JPS62103546A - Surface defect inspecting device - Google Patents

Abstract

PURPOSE:To enable the projection of a slit image on a screen in a detectable range, by arranging a cylindrical lens at a proper space on the incident surface side of a screen where a reflected slit light from a surface to be inspected is projected. CONSTITUTION:A slit light LST from a slit light generator 1 is projected to a surface 2 to be inspected and the reflected light thereof is projected to a screen 3 through a cylindrical lens 8 to form a slit image. The emitted light diffused is focused with a condenser lens 4 at a camera section 6 to form an image on a line sensor 5. A detection output of the line sensor 5 is binary processed to detect a defect on the surface 2 to be inspected. In this case, for example, when the surface 2' to be inspected is inclined by angle alpha across the slit width from the normal condition, a lens 8 allows the reflected light LST' from the the surface 2' being inspected to refract to ward the focal line thereof when passing through the lens 8 and so approach the optical axis O. Thus, the slit image can be projected at the part (b) within a detectable range on the screen 3.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a surface defect inspection device for inspecting surface defects on objects to be inspected, such as the painted surface of an automobile body panel or a rolled steel strip.

[Conventional technology]

Scratches and protrusions on the surface of the inspected object as described above.

Inspection for defects such as spots and stains is moving from visual inspection by inefficient and individual workers to automatic inspection using, for example, highly directional laser light.

As shown in FIG. 7, a surface defect inspection device using such a laser beam projects a slit light LST from a slit light generator 11, which is a light source, onto a surface to be inspected 2, which is the surface of an object to be inspected. , the reflected light LST' is projected onto a screen B formed by a diffusion plate, and the image on the screen is focused by a condensing lens 4 of a camera section and detected by a line sensor 5 such as a COD, thereby detecting surface defects. The applicant of the present invention has previously proposed a surface defect inspection device designed to detect surface defects (Japanese Patent Application No. 1983-83890).

According to this surface defect inspection device, for example, as shown in FIG. Since the light LST is scattered there, the surface to be inspected 2
On the screen 3 that receives specularly reflected light LST' from
As shown in the figure, a cut slit image SL is projected at a location corresponding to the defect a.

Therefore, the output signal of the line sensor 5 shown in FIG. 7, which constantly photographs the position where the slit image SL is projected on the screen 3, becomes as shown in FIG. S (a), and as shown in FIG. The envelope signal Vs shown in the figure is compared with the averaged comparison signal Vr (threshold level), and the result is shown in the figure (C
) As shown in FIG. a of
) can be detected when the level of this binarized signal becomes H.

In this case, the line sensor 5 shown in FIG.
By receiving the light, the projected slit image SL on the screen 3 is captured, so the focus of the condensing lens 4 can be fixed at all times, and the projected slit image SL is expanded by diffusion, so that one surface Defect detection resolution is improved.

[Problem that the invention seeks to solve]

In order to inspect a large surface to be inspected, such as the painted surface of a car body panel, using such a surface defect inspection device, the device must be attached to, for example, a robot's hand, and the slit must be placed at a constant distance from the surface to be inspected. Inspection is performed by scanning so that the angle of incidence of light is also constant.

Therefore, the relative positional relationship between the slit light generator 1, the screen 3, and the surface to be inspected 2 is adjusted to, for example, the state shown by the solid line in FIG. Suppose that the slit image SL is formed within a range 3a that can be imaged by the line sensor 3 (hereinafter referred to as "detectable range").

However, if the surface to be inspected 2 is tilted as shown by the broken line in the figure with respect to the normal state shown by the solid line during scanning, the angle of incidence and the reflection position of the slit light LST on the surface to be inspected will change. Slit image SL that changes and is formed on the screen
' is shifted and tilted two-dimensionally with respect to the slit image SL in the normal state, and is out of the detectable range 3a, making inspection impossible.

Therefore, it is necessary to make corrections to always maintain the normal relative positional relationship with a certain degree of accuracy, which poses the problem that not only does the apparatus become complicated and expensive, but also the inspection speed cannot be very fast.

It is an object of the present invention to solve these problems, simplify the structure of an inspection device, and increase inspection speed.

[Means for solving problems]

Therefore, the present invention solves the above problem by arranging cylindrical lenses at intervals on the incident surface side of the screen in a surface defect inspection apparatus as shown in FIG. .

[Effect]

Even if the relative positional relationship between the surface defect inspection device and the surface to be inspected deviates from the normal state, and the reflected light of the slit light from the surface to be inspected deviates from the optical axis direction of the condenser lens 4 in FIG. Since the slit image formed on the screen is always refracted toward the focal line by the cylindrical lens placed in front of the detectable cylinder 1 in FIG.
713a.

Therefore, all you have to do is scan this surface defect inspection device so that the reflected light of the slit light from the surface to be inspected is always incident on the cylindrical lens, so there is no need to install a complicated correction device. , inspection speed can also be increased.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a schematic layout diagram showing one embodiment of the present invention, and parts corresponding to those in FIGS. 7 and 8 are given the same reference numerals.

The slit light generating bag W11 in this embodiment is as follows.

A lens system 1b including a laser oscillation tube 1a, a cylindrical lens for converting the laser beam generated by the tube into slit light, and a Fresnel lens for converting the slit light into parallel slit light that does not spread in the elongated direction is attached to the tip. It consists of a hood part 1c.

The condensing lens 4 and the line sensor 5 are provided inside the camera section 6, and a detection tube 7 is integrally attached to the front surface of the camera section 6.
A cylindrical lens 8 is placed near the tip of the screen 3 at a distance from the entrance surface of the screen 3, and the detector 10
It consists of

Furthermore, as a line sensor, PCD (PlasmaCoup) has a much wider detection width than a CCD line sensor.
If you use a led device) line sensor,
A slight variation in the relative positional relationship between the inspection device and the surface to be inspected is allowed.

The detector 10 and the slit light generator 1 have optical axes of 0
1 and 02 are held by a holding member (not shown) so that they intersect at a predetermined angle θ.

Line sensor 5 of detector 10. The screen 3° and the cylindrical lens 8 are arranged on the optical axis of the condenser lens 4 so that the projected image on the screen 3 is focused onto the line sensor 5 by the condenser lens 4.

Furthermore, the direction in which the light receiving elements of the line sensor 5 are arranged and the direction of the cylindrical axis of the cylindrical lens 8 are such that the surface to be inspected 2 has both optical axes 0. ．． The slit light LST is reflected at the intersection o2, and when the angle of incidence and the angle of reflection are equal to each other and the slit light LST is in a regular positional relationship, the slit light LST is arranged so as to match the slit direction of the reflected slit light.

Although the distance d between the screen 3 and the cylindrical lens 8 can be arbitrarily selected, it may be set to the focal length of the cylindrical lens 8, for example. Further, it is preferable to use a cylindrical lens 8 that is as wide as possible.

Next, the operation of this embodiment will be explained with reference to FIGS. 2 to 4.

Slit light L from the slit light generating bag W11 as a light source
The ST is projected onto the surface to be inspected 2, and the reflected light is projected onto the screen 3 through the cylindrical lens 8 to form a slit image in the same way as in the previous example, and the diffused emitted light is focused by the camera unit 6. The light is focused by the lens 4 and formed into an image on the line sensor 5, and the detection output of the line sensor is binarized as explained with reference to FIG. 9, thereby detecting defects on the surface to be inspected 2.

In this case, when the relative positional relationship between the slit light generator 1 and the detector 10 and the surface to be inspected 2 is in a normal state as shown in FIG. 1, it is the same as in the conventional case. 2
As shown in ', the surface to be inspected is in a normal state (surface to be inspected 2)
The effect when the slit is inclined by an angle α in the slit width direction will be explained with reference to the enlarged view of FIG.

In this case, the reflected light LST' of the slit light LST from the surface to be inspected 2' deviates from the optical axis 02 of the detector 10,
If the cylindrical lens 8 were not present, the slit image would continue straight ahead and project a slit image onto the end a portion of the screen 3.

However, part a on the screen 3 is outside the detectable range W by the line sensor 5 and cannot be detected.

However, because the cylindrical lens 8 is present, the slit reflected light LST' from the surface to be inspected 2' is refracted in the direction of its focal line when passing through the cylindrical lens 8, so it approaches the optical axis o2 and is reflected on the screen 3. The Surin 1-image can be projected onto part b within the detectable range W of .

Also, as shown in Fig. 10, when the surface to be inspected is tilted with respect to the slit direction (longitudinal direction) of the slit light, and one reflected slit light LST' is tilted with respect to the normal slit direction. Also, if there is no cylindrical lens 8, 5
The slit image projected onto the screen A is tilted as shown by the virtual line a in FIG. When passing through the screen, the slit image is refracted so as to be parallel to the focal line, and the slit image projected onto the screen A is corrected to the approximately normal slit image position as shown by the solid line.

within the detectable range.

Therefore, even if the relative positional relationship between the inspection device and the surface to be inspected is slightly shifted, as long as the reflected light from the surface to be inspected is incident on the sylindrical lens 8, surface defects can be inspected.

Next, FIGS. 5 and 6 show practical embodiments of the surface defect inspection apparatus according to the present invention, in which parts corresponding to those in FIG. do.

In this embodiment, in order to make the detector 10 smaller and to increase the reduction magnification of the slit image, the detection tube 7 is made into a bent shape, and two mirrors (plane mirrors) 11 and 12 are arranged inside. The slit image projected onto the screen 3 is reflected onto the mirrors 11 and 12, and the image is formed onto the line sensor 5 by the condenser lens 4.

This detector 10 is fixed to the proximal end of a hawk-shaped holding member 13, and a slit light generating device i1 is pivotally supported at the tip of the holding member 13 by a pivot 14, and the angle with respect to the detector 10 is adjusted. It can be fixed in place.

The intermediate portion of the holding member 13 is provided with a bracket 15 for attaching the surface defect inspection device to a scanning device such as a robot (not shown) or a fixed portion.

〔Effect of the invention〕

As explained above, the surface defect inspection bag according to the present invention has cylindrical lenses spaced apart from each other on the incident surface side of the screen that projects the reflected slit light from the surface to be inspected. Even if the relative positional relationship is slightly shifted and the reflected slit light from the surface to be inspected deviates from the optical axis of the detector, the slit image can be projected within the detectable range on the screen, making surface defect inspection possible. The permissible range of the posture of the object to be inspected (panel) relative to the device is widened.

Therefore, for example, when carrying this surface defect inspection device in a robot for scanning, surface defects can be inspected without complicated position correction by simply teaching the robot its movements in advance. .

That is, the structure of the surface defect inspection device is simplified and the inspection speed is also increased.

[Brief explanation of drawings]

FIG. 1 is a schematic layout diagram showing an embodiment of the present invention. 2 to 4 are explanatory diagrams for explaining the operation thereof, and FIG. 5 is a front view showing a practical embodiment of the invention. FIG. 6 is a side view seen from the direction of arrow A in FIG. FIG. 7 is a principle diagram of a conventional surface defect inspection device using slit light, and FIG. 8 is an explanatory diagram illustrating its operation. Figure 9 also shows the output signal of the line sensor and part 2.
FIG. 10 is a signal waveform diagram for explaining the process of value conversion processing. FIG. 10 is an explanatory diagram for explaining the problems of the conventional device. 1... Slit light generating bag W 2... Surface to be inspected 3.
... Screen 4 ... Condensing lens 5 ... Line sensor 6 ... Camera section 7 ... Detection tube
8... Cylindrical lens 10... Detector
11.12... Mirror 13... Holding member
14...Axis Figure 1 Figure 2 Figure 6 Cause Figure 7 Figure 8 Figure 9 + 1024 Procedural Amendment Amendment Side January 21, 1985 Mr. Michibe Uga, Commissioner of the Patent Office■, Indication of the incident Patent Application No. 60-243622 2 Name of the invention Surface defect inspection device 3 Relationship with the person making the amendment Case Patent applicant Nissan Motor Co., Ltd. 4, 2-399 Takaracho, Kanayō-ku, Yokohama, Kanagawa Prefecture, Agent 1-20-5 Higashiikebukuro, Toshima-ku, Tokyo
, otherwise the level becomes ``H'''' is corrected as follows. ``The high level becomes ``H'' only, and the guard becomes the low level ``L#'' in other cases.

Claims (1)

[Claims] 1. Slit light is projected from a light source onto the surface of the object to be inspected, the reflected light is projected onto a screen formed by a diffuser plate, and the image on the screen is detected by a line sensor via a condensing lens. A surface defect inspection apparatus for inspecting surface defects of the object to be inspected by: cylindrical lenses are disposed at intervals on the incident surface side of the screen.