comprising: means for changing a projection angle of a stripe image projected by the projection means; and arithmetic means for calculating an amount of change in a pitch of a stripe image obtained by the imaging means. It is an inspection device.

According to the present invention, by projecting a stripe image on the surface of a work, if there is a defect such as distortion or waving on the surface of the work, the pitch or linearity of the projected stripe image changes. Therefore, the inspection apparatus detects such a defect on the surface of the work by photographing the projected stripe by the imaging means and calculating the amount of change in the pitch of the stripe from the obtained image. Is made variable, it is possible to project the stripe image on the work surface at an angle at which the stripe image can be most easily taken. Thus, for example, even when the work surface has no gloss, a clear stripe can be projected on the work surface, and a change in the stripe image on the work surface can be captured.

According to a second aspect of the present invention, in the configuration of the first aspect, the surface defect inspection apparatus determines a periodicity of the change amount from the change amount of the stripe pitch obtained by the arithmetic means. And a wavy defect on the surface of the work is detected.

According to the present invention, a wavy defect occurring on the surface of a work is detected by detecting the periodicity of the stripe from the variation in the pitch of the stripe obtained by the arithmetic means.

According to a third aspect of the present invention, in the configuration of the first aspect, the surface defect inspection apparatus checks the linearity of each stripe of the stripe image obtained by the imaging means, and The method is characterized in that a partial defect on the surface is detected.

According to the present invention, for example, a defect such as a partial dent or distortion on the work surface is detected by checking the linearity of each straight line of the stripe imaged by the imaging means.

According to a fourth aspect of the present invention, in the configuration according to any one of the first to third aspects, the work is a resin-formed product.

The present invention is particularly suitable for detecting a surface defect of a resin-formed product.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of the present invention will be described.

FIGS. 1 and 2 are views showing the structure of a surface defect inspection apparatus to which the present invention is applied.

This apparatus is roughly divided into a measurement head unit 10 (FIG. 1), which is a measurement optical system, and a measurement processing unit 1 (FIG. 2) for controlling the measurement head unit 10 and calculating a measurement result. Can be

The measuring head unit 10 includes a projection device 11 as a projection unit for projecting a stripe image on a measurement surface of the work 50, an imaging camera 12 as an imaging unit for photographing the projected image, and a projection device 11. And imaging camera 1
2 and a support 30 which is a variable means capable of changing the angle with respect to these measurement surfaces.

A light source 21 is provided in the projection device 11, and a light beam from the light source 21 is applied to the measurement surface through a slit 22 and a lens 23 to project a stripe image on the measurement surface.

The image pickup camera 12 has a CCD camera (not shown) therein, and takes an image of a measurement surface.

In the support 30, the angle of incidence α of the light from the projection device 11 to the measurement surface always coincides with the light reception angle α ′ of the imaging camera 12 that receives the reflection from the measurement surface. A semi-circular support ring 3 for supporting the imaging camera 12 variably in angles of an incident angle α and a light receiving angle α ′.
1 and a support arm 32 that supports the upper ends of the projection device 11 and the imaging camera 12 and that moves up and down by a feed screw that is rotated by the operation of a motor 33. The operation of the support 30 is determined by the measurement processing unit 1 described later.
When the motor 33 operates and the feed screw rotates in response to the instruction from the controller, the support arm 32 moves up and down. The angle is changed while the angle α 'is matched. Here, a pulse motor is used as the motor 33 to control the rotation amount of the feed screw, and the motor 33 rotates by a required amount according to a pulse signal from the measurement processing unit 1.

The inside of the measurement processing unit 1 performs various arithmetic processing to be described later and controls the entire apparatus, and also has an arithmetic unit 2 functioning as arithmetic means for calculating an amount of change in the stripe pitch, and an image captured by the imaging camera 12. , A video signal input / output interface 4 for receiving an image signal (video signal) from the imaging camera 12 and outputting an image to the monitor 7, and an operation instruction signal for the motor 33, which is necessary for the motor 33. It comprises a motor control interface 5 for outputting the number of pulses, and a storage device 6 for storing received images as necessary.

FIG. 3 is a flowchart showing the operation procedure of the surface defect inspection apparatus.

First, when an instruction to start measurement is given (S
1), the angle α of the projection device 11 and the imaging camera 12;
α ′ is set to 10 degrees as an initial position (S2). In this state, a stripe image is projected from the projection device 11 onto the measurement surface, and the image is read by the imaging camera 12 (S3).

Then, the brightness of the entire captured image (CC
It is determined whether or not the average value of the entire image captured by the D camera is equal to or greater than a predetermined threshold value (S4). If the angle is equal to or smaller than the threshold value, the angles α and α ′ of the projection device 11 and the imaging camera 12 are further increased by +10 degrees (see FIG. 1).
(In the direction in which the angles α and α ′ open) at (S)
5). In step S4, steps S3 to S3 are performed until the brightness of the captured image becomes equal to or higher than the threshold value.
The process is repeated until S5. When the angles α and α ′ reach a limit (theoretically 90 degrees, but depending on the actual apparatus configuration, an angle smaller than that (for example, about 80 to 85 degrees), measurement is disabled and processing is stopped. I do.

As described above, by changing the angles of the projection device 11 and the imaging camera 12, a stripe image suitable for measurement can be projected even on a non-glossy work or a measurement surface having a grain (satin-finished surface). , It can be imaged.

In the step S5, the angles α and α 'are changed by +10 degrees, but this may be any angle, and is not limited to +10 degrees. Also,
Instead of the processing in steps S3 to S5, for example, the angles α and α ′ may be continuously changed, the angle at which the image becomes brightest may be stored, and the image may be captured at that angle.

If it is determined in step S4 that the brightness of the captured image is equal to or greater than the threshold value, the captured image is stored in the memory 3, and the arithmetic processing unit 2 processes the stored image. Then, the amount of change in the pitch of the projected stripe is obtained (S6). Then, based on the result of the arithmetic processing, the inspection result is displayed on the monitor 7 (S7), and the inspection ends.

Hereinafter, the calculation processing in step S6 will be described.

First, the relationship between the stripe projected on the measurement surface and a surface defect such as partial distortion or overall undulation of the measurement surface will be described.

FIG. 4 is a drawing showing the state of the measurement surface and the stripe image projected thereon. The stripe image to be projected here is formed by the slit 22 of the projection device 11 as described above, and is projected onto the measurement surface as a stripe image at even intervals through the lens 23.

First, as shown in FIG. 4A, when the measurement surface is flat, stripe images on the measurement surface are displayed as stripes at equal intervals. Therefore, if the pitch of the stripes is substantially equal, it can be understood that the surface is an equilibrium surface.

Next, as shown in FIG. 4B, when the measurement surface has a partial inclination, the pitch of the stripe projected on the measurement surface changes at the inclined portion. Therefore, if there is a portion where the stripe pitch is partially changed, it is understood that there is a partial inclination on the measurement surface where the stripe pitch is changed.

Next, as shown in FIG. 4C, when there is a dent or distortion on a part of the measurement surface, the linearity of the stripe is partially reduced where the dent or distortion is present. Crumble. Therefore, it can be seen that there are partial dents, protrusions, distortions, and the like in portions where the linearity of the stripe is broken.

Next, as shown in FIG. 4D, when the measurement surface is entirely wavy, the stripe pitch changes periodically. Therefore, it can be seen from the periodicity of the change in the stripe pitch that the measurement surface is wavy. In this case, the wavelength and the amplitude of the wave on the measurement surface are obtained by the calculation described later.

The arithmetic processing for confirming the state of each stripe is performed by binarizing and storing the image captured by the imaging camera 12 in the memory 3 and calculating based on the stored image.

First, as shown in FIG. 5, numbering is performed on each straight line of the stripe in the image stored in the memory 3. Then, for each straight line, the position of each straight line (the coordinate (X coordinate) of each straight line in the stripe interval direction) is obtained.

Subsequently, the pitch of the stripe is calculated from the obtained X coordinate of each straight line. Then, if there is a change in the obtained pitch and the change is periodic, it means that the measurement surface is wavy as shown in FIG. 4D. In this case, the wavelength of the wave is further increased. Specifically, as shown in Fig. 6, the difference between the straight lines of the stripe is determined by taking the difference between the straight lines to determine the stripe pitch, and the obtained stripe pitch is Fourier-transformed to obtain the largest frequency. From the relationship between the coordinate pitch on the image (for example, pixel pitch) and the distance on the actual measurement surface (the pixel resolution of the image, for example, mm / dot), the wavelength is calculated based on the obtained frequency. Convert.

The amplitude is obtained by extracting the maximum pitch value Wmax of the stripe pitch obtained as described above, and calculating the difference (Wmax-Wav) between the maximum pitch Wmax and the stripe pitch value Wav on the plane previously determined. ). Then, the amplitude is determined from the wavelength and the optical positional relationship of the measurement head unit 10.

Next, as shown in FIG. 7, for each straight line of the stripe, the linear direction coordinates (Y coordinate) of the pixels arranged in the linear direction are obtained, and the straight line is approximated by the least square method.
At this time, the coordinate values in the linear direction need not be obtained for all the pixels in the linear direction.
Alternatively, an appropriate interval such as every 20 pixels may be used. However, if the interval is too wide, accurate measurement cannot be performed, so that the interval should not be too wide.

Then, a difference between the coordinates of each pixel of the actual stripe line and the approximate straight line is obtained, and if this difference is larger than a predetermined value, it can be determined that there is partial distortion.

The values of the wavelength, amplitude, distortion, and the like thus obtained are displayed on the monitor 7 together with the image on the measurement surface.
If these are larger than the specified values, it indicates that there is a defect.

As described above, even a component having a low glossiness, such as a resin-formed product, can be inspected for surface defects such as distortion, undulation, and undulation on the measurement surface.

[0043]

According to the present invention described above, the following effects can be obtained for each claim.

According to the first aspect of the present invention, the projection angle of the projection means for projecting the stripe image on the work surface is variable, so that the optimum stripe pattern can be adjusted according to the state of the work surface, for example, the glossiness. Can be projected on the work surface, and by detecting the pitch change amount of the stripe projected on the work surface, the defect on the work surface can be easily detected from the change amount of the projected stripe pitch due to the work surface defect. Can be.

According to the second aspect of the present invention, by detecting the periodicity of the pitch change amount of the stripe projected on the work surface, it is possible to easily detect a wavy defect on the work surface.

According to the third aspect of the present invention, by examining the linearity of the stripe projected on the work surface, it is possible to easily detect a distortion defect such as a partial dent or distortion on the work surface.

According to the fourth aspect of the present invention, even in the case of a work which has conventionally been difficult to inspect by hand, such as a work having a low glossiness on the surface, such as a resin-formed product, the first to third embodiments are also applicable. With the configuration described in any one of the above, an inspection for a surface defect can be performed.

[Brief description of the drawings]

FIG. 1 is a drawing showing a configuration of a measuring head unit of a surface defect inspection apparatus to which the present invention is applied.

FIG. 2 is a drawing showing a configuration of a measurement processing unit of the surface defect inspection device.

FIG. 3 is a flowchart showing an operation procedure of the surface defect inspection apparatus.

FIG. 4 is a drawing showing a relationship between a state of a measurement surface and a stripe image.

FIG. 5 is a drawing for explaining the arithmetic processing by the above device.

FIG. 6 is a drawing for explaining the arithmetic processing by the above device.

FIG. 7 is a diagram for explaining a process of checking the linearity of a stripe by the above-described device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Measurement processing part, 2 ... Calculation part, 3 ... Memory, 4 ... Video signal input / output interface, 5 ... Motor control interface, 6 ... Storage device, 7 ... Monitor, 10 ... Measurement head part, 11 ... Projection device, 12 ... Imaging camera, 21 ... Light source, 22 ... Slit, 23 ... Lens, 30 ... Support, 32 ... Support arm, 33 ... Motor, 50 ... Work.

Claims (4)

[Claims] A projection unit configured to project a stripe image on a work surface; an imaging unit configured to capture an image of a work surface on which the stripe image is projected; and a variable unit configured to change a projection angle of the stripe image projected by the projection unit. A surface defect inspection apparatus, comprising: an arithmetic unit for calculating an amount of change in the pitch of the stripe image obtained by the imaging unit. 2. The apparatus according to claim 1, wherein the surface defect inspection apparatus obtains a periodicity of the change amount from a change amount of the stripe pitch obtained by the calculation means, and detects a wavy defect on the work surface. Item 2. A surface defect inspection device according to Item 1. 3. The apparatus according to claim 1, wherein the surface defect inspection apparatus checks a linearity of each stripe of the stripe image obtained by the imaging means, and detects a partial defect on the surface of the work. The surface defect inspection device according to the above. 4. The surface defect inspection apparatus according to claim 1, wherein the workpiece is a resin-formed product.