JP2001349716A - Surface irregularity inspection method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect irregularities on the surface of an object surely with a simple formation. SOLUTION: Illumination is executed on the surface of a test body 1 from a lattice-shaped illumination device 2 in the state where the border 6 between a bright part 4 and a dark part 5 is clear. A sensor 3 includes a movement- detecting solid-state image pick up device and picks up the periphery image of a part where the border 6 passes on the surface of the test body 1. If a irregularity defect 7 exists, brightness inversion parts 8, 9 are generated when the border 6 passes. The movement-detecting solid-state image pick up device in the sensor 3 picks up the images in each frame by pixels arranged matrically and detects the movement based on the difference of the images between the frames. Since the brightness inversion parts 8, 9 are generated when the border 6 passes on the irregularity defect 7 on the surface of the test body 1, the irregularity defect 7 can be determined easily as the movement of the images.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface unevenness inspection method and apparatus for optically inspecting the unevenness of various object surfaces.

[0002]

2. Description of the Related Art In various industrial products, even if minute irregularities are formed on a smooth surface, it is prevented from being shipped as it is as a poor appearance. Although unevenness defects are being automated, for example, by automatically detecting them by using image processing, etc., it is sometimes difficult to find out about delicate surface unevenness defects if a skilled inspector does a visual inspection. Many.

[0003]

It is difficult for even a skilled inspector to find minute surface irregularities and the like on the surface of a smooth object. In addition, if a mass-produced product is continuously inspected with the naked eye, attention is reduced due to fatigue, and the possibility of oversight is increased with the passage of time.

An object of the present invention is to provide a method and an apparatus for inspecting surface irregularities which can reliably detect even minute surface irregularities and the like.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a method for inspecting irregularities on the surface of an object, which comprises illuminating an externally smooth surface of the object so as to form a boundary between light and dark, and illuminating the boundary. The object is moved with respect to the surface of the object, and an image of the vicinity of the moving boundary is captured by the solid-state imaging device for motion detection. This is a method for inspecting surface irregularities.

According to the present invention, an object surface that is smooth in appearance is illuminated so that a boundary between light and dark occurs. When the boundary between light and dark is moved with respect to the surface of the object, a phenomenon occurs in which light and dark are reversed in the uneven portion, and when an image is captured by a solid-state imaging device for motion detection, the light and dark reversed is detected as motion. It can be reliably determined that the unevenness exists.

In the present invention, when the object is transparent,
It is characterized in that the back side is shielded from light.

According to the present invention, the back side of a transparent object is shielded from light and illuminated so that a light-dark boundary is formed on the front side, and the movement corresponding to the unevenness on the front side is not affected by the light on the back side. Can be detected.

Further, the present invention relates to an apparatus for inspecting irregularities on the surface of an object, which illuminates the surface of the object so that a boundary between light and dark is generated, and a part illuminated by the illuminating apparatus. A moving device that moves relatively to the surface of the object, a plurality of pixels are arranged in a matrix, and together with an image output for each frame, motion detection is possible based on a luminance difference between the frames, When an output from the motion detection imaging device that captures the light and dark areas of the camera and an output from the motion detection solid-state imaging device is input and motion is detected by the motion detection solid-state imaging device, it is determined that the object surface has irregularities. A surface unevenness inspection apparatus characterized by including an image processing apparatus.

According to the present invention, the surface unevenness inspection device includes an illumination device, a moving device, a solid-state imaging device for motion detection, and an image processing device. The illuminator illuminates the surface of the object such that a boundary between light and dark occurs. The moving device moves a portion illuminated by the lighting device relative to a surface of the object. That is, by moving the illumination side, moving the object side, or both, the light-dark boundary is moved with respect to the surface of the object. When the boundary between light and dark passes through the uneven portion on the surface, the boundary or near light and dark is partially distorted and inverted, reflecting the unevenness on the surface. The solid-state imaging device for motion detection has a plurality of pixels arranged in a matrix, and is capable of detecting and outputting motion between frames together with image output for each frame. The appearance of the light-dark reversal part can be easily detected as motion by the motion detection solid-state imaging device. The image processing device to which the output from the motion detection solid-state imaging device is input can determine that the surface of the object has irregularities when the motion is detected.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a basic configuration for surface unevenness inspection as one embodiment of the present invention, and a principle capable of detecting surface unevenness. FIG. 1A shows a basic configuration for surface unevenness inspection, FIG. 1B shows an image near unevenness, and FIG. 1C shows an image detected as a motion. As shown in FIG. 1A, a basic configuration for detecting unevenness from the surface of a specimen 1 includes a grid-like illumination device 2 and a sensor 3 including a solid-state imaging device for motion detection. The specimen 1 is, for example, a film for optical use used as a polarizing plate in a liquid crystal display device, and it is desired that there is no minute unevenness on the surface. Lattice lighting device 2
Performs illumination such that a boundary between a bright part and a dark part becomes clear on the surface of the specimen 1. The solid-state imaging device for motion detection included in the sensor 3 outputs an imaging result as an analog image signal and a digital moving object signal as a motion detection result, as disclosed in, for example, Japanese Patent Application Laid-Open No. 10-313426. .

FIG. 1B shows an example of an image of a concave / convex defect portion appearing in an analog image signal from a solid state imaging device for detecting the movement of the sensor 3. In the image captured by the sensor 3, illumination is performed in which the boundary 6 between the bright part 4 and the dark part 5 is clear by the lattice illumination device 2 of FIG. The boundary 6 between the light part 4 and the dark part 5 moves on the surface of the specimen 1. When the unevenness defect 7 exists on the surface of the sample 1 and the boundary 6 between the light part 4 and the dark part 5 moves to the part of the unevenness defect 7, light-dark reversal parts 8 and 9 are generated in the part related to the unevenness defect 7. The light-dark reversal portion 8 occurs on the light portion 4 side of the boundary 6 and becomes an image darker than the light portion 4. The light-dark reversal portion 9 occurs on the dark portion 5 side of the boundary 6 and has higher brightness than the surrounding dark portion 5. Light / dark reversal parts 8, 9
Does not occur unless the boundary 6 between the light part 4 and the dark part 5 moves to the position of the concave / convex defect 7, so that the state where the light-dark reversal parts 8 and 9 are generated and the state where they are not generated are compared. A motion detection unit 10 as shown in FIG. 1C is obtained. As will be described later, the motion detection solid-state imaging device included in the sensor 3 captures an image as a frame on a one-chip semiconductor integrated circuit at a frame cycle, and FIG. The motion detector 10 as shown can be obtained.

The irregularities on the surface of the object which can be detected in the present embodiment include minute dents or protrusions of several μm, and have a diameter of several tens.
It has a crater-like, pyramid-like, circular or streak-like shape of μm. Such fine irregularities are very difficult to detect with the naked eye, but in the case of coating various films and sheets, plate glass, or the body of an automobile, etc., the appearance quality is impaired or the optical characteristics are impaired. Therefore, it is important to reliably detect and take measures.

FIGS. 2A and 2B show an example of illumination by the grid illumination device 2 as shown in FIG. 1, and FIG. 2B shows an example in which the same effect can be obtained with other illuminations. Lattice lighting device 2
Can be formed by attaching a grid-like sheet having a light transmitting portion and a light blocking portion to the surface of a surface light source. Illumination as shown in FIG. 2B can be performed using a linear light source such as a fluorescent tube, a transmission light, or an optical fiber line illumination. In the transmission light, light sources are arranged at both ends or one end of a rod made of a material that transmits light, and light introduced from an end face is extracted from a side face and can be used as a linear light source. The optical fiber line illumination uses a large number of optical fibers, and one end guides light from a light source in common, and the other end is linearly arranged and used as a linear light source. The boundary 6 between the light part 4 and the dark part 5 does not necessarily have to be a straight line, and it is sufficient that the difference between the light part 4 and the dark part 5 is clear. However, as shown in FIG. 1B, even if the boundary 6 between the light part 4 and the dark part 5 is clear, the contrast in the analog image is small, and the light-dark reversal parts 8 and 9 are actually detected from the analog image. Therefore, it is difficult to determine that the unevenness defect 7 exists. When the boundary 6 between the bright part 4 and the dark part 5 is relatively moved to pass through the part of the unevenness defect 7, the part of the boundary 6 which is the linear edge of the illumination collapses, and A light-dark reversal part 8 is generated as a dark part, and a light-dark reversal part 9 is generated in the dark part 5 as a light part. Even when the boundary 6 is a linear illumination edge, depending on the depth and height of the unevenness of the unevenness defect 7 and the inclination angle and the size of the defect, the degree of collapse of the light-dark reversal portions 8 and 9 and the brightness level of light and dark are determined. Will be different. When difference processing and binarization processing are performed on an image obtained by capturing the unevenness defect 7 before and after passing through the boundary 6 which is an illumination edge portion, only a broken image is extracted, and motion detection as shown in FIG. The part 10 is obtained.

The detection of the unevenness defect 7 cannot be performed in the bright part 4 or the dark part 5. In the bright portion 4, if the unevenness defect 7 is minute, the scattering of light due to this is too small to be detected as a change in luminance. Dark part 5
However, light scattering is too small to detect as a change in luminance. Only at the boundary 6 between the light part 4 and the dark part 5, the edge part is broken and the light-dark reversal parts 8 and 9 are generated. Therefore, the unevenness defect 7 is detected as a movement when the boundary 6 between the light part 4 and the dark part 5 is moved. can do.

FIG. 3 shows a schematic electrical configuration of a surface inspection apparatus 11 for automatically performing an unevenness inspection based on the basic configuration of unevenness detection shown in FIG. The sensor 3 is provided with a timing pulse from the pulse generation circuit 12 to
An image of the surface of the sample 1 is taken via the device 3. The sensor 3 outputs an image signal representing a captured image as an analog signal and a moving object signal representing a detection result of movement between images as a digital signal. The image signal and the moving object signal are provided to the image processing circuit 14. From the image processing circuit 14, an image representing the inspection result is output to the display 15 or the like. The output from the image processing circuit 14 displays a surface image in which a mark or the like is added at a position corresponding to the surface unevenness based on the moving object signal.

FIG. 4 shows a schematic electrical configuration of the motion detecting solid-state imaging device 20 used in the sensor 3 of FIG. FIG. 4A shows the overall configuration, and FIG. 4B shows the configuration in pixel units. As shown in FIG. 4A, the solid-state imaging device 20 for motion detection is formed as a one-chip semiconductor integrated circuit, and includes a pixel array 21, a video circuit 22, a horizontal scanning circuit 23, a vertical scanning circuit 24, and a moving object detection circuit. 25 and a register / shift register 26. As shown in FIG. 4B, an embedded photodiode (hereinafter abbreviated as “BPD” from Buried Photodiode) 3 is provided in the unit pixel.
0 and a junction field effect transistor (hereinafter abbreviated as “JFET”) that operates as a readout transistor
31, three MOS FETs 32, 33 and 34 are included. The unit pixels as shown in FIG. 4B are arranged in a two-dimensional array of, for example, 256 pixels × 256 pixels in a pixel array 21 as shown in FIG. , XY address system.

The incident light is incident on the BPD 30. BP
In D30, holes are generated and accumulated according to the incident light. This hole is used for the MOS FET 33 serving as a transfer gate.
Is transferred to the gate region of JFET 31 through
By the source follower operation of the FET 31, the data is output to the vertical read line via the row selection MOS FET 32. Here, the signal charge transferred to the gate of the JFET 31 is held by the gate of the JFET 31 until it is discharged and reset by the MOS FET 34 serving as a reset gate. Reading is performed, and this gate can be used as a frame memory. During this time, the BPD 30 generates and accumulates signal charges corresponding to new incident light, so that two consecutive frames of signals are held in one unit pixel.

The signal output from the pixel array 21 to the vertical readout line is input to the video circuit 22 and the moving object detection circuit 25, and processed for each column. Here, from each unit pixel, a signal output corresponding to one frame before, a dark output after reset, and a signal output corresponding to the current frame are sequentially output. The moving object detection circuit 25 takes in the outputs of the above and performs binarization by difference processing and threshold processing. As a result, all "motion" in which the luminance difference between two consecutive frames exceeds a certain value is detected. The result is stored in the register portion of the register / shift register 26, and is output to the outside as a serial digital signal during the horizontal transfer period.

The video circuit 22 generates an image signal by correlated double sampling. That is, the pixel output from the above is taken in and the difference processing is performed. In general,
In a configuration like the pixel array 21, reset noise or 1 / f noise such as so-called kTC noise is generated based on a difference in characteristics of each pixel. Further, since the J-FET 31 is used, fixed pattern noise or the like is likely to occur due to the variation in the threshold value. By performing correlated double sampling, the effects of these noises can be suppressed, and a high-quality image signal can be obtained.

The detailed technical contents of the solid-state imaging device 20 for motion detection are disclosed in Japanese Patent Application Laid-Open No. Hei 10-313426 as described above. Since the solid-state imaging device 20 for motion detection has a built-in configuration for performing the difference processing and the binarization processing on the same semiconductor chip, these processings necessary for general image processing are performed in this embodiment. This is not necessary in the image processing circuit 14 of the embodiment, and the configuration can be simplified and the cost can be reduced.

FIG. 5 shows a configuration for performing a surface irregularity inspection on a transparent specimen 41 such as a transparent optical film or sheet. Components corresponding to those shown in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted. In the present embodiment, a black light-blocking plate 42 is arranged on the rear surface of the transparent sample 41 on the rear surface of the sample 41 in order to exclude the influence of light on the rear surface of the transparent sample 41 being incident on the sensor 3. The sample 41 is continuously fed from the roll 43, and the surface of the sample 41 is inspected for irregularities by the fixed grid-like illumination device 2 and the sensor 3. In other words, the specimen 41 moves with respect to the boundary between the bright part and the dark part illuminated from the lattice illumination device 2, and if the unevenness of the surface crosses the boundary, the shape of the boundary is broken and the brightness is reversed,
The movement is detected by the sensor 3, and it can be determined that the unevenness exists. 5 is used as a film or a sheet in a liquid crystal, a plasma display panel (PDP), a projection television (PJTV), or the like, has a single-layer or multilayer structure, and has an optical characteristic on the surface. Has been applied.

Accordingly, there are many types of defects that can occur, and all noticeable defects are defective. Many defect inspection devices have been developed and automated to automatically detect these defects. However, inspection of minute irregularities has hardly been put to practical use. According to the present embodiment, even a minute surface unevenness can be easily and reliably detected by a linear illumination device such as the lattice illumination device 2 or a general-purpose fluorescent lamp. In addition, the brightness of irradiation, the angle and arrangement of imaging, slight fluttering and undulation of the specimen, or out of focus can be allowed to some extent, and if movement is detected, it can be detected as surface irregularities. Therefore, illumination can be performed using a general-purpose product, and installation accuracy including the sensor 3 is not required, so that the construction cost of the gantry and the like can be reduced. In addition, it is not necessary to precisely set the arrangement accuracy of the optical system, and it is hard to be affected by the vibration of the device. Therefore, it is possible to improve reliability and detection accuracy and stabilize.

The concept of the present invention is that not only films and sheets for optical use as shown in FIG. 4 but also inspections of, for example, the coating of automobile bodies are performed while moving on a conveyor of an assembly line. It can also be applied when performing. Defects such as spots and streaks bulging due to foreign matter and the like, coating omissions due to paint flipping during coating, uneven thickness of the coating, and coating liquid dripping may occur in the coating of an automobile body. By applying the present invention to these defects,
The inspection can be performed easily and reliably. Inspections such as painting of products can be applied to many kinds of industrial products such as various electric appliances and furniture as well as automobile bodies.

Further, if the sensor 3 detects a defect, the moving object signal is directly used as a signal for generating an alarm,
It can also be used for marking defects and managing defect information.

[0026]

As described above, according to the present invention, when unevenness is present on the surface of an object, when the boundary between light and dark illuminating the surface moves, the light and dark are partially inverted at the boundary. The motion can be detected by the imaging device, and the inspection for light and dark can be reliably performed. Even small irregularities that are difficult to recognize with the naked eye can be reliably detected as inversion of light and dark at the boundary, so that a highly reliable inspection can be performed.

Also, according to the present invention, since the back side of a transparent object is shielded from light to determine the unevenness of the front side, a reliable judgment can be made without being affected by the light on the back side.

Further, according to the present invention, the illumination is performed so that a light-dark boundary is formed on the surface of the object by the lighting device, and the light-dark boundary and the surface of the object are relatively moved by the moving device. If unevenness is present on the surface of the object, a partial inversion of light and dark occurs when the boundary between light and dark passes through the portion with unevenness. Since the vicinity of the boundary between light and dark is imaged by the solid-state imaging device for motion detection, if partial light / dark inversion occurs, it can be easily detected as motion. The image processing apparatus receives an output from the solid-state imaging device for motion detection and determines that there is unevenness when motion is detected, so that the presence of unevenness can be reliably determined.

[Brief description of the drawings]

FIG. 1 is a simplified perspective view showing a state in which surface irregularities are inspected in one embodiment of the present invention, and an analog image of a surface of a specimen 1 to be inspected and a digital image based on a motion detection result. FIG.

FIG. 2 is a diagram showing an example of illumination that can be used in the present invention.

FIG. 3 is a simplified block diagram showing an electrical configuration related to the sensor 3 of FIG.

FIG. 4 is an equivalent circuit diagram of the motion detection solid-state imaging device 20 provided in the sensor 3 of FIGS. 1 and 3;

FIG. 5 is a simplified perspective view showing a configuration for continuously inspecting irregularities on the surface of a specimen 41 in another embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1,41 sample 2 lattice-like illumination device 3 sensor 4 bright portion 5 dark portion 6 boundary 7 unevenness defect 8,9 light / dark inversion portion 10 motion detection portion 11 surface inspection device 12 pulse generation circuit 14 image processing circuit 20 motion detection solid-state imaging device 21 pixel array 25 moving object detection circuit 30 BPD

Continued on the front page F-term (reference) 2F065 AA49 BB01 BB13 BB15 BB22 CC02 CC11 DD02 DD03 DD11 FF01 FF08 GG18 HH06 HH12 JJ03 JJ08 JJ26 LL02 MM03 PP15 QQ01 QQ04 QQ13 QQ25 QQ34 SS07 SS09 AUAA ABUA ABA ABA AB BB17 BC06 CA03 CA04 DA06 EA08 EA11 EA14 ED07

Claims (3)

[Claims] 1. A method for inspecting unevenness of an object surface, comprising illuminating an externally smooth object surface so as to generate a light-dark boundary, moving the boundary with respect to the object surface, A surface irregularity inspection, wherein an image of the vicinity of the boundary during movement is taken by a solid-state imaging device for motion detection, and when motion is detected by the solid-state imaging device for motion detection, it is determined that surface irregularities are present. Method. 2. The method according to claim 1, wherein when the object is transparent, the back side is shielded from light. 3. An apparatus for inspecting irregularities on the surface of an object, comprising: an illuminating device for illuminating the surface of the object so that a boundary between light and dark is generated; and a part illuminated by the illuminating device, A moving device for relatively moving the object, a plurality of pixels are arranged in a matrix, and together with an image output for each frame, motion detection can be performed based on a luminance difference between the frames, and the vicinity of the object surface A motion detection imaging device that captures an image of an object, and an image processing that receives an output from the motion detection solid-state imaging device and determines that there is unevenness on the surface of the object when the motion is detected by the motion detection solid-state imaging device. And a device for inspecting surface irregularities.