JP2001050720A - Surface inspection method and device thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide excellent defect detecting performance by shading a part of reflecting light from an inspected object irradiated by an irradiation means, and discriminating the surface condition of the inspected object from the change of a quantity of light according to the change of reflecting angle on the surface of the inspected object. SOLUTION: Illuminating light from a illuminating source 4 is projected on a chart 5 for slit, and the slit image is projected on the surface of an inspected object 1 by a converging optical system 6. The reflected light 9 of light irradiating the inspected object 1 is received by a light receiving means 8 constituted of a shading means 10, a converging optical system 11, and a light receiving sensor 12. Hereat in the reflected light 9, a part of the light is shaded by a shading means 10 movable along the direction 14, the passed light is converged by a converging optical system 11, and it is formed into an image on the light receiving sensor 12. The shading means 10 is set so as to shade the upper side dividing the light flux of the reflected light 9 into two in the lengthwise direction of the slit. By constituting it in this way, when recessed and projecting parts exist on the inspected object 1, reflected light fluxes corresponding to the inclination of the recessed and projecting parts are converged by the light receiving sensor 12 to be output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting a defect present on a surface of a functional component or the like used in various apparatuses,
In particular, the present invention relates to a method and an apparatus for inspecting a fine unevenness defect.

[0002]

2. Description of the Related Art Conventionally, surface defect inspection has been carried out by capturing specularly reflected light or diffusely reflected light at a light receiving section using an optical method. For example, FIG. 6 is a diagram schematically illustrating a conventional method. When inspecting a defect on the surface of an inspection target 61 to be inspected in the drawing, a belt-like light 62 as shown is projected. Then, the surface to be inspected is illuminated in a slit shape by the band light 62 (slit illumination 63).

[0003] The reflected light 64 of the slit light from the surface to be inspected is received by a light receiving sensor 65, and a defect is detected by judging the reflection state of the light. Actually, the light projection and the light reception are configured to have an optical imaging relationship with respect to the inspection object by a lens or the like. In general, a method of detecting a defect in the surface of the inspection target while moving the inspection target in a plane direction in a direction (arrow B) perpendicular to the slit light (arrow A in FIG. 6) is used. As the light receiving sensor 65, a one-dimensional line sensor is often used.

FIG. 7 is a diagram showing a specific configuration of such a method as viewed from a direction of a plane to be inspected orthogonal to the slit light. In this method, slit light is projected, and the reflected light is received by a one-dimensional sensor or the like. The signal waveform at this time is as shown in FIG. 8, and the sensor light receiving position in the figure is arranged so as to correspond to the longitudinal direction of the slit light (FIG. 6, arrow A). Thereby, a slit light image of the inspection target surface is formed on the sensor. In FIG.
For example, reference numeral 81 denotes a defect portion, and a defect such as a dust defect having a change in reflectance or a flaw defect having a large change in the reflection direction can be easily identified by signal processing.

[0005]

However, in the conventional example, the slit light illumination 73 will be described with reference to the example of FIG.
Is emitted to the inspection target 71 on the mounting table 72. The method of receiving the diffuse reflection light 77 from the surface of the inspection target 71 by the detector 74 is effective for a defect whose surface changes rapidly, but it is difficult to detect a gentle unevenness.

In the method of receiving the specularly reflected light 78 with the detector 75, the specularly reflected light 78 cannot be properly detected due to a large undulation component on the surface which is not a defect. Therefore, by increasing the numerical aperture of the optical system used for the light receiving means so as not to be affected by the swell component,
Such inconvenience is avoided. However, when the numerical aperture is increased, the defect is buried as well as the background, and it becomes difficult to detect the defect.

FIG. 9 illustrates the state of defect detection. In FIG. 9 (a), when there is a concave defect 92a on the inspection target surface 91, the slit light 93 becomes reflected light 96 by reflection. As shown in the figure, the defective portion deviates from the imaging optical system 94 for the light receiving sensor, so that the defective portion and the other reflected light 95 appear as a difference in sensor output on the light receiving sensor,
As a result, the defect can be detected.

On the other hand, when the concave defect 92b is shallow as shown in FIG. 9B, the reflected light 96 due to the defect is imaged on the sensor by the imaging optical system 94 in the same manner as the reflected light 95 other than the defect. Will be. Therefore, in this case, the defect cannot be identified. Further, as shown in FIG. 9, since the direction and position of the reflected light change, there is a problem that it is not possible to simply reduce the numerical aperture with respect to the problem of the influence of a large waviness component on the surface. In addition, the size of the unevenness defect required for the inspection object is such that the angular change of the unevenness defect is about 0.5 ° with respect to the global change in the waviness component of the inspection object of about 0.5 ° with the increase in the definition of the copying machine used. An extremely fine level of about 1/10 with a step of about 1 μm poses a problem. That is, finer irregularity defects must be detected.

The present invention has been made in view of the above circumstances, and has as its object to provide a surface inspection method and apparatus which realize excellent defect detection performance.

[0010]

A surface inspection method according to the present invention is a surface inspection method in which reflected light from an inspection object irradiated by an irradiation unit is received by a light receiving unit, and a surface of the inspection object is inspected from a light reception signal. A method of receiving reflected light from an inspection target by a light receiving unit, shielding a part of the reflected light, and detecting a change in a light amount according to a change in a reflection angle on a surface of the inspection target, thereby detecting the light of the inspection target. It is characterized by identifying the surface state.

Further, in the surface inspection method of the present invention, the slit light in a predetermined direction is irradiated from the irradiation means while the inspection object is moved, and the slit-shaped reflected light is received by the light receiving means.

Further, in the surface inspection method of the present invention, a variation in the surface shape of the inspection object is measured, and the reflected light from the inspection object is shielded according to the variation.

Further, the surface inspection apparatus of the present invention is a surface inspection apparatus for receiving reflected light from an inspection object irradiated by an irradiation means by a light receiving means, and inspecting the surface of the inspection object from the received light signal. Moving means for moving the test object in the plane direction, illuminating means for irradiating the test object with slit light, light receiving means for receiving reflected light from the test object irradiated by the irradiation means, and light receiving means It is characterized by comprising a detecting means for identifying a defect from a light receiving signal, and a light shielding means arranged at an appropriate position in the light receiving optical path of the light receiving means and shielding a part of the reflected light.

Further, in the surface inspection apparatus of the present invention, the light shielding means is configured to shield a part of the reflected light in accordance with a change in the reflection angle on the surface to be inspected.

Further, the surface inspection apparatus of the present invention is characterized in that the surface inspection apparatus further includes surface shape measuring means for measuring a change in the surface shape of the inspection object.

According to the present invention, when inspecting defects such as fine irregularities on the surface of a planar object such as a rubber plate which is a functional component of a copying machine or a laser beam printer by an optical method, the light receiving means is used. The opening is provided with a light-shielding means for transmitting light at a predetermined portion of the opening. When the one-dimensional sensor receives the slit-shaped regular reflection light from the inspection target by the illumination means, the change in the surface angle of the inspection target is regarded as a change in the amount of light, thereby greatly improving the detection ability.

Further, there is provided a surface shape measuring means for measuring a change in the plane of the surface shape of the inspection object, and the light shielding means is moved according to the change in the plane shape of the inspection object from the surface shape measuring means. As a result, a large undulation component to be inspected can be removed, and only fine irregularities can be accurately detected.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a surface inspection method and apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram that best illustrates the features of the present invention. In FIG. 1, reference numeral 1 denotes an inspection target, 2 denotes a moving unit of the inspection target 1, and 3 denotes an illumination unit. In this example, inspection target 1
Has a planar shape and extends in a direction orthogonal to the plane of the paper. The moving means 2 can move the inspection target 1 in the direction of arrow C. The configuration of the illuminating means 3 includes an illuminating light source 4, a slit chart 5, and a condensing optical system 6.

The illumination light from the illumination light source 4 is projected on the slit chart 5, and the slit image is projected on the surface of the inspection object 1 by the condenser optical system 6. On the other hand, the light 7 illuminating the inspection object 1 becomes reflected light 9 by reflection, and becomes a reflected light 9.
Is received at. The light receiving means 8 includes a light shielding means 10, a light collecting optical system 11, and a light receiving sensor 12.

Here, a part of the reflected light 9 is shielded by the light shielding means 10 in front of the condensing optical system 11.
The passed light is condensed by the condensing optical system 11 and forms an image on the light receiving sensor 12. At this time, the light shielding means 10 shields the light flux of the reflected light 9 at about half the center of the optical axis and in parallel with the longitudinal direction of the slit, and in the example of FIG. Keep it.

The light-shielding means 10 has light-shielding part moving means which can move in the direction 14. Note that the light blocking means may be arranged below the optical axis instead of above. Here, an example is shown in which it is arranged on the upper side. Reference numeral 13 denotes a surface shape measuring unit for the inspection object 1, and a position of a plane in a direction orthogonal to the plane of the inspection object 1 using a length measuring device such as an optical micrometer utilizing the principle of triangulation, in the figure, the vertical direction. Is measured.

Next, a description will be given of how to detect a fine and gentle irregularity defect in the inspection object 1 when it is present. FIG. 2 shows a case where a defect having a dent is present in the inspection object 1 in the moving direction or the feed direction of the moving means 2 of the inspection object 1 (arrow C in FIG. 1). In the figure, reference numerals 21 and 22 denote inclined surfaces of the defect, and the slit light is in a state of being illuminated long in a direction orthogonal to the paper surface. Reference numeral 23 denotes an output change near the defective portion. The horizontal axis represents the moving direction of the moving means 2 of the inspection object 1, and the vertical axis represents the output of the one-dimensional sensor at the position in the slit longitudinal direction. FIG. 3 shows only the light-receiving part as the inspection target 1
FIG. 5 shows a state of a light beam of reflected light when the angle of the inspection target 1 changes assuming that the light is reflected perpendicularly to.

First, in FIG. 2, on the left side of the position 24 and on the right side of the position 26, a light beam as shown in FIG. That is, about half of the reflected light beam is focused on the light receiving sensor 12. Further, in FIG. 2, in the section between the position 24 and the position 25, there is an inclined portion due to the depression of the inspection target 1. The reflected light flux in this section is shown in FIG.
As shown in (b), since the main axis of the light beam is inclined, the light beam blocked by the light shielding means 10 decreases. Correspondingly, the amount of luminous flux reaching the light receiving sensor 12 increases as compared with the case of FIG. Conversely, in the section between the position 25 and the position 26 in FIG. 2, the state is as shown in FIG. The main axis of the light beam is also inclined, but in this case, the light beam received by the light receiving sensor 12 is reduced because much of the light beam is blocked. As described above, when the inspection target has irregularities, the light amount corresponding to the inclination is output from the light receiving sensor 12.

The light shielding means 10 does not need to be on the upper side, but may be on the lower side. On the lower side, the sensor output intensity on the slope due to the defect to be inspected is reversed from that described above. In the above description, the slope in the feed direction of the inspection target has been described. However, the slope in the direction perpendicular to the feed direction can also be detected by changing the shape position of the light shielding means.

Next, the removal of the waviness component to be inspected will be described. Generally, large plane waviness components are not a problem due to the function of the blade in question. That is, a sudden change in the angle affects the performance. Further, in the present system in which the light-shielding means 10 is provided and the angle change is regarded as a change in the amount of light, a fine unevenness change is captured due to the waviness component of the inspection object 1 when the light-shielding means 10 remains at a fixed position with respect to the optical system. Optical conditions are not satisfied. This is because the angle change of the waviness component is larger than the angle change of the defective portion.

This will be described with reference to FIG. FIG. 4 shows a state in which the shielding means is fixed at a certain position (see the solid line in FIG. 4). The horizontal axis shows the angle of the reflected light beam, and the vertical axis shows the sensor output level. At this time, the sensor sensitivity is obtained with respect to the angle change in the range of the region 42, and the angle detection cannot be substantially performed in other regions.
This is because the F-number of the illumination needs to be large, that is, a state in which the luminous flux is narrowed, in order to catch the change in the angle sensitively. Then, the measurable range is narrowed, which causes a decrease in the dynamic range of the angle change.

In the method of the present invention, the width of the region 42 in FIG. 4 is not changed, but the position of the sensitivity region is displaced as shown by a dotted line 43 and a dotted line 44. Therefore, specifically, as a method of removing the global undulation component, the variation in the planar direction of the inspection target 1 is measured by the surface shape measuring means 13 of the inspection target 1 and the moving means 2 of the inspection target 1 in FIG. . For example, FIG.
Shows the measurement result of the inspection target 1 in the feed direction by the surface shape measuring means 13 of the inspection target 1. The changes are highlighted here.

In this example, the position in the vertical direction fluctuates on a plane at both ends, and it is angled. In addition, in the drawing, the unevenness defect portion 51 is a portion schematically showing the change, but in practice, an object whose angular fluctuation is smaller than this is also a target. From this measurement result, a change in the plane position with respect to the moving direction is calculated. FIG. 5B shows this state. The curve in the figure shows the change in the measurement result of FIG. 5 (a).

When calculating this change curve, FIG.
The calculation is performed in such a manner as to remove high-frequency components such as the irregularity defect portion 51 of FIG. Further, 52 in FIG. 5B indicates a position when the angle is 0 °. At the time of the defect detection operation, the position of the light shielding means 10 is moved according to the movement position corresponding to the curve in FIG. As a result, even if the inspection target 1 has large planar undulations, the reflected light 9 is almost always divided into two at the center of the light beam by the light shielding means 10 (level 45 in FIG. 4).
). This makes it possible to detect only high-frequency components, that is, only minute concave / convex defect portions, as the amount of change.

[0030]

As described above, according to the present invention, defects such as fine irregularities on the surface of a planar object such as a rubber plate which is a functional part of a copying machine or a laser beam printer are inspected by an optical method. When receiving the slit-shaped regular reflection light from the inspection target with the one-dimensional sensor,
The detection capability is improved by capturing the change in the surface angle of the inspection target as the change in the amount of light. Further, by providing a means for removing the waviness component of the inspection object, it is possible to detect fine irregularities on the surface without lowering the sensitivity to a large fluctuation of the inspection object.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of an apparatus used in a method of the present invention.

FIG. 2 is a diagram illustrating a relationship between a defective portion and a detection output according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating a relationship between a tilt of an inspection target and a reflected light beam and a light receiving unit according to the embodiment of the present invention.

FIG. 4 is a diagram illustrating a relationship between a change in the angle of an inspection target and a detection output according to the embodiment of the present invention.

FIG. 5 is a diagram illustrating a method of removing undulations of an inspection object according to the embodiment of the present invention.

FIG. 6 is a diagram illustrating an example of an arrangement configuration of a detection unit in a conventional example.

FIG. 7 is a diagram illustrating a configuration example of a detection device in a conventional example.

FIG. 8 is a diagram illustrating a sensor output in a conventional example.

FIG. 9 is a diagram illustrating the principle of defect detection in a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inspection object 2 Inspection object moving means 3 Illumination means 4 Illumination light source 5 Slit chart 6 Condensing optical system 8 Light receiving means 9 Reflected light 10 Light shielding means 11 Condensing optical system 12 Light receiving sensor 13 Surface shape measuring means

Claims (6)

[Claims] 1. A surface inspection method for receiving a reflected light from an inspection target irradiated by an irradiation unit by a light receiving unit and inspecting a surface of the inspection target from a received light signal, wherein the reflected light from the inspection target is detected. Surface inspection characterized in that a part of the reflected light is shielded when light is received by the light receiving means, and a surface state of the inspection target is identified by detecting a change in the amount of light corresponding to a change in the reflection angle on the surface of the inspection target. Method. 2. The method according to claim 1, further comprising: irradiating slit light in a predetermined direction from the irradiating means while moving the inspection object, and receiving the slit-like reflected light by the light receiving means.
Surface inspection method described in 1. 3. The surface inspection method according to claim 1, wherein a change in the surface shape of the inspection object is measured, and reflected light from the inspection object is shielded according to the variation. 4. A surface inspection apparatus which receives reflected light from an inspection object irradiated by an irradiation means by a light receiving means, and inspects the surface of the inspection object from a received light signal, wherein the inspection object is moved in a plane direction. Means for moving the inspection object to be inspected, illumination means for irradiating the inspection object with slit light, light receiving means for receiving reflected light from the inspection object irradiated by the irradiation means, and detection for identifying a defect from a light reception signal of the light receiving means A surface inspection apparatus characterized by comprising: means; and light blocking means arranged at an appropriate position in the light receiving optical path of the light receiving means to block a part of reflected light. 5. The surface inspection apparatus according to claim 4, wherein the light shielding unit is configured to block a part of the reflected light in accordance with a change in the reflection angle on the surface of the inspection object. 6. The surface inspection apparatus according to claim 4, further comprising surface shape measuring means for measuring a change in the surface shape of the inspection object.