JP5610672B2 - Surface inspection device - Google Patents

Description

  The present invention relates to a surface inspection apparatus for inspecting the surface of an object, and more particularly to a surface inspection apparatus suitable for inspecting an object having a curved surface.

  The surface inspection apparatus as described above irradiates an object with illumination light, and inspects foreign objects such as dust and defects on the surface based on an image obtained by reflected light on the surface of the object. There is something to do. In such a surface inspection apparatus, it is easy to detect foreign matter and defects by irradiating illumination light from a direction close to the tangential direction of the surface (curved surface) of the object, scattering and reflecting the image, and imaging the surface from the normal direction. It has been known.

Such a surface inspection apparatus is often used when, for example, inspecting the surface of a cylindrical object such as a photosensitive drum or a fixing roller used in a copying machine or a laser printer. An example in which a similar apparatus is applied to human cornea examination is disclosed in Patent Document 1.
Japanese Patent Laid-Open No. 2004-194689

  However, in the conventional surface inspection apparatus, when the surface of an object has non-uniformity (unevenness or the like) as a normal surface state, it is difficult to distinguish the surface state from foreign matters or defects. In other words, in the surface inspection, it is important to separate a normal surface state from a foreign object or a defect.

  The present invention provides a surface inspection apparatus in which the influence of a normal surface state of an object is reduced and foreign objects and defects existing on the surface can be detected with high accuracy.

A surface inspection apparatus according to one aspect of the present invention inspects an object whose surface is a cylindrical surface. The surface inspection apparatus illuminates a first region of the cylindrical surface from a direction that forms a first angle smaller than 90 ° with respect to a generatrix direction of the cylindrical surface as a tangential direction of the first region. The first illumination means and the second region, which is a region different from the first region of the cylindrical surface in the circumferential direction of the cylindrical surface, is set to 0 ° or more and 10 ° with respect to the tangential direction of the second region. A second illuminating means that illuminates from a direction that is less than or equal to 0 ° and that forms a second angle smaller than the first angle , and the first and second illuminators illuminated by the first and second illuminating means, respectively. And an imaging unit that simultaneously images the region from a direction normal to the first region and tilted with respect to the normal direction of the second region.

According to the present invention, it is possible to detect a foreign object or a defect existing on the surface (cylindrical surface) of an object with high accuracy while reducing the influence of a normal surface state.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  1 (A) and 1 (B) show a surface inspection apparatus that is Embodiment 1 of the present invention.

  In these drawings, reference numeral 6 denotes an object (inspected object) having a surface as a cylindrical surface, and specifically, a photosensitive drum or a fixing roller used in a copying machine or a laser printer. The object 6 is driven to rotate around the central axis by a rotation mechanism (not shown).

  Reference numeral 4 denotes an imaging apparatus (imaging means: hereinafter referred to as a camera) such as a digital still camera or a video camera. FIG. 1A is a view of the device viewed from a direction perpendicular to a plane including the central axis of the object 6 and the imaging optical axis 5 of the camera 4, and FIG. It is the figure seen from the axial direction of the object.

  Reference numeral 9 denotes a first light source composed of a xenon lamp or the like, and reference numeral 10 denotes a first lens that converts a light beam from the first light source 9 into a parallel light beam (which may include some divergent and convergent light beams). is there. The first light source 9 and the first lens 10 constitute a first illumination system (first illumination means).

  The first illumination system is shown in FIGS. 1B and 2 out of the cylindrical surface of the object 6 by illumination light (hereinafter referred to as first illumination light) imparted with directivity by the first lens 10. The first region 11 is illuminated from a direction that forms a first angle θ1 with respect to the tangential direction T1 of the first region 11. In other words, the optical axis AXL1 of the first illumination system forms a first angle θ1 with respect to the tangential direction T1. FIG. 2 shows the object 6 as viewed from the camera 4 side.

  The first area 11 is an area facing the camera 4 (imaging lens). That is, as shown in FIGS. 1A and 1B, the camera 4 is arranged in the normal direction of the first region 11.

  The first illumination light is actually applied to a wider range in the circumferential direction than the first region 11 in the cylindrical surface of the object 6 (almost half of the cylindrical surface). The first area 11 where the scattered reflected light is directed to the camera 4 with a predetermined intensity is an effective inspection area for the first illumination system.

  The tangential direction T1 of the first region 11 corresponds to the generatrix direction of the cylindrical surface of the object 6 (direction parallel to the axial direction of the object).

  7 is a second light source composed of a xenon lamp or the like, and 8 is a second lens that converts a light beam from the second light source 7 into a parallel light beam (which may include a slight divergence and a convergent light beam). is there. The second light source 7 and the second lens 8 constitute a second illumination system (second illumination means).

  The second illumination system is shown in FIG. 1B and FIG. 2 in the cylindrical surface of the object 6 by illumination light (hereinafter referred to as second illumination light) provided with directivity by the second lens 8. The second region 12 is illuminated from a direction that forms a second angle θ2 with respect to the tangential direction T2 of the second region 12. In other words, the optical axis AXL2 of the second illumination system forms a second angle θ2 with respect to the tangential direction T2. The tangential direction T2 of the second region 12 corresponds to the generatrix direction of the cylindrical surface of the object 6.

  Here, the second angle θ2 is an angle of 0 ° or more and smaller than the first angle θ1, and is preferably as close to 0 ° as possible.

  The second region 12 is a region adjacent to the first region 11 in the circumferential direction on the cylindrical surface of the object 6. The normal direction n of the second region 12 is inclined with respect to the normal direction of the first region 11.

  The camera 4 receives the scattered and reflected light from the first and second regions 11 and 12 to capture the first and second regions 11 and 12 and generate an inspection image. As described above, the camera 4 is arranged in the normal direction of the first region 11. As shown in FIG. 1B, the camera 4 is disposed in a direction inclined with respect to the normal direction n of the second region 12. In other words, the imaging optical axis 5 of the camera 4 coincides with the normal direction of the first region 11 and is inclined with respect to the normal direction of the second region 12.

  A plurality of inspection images in which the entire cylindrical surface of the object 6 is imaged can be generated by imaging the object 6 a plurality of times while rotating the object 6 by a predetermined angle.

  The inspection image is captured by a computer (not shown) or displayed on a monitor. Then, foreign matter and defects existing in the first and second regions 11 and 12 can be detected by image analysis processing on the inspection image by the computer and visual inspection of the inspection image by the inspector. In the figure, reference numeral 3 denotes a foreign substance or a defect present in the second region 11.

  By causing the first light source 9 and the second light source 7 to emit light simultaneously in synchronization with the imaging timing of the camera 4, the first region 11 and the second region 12 can be captured in one image. In this way, by imaging the first area 11 and the second area 12 at the same time, the number of times of imaging for one object 6 is reduced, or the time until the image obtained by imaging is transferred to a computer or monitor is reduced. It can be shortened. However, separate imaging may be performed on the first region 11 and the second region 12 at different timings. This is the same in the embodiments described later.

  Here, the optical axis of the first illumination system is substantially included in the camera 4 among the first illumination light that is irradiated on the first region 11 from the first direction and is scattered and reflected by the first region 11. Light scattered and reflected in a direction along a plane including the AXL 1 and the imaging optical axis 5 of the camera 4 is captured. This light has a large amount of light over almost the entire first region 11. For this reason, the foreign substance and the defect contained in the 1st area | region 11 will be mixed with the normal surface state (unevenness | corrugation etc.) of this 1st area | region 11 depending on the magnitude | size and shape, and may not be detected.

  For this reason, in the present embodiment, the second illumination light is irradiated in an irradiation direction (the angle formed with respect to the tangential direction of the cylindrical surface of the object 6 is smaller than the irradiation direction (first direction) of the first illumination light ( The second region 12 is irradiated from the second direction). Further, the side scattered light traveling in the direction greatly inclined from the normal direction n of the second region 12 out of the light scattered and reflected by the second region 12 is mainly captured by the camera 4.

  As a result, the amount of light that is scattered and reflected by a foreign object or a defect and captured by the camera 4 as compared with the amount of light that is scattered and reflected by the portion having the normal surface state in the second region 12. Becomes larger. Accordingly, even in the first region 11, a foreign substance or a defect having a size or shape that would be lost in a normal surface state can be easily detected in the second region 12.

  The principle of detecting foreign matter and defects by scattered light will be described with reference to FIGS. First, in FIG. 3, reference numeral 1 denotes a minute region (small surface) of a curved surface. The minute surface 1 is approximated by a plane having a certain inclination. The normal direction of the minute surface 1 is n, and the illumination light incident on the minute surface 1 is 2. The imaging optical axis 5 of the camera 4 is set in a plane including the normal direction n and the illumination light beam 2 (herein referred to as an incident surface), forms an angle θ with respect to the normal direction, and is an angle with respect to the illumination light beam 2. Make φ.

  At this time, the direction of the reflected light beam on the minute surface 1 incident on the camera 4 is set so as to form an angle of 90 ° or more with the direction of the illumination light beam 2 in the incident surface. As a result, it is possible to perform imaging with backscattered light traveling in a direction greatly inclined from the normal direction n within the incident plane. Note that light scattered and reflected in the normal direction n does not enter the camera 4. In this way, by using the camera 4 to perform imaging using the backscattered light without using the reflected light in the normal direction n, the camera 4 is sensitive to foreign matters and defects having a large light scattering property (that is, In other words, a detection image having a large amount of reflected light from a foreign object or a defect can be generated.

  In this embodiment, since the imaging optical axis 5 does not coincide with the normal direction n of the second region 12, it is difficult to focus the camera 4 on the entire second region 12. However, the blur of the image in the second region 12 can be suppressed to a range necessary for resolving a foreign object or a defect by adjusting the F value of the camera 4 or appropriately setting the focus position. In the present embodiment, the fine structure of the foreign matter and the defect is not obtained, but the purpose and the size of the foreign object and the defect are evaluated. Therefore, there is no problem even in a slightly defocused state.

  Further, it is possible to acquire an image that is sensitive to foreign matters and defects by performing imaging using backscattered light even when performing imaging using side scattered light.

  In FIG. 4, the imaging optical axis 5 is set in a plane inclined by an angle η with respect to the incident plane. In this case, it is possible to perform imaging with side scattered light traveling in a direction greatly inclined from the normal direction n outside the incident surface. Note that light scattered and reflected in the normal direction n does not enter the camera 4. In this way, by using the camera 4 to perform imaging using side scattered light without using reflected light in the normal direction n, a detection image sensitive to a foreign matter or defect having a large light scattering property. Can be generated.

According to the experiment, as shown in FIG. 5, the irradiation direction (AXL2) of the second illumination light is
0 ° ≦ θ2 ≦ 10 °
By setting to this range, it was possible to detect the foreign matters and defects that are lost in the normal surface state particularly well in the first region 11 without being greatly affected by the normal surface state.

  FIGS. 6A and 6B show a surface inspection apparatus that is Embodiment 2 of the present invention. Note that, in these drawings, the same reference numerals as those in the first embodiment are assigned to components common to the first embodiment. 6A is a view of the device viewed from a direction perpendicular to a plane including the central axis of the object 6 and the imaging optical axis 5 of the camera 4, and FIG. 6B illustrates the device. It is the figure seen from the axial direction of the object.

  Also in the present embodiment, the first illumination system uses the first illumination light to which directivity is imparted by the first lens 10, and the first illumination system shown in FIGS. 6B and 7 among the cylindrical surfaces of the object 6. The region 11 is illuminated from a direction that forms a first angle θ1 with respect to the tangential direction T1 of the first region 11. Also in the present embodiment, the tangential direction T1 of the first region 11 corresponds to the generatrix direction of the cylindrical surface of the object 6. The first area 11 is an area facing the camera 4 (an area where the camera 4 is arranged in the normal direction), as in the first embodiment.

  On the other hand, also in the second illumination system, the second region 12 shown in FIGS. 6B and 7 in the cylindrical surface of the object 6 by the second illumination light imparted with directivity by the second lens 8. Are illuminated from a direction that forms a second angle θ2 with respect to the tangential direction T2 of the second region 12. However, unlike the first embodiment, the tangential direction T2 of the second region 12 is a direction that intersects the generatrix direction of the cylindrical surface of the object 6. The intersecting direction may be a direction orthogonal to the generatrix direction or may be inclined from the orthogonal direction. FIG. 7 shows the object 6 as viewed from the camera 4 side.

  The second angle θ2 is an angle of 0 ° or more and smaller than the first angle θ1, and is preferably as close to 0 ° as possible (0 ° ≦ θ2 ≦ 10 °).

  The second region 12 is a region adjacent to a part of the first region 11 in the circumferential direction on the cylindrical surface of the object 6. The normal direction n of the second region 12 is inclined with respect to the normal direction of the first region 11.

  The camera 4 receives the scattered and reflected light from the first and second regions 11 and 12 to capture the first and second regions 11 and 12 and generate an inspection image. A single object 6 is imaged a plurality of times while the object 6 is rotated by a predetermined angle, and the second illumination system is moved by a predetermined amount in the generatrix direction of the cylindrical surface every rotation. In this way, a plurality of inspection images in which the entire cylindrical surface of the object 6 is copied can be generated.

  Also in the present embodiment, the second illumination light is irradiated in an irradiation direction (second direction) that is smaller in angle with respect to the tangential direction of the cylindrical surface of the object 6 than the irradiation direction (first direction) of the first illumination light. The second region 12 is irradiated from the (direction). Then, as described with reference to FIG. 3, the backscattered light traveling in the direction greatly inclined from the normal direction n of the second region 12 out of the light scattered and reflected by the second region 12 is mainly captured by the camera 4. For this reason, in the 1st area | region 11, even the foreign material and defect which are lost in the normal surface state can be easily detected in the 2nd area | region 12.

  Each embodiment described above is only a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

  In the first embodiment and the second embodiment, the case where the generatrix direction of the cylindrical surface of the object 6 and the direction intersecting this are defined as the tangential direction has been described. It's okay.

  In addition, the second illumination system according to the first embodiment and the second illumination system according to the second embodiment may be combined to irradiate the second region with the second illumination light from different directions. Thereby, stable evaluation can be performed even with respect to the anisotropy of the foreign matters and defects existing in the second region.

  For example, a foreign object or a defect is first detected using the second illumination system of the first embodiment, and when the presence of the foreign object or defect cannot be determined by the detection, the second illumination system of the second embodiment is used. Perform rediscovery. Of course, the detection image may be acquired by simultaneously performing illumination by the second illumination system of the first embodiment and the second illumination system of the second embodiment.

  Furthermore, in the first and second embodiments, the case where an object whose surface is a cylindrical surface is inspected has been described. However, the present invention is widely applied to apparatuses for inspecting an object whose surface is a curved surface other than a cylindrical surface such as a spherical surface. can do.

The top view (A) and side view (B) of the surface inspection apparatus which are Example 1 of this invention. FIG. 3 is a diagram illustrating an object illuminated by the surface inspection apparatus according to the first embodiment. The figure which shows the principle of the surface inspection apparatus of the Example of this invention. 1 is a diagram illustrating the principle of a surface inspection apparatus according to a first embodiment. The figure which shows the irradiation angle range of the 2nd illumination light in the surface inspection apparatus of Example 1. FIG. The top view (A) and side view (B) of the surface inspection apparatus which are Example 2 of this invention. The figure which shows the object illuminated by the surface inspection apparatus of Example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Minute surface on curved surface 3 Foreign material and defect 4 Camera 5 Imaging optical axis 6 Object 7, 9 Light source 8, 10 Lens 11 1st area | region 12 2nd area | region T1, T2 Tangential direction

Claims (2)

A surface inspection apparatus for inspecting an object having a cylindrical surface,
A first illuminating means for illuminating a first region of the cylindrical surface from a direction forming a first angle smaller than 90 ° with respect to a generatrix direction of the cylindrical surface as a tangential direction of the first region; ,
A second region of the cylindrical surface that is different from the first region in the circumferential direction of the cylindrical surface is 0 ° or more and 10 ° or less with respect to a tangential direction of the second region , and Second illumination means for illuminating from a direction forming a second angle smaller than the first angle ;
The first and second regions illuminated respectively by the first and second illumination means are inclined in the normal direction of the first region and the normal direction of the second region. A surface inspection apparatus comprising: an imaging unit that simultaneously images from a direction.   The surface inspection apparatus according to claim 1, wherein a tangential direction of the second region is a generatrix direction of the cylindrical surface or a direction intersecting the generatrix direction of the cylindrical surface.