JPH01216243A - Defect inspecting method - Google Patents

Abstract

PURPOSE:To detect principally a band-shape defect which can not be detected before by employing an image pickup camera as a camera which has such a linear image sensor whose longitudinal-lateral shape ratio of one unit element is >=(1:50) and providing a swing and tilt mechanism to its sensor fitting part. CONSTITUTION:The image pickup camera is used as the camera which has the linear array image sensor 1a whose longitudinal-lateral shape ratio of one unit element 6a is >=(1:50). The swing and tilt mechanism is provided to the fitting part of the sensor 1a. The image of an element 6a of the sensor 1a corresponds to a unit equivalent visual field 7 on a running sheet 3 to be scanned. Defects 4 and 5 which are long in a scanning direction are added optically. The accumulation of errors due to electronic addition and a decrease in defect deciding ability are eliminated. When the position of the sensor 1a is FF, a focusing position is E'F' because of the swing and tilt mechanism and the focus is obtained on the sheet 3. Consequently, the detection of principally the band-shaped defect which can not be detected before is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for inspecting mainly band-shaped defects present in sheet-like objects, cylindrical objects, etc.

[Conventional technology]

In the conventional method of mainly inspecting band-shaped defects, a camera having a linear array image sensor in which the aspect ratio of one unit element is approximately 1:1 is used as an imaging camera. Usually, the sheet-like object to be inspected travels, and the band-like defects are parallel to the traveling direction.

The conventional technique was to electronically add the output signals of one unit element in the running direction at a ratio of approximately 1:1.

[Purpose of the invention]

The present invention eliminates the poor detection performance associated with the electronic addition,
The purpose is to improve the detection performance of mainly band-shaped defects that are faint and have low optical contrast.

[Summary of the invention]

In order to achieve the above object, the present invention has the following features: - unit element is 1:
A linear array image sensor of 50 or higher is used as a sensor, using an optical addition method instead of an electronic addition method, and a tilt mechanism is installed at the linear array image sensor mounting part so that the entire surface of the linear array is focused on the sheet material to be inspected. This improves the detection performance of band-like defects.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In Fig. 1, IA is a linear array image sensor in which the aspect ratio of one unit element is 1=50 or more, and 8 is the equivalent field of view of the linear array image sensor obtained through the imaging lens 2. This is the image on sheet 3. Therefore, the image of one unit element 6A of the linear array image sensor IA becomes a unit equivalent field of view 7 on the traveling sheet to be inspected. Defects to be detected in the present invention and L1 are mainly band-shaped defects 4
, a linear defect 5, an elliptical defect 10, etc. These defects are characterized by being long along the running direction 9 of the running sheet. Types of defects include dirt, scratches, discoloration, foreign matter, uneven coating, streaks, doctor lines, etc.

In FIG. 2, IB is a linear array image sensor in which each unit element has a ratio of approximately 1:l, and conventionally, the output signal of approximately square unit element 6B is electronically added in the running direction of the inspected material. A processing method was used. The reason for electronic addition is that the optical contrast of the defects to be detected is generally low and stable defect discrimination cannot be achieved by judging only one field of view, so the defect discrimination ability is improved by adding and averaging multiple fields of view in the running direction. It was something. IA is a linear array image sensor used in the present invention, in which the aspect ratio of unit elements is 1=50 or more, and is an assembly of a large number of rectangular unit elements 6A.

In the present invention using rectangular unit elements, as is clear from FIG. 1, defects that are long in the running direction are optically added. Therefore, the error accumulation due to electronic addition,
There is no decline in defect discrimination ability. Generally, the variation in sensitivity between unit elements becomes larger as the area of the unit element becomes smaller. The reason is that the sensitivity of one unit element is proportional to its area. Therefore, the IJ near array image sensor IA, which has a larger area per unit element, has smaller variations in sensitivity than the IB, and therefore has better defect detection ability.

It is clear from FIG. 1 that the present invention can be applied to moving objects or stationary objects. On the other hand, the conventional technology cannot be applied to vehicles that are not running. It is also clear that the running direction can also be applied in the direction 11 perpendicular to the arrow direction 9 in FIG.
It is also clear that the conventional technology cannot cope with this problem.

The vertical and horizontal shape ratio of one unit element is 1:1.1:10.1:20
．． When a 1:50.1:100 linear array image sensor was applied to a strip defect and the signal-to-noise ratio, that is, the ratio of the defect signal amount to the background signal amount, was measured, it was 1.01.1, respectively. .1.1.15, z5.26. Therefore, it is effective that the aspect ratio of one unit element is 1=50 or more.

In FIG. 1, the illumination light source 12 shows a reflective illumination arrangement;
It is clear that the present invention is also applicable to a transmitted illumination arrangement in which the illumination light source 12 is located on the opposite side of the sheet material to be inspected from the linear array image sensor position. Furthermore, it is clear that the present invention is also applicable even if the material to be inspected is not a sheet material but a cylindrical drum.

In Figure 3, a normal linear array image sensor IA
In the arrangement CD, the position focused by the imaging lens 2 is C.
'σ, and is not focused on the sheet material 3 to be inspected. When the position of the linear array image sensor is set to EF using a tilt mechanism (not shown), the focal position becomes F', and the focus can be set on the sheet material 3 to be inspected. Therefore, the defect detection ability is improved compared to the case where the arrangement is CD. Points C, D, E, and F in FIG. 3 correspond to points C, D, E, and F in FIG. 2. In addition, the 12 light sources in Figure 3 (reflected lighting arrangement),
Light source 12B (transmitted illumination arrangement) corresponds to light source 12 in FIG.

〔Effect of the invention〕

As explained above, according to the present invention, it becomes possible to detect mainly band-shaped defects, which were conventionally undetectable.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of the defect inspection method according to the present invention, FIG. 2 is a comparison diagram of a linear array image sensor, and FIG. 3 is a layout diagram of a linear array image sensor and a light source. 1... Linear array image sensor, 2.
...Imaging lens, Z, 3...Traveling sheet to be inspected, 4...Band defect, 5...Line defect, 12... lighting source. Patent applicant Hietic Co., Ltd. No. 2t4 (F)

Claims (1)

[Claims] A camera having a linear array image sensor in which the aspect ratio of one unit element is 1:50 or more is an imaging camera,
A defect inspection method characterized in that a tilting mechanism is provided at a mounting portion of a linear array image sensor.