JPH0812152B2 - Reflected light flaw detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a flaw detection device for automatically detecting flaws on an inspected object having a smooth surface, such as a synthetic resin plate, a glass plate, a polished steel plate, and a lens. Regarding More specifically, the present invention relates to a reflected light type flaw detection device that irradiates an object to be inspected with light and detects a flaw from the reflected light.

[Prior Art] In general, as a flaw detection device, there is a transmitted light type device that detects a flaw from transmitted light that has passed through an object to be inspected, in addition to the above-described reflected light type device. However, the transmitted light type can be applied only to a transparent inspection object, and the reflected light type which can be applied to an opaque inspection object is excellent in this respect.

Conventionally, as a reflected light type flaw detection device, an object to be inspected is irradiated with light from a light source such as a laser oscillator, and the reflected light is received through a slit or a hole, for example, a photodiode or a photomultiplexer, and the amount of light received. It is known that a sensor that directly converts the light into an electric signal is used to detect a flaw based on a change in the amount of reflected light captured by the sensor. That is, when the inspection object has a scratch, the scattered light due to the scratch does not reach the sensor because it goes out of the slit or hole, and the amount of light received by the sensor changes, and the electrical signal output from the sensor is changed. Is used to detect scratches.

By the way, generally, the flaw detection is performed while the inspection object is being transferred, but the inspection object is constantly subjected to an irregular movement due to vibration or the like for the transfer. If the product is easily scratched due to manufacturing conditions, such as a synthetic resin plate, the scratches are detected at the front stage of the manufacturing line, and if scratches are detected, the manufacturing conditions are adjusted directly to reduce product loss. Will be required. However, the object to be inspected in the middle of the manufacturing line often has irregular ears, burrs, and the like protruding, and is often sent with an irregular inclination or warp.

On the other hand, the location of the scratch is unknown, and since the area of the inspected object such as synthetic resin plate, glass plate, and polished steel plate is large, the irradiation position of the inspected object must be greatly moved to improve the inspection accuracy. Therefore, it is necessary to widen the scanning range. Irregular movement, tilt,
When the irradiation position is largely moved in order to widen the scanning range in addition to the warpage and the like, a large displacement of the reflected light is likely to occur. In order to detect scratches regardless of the positional deviation of the reflected light, in the conventional reflected light type flaw detecting device, the slits and holes are made slightly larger, and the sensor receives light even if the positional deviation of the reflected light is slight. Being able to do so is being done.

[Problems to be Solved by the Invention] However, if the slits or holes of the conventional device are enlarged, the scattered light is not blocked by the slits or holes due to small scattering of light due to slight scratches, and the sensor receives the light. Therefore, there is a problem that the flaw cannot be detected. According to the knowledge of the present inventors, extremely shallow uneven scratches called surface irregularities, transverse waves, roll touch defects, undulations and the like that occur during molding of a synthetic resin plate have hardly been detected.

From the above, when strict quality control is required, an inspector must be assigned to carry out visual inspections one by one, and inspect for faint scratches that can only be found visually from various angles. It puts a heavy burden on the inspection personnel. Further, the accuracy of the inspection depends on the skill of the inspection and nurturing, and the shipment of products of constant quality is apt to be hindered.

[Means for Solving Problems] Means for solving the above problems will be described with reference to FIG. 1 corresponding to one embodiment of the present invention. Light source 2 which irradiates light through the incident light mirror 8a, a screen 3 which receives reflected light from the inspection object 1 through the reflected light mirror 8b, and displays an image of the reflected light; A mirror 7a and a mirror 8b for reflected light are mounted, and a scanner 7 for moving the light irradiation position on the inspection object 1 by moving on the guide rail 6 and a camera for taking an image of the reflected light on the screen 3 4 and a detector 5 for detecting a flaw from the change in the area of the image of the reflected light captured by the camera 4, which is a reflected light type flaw detecting device.

[Operation] When the inspected object 1 has a scratch, the area of the image of the reflected light on the screen 3 is enlarged due to the scattering of the light due to the scratch. The camera 4 serves as an eye for catching the change in the area of the image, and the detector 5 calculates the area of the image of the reflected light based on the video signal from the camera 4, and this area has a predetermined value. It is determined that there is a scratch when it exceeds the value.

In the present invention, the reflected light is received on the screen 3 as described above, and the image of the reflected light on the screen 3 is captured by the camera 4 to obtain a signal necessary for the flaw detection. Therefore, camera 4
If there is an image of the reflected light in the visual field range of, the necessary signal can be obtained, and reliable scratch detection can be performed regardless of the irregular movement of the reflected light.

[Embodiment] As shown in FIG. 1, above the plate-shaped ratio inspection object 1 transferred in the direction perpendicular to the plane of the drawing, in the width direction of the inspection object 1 (a plane perpendicular to the transfer direction). Direction) is provided with a guide rail 6. The guide rail 6 guides the movement of the scanner 7 moving above it.

An incident light mirror 8a and a reflected light mirror 8b are provided on the scanner 7.

On the other hand, the light source 2 is provided toward the incident light mirror 8a. As the light source 2, for example, a laser oscillator or the like is used.

The light emitted from the light source 2 is bent in the direction of the inspection object 1 by the incident light mirror 8a and is irradiated to the inspection object 1. The irradiation of the light on the inspection object 1 is an angle close to a right angle with respect to the upper surface of the inspection object 1 in order to suppress the movement amount of the reflected light due to the irregular movement, inclination, warpage, etc. of the inspection object 1. It is preferable to carry out.

A reflected light mirror 8b is provided at a position where the reflected light from the inspection object 1 based on the irradiation of the light is received. And
A screen 3 is provided in the traveling direction of the reflected light that is bent by the reflected light mirror 8b. Therefore, the inspection object 1
The reflected light from is bent by the reflected light mirror 8b and guided to the screen 3, and its image is projected on the screen 3. The projected image of the reflected light on the screen 3 is
To prevent the shape of the reflected light from being distorted, the reflected light should be
It is preferable to perform it by applying a right angle with respect to.

In the vicinity of the screen 3, a camera 4 for taking an image of reflected light projected on the screen 3 is provided.
The camera 4 is connected to the detector 5 and the image monitor 9. The camera 4 may be any camera as long as it can continuously capture the image of the reflected light projected on the screen 3 and convert it into an electric signal. For example, an image pickup tube type camera or a charge-coupled device camera (CCD camera). Etc. can be used. A CCD camera is preferable because of its high reliability and small size.

As shown in FIG. 2, the detector 5 A / D-converts the image signal from the camera 4, and then calculates the area of the image of the reflected light based on the obtained digital signal. Next, after calculating the area ratio of the calculated area to the preset area, the signal of this area ratio is D / A converted. Furthermore, when the obtained analog signal is passed through a high pass filter,
Only the analog signal when the calculated area is larger than the set area passes through the high-pass filter, and the presence of the flaw is detected.

An alarm lamp 10 is connected to the detector 5, and when a flaw is detected, it is lit by an alarm signal issued from the detector 5. The alarm lamp 10 may be turned on immediately after a signal that passes through the high-pass filter is generated even once for one inspected object 1. However, the quality of the inspected object 1 is required. In addition, it may be performed when the signal is generated a preset number of times. Further, the passing level of the high pass filter can be adjusted according to the required quality of the inspection object 1.

The present apparatus and the object to be inspected 1 are continuously transferred, and the scanner 7 is moved left and right along the guide rail 6 to detect scratches, and the image monitor 9 projects the image of the image of the reflected light during this time. . In particular, if the image recorded on the image monitor 9 is recorded by a video recorder, when a flaw is detected, it is reproduced to determine the content of the flaw and the cause of the flaw from the shape of the image of the reflected light at the relevant location. It is also possible to estimate.

In the present invention, the light emitted from the light source 2 is usually a single line of light having a circular cross section, but it may be two or more lines.
It is possible to inspect a wide surface of the inspection object 1 as much as possible by emitting the light in a slit shape.
If the screen 3 receives the transmitted light from the inspection object 1, it can be used as a transmitted light type flaw detection device.

[Effects of the Invention] As described above, according to the present invention, the reflection type flaw detection device applicable to the opaque inspection object 1 can be reliably performed despite the irregular movement of the reflected light. It is possible to detect various scratches, and it becomes possible to perform strict quality control by the device without arranging inspection personnel.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of the present invention, and FIG. 2 is a flow chart of the detector. 1: Inspected object, 2: Light source, 3: Screen, 4: Camera, 5: Detector, 6: Guide rail, 7: Scanner, 8a: Incident light mirror, 8b: Reflected light mirror, 9: Image monitor , 10: Alarm lamp.

Claims (1)

[Claims] 1. A light source for irradiating an object to be inspected with light through a mirror for incident light, and a reflected light from the object to be inspected through a mirror for reflected light,
A screen that displays an image of the reflected light, a mirror for incident light and a mirror for reflected light, and a scanner that moves the light irradiation position on the inspection object by moving on the guide rail, and a reflection on the screen A reflected light type flaw detection device, comprising: a camera that captures an image of light; and a detector that detects a flaw based on a change in the area of the image of reflected light captured by the camera.