JPH10282014A - Surface defect detector with polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface defect detector which enables not only accurately detecting of a microscopic defect caused in an object to be inspected without expanding the object to be inspected such as resin or metal larger than required but also keeping of the defect from being overlooked even when the color of the surface of the object to be inspected is black or dark. SOLUTION: Light information reflected from an object 3 to be inspected is received by a photodetecting section 5 and converted into an electrical signal to be outputted to a comparison/judging device 6. The comparison/judging device 6 compares the electrical signal inputted with a preset target value to judge the presence of a defect of an object 3 to be inspected based on the results of the comparison. Now, a first polarizing plate 2 is mounted on the irradiation side of light of a projecting part 1 forming a photosensor and a second polarizing plate 4 having an angle of polarization with respect to the first polarizing plate 2 is mounted on the condensing side of the photodetecting section 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface defect detecting device for detecting defects such as cracks and scratches on the surface of an object to be inspected, and has a polarizer mounted on a light projecting portion and a light receiving portion of the light detecting device. The present invention relates to a surface defect detecting device provided with a polarizer.

[0002]

2. Description of the Related Art Conventionally, surface defect detectors for detecting surface defects such as resin and metal have been widely used. In general, these detection devices irradiate a test object with light from a light source, collect reflected light information with a light detection device or the like, and convert the light information into an electric signal.

[0003] Then, an electric signal is output to a control device or the like and a comparison judgment is made to detect the presence or absence of a defect. Here, the light detection device and the like are mainly illumination for obtaining necessary optical information from the inspection object, and a light projecting unit including an illumination source and an illumination optical system, and extract and collect the optical information. It has a function, a light receiving unit formed of a lens, a filter, or the like, and a photoelectric conversion unit, which has a function of converting optical information into an electric signal and is formed of an imaging tube, a solid-state imaging device, a photoelectric conversion device, or the like. .

Further, a scanning unit having a function of converting two-dimensional optical information into a time-series one-dimensional electric signal may be provided. The scanning unit may control the photoelectric conversion unit like an ITV camera or a solid-state camera, or may mechanically move the inspection object or the photoelectric conversion element.

Next, a control device and the like include an A / D converter for converting an analog electric signal from a photodetector and the like into a digital signal, a pre-processing unit for converting the digital signal into a binary signal, and a binarized signal. The signal is formed by a logical operation determination unit using either a method of extracting the geometric feature of the inspection object and using it for comparison and determination, or a method of comparing and determining by superimposing the pattern itself.

[0006] The control device or the like may be provided with a monitor TV or the like for displaying a waveform or a comparison / judgment result. The feature of the surface defect detection device is that the data collection and input / output functions of hardware are enhanced, and different defect determination criteria and operation specifications are dealt with by software.

Further, the functions required for the surface defect detection apparatus include a high defect inspection / resolving function, no influence of surface deposits, a high reliability without oversight of defects, and an uneven surface state. And high-speed various processing and display of abnormal places and contents by self-diagnosis.

[0008]

By the way, the width is several tens μm.
In order to inspect for defects such as cracks and scratches as small as about m, it is necessary to enlarge the defective portion using a lens. By the way, when the surface color of the inspection object is white or light, the surface defect generated on the inspection object appears as black in contrast to white, so it is easy to find the defect with the brightness or color contrast. Can be.

However, especially when the surface color of resin or metal is black or dark, a higher magnification is required for discrimination because the contrast between the defective portion and the normal portion is low. For example, when a crack having a width of about 20 μm generated in a black molded product is observed under ordinary illumination, there is a problem that it is difficult to clearly observe the crack even if the defect is expanded to the full field of view.

When the differential interference optical system and the magnifying optical system are used in combination, the contrast is increased and fine irregularities on the surface are enlarged. Therefore, the presence can be confirmed with the naked eye, but when such a device is used to automate defect detection, cracks must be separated from noise due to unevenness, and advanced image processing means is required. Will be needed. Further, the differential interference optical system has a problem that it is expensive and difficult to adjust as compared with ordinary illumination.

Further, in the case of enlarged detection, the field of view becomes narrow and the inspection object has to be moved vertically or horizontally in accordance with the range to be inspected in order to inspect the entire surface of the inspection object.

At the same time, the depth of focus also increases,
There is also a problem that it is difficult to move the observation position while maintaining the state where the inspection object is focused. Such a method of detecting a defect by enlarging greatly reduces the efficiency of inspection.

The present invention has been improved in view of the above. In other words, it is possible to accurately detect minute defects generated in the inspection object without expanding the inspection object such as resin or metal more than necessary, and to detect the defect even when the surface color of the inspection object is black or dark. A technical problem is to provide a highly reliable surface defect detection device that is not overlooked.

It is another object of the present invention to provide an inexpensive surface defect detecting device which can simplify the structure of the surface defect detecting device and detect defects with an easy image processing means, and which can be easily adjusted and is inexpensive. I do.

[0015]

The present invention employs the following means in order to solve the above-mentioned problems. The surface defect detection device with a polarizing plate according to the present invention irradiates the inspection object with light from a light projecting unit, receives light information reflected from the inspection object at a light receiving unit, and transmits the optical information to an electric signal. A photodetector that converts and outputs the light, and is connected to the photodetector,
A comparison / determination device that compares the electrical signal from the photodetector with a preset target value and determines whether the inspection object has a defect based on the comparison result.

A first polarizing plate is mounted on the light irradiation side of the light projecting unit, and a first polarizing plate is provided on the light collecting side of the light receiving unit so as to have a predetermined polarization angle with respect to the first polarizing plate. Second
Is mounted.

According to the present invention, the light information reflected from the inspection object is received by the light receiving section, and the light information is converted into an electric signal and output to the comparison / determination device. Then, the comparison and determination device that has received the electric signal extracts the geometrical feature of the inspection object and performs the comparison or determination by superimposing the pattern itself or using the pattern itself.
Perform a comparison operation.

Next, a first polarizing plate is mounted on the light irradiation side of the light projecting portion forming the optical sensor, and a second polarizing plate having a predetermined polarization angle with respect to the first polarizing plate is mounted. Attach to the light collecting side of the light receiving section. This makes the normal part of the inspection object darker and the defective part lighter.

The principle is that, by arranging the second polarizing plate at a polarization angle of about 90 ° with respect to the first polarizing plate, the transmittance of the reflected light transmitted through the second polarizing plate is increased. descend. Therefore, the surface of the normal part becomes dark. However, it is considered that the defective portion has a different light reflection angle than the normal portion, and the transmittance of the light passing through the second polarizing plate is less reduced than the normal portion. Therefore, the normal part becomes darker in color than the defective part, and the contrast between the normal part and the defective part becomes clear.

Next, the surface defect detecting device with a polarizing plate is configured such that the light projecting portion is formed in a ring shape and the first polarizing plate is formed in a ring shape corresponding to an irradiation range of the light irradiated from the light projecting portion. It was done.

According to the present invention, the light emitted from the light projecting section is formed in a ring shape to irradiate light over a wide area, and the first polarizing plate is formed in a ring shape so as to correspond to the light irradiation range. Light is transmitted through the first polarizing plate.

In the surface defect detecting device with a polarizing plate, the light receiving section is a television camera equipped with the second polarizing plate, and a monitor television is provided in the comparing and judging device.

According to the present invention, information is fetched by the Delevi camera, and this information is output to the comparison / judgment device.
Further, the comparison / determination apparatus is provided with a monitor television for monitoring and verifying the function selected from the analysis results of the comparison / determination, and monitors whether or not the inspection target has a surface defect.

Further, in this surface defect detecting device with a polarizing plate, the light receiving unit is a television camera equipped with the second polarizing plate, and the comparison and judgment device is provided with an image processing unit.

According to the present invention, the electric signal input from the television camera is decomposed into pixels, and the pixels are processed by dividing the brightness into several levels according to the strength of the electric signal for each pixel. Next, the surface defect detection device with a polarizing plate irradiates the inspection object with light from the light projecting unit, receives light information reflected from the inspection object at the light receiving unit, and converts the optical information into an electric signal. And a display for converting an electrical signal from the photodetector into an image.

A first polarizing plate is mounted on the light-irradiation side of the light projecting unit, and a first polarizing plate is provided on the light-collecting side of the light receiving unit so as to have a predetermined polarization angle with respect to the first polarizing plate. Second
Is mounted.

According to the present invention, light information reflected from the inspection object is received by the light receiving section, and the light information is converted into an electric signal and output to a display. Then, the display to which the electric signal is input displays an image of the inspection object.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A surface defect detecting apparatus with a polarizing plate according to the present embodiment will be described below with reference to FIGS. First Embodiment (1) First, a schematic configuration of a surface defect detection device with a polarizing plate according to the first embodiment will be described. As shown in FIG. 1, the surface defect detection device with a polarizing plate includes a light projecting unit 1 for irradiating light, and a first polarizing plate 2 provided on the irradiation side of the light projecting unit 1.
Then, the light transmitted through the polarizing plate 2 is reflected on the inspection object 3, the second polarizing plate 4 transmitting the reflected light, and the light transmitted through the polarizing plate 4 is collected, and this optical information is converted into an electric signal. It is formed by a comparison / determination device 6 having a television camera 5 for conversion and having an image processing unit for subjecting an electric signal from the television camera 5 to pixel decomposition and processing, and a monitor television 7 connected to the comparison / determination device 6. (2) Next, the surface defect detecting device with a polarizing plate according to the first embodiment will be specifically described.

First, the light projecting section 1 for irradiating light is formed by an illumination source, an illumination optical system or the like, and determines illumination conditions according to the shape and surface state of the inspection object 3 or the inspection level. Here, as the illumination source, a tungsten lamp, a halogen lamp, a fluorescent lamp, or the like is used for continuous light, and a xenon lamp is used for intermittent light.

In the first embodiment, the illumination condition is provided with illumination slightly brighter than the surrounding brightness in order to clarify the contrast between the normal portion and the defective portion. Therefore, the lighting equipment can be made inexpensive. Note that a light-emitting diode or laser light can also be used as an illumination source.

Next, as an illumination optical system, desired optical characteristics are obtained by using a combination of members such as a light projecting lens, a reflecting mirror or a reflecting cylinder, a reflecting material, a diffusing material, and a holder.
In addition, the optical fiber can be used as a light guide for illumination of a special shape or illumination of a narrow place.

Next, as the first polarizing plate 2 provided on the irradiation side of the light projecting section 1 and the second polarizing plate 4 provided on the condensing side of the light receiving section, a polarizer having direct polarization characteristics is used. Here, a polarizing filter, a polarizing prism, or tourmaline can be used as the polarizer.

Then, as shown in FIG.
, The second polarizing plate 4 is arranged so that the polarization angle becomes 90 °. By doing so, when the light reflected from the inspection object 3 passes through the second polarizing plate 4, the transmittance thereof decreases. Therefore, the surface of the normal part becomes darker. On the other hand, in the defective portion, the second
It is considered that the decrease in transmittance of light transmitted through the polarizing plate 4 is small. Therefore, the defective part looks brighter than the normal part, and the contrast between the normal part and the defective part becomes clear.

Then, the light transmitted through the second polarizing plate is received by the television camera, and the received light information is converted into an electric signal and transferred to the comparison / determination device 6. Here, the comparison determination device 6 determines the presence or absence of a defect such as a scratch by performing a comparison calculation with a preset target value.

It is to be noted that a display for displaying an electric signal as an image without providing the comparison / determination device 6 may be provided. And
Since the contrast between the normal part and the defective part is clear, the presence or absence of a flaw can be recognized very easily even by directly displaying the image on the monitor television.

Therefore, the burden on the inspector can be greatly reduced, and the efficiency can be improved. In addition, the comparison / determination device can detect the signal by a simple processing operation in which the signal is differentiated and binarized.

Further, by providing an inspection window by limiting a site where a scratch or the like occurs, a noise source such as an edge of the inspection target 3 can be removed from the inspection target 3. As described above, the detection accuracy can be improved by utilizing the characteristics such as a flaw.

Further, the direction of the differential operation can be set in consideration of the directionality of a flaw or the like. Normally, the differential operation can be performed in the horizontal and vertical directions, but when differentiated at right angles to the longitudinal direction of the flaw, the flaw can be reliably caught, and at the same time, those without surface irregularities such as surface irregularities can be removed. S of the image
/ N ratio can be improved.

Next, although not shown, the monitor television 7 connected to the comparison / determination device 6 is formed by a memory, a VTR having a recording function, and a television. Here, the signal from the television camera 5 is converted into a digital signal by a high-speed A / D converter and stored in a memory. The memory is composed of predetermined bits and stores the surface of the inspection object 3 as one frame.

The stored contents are converted by a high-speed D / A converter, taken out as a standard television signal, and a still image is output on a television. By the way, during the line operation, the inspector can check this image, drive the inspection result regarding the defect into the system, and supplement the inspection result to the system. Further, a large amount of image data can be recorded on a VTR. Second Embodiment (3) Next, a surface defect detection device with a polarizing plate according to a second embodiment will be described.

As shown in FIG. 3, the surface defect detecting device with a polarizing plate according to the second embodiment is guided from a light source 10 to a ring light 12 by a plurality of optical fibers 11, and
The optical fiber 11 arranged in a ring shape at the hole end 19 of the second
An annular light source that irradiates light from the end surface (for example, a milite manufactured by Asahi Glass Co., Ltd.) and a first polarizing plate 13 provided on the irradiation side of the ring light 12, and the light transmitted from the ring light 12 through the polarizing plate 13 is inspected. And a second polarizing plate 15 that transmits the reflected light.

The other configuration is the same as that of the first embodiment, and the description is omitted. Next, as shown in FIG. 4, the first polarizing plate 13 is formed in an annular shape in which a hole having an equal circle is opened from the center. The illumination is also annular illumination, and is arranged such that light emitted from the illumination is transmitted through the annular polarizing plate 13.

In this way, when the inspection object covers a wide area, the inspection object 14 can be uniformly irradiated with light. If the hole diameter of the polarizing plate 13 is too small, the field of view of the camera is narrowed.

On the other hand, if it is too large, unpolarized light passing through the hole directly irradiates the inspection object 14, and the degree of improvement in contrast is reduced. Therefore, it is preferable to adjust this hole diameter as appropriate according to the shape and size of the inspection object 14.

The light emitted from the illumination may be emitted at right angles to the inspection surface of the inspection object. However, the contrast is better when the light is emitted obliquely as shown in FIG. 1 or FIG. 3 using ring illumination. It is more preferable because it becomes higher. (4) Next, an example of a surface defect detection operation of the comparison / determination device 6 forming the surface defect detection device with a polarizing plate according to the present embodiment will be described with reference to a flowchart.

First, a target value of a judgment condition is set (step 1). Next, the surface images of the inspection objects 3 and 13 are taken in by the television camera 5 (step 2). Here, the image is captured as a gray scale digital image of about 256 to 64 steps. Then, an input is made to the comparison determination device 6 (step 3).

Next, if the portion where the defect occurs can be limited in advance, an inspection window is set (step 4) to prevent erroneous determination. Then, a differential operation is performed on the input digital image (step 5). Here, if the direction in which the defect occurs can be predicted in advance, the influence of unevenness without directivity can be reduced by performing a differential operation at right angles to the direction.

Then, a threshold value is set and binarized to white or black (step 6). Next, since the pixels classified into white correspond to the defective portions, the number of white pixels is counted (step 7).

Next, the count number is compared with a judgment condition (step 8), and when the count number is within the judgment condition, it is judged that the inspection objects 3 and 13 have no defect (step 9). . Here, if the count is small,
Ignore it as noise.

If the counted number is out of the determination condition, it is determined that the inspection objects 3 and 13 are defective (step 10). The above detection operation is performed on the inspection objects 3, 1
This process is repeated every three times to detect the presence or absence of a defect.

[0051]

According to the present invention, it is possible to accurately detect a defect such as a minute surface scratch or the like generated on an inspection object without expanding the inspection object such as resin or metal more than necessary.

In particular, even if the surface color of the object to be inspected is black or dark, the contrast of the brightness between the dark normal portion and the light defective portion becomes clear, and the defective portion is not missed and the polarized light is highly reliable. A plate-mounted surface defect detection device can be provided.

Further, since the defect portion and the normal portion can be easily distinguished as described above, the configuration of the surface defect detection device can be simplified, and the defect can be detected by an easy image processing means. Furthermore, it is possible to provide an inexpensive surface defect detection device with a polarizing plate that is easy to adjust without the necessity of delicately moving the inspection object.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a surface defect detection device with a polarizing plate according to a first embodiment.

FIG. 2 is a layout diagram of a polarizing plate according to the first embodiment.

FIG. 3 is a configuration diagram of a surface defect detection device with a polarizing plate according to the second embodiment.

FIG. 4 is a layout diagram of a polarizing plate according to the second embodiment.

FIG. 5 is a flowchart of a detection operation of the comparison and determination device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light projection part 2 ... 1st polarizing plate 3 ... Inspection object 4 ... 2nd polarizing plate 5 ... Television camera 6 ... Comparison judgment apparatus 7 ... Monitor DESCRIPTION OF SYMBOLS 10 ... Light source 11 ... Fiber 12 ... Ring light 13 ... 1st polarizing plate 15 ... 2nd polarizing plate 16 ... Television camera 17 ... Comparison judgment apparatus 18 ... monitor

Claims (5)

[Claims] A light detecting device that irradiates a light to a test object from a light projecting unit, receives light information reflected from the test object by a light receiving unit, converts the light information into an electric signal, and outputs the electric signal; A surface connected to the light detection device, comprising: a comparison / determination device that compares an electric signal from the light detection device with a preset target value and determines presence / absence of a defect in the inspection object based on the comparison result. In the defect detection device, a first polarizing plate is mounted on a light irradiation side of the light projecting unit, and a light is collected on a light collecting side of the light receiving unit so as to have a predetermined polarization angle with respect to the first polarizing plate. A surface defect detection device provided with a polarizing plate, comprising a second polarizing plate. 2. The light-emitting device according to claim 1, wherein the light-projecting portion is formed in a ring shape, and the first polarizing plate is formed in a ring shape in correspondence with an irradiation range of light emitted from the light-projecting portion. Surface defect detector with polarizing plate. 3. The surface defect detecting device with a polarizing plate according to claim 1, wherein the light receiving section is a television camera equipped with the second polarizing plate, and the comparison and determination device is provided with a monitor television. . 4. The apparatus according to claim 1, wherein the light receiving section is a television camera equipped with the second polarizing plate, and the comparison and determination device is provided with an image processing section. Surface defect detection device. 5. A photodetector that irradiates an inspection object with light from a light projecting unit, receives light information reflected from the inspection object at a light receiving unit, converts the optical information into an electric signal, and outputs the electric signal. A display for converting an electric signal from the photodetector into an image, wherein a first polarizing plate is mounted on the light irradiation side of the light projecting unit, and a predetermined polarization angle with respect to the first polarizing plate is provided. Wherein a second polarizing plate is mounted on the light-collecting side of the light receiving section so as to have the following.