JPS60209150A - Device for surface inspection - Google Patents

Abstract

PURPOSE:To obtain a highly sensitive detection capacity without using numerous light detectors by using in common waveguide means and light detector. CONSTITUTION:A sheet 1 is fed to the arrow direction A by a feeding roller 2. The light point by a light beam 5 is scanned on a inspecting face 3 by a scanning line 6 showed with an alternate long and two short dashes line utilizing a multiface rotary mirror, etc. And the reflected light becomes a detecting light 7 having the surface information at the irradiating position of the beam 5. For instance when a face 3 is normal the beam 5 is turned into the light 7 reflected at the specified angle from the face 3 and is made incident at the specified angle on a light collector 10 consisting of cylindrical lens 8, 9. And it passes through the specified light collecting point 4 along the prearranged light path. A space filter 15 is placed at the position of the point 4 to position a through hole 13 and the light 7 is made incident on a light guiding rod 18 through the hole 13. On the other hand when something is abnormal with the face 3 at the irradiating position of the beam 5, the light 7 is not made incident on the rod 18 since the light 7 is made incident on the lens 8 at different angle from that of the normal light 7 like detecting lights 7a, 7b. A high sensitive detection is thus obtainable even on the face 3 with a wide width.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a surface inspection device that optically inspects the surface of an object. More specifically, the present invention relates to a surface inspection device that optically inspects an object surface. The present invention relates to a device for inspecting the surface of an object based on transmitted light or reflected light.

[Prior art]

An inspection device that optically inspects the surface shape of an object by irradiating light onto the surface and monitoring the detection light obtained by passing through the surface or being reflected by the surface. is used. In such a surface inspection device, a light spot is scanned on the surface of an object, and the detected light at each scanning point is guided to a photodetector, such as a photomultiplier tube, that performs a photoelectric conversion function to obtain information about the surface of the object. The signal is configured to be obtained as an electrical signal.

Conventional surface inspection devices include: (1) The detection light at each scanning point is always made to pass through a fixed position using a lens or concave mirror, and a spatial filter and a photodetector are placed at that position (for example, Japanese Patent Application Publication No. 5
8-21545), (2) The detection light at each scanning point is made to enter individual optical fibers arranged with their input ends aligned in a line, and the light is transmitted at the output end side. A method in which several fibers are grouped together and a photodetector is placed there (for example, Japanese Patent Laid-Open No. 57
(3) The detection light at each scanning point is made to enter from a line-shaped light incidence band formed on the side surface of the light guide rod, and the end surface of the light guide rod is Those in which a photodetector is arranged (for example, those described in Japanese Patent Application Laid-Open No. 56-24559 and Japanese Patent Publication No. 54-39753) are known.

However, in the device (1) above, if the width of the surface to be inspected is large, it may become difficult to collect the detection light at a fixed position due to the effects of astigmatism in the optical system consisting of lenses and concave mirrors. , the bank focus of these optical systems is long (
Considering that the device becomes larger, a plurality of optical systems and photodetectors are required, making the device itself expensive and making adjustments complicated. Even in the device (2), if a wide surface to be inspected is to be inspected, not only a photodetector but also a large number of optical fibers are required, making the device very expensive. Also,(
The device 3) has the disadvantage that even if there is an abnormality in the detection light in the direction of the light incident zone of the light guide rod, it cannot be detected.

[Purpose of the invention]

The present invention was made in view of the above-mentioned conventional technology, and even if the surface to be inspected becomes wide, it does not require many photodetectors.
Moreover, it is an object of the present invention to provide a surface inspection device having a highly sensitive detection ability.

[Structure of the invention]

In order to achieve the above object, in the present invention, the detection light from the surface to be inspected obtained each time the light spot is scanned is made to pass through a predetermined light convergence point by a condenser, and It is configured such that the detected light is sorted based on its spatial distribution by the provided spatial filter and then guided to the photodetector by the light guide means.

[First Embodiment] In FIG. 1 showing a first embodiment of the present invention, a sheet 1 is sent by a feed roller 2 in the direction of arrow 3 in the figure.

At the same time, the surface 3 to be inspected of the sheet 1 is, for example, He-
A minute light spot is irradiated by the light beam 5 from the Ne laser light source. The light beam 5 is scanned using a rotating polygon mirror or the like, and the light spot on the surface 3 to be inspected is scanned along a scanning line 6 shown by a two-dot chain line.

The light beam 5 irradiated on the surface to be inspected 3 is reflected there,
The reflected light becomes detection light 7 containing surface information about the irradiation position of the light beam 5 on the surface 3 to be inspected. For example, if the surface to be inspected 3 is normal at the irradiation position of the light beam 5, the light beam 5 becomes the detection light 7 reflected from the surface to be inspected 3 at a predetermined angle.

This detection light 7 enters a condenser 10 made up of cylindrical lenses 8 and 9 at a predetermined angle, travels along a predetermined optical path, and passes through a predetermined condensing point 4 .

The through hole 13 is located at the position of the light condensing point 4,
A spatial filter 15 is placed, and the detection light 7 passes through the through hole 13.
The light passes through and enters a light guide rod 18, which will be described later. The spatial filter 15 is constructed by forming through holes 13 and 14 in a light shielding plate 12 with nine predetermined shapes and dimensions. Note that the sheet 1 may be continuously fed during scanning with the light beam 5 or may be fed intermittently every 1 scanning lines 6.

On the other hand, if there is an abnormality on the surface to be inspected 3 at the position irradiated with the light beam 5, the light beam 5 becomes the detection light 7a.

7b, the detection light 7 enters the cylindrical lens 8 at a different angle from that of the detection light 7 in the normal case. Therefore,
Since these detection lights 7a and 7b cannot pass through the spatial filter 15, they do not enter the light guide rod 18.

That is, the spatial filter 15 detects the detection light 7 or 7a.
, 7b performs the function of selecting whether or not to allow the light to pass depending on the spatial distribution of the light in the vicinity of the condensing point 4.

Note that when the surface to be inspected 3 has a certain degree of diffusivity, the detection light 7 and the detection light 7a or 7b are incident on the light guide rod 18 with a difference in light intensity by the condenser 10 and the spatial filter 15. That will happen. Further, the above-mentioned effect is the same regardless of the scanning position of the light beam 5 on the scanning line 6. However, in the illustrated embodiment, the entire scanning area of the light beam 5 is divided into two, and the light condensing action in each scanning area is performed by a condenser 1o consisting of two cylindrical lenses 8.9. Therefore, the disadvantages of using a single cylindrical lens over the entire scanning area, namely, that astigmatism increases and light collection efficiency deteriorates, and that the back focus becomes longer and the inspection device itself becomes larger in the depth direction can be avoided. Preventing.

This also applies when a condenser such as a concave mirror is used instead of a cylindrical lens.

The spatial filter 15 has the through holes 13 and 14 as described above, and the detection light 7 to be incident on the light guide rod 18 is selected by the through holes 13 and 14. .

The shapes and dimensions of the through holes 13 and 14 are assumed to be the same, but they vary depending on the properties of the surface to be inspected 3, the characteristics of the cylindrical lens 8.9, and the detection accuracy, for example, as shown in FIG. formed as shown. Figure 2 (A) ~
(C) shows an example in which circular, rectangular, and elliptical through holes 13a, 13b, and 13c are respectively formed in the light shielding plate 12, and the smaller the dimensions, the higher the detection accuracy.
Accordingly, the optical performance of the cylindrical lenses 8 and 9 becomes stricter, and if the surface 3 to be inspected has diffusivity, the amount of detection light incident on the light guide rod 18 naturally decreases.

The detection light 7 passing through the through hole 13 of the spatial filter 15 in FIG. 1 is transmitted through the spatial filter 1 as shown in FIGS.
The light enters the light guide rod 18 from the side facing the light guide 5 . A diffuse reflection surface 23.24 is formed on a part of the side surface of the light guide bar 18 opposite to the side surface, that is, the side surface opposite to the side surface facing the spatial filter 15, corresponding to the through hole 13°14. has been done. Therefore, the detection light 7 becomes scattered light at various angles on the diffuse reflection surface 23 and is diffused into the light guide rod 18. Since the surfaces of the light guide rod 18 other than the diffuse reflection surfaces 23 and 24 are formed as optical surfaces, scattered light is transmitted within the light guide rod 18 directly or while being totally reflected. The light is incident on the photodetector 20°21. As a result, the photodetectors 20 and 21 output electrical signals corresponding to the detected light 7.

Note that since the detection lights 7a- and 7b do not enter the light guide rod 18, almost no electrical signals are obtained from the photodetectors 20.21. Therefore, by monitoring the output signal of the photodetector 20.21, the surface to be inspected 3 is detected by the light beam 5.
It is possible to identify whether the surface is a normal surface that reflects light within a predetermined angular range, or whether it is a defective surface that cannot reflect within a predetermined angular range.

Note that the light guide rod 18 may be covered with a cylindrical reflecting mirror whose inner surface is a reflective surface so that the light that is totally reflected within the light guide rod 18 and escapes to the outside is allowed to re-enter the light guide rod 18 . In this case, it is also possible to provide the above-mentioned through holes 13 and 14 in the cylindrical reflecting mirror and use them also as a spatial filter. In addition, when forming the diffuse reflection surfaces 23 and 24, the standard is the maximum incident angle at which the detected light 7 enters the light guide rod 18 when the surface 3 to be inspected is normal. By setting the width of the light guide rod 18, it is possible to prevent the light scattered within the light guide rod 18 from re-entering the diffuse reflection surface 23, 24 and the light transmission efficiency from being extremely reduced.

Furthermore, changes such as omitting one of the photodetectors 20 and 21 and making the end surface a mirror surface, and further dividing the scanning line 6 to increase the number of cylindrical lenses arranged in parallel, Of course, modifications such as increasing the number of are also possible. Note that if the diffuse reflection surfaces 23 and 24 formed on the light guide rod 18 are extended in a strip shape along the longitudinal direction of the light guide rod 18, the number of cylindrical lenses arranged in parallel can be adjusted according to the width of the surface to be inspected 3. Since the degree of freedom is increased by being able to freely increase or decrease the number of filters, the cylindrical lens and the spatial filter 15 can be made removable as a replaceable unit.

[Second Embodiment] In the second embodiment of the present invention shown in FIG. 5, the configuration of the cylindrical lens 8.9 and subsequent parts of the first embodiment is changed. Note that the same reference numerals are given to the same members as in the first embodiment.

In this embodiment, the front surface of the spatial filter 30 is a mirror surface 31 and the through holes 13 and 14 are formed, and the spatial filter 30 is arranged so that the mirror surface 31 faces downward at approximately 45 degrees. Further, another light guide rod 32 is provided below the light guide rod 18, and photodetectors 34 and 35 are provided at both ends thereof.

According to the above configuration, if the surface to be inspected 3 is normal, the detection light enters the light guide bar 18, and if it is abnormal, the detection light is reflected by the mirror surface 31 and then enters the light guide bar 32. It is incident. Therefore, photodetector 20°21 and photodetector 34
．． By monitoring the output signals from 35 in parallel, two different types of surface information can be obtained from the same portion of the surface 3 to be inspected, and the ability to discriminate surface defects is greatly improved.

〔Effect of the invention〕

As described above, according to the surface inspection apparatus to which the present invention is applied, even if the surface to be inspected becomes wide, the inspection can be performed while maintaining high detection power. Further, since the number of light condensers to be used can be freely selected while using the light guide means and the photodetector in common, the degree of freedom in design is increased, and there is no disadvantage in terms of cost. Furthermore, light guide means.

Since the photodetector can be used in common, adjustments can be made quickly and easily when the width of the surface to be inspected changes.

[Brief explanation of drawings]

FIG. 1 is an external view showing a first embodiment of the present invention. FIG. 2 is an explanatory diagram illustrating the shape of through holes formed in the spatial filter. FIG. 3 is a cross-sectional view of the light guide rod. FIG. 4 is a longitudinal sectional view of the light guide rod. FIG. 5 is an external view showing a second embodiment of the present invention. 1... Sheet 3... Surface to be inspected 5... Light beam 7... Detection light 10... Concentrator 15... Spatial filter 18... Light guide rod 20, 21... Photodetector 23 .24... Diffuse reflection surface 30... Spatial filter 32... Light guide rod 34, 35... Photodetector. Procedural amendment May 140, 1980 Patent layer No. 63299 2, Name of the invention Surface inspection device 3, Relationship with the person making the amendment Patent applicant address 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture Name (520)
) Fujisha Refilm Co., Ltd. 4, Agent Address: 406 Kita-Otsuka Building, 2-16-9 Kita-Otsuka, Toshima-ku, Tokyo 170 Japan

Claims (1)

[Claims] (11 Irradiating a light spot on the surface to be inspected and scanning it,
In a surface inspection device that inspects the surface to be inspected by guiding detection light obtained by passing through the surface to be inspected or being reflected by the surface to be inspected to a photodetector every time a light spot is scanned, the detection light is a condenser for condensing light onto a predetermined condensing point over a scanning area of points, and a condenser arranged near the condensing point to sort the detection light obtained each time the light spot is scanned according to its spatial distribution. A surface inspection characterized in that it is equipped with a spatial filter means for filtering, and a light guide means for receiving the light selected by the spatial filter means and guiding the incident light to the photodetector. Device. (2) The light guide means is constituted by a light guide rod having a longitudinal shape along the scanning direction of the light spot, and the detection light enters from the side surface of the light guide rod, and the detection light enters the light guide rod from the inner surface of the light guide rod. 2. The surface inspection device according to claim 1, wherein the light is totally reflected and guided to a photodetector provided at at least one end of the light guide rod. (3) A plurality of the condensers are provided, and each condenser is configured to condense detected light from a different range of the scanning area of the light spot onto a respective condensing point. A surface inspection device according to claim 2. (4) The spatial filter means is constituted by a reflecting mirror in which a through hole of a predetermined shape is formed, and the light passing through the through hole and the light reflected by the reflecting mirror are incident on separate light guiding means. Claims rIfJ characterized in that
The surface inspection device according to item 2. (5) The surface inspection device according to any one of claims 1 to 4, wherein the condenser is constituted by a cylindrical lens.