JP2701538B2 - Surface defect inspection equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a surface defect inspection apparatus for inspecting a defect on a surface of a work after being processed by a machine tool or the like.

(Prior art) Generally, a manufacturing processing line in a production factory or the like includes:
Inspection processes for inspecting the quality of processed products are provided, but today, as automation has advanced, the quality inspection of products using optical devices such as cameras has been performed instead of visual inspection by workers. ing.

Among the quality inspections, there is a surface defect inspection for inspecting whether a defect such as a scratch is present on the surface of the processed product, and this surface defect inspection is provided with a surface defect inspection device, for example. This is performed in a processing line as shown in FIG.

The piston 1, which is a work, waits at a predetermined position of the transfer device 3 after the surface is cleaned by the cleaning machine 2,
Inspection table 5 placed on inspection stage by loader 4
Is mounted on the turntable 6. Then, while the work is rotated once by the turntable 6, a surface defect inspection of the inspection surface of the piston 1 is performed by the camera 7 provided around the turntable 6, and if the inspection result is OK. If the piston 1 is sent to the rust-preventive oil tank 9 by the distribution pusher 8, the piston 1 is sent to the work stock area 10 by the distribution pusher 8 if it is NG. Those that are OK are stored on the pallet 12 by the palletizing robot 11, and those that are NG are placed in the rust-proof oil tank 14 after being visually inspected by the operator on the worktable 13, and stored on the pallet 15.

FIG. 6 shows a schematic configuration diagram of the inspection stage shown in FIG.

As shown in the figure, the inspection stage is provided with a turntable 6 that supports and rotates the piston 1, and the turntable 6 is rotated by a motor 20. The turntable 6 has an air chuck.
The piston 1 is supported by the air chuck 21.

As shown, a lamp 22 for irradiating the inspection surface S of the piston 1 with light horizontally around the turntable 6,
A camera 7 for inputting an image of the surface S to be inspected of the piston 1 illuminated by the lamp 22 is disposed, and the illumination condition for the surface S to be inspected formed by the lamp 22 and the camera 7 is It is set so as to be optimal for detecting various surface defects of the surface S.

This setting is performed as shown in FIG. That is, the lamp 22 is provided at a position that irradiates light from the horizontal direction to the inspection surface S of the piston 1, and the camera 7
It is arranged at a position where it can receive light radiated from the lamp 22 and regularly reflected from the inspection surface S. The light emitted from the lamp 22 is spot light.

By arranging the lamp 22 and the camera 7 in such a position,
When an image of the inspected surface S is input by the camera 7, for example, if a deep small defect a such as a scratch exists in the inspected surface S, diffuse reflection occurs at the defect a portion. When the amount of reflected light input to the camera 7 from that portion decreases, and the signal from the camera 7 in this portion is image-processed, the video waveform after the image processing has the defect a as shown in FIG. The part corresponding to appears as a drop. When this is binarized, a binarized waveform as shown in FIG. 8 (B) is obtained.
By detecting the presence of the 0 signal in the binarized waveform, the presence of the defect a can be detected.

(Problems to be Solved by the Invention) However, in such a conventional surface defect inspection apparatus, a defect can be detected with high accuracy even when the surface to be inspected S is extremely flat. Is the inspection surface S
For example, in the case of a work 1 'whose surface is not flat and whose reflectivity is not uniform, for example, as shown in FIG. Becomes

That is, when an image of the inspection surface S of the work 1 'as shown in FIG. 9 is input by the camera 7 and the signal from the camera 7 is processed, the video waveform after the image processing is shown in FIG. As shown in FIG. 10, since a portion where the degree of diffuse reflection is large appears as a periodic drop, it is very difficult to avoid this drop and to select a threshold voltage for detecting a defect (FIG. 10). When the threshold voltage is selected to be relatively low as shown in FIG.
The binarized waveform is as shown in FIG. 10 (B), and erroneous detection of a defect is prevented, but the detection accuracy is reduced. On the other hand, when the threshold voltage is selected to a relatively high level, the Although the detection accuracy is improved, the possibility of erroneous detection increases. ), It becomes extremely difficult to determine the presence or absence of a defect, and the detection accuracy deteriorates.

The present invention has been made in order to solve such a conventional problem, and it is possible to detect with high accuracy the presence or absence of a defect present on a surface to be inspected even if the surface to be inspected is not flat. It is an object to provide a possible surface defect inspection device.

(Means for Solving the Problems) According to the present invention for achieving the above object, there is provided an illumination for irradiating light to a surface to be inspected of a workpiece, and a Fourier transform of reflected light from the surface to be inspected irradiated by the illumination. Fourier transform means for converting, a storage means for storing a spatial frequency image of light passing through the Fourier transform means as image data,
Based on the image data stored in the storage means,
A spatial frequency mask forming means for forming a spatial frequency mask corresponding to the surface to be inspected of the workpiece, a light quantity detecting means for detecting a quantity of light passing from the spatial frequency mask forming means, and a light quantity detected by the light quantity detecting means. Determining means for determining the presence or absence of a defect on the inspection surface of the workpiece based on the determination.

(Operation) With this configuration, the image data after the Fourier transform of the entire inspection surface of the work illuminated by the illumination is stored in the storage unit, and the spatial frequency mask forming unit converts the image data stored in the storage unit into the image data. A corresponding spatial frequency mask is formed. The work used in this case is a master work having no defect.

Then, when the reflected light from the surface to be inspected is applied to the spatial frequency mask forming means via the Fourier transform means,
Since this spatial frequency mask forming means forms the spatial frequency mask based on the inspection surface of the master work, if the inspection surface is a normal work having no defect, the light does not reach the light amount detection means, As a result, the determining means determines that there is no defect. On the other hand, if the work has a defect, the light reaches the light amount detecting means, and the determining means determines the presence or absence of the defect according to the degree.

Therefore, it is possible to detect a defect with high accuracy even for a workpiece in which the shape of the surface to be inspected is not flat and the reflectance of the surface is partially changed.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an optical system in a surface defect inspection apparatus according to the present invention.

As shown in the figure, in the surface defect inspection apparatus according to the present invention, laser
The inspection target surface S
Is irradiated with the light output from the laser 30 via the beam expander 31. Then, centering on the optical axis of the reflected light from the inspection surface S, a Fourier transform lens 32 as a Fourier transform unit, a half mirror 33, an electronic array shutter 34 as a spatial frequency mask forming unit, and a light amount detecting unit as a light amount detecting unit The light quantity sensors 35 are sequentially arranged,
In the direction of the reflection axis of the half mirror 33, a 2D sensor 36 for detecting a spatial frequency image of light passing through the Fourier transform lens 32 is provided.

FIG. 2 is a configuration diagram of a control system of the surface defect detection device according to the present invention.

As shown in the figure, a teach data storage unit 38 as storage means is connected to the 2D sensor 36 via a sensor driver 37 for sequentially taking out data relating to the spatial frequency image detected by the 2D sensor 36. Memory
38, a rotation control unit 39 for controlling the rotation of the work 1 'and outputting the rotation position data, and a teach data storage unit 38 based on the rotation position data from the rotation control unit 39.
And a data control unit 40 for sequentially taking out the data stored in the memory.

Further, a shutter driver 41 is connected to the electronic array shutter 34, and a spatial frequency mask pattern is formed on the electronic array shutter 34 by the shutter driver 41 based on the spatial frequency image detected by the 2D sensor 36. The determination unit 42 is connected to the light amount sensor 35, and determines whether or not the work has a defect based on the light amount incident on the light amount sensor 35.

The surface defect inspection apparatus thus configured operates as follows based on the operation flowcharts shown in FIGS. 2 and 3.

First, a process of performing teaching using master work will be described.

Step 1 First, when the program is started, the laser 30 irradiates light to the surface S to be inspected of the work 1 ', moves the irradiation position, and drives the motor 20 shown in FIG. Then, the work 1 'is rotated at a predetermined speed in a predetermined direction.

Steps 2 and 32 The 2D sensor 36 converts the light amount distribution of the reflected light from the surface S to be inspected incident through the Fourier transform lens 32 and the half mirror 33 into the sensor driver 37 together with the rotational position data from the rotation control unit 39. In the teach data storage unit 38.

Therefore, the teach data storage unit 38 stores the light amount distribution data of each part of the inspection surface of the work 1 ', and the data for forming a spatial frequency mask pattern serving as a master for one rotation of the inspection surface of the work 1'. Will be stored.

That is, when the reflected light from the surface to be inspected S passes through the Fourier transform lens 32, the spatial frequency component contained in the reflected light is spatially expanded by the Fourier transform lens 32 into a Fourier series. When the light after the series expansion is irradiated on the 2D sensor 36, the light amount distribution state becomes
The DC information component of the spatial frequency components included in the reflected light is converged on the optical axis and radially diffuses from low-frequency information to high-frequency information toward the outside.

Accordingly, the teach light storage unit 38 stores the light amount distribution state of the 2D sensor 36, that is, the light amount distribution data.

 Next, processing at the time of inspection will be described.

Step 10 The laser 30 irradiates light to the surface S to be inspected of the work 1 ′ and moves the irradiation position thereof.
By driving the motor 20, the work 1 'is rotated at a predetermined speed in a predetermined direction.

Step 11 The data control unit 40 extracts the light quantity distribution data stored in the teach data storage unit 38 in steps 2 and 3 based on the rotation position data from the rotation control unit 39, and the shutter driver 41 A spatial frequency mask pattern is formed on the surface of the electronic array shutter 34 based on the light quantity distribution data. That is, a mask pattern is formed on the surface of the electronic array shutter 34 such that no light passes through depending on the light amount distribution in the master work.

Step 12 The light amount sensor 35 detects the amount of light passing from the electronic array shutter 34, performs photoelectric conversion, and outputs an amount of electricity corresponding to the detected amount of light to the determination unit 42.

Step 13 The determination unit 42 determines whether or not a defect exists in the inspection surface S of the work 1 'based on the electric quantity output from the light quantity sensor 35.

In other words, when the laser light that has passed through the Fourier transform lens 32 hits the electronic array shutter 34 of the master work on which the spatial frequency mask is formed, in the case of a work having no defect, the work is formed by the electronic array shutter 34. Although the transmitted light is completely blocked by the mask pattern, in the case of a defective work, the spatial frequency component of the reflected light after passing through the Fourier transform lens 32 is different, so that the mask formed by the electronic array shutter 34 is different. Since light of a frequency component that is not blocked depending on the pattern exists, this light reaches the light amount sensor 35, and the light amount sensor 35
Rare transmission is performed by 35, and the determination unit 42 determines that there is a defect.

As described above, in the present embodiment, the presence or absence of a defect in a work is spatially analyzed based on anti-shielding from a surface to be inspected in the work.

(Effect of the Invention) As is clear from the above description, according to the present invention,
Illumination for irradiating the inspection surface of the work with light, Fourier transform means for performing Fourier transform of reflected light from the inspection surface illuminated by the illumination, and a spatial frequency image of light passing through the Fourier transformation means Storage means for storing as data, spatial frequency mask forming means for forming a spatial frequency mask corresponding to the surface to be inspected of the work based on image data stored in the storage means, and spatial frequency mask forming means Light quantity detecting means for detecting the amount of light passing from the workpiece, and judging means for judging the presence or absence of a defect on the inspected surface of the workpiece based on the light quantity detected by the light quantity detecting means. Can be detected with high accuracy even when the workpiece is not flat and the reflectance of the surface is partially changed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an optical path system of a surface defect inspection device according to the present invention, FIG. 2 is a schematic configuration diagram of a control system of the surface defect inspection device according to the present invention, FIG. 3 and FIG. 5, an operation flowchart of the surface defect inspection apparatus according to the present invention, FIG. 5 is a diagram showing an example of a conventional defect inspection process, FIG. 6 is a schematic configuration diagram of the inspection stage shown in FIG. 3, FIG. FIGS. 8A and 8B are diagrams showing illumination conditions when performing a surface defect inspection, FIGS. 8A and 8B are diagrams showing processing waveforms of images input from a camera, FIGS. FIG. 2B is a diagram for explaining a problem of the conventional surface defect inspection apparatus. 1,1 '... work, 30 ... laser (illumination), 32 ... Fourier transform lens (Fourier transform means), 34 ... Electronic array shutter (spatial frequency mask forming means), 35 ...
Light amount sensor (light amount detecting means), 38 ... teach data storage section (storage means), 42 ... determination section (determination means).

Claims (1)

(57) [Claims] An illumination for irradiating the inspection surface of the workpiece with light; a Fourier transform unit for performing a Fourier transform on reflected light from the inspection surface irradiated by the illumination; A storage unit that stores the spatial frequency image as image data, and based on the image data stored in the storage unit,
A spatial frequency mask forming means for forming a spatial frequency mask corresponding to the surface to be inspected of the work, a light quantity detecting means for detecting a passing light quantity from the spatial frequency mask forming means, and a light quantity detected by the light quantity detecting means. A surface defect inspection apparatus, comprising: a determination unit configured to determine presence or absence of a defect on the inspection surface of the workpiece based on the determination.