JP2014025884A - Visual inspection method and visual inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a visual inspection method and a visual inspection device that enables inspection of a fault on an entire surface of an inspected object with a simple operation.SOLUTION: A visual inspection device 1 comprises: inspected object holding means 2 for holding an inspected object 50 with a surface having a curved surface shape, so as not to interrupt irradiation of light from a lower side; a first ring illumination 3 for emitting the light to the inspected object 50 from the lower side; a second ring illumination 4 for emitting the light to the inspected object 50 from the lower side so as to have a different incident angle of the light from the first ring illumination; imaging means 5 for acquiring first imaging data for the inspected object 50 exposed to the light by the first ring illumination 3 and also acquiring second imaging data for the inspected object 50 exposed to the light by the second ring illumination 4; and a chamber 6.

Description

  The present invention relates to an appearance inspection method and an appearance inspection apparatus for inspecting an appearance shape of an inspection object having a curved surface shape, and in particular, an appearance inspection method and an appearance inspection capable of determining the appearance shape of an optical element or the like with a simple operation. Relates to the device.

  Optical elements such as lenses are manufactured by polishing optical materials or press molding, but in the manufacturing process, streaky scratches or bubble-like defects may occur on the element surface. Affects product performance. For this reason, the final product or the like is inspected for the presence or absence of the above-described defects to ensure its performance.

  Conventionally, in order to inspect the presence or absence of defects, experts have visually inspected optical products such as lenses, prisms, etc., which are inspected, and after that, visual inspection equipment that automates this has been proposed (For example, refer to Patent Document 1).

  Further, even when the test object is an optical member having a curved surface with a large curvature, an appearance inspection apparatus in which the test optical system and the imaging optical system are arranged in a predetermined relationship in order to detect foreign matter with high accuracy. Is also known (see, for example, Patent Document 2).

  Furthermore, it is a device that recognizes a defective part by irradiating light from below the inspection object, and shields unnecessary light outside the outer periphery of the inspection object, enabling transmission light of the inspection object to be imaged and improving contrast. An external appearance inspection apparatus is also known (see, for example, Patent Document 3).

JP 09-15159 A Japanese Patent No. 4886315 Japanese Patent Laid-Open No. 11-23414

  However, in the inspection using the point light source as in Patent Documents 1 and 2, since the defects on the entire surface of the optical element cannot be seen at the same time, the inspection object and the light source must be relatively moved to inspect the defects. did not become. In such a method, when inspecting one optical element, it is necessary to inspect two or more times, and the operation is complicated.

  Moreover, in patent document 3, although it is said that the presence or absence of the defect of an external appearance can be confirmed by one test | inspection, without moving a to-be-inspected object using ring-shaped illumination, depending on the property of to-be-inspected object, In some cases, the ring-shaped light source is reflected on the object to be inspected, and it becomes impossible to inspect the defect where the reflection occurs.

  Therefore, the present invention has been made to solve such problems, and in the appearance inspection of optical elements and the like, the entire surface of the object to be inspected can be easily operated without moving the object to be inspected. An object of the present invention is to provide an appearance inspection method and an appearance inspection apparatus that can inspect defects.

  According to the visual inspection method of the present invention, a first light irradiation step of irradiating a test object having a curved surface on the surface with a first ring illumination from below, and an imaging arranged above the test object. Means for acquiring imaging data of the inspection object irradiated with light by the first light irradiation process, and the first ring illumination from below to the inspection object. A second light irradiation step of irradiating light with a second ring illumination having a different incident angle of light, and imaging data of the inspection object irradiated with light in the second light irradiation step by the imaging means And a second imaging step to be acquired.

  According to another visual inspection method of the present invention, a first light irradiation step of irradiating light having a curved surface on the surface with ring illumination from below is disposed above the inspection object. The first imaging step of acquiring imaging data of the inspection object irradiated with light by the first light irradiation step by the imaging means and the ring illumination are moved upward or downward to move the first An illumination moving step for moving and arranging the light to a position different from the light irradiating step, a second light irradiating step for irradiating the inspection object with light from below with the ring illumination after the illumination moving step, and the imaging means And a second imaging step of acquiring imaging data of the inspection object irradiated with light in the second light irradiation step.

  The appearance inspection apparatus according to the present invention includes an inspection object holding means for holding an object having a curved surface on the surface so as not to prevent light irradiation from below, and light from below to the inspection object. The first ring illumination to be irradiated and the first ring illumination have a second ring illumination for irradiating light on the object to be inspected from below so that the incident angle of light is different, and the first ring illumination. Imaging means for acquiring first imaging data of an inspection object irradiated with light by illumination and second imaging data of the inspection object irradiated with light by the second ring illumination. It is characterized by.

  In addition, another appearance inspection apparatus of the present invention has an inspection object holding means for holding an object having a curved surface on the surface so as not to prevent light irradiation from below, and the inspection object. Ring illumination for irradiating light from below, illumination moving means for holding the ring illumination so as to be movable up and down, and imaging data of an object irradiated with light from the ring illumination as the imaging data by the illumination moving means. And imaging means for acquiring first imaging data before the illumination moves and second imaging data after the illumination moves.

  According to the appearance inspection method and the appearance inspection apparatus of the present invention, the appearance shape of the object to be inspected can be inspected with a simple operation and efficiently. In particular, even if the object to be inspected is an optical element and ring illumination is reflected, it can be processed so as not to be affected by the reflection, and the appearance of the entire optical element can be grasped.・ Defects can be determined quickly.

It is a schematic block diagram of the external appearance inspection apparatus which is one Embodiment of this invention. It is the figure which showed an example of the 1st imaging data. It is the figure which showed an example of the 2nd imaging data. It is the figure which showed an example of the data for determination produced from 1st imaging data and 2nd imaging data. It is the figure which showed the origin of the data used when creating the data for determination of FIG. 2C. It is a schematic block diagram of the external appearance inspection apparatus which is other embodiment of this invention.

Hereinafter, the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram showing a schematic configuration of an appearance inspection apparatus according to an embodiment of the present invention. The inspection object holding means and the chamber are shown as sectional views.

  The appearance inspection apparatus 1 shown in FIG. 1 applies light to the inspection object 50 from below and the inspection object holding means 2 that holds the inspection object 50 so as not to prevent light irradiation from below. The first ring illumination 3 to be irradiated and the first ring illumination 3 have a second ring illumination 4 that irradiates the object 50 with light from below, and the first ring illumination 3 so that the incident angle of light is different. Consists of an imaging means 5 for individually acquiring imaging data of the inspection object 50 irradiated with light by the ring illumination 3 and the second ring illumination 4, and a chamber 6 for housing each of the members therein. Is done.

  The inspection object holding means 2 in the present invention is a member that holds the inspection object 50 that is an inspection object, and holds the inspection object portion of the inspection object 50 so that irradiation of inspection light is not hindered. . That is, the inspection object holding means 2 has a shape in which light to be irradiated from ring illumination described later is sufficiently irradiated to the inspection object 50. For example, when the object to be inspected 50 is an optical element such as a lens, a shape that does not hinder the light of the ring illumination is set within the effective diameter so that at least the effective diameter of the optical element can be inspected.

  Although FIG. 1 shows a structure that supports the outer edge portion of the inspection object 50 from below, the holding mechanism is not limited to this as long as light irradiation is not hindered. This holding container may be formed by using a transparent material having excellent light transmittance in order to ensure the irradiation of light to the object to be inspected. It is preferable to use a light-impermeable member outside the outer shape of the object to be inspected so that unnecessary light is not mixed into the inspection data.

  Here, examples of the inspection object 50 include those having a curved surface on the surface, and in particular, an optical element, a preform immediately before being molded into the optical element, and the like. In the case of an optical element or the like, the shape of each of biconvex, biconcave, planoconvex, planoconcave, convex meniscus, and concave meniscus can be inspected.

  In addition, an optical element particularly suitable in the present invention is preferably an optical element in which illumination is easily reflected on the inspection object in an inspection by ring illumination, for example, an optical element having a focal length of 10 to 80 mm. In this way, when the focal length is short, there is often a reflection due to the irradiation of the ring illumination, but in the present invention, even if the reflection occurs, the surface shape of the object to be inspected with a simple operation, Accurately grasp.

  The first ring illumination 3 according to the present invention irradiates the inspection object 50 with ring-shaped light from below. Moreover, the 2nd ring illumination 4 in this invention irradiates ring-shaped light with respect to the to-be-inspected object 50 from the downward direction similarly to the 1st ring illumination 4. FIG. These ring illuminations 3 and 4 are arranged so that the incident angles of light to the inspection object are different, and their relationship is not particularly limited as long as the inspection object 50 can be irradiated with light properly. That is, when irradiating the inspection object 50 with light, the ring illuminations 3 and 4 may be arranged such that they are not interfered with each other by the other ring illumination main bodies (light irradiation is not hindered). Further, in order to prevent the light irradiation from interfering and to make the inspection efficient, the center of the inspection object 50 and the center of the ring of the ring illuminations 3 and 4 may be arranged in the vertical direction. The center of the device should also be aligned vertically.

  These ring illuminations only need to be able to irradiate ring-shaped light upward. -4 (above, trade name, manufactured by ITEC System Co., Ltd.) and the like. These commercially available ring lights use LEDs as a light source, and the irradiated light has a predetermined irradiation angle and a predetermined diffusion angle. Other than that, since light is not irradiated, generation | occurrence | production of the noise of a measurement etc. can be reduced and it is preferable.

  Moreover, it is preferable that the first ring illumination and the second ring illumination each have a diameter larger than the diameter of the inspection object 50 to be inspected. With such a large diameter, in the inspection based on dark field illumination as in the present invention, light that becomes noise can be reduced, and an efficient inspection is possible.

  Furthermore, as shown in FIG. 1, when considering the case where the first ring illumination 3 is placed on the lower side and the second ring illumination 4 is placed on the upper side, the respective irradiation lights can reach the inspected object 50 sufficiently. To achieve this, the diameters of the first and second ring illuminations are both larger than the effective diameter of the object to be inspected 50, and the diameter of the second ring illumination is larger than that of the first ring illumination. A large relationship is preferable. When this relationship is satisfied, there is no possibility that the irradiation light from the first ring illumination 3 is blocked by the second ring illumination 4.

  And as for the 1st ring illumination 3 used here, the diameter is 20-60 mm, for example, and 30-55 mm is more preferable. For example, the diameter of the second ring illumination 4 is preferably 90 to 150 mm, and more preferably 100 to 130 mm.

  The first ring illumination 3 and the second ring illumination 4 are arranged so as to irradiate the inspection target surface of the inspection object 50 with light. However, if the position of the ring illumination and the position of the inspection object 50 are too far, it is impossible to irradiate a sufficient amount of light, and if it is too close, it is difficult to irradiate light within the effective diameter, or a sufficient amount of light is secured for inspection. It becomes impossible. Therefore, the arrangement position of the ring illumination is preferably 10 to 50 mm downward from the upper end of the inspection object 50 for the first ring illumination 3, and 10 to 20 mm downward from the upper end of the inspection object 50 for the second ring illumination 4. . Furthermore, if the first ring illumination 3 and the second ring illumination 4 are in a range of ± 40 mm from the focus of the object to be inspected 50, further defects and appearance defects (such as scratches) inside the lens are clearly displayed. Preferably, ± 30 mm is more preferable, and ± 20 mm is particularly preferable.

  More specifically, for example, when the inspection object 50 is an optical element and has a biconvex shape with a refractive index of 1.5 to 1.6 and a focal length of 37 to 45 mm, 40 to 60 mm. The first ring illumination 3 having a diameter of 20 to 40 mm below the upper end of the inspection object 50 and the second ring illumination 4 having a diameter of 100 to 130 mm from the upper end of the inspection object 50 are 10. Place 20 mm below. At this time, the first ring illumination 3 and the second ring illumination 4 are arranged 10 to 40 mm apart in the height direction. Here, the radius of curvature of the front surface represents the radius of curvature of the inspection object 50 on the ring illumination side, and the radius of curvature of the rear surface represents the radius of curvature of the opposite surface (imaging means side).

  As another specific condition, for example, when the inspection object 50 is an optical element and has a concave meniscus shape with a refractive index of 1.8 to 1.9 and a focal length of 33 to 37 mm. The first ring illumination 3 having a diameter of 25 to 35 mm is disposed 25 to 35 mm below the upper end of the inspection object 50, and the second ring illumination 4 having a diameter of 90 to 110 mm is disposed on the inspection object 50. It arrange | positions 10-20 mm below from the upper end of. At this time, the 1st ring illumination 3 and the 2nd ring illumination 4 are arrange | positioned 10-20 mm apart in the height direction.

  The image pickup means 5 in the present invention is arranged above the object to be inspected 50, and only needs to be able to take an image of the object under inspection 50 irradiated with light by ring illumination, and a known image pickup means may be used. Examples of the imaging unit 5 include a CCD camera and a C-MOS camera. Further, the imaging means 5 is connected to a storage means for storing captured image data, and the data is accumulated so that the stored data can be called as appropriate and compared with other data.

  Then, based on the imaging data obtained by the imaging means 5, it is determined whether or not there is a defect that causes a shape defect on the surface of the inspection object 50. Judgment of defects of this shape defect can be made by displaying the imaging data on a display or printing it on paper, or by a skilled person to make a visual decision, or by making full use of computing means or image processing by a computer, The imaging data may be processed to create data for determining the surface shape of the object to be inspected, and the surface shape may be determined by automating the presence or absence of defects and the detection of the shape of the defects from the determination data.

  The chamber 6 in the present invention is a housing that prevents external light sources other than the ring illumination from affecting the inspection result so that the inspection by the dark field illumination of the present invention can be performed smoothly. That is, the chamber 6 is a member that accommodates each of the above-described members and blocks external light from reaching the inside of the apparatus.

Next, an appearance inspection method using the appearance inspection apparatus 1 will be described.
First, the inspection object 50 to be inspected is arranged at a predetermined position of the inspection object holding means 2. At this time, attention should be paid so that the surface to be inspected of the inspection object 50 is sufficiently irradiated with light and the irradiation is not hindered by the inspection object holding means 2.

  Next, the object 50 is irradiated with light from below by the first ring illumination 3. The inspected object 50 irradiated with light is photographed and stored by the imaging means 5 from above and used as first imaging data. When the first imaging data is obtained, the irradiation of light from the first ring illumination 3 is stopped.

  Subsequently, the object 50 is irradiated with light by the second ring illumination 4 from below. The inspection object 50 irradiated with light is photographed and stored by the imaging means 5 from above and used as second imaging data. When the second imaging data is obtained, the irradiation of light from the second ring illumination 4 is stopped.

  The obtained first imaging data and second imaging data are compared, and the magnitude of the reflection of the ring illumination in each imaging data is confirmed and compared. Here, the first ring illumination 3 and the second ring illumination 4 are arranged so that the incident angles of the light to the inspection object 50 are different as described above, so that they are reflected on the inspection object 50. If this occurs, the size will be different. The reflection is formed in an annular shape on the surface of the inspection object 50, and from the imaging data with the larger reflection, the inner portion that is not affected by the reflection is taken from the imaging data with the smaller reflection. From the outside, the outer part that is not affected by the reflection is the inspection target.

  Two pieces of imaging data of the corresponding part to be inspected are combined to create determination data. This determination data is obtained by removing the reflection as described above, and the entire surface of the inspection object 50 is not reflected by the synthesis.

  For example, when the image obtained as the first imaging data is FIG. 2A and the image obtained as the second imaging data is FIG. 2B, the determination data is created as follows.

  First, the magnitude of the ring illumination in FIG. 2A and FIG. 2B will be compared. Here, FIG. 2A is a small reflection and FIG. 2B is a large reflection (in both drawings, the outer white circle is due to scattered light from the outer edge portion of the optical element that is the object to be inspected). Then, the inside of the reflection is extracted from the imaging data of FIG. 2B having a large reflection, and the outside of the reflection is extracted from the imaging data of FIG.

  The determination data obtained by the synthesis is shown in FIG. 2C. In FIG. 2C, image portions that are affected by the reflection are excluded, and the data on the entire surface are extracted from FIGS. 2A and 2B without omission and combined. In FIG. 2C, the origin of the image data is shown in FIG. 2D. Here, the region 2b derived from FIG. 2B is represented by a diagonal line of −45 degrees, and the region 2a derived from FIG. 2A is represented by +45 degrees. Represented by diagonal lines. The grid-like area 2c shown in the middle part represents the overlapping part between 2a and 2b. In this way, the data is extracted and synthesized so as to have the overlapping area, and the surface shape data without leakage is created. it can.

  With respect to the determination data obtained in this way, the presence or absence of scratches or dot-like defects in the surface shape is determined. This determination may be a visual determination by a skilled person, or data may be automatically determined by image processing. In the case of image processing, it is easy to recognize the shape of the defect by, for example, coloring the portion where the defect exists, and if this is displayed on a display or the like, the presence or absence of the defect and the shape of the defect depend on the skill level. Therefore, it can be understood immediately and the quality of the inspection object 50 can be easily determined. Further, it may be determined whether the inspection object 50 is good or bad only by automatic determination by image processing of the obtained determination data.

  In the above description, the flow of determining the presence / absence of a defect and the shape after creating determination data has been described. However, the presence / absence of a defect in each of the inspection target areas of the first imaging data and the second imaging data is described. The shape may be determined, and the image after the determination may be synthesized so that the determination result of the entire surface can be understood.

  In addition, the above describes the case where the reflection of illumination occurs in the imaging data, but when the reflection does not occur and the imaging data can be used for shape evaluation, The data synthesis step may be omitted.

(Second Embodiment)
FIG. 3 is a diagram showing a schematic configuration of an appearance inspection apparatus according to another embodiment of the present invention.
The appearance inspection apparatus 11 shown in FIG. 3 has an inspection object holding means 2 that holds the inspection object 50 so as not to interfere with light irradiation to the effective diameter, and the inspection object 50 from below. Ring illumination 13 for irradiating ring-shaped light, illumination moving means 14 for moving the ring illumination 13 up and down, and imaging means for acquiring imaging data of the inspection object 50 irradiated with ring-shaped light by the ring illumination 13 15 and a chamber 16.

  The appearance inspection apparatus 11 shown here is different in that only one ring illumination is provided and that the ring illumination can be moved up and down, and other configurations are the appearance inspection described in the first embodiment. Same as device 1. That is, the inspection object holding means 12, the imaging means 15, and the chamber 16 are the same as the inspection object holding means 2, the imaging means 5, and the chamber 6, respectively. Therefore, in the present embodiment, only differences will be described.

  The ring illumination 13 is basically the same as that in the first embodiment, and irradiates the inspection object 50 with ring-shaped light from below. Here, since the height of the ring illumination 13 is changed and used when acquiring the first imaging data and the second imaging data, the diameter of the ring illumination 13 is 20 to 60 mm from such a viewpoint. Preferably, 30 to 55 mm is more preferable.

  The illumination moving means 14 moves the ring illumination 13 up and down to change the height so that the relative position between the inspection object 50 and the ring illumination 13 can be changed.

  At this time, it is preferable that the distance between the ring illumination 13 and the inspection object 50 can be moved between 10 to 60 mm by the illumination moving means 14. The distance here also represents the distance between the upper end portion of the inspection object 50 and the light irradiation portion of the ring illumination 13.

  The illumination moving means 14 is not particularly limited as long as it is a member having a mechanism that can move the ring illumination 13 to a desired position. For example, an arm that can hold the ring illumination 13 and a drive that moves the arm up and down. The thing which has a mechanism is mentioned.

  In the present embodiment, the ring illumination 13 is moved to a predetermined position. Here, the object 50 is irradiated with light from below, and the first imaging data is acquired by the imaging means 15. Next, the ring illumination 13 is moved by the illumination moving means 14 to change the height. Here, the object 50 is irradiated with light from below, and second imaging data is acquired by the imaging means 15.

  At this time, the position of the ring illumination 13 at the time of acquiring the first imaging data and the second imaging data is to move the distance by which the magnitude of the reflection of the ring illumination changes significantly. Considering the irradiation distance of light to the inspection object 50, the moving distance in the height direction is preferably 30 to 50 mm, and more preferably 35 to 40 mm.

  By the way, in this embodiment, the magnitude of the reflection changes depending on the distance between the ring illumination and the object to be inspected, but the relationship is the one where the distance is shorter in the type where light is condensed like a biconvex lens. However, when the distance increases, the reflection tends to decrease.On the other hand, in the type where light diverges, such as a biconcave lens, the closer the distance, the smaller the reflection. There is a tendency for reflection to become larger in the far side.

  The processing of the obtained imaging data may be performed in the same manner as in the first embodiment. That is, determination data is created, and based on the determination data, the presence / absence or shape of the defect is determined in the surface shape of the inspection object 50, or the defect is determined from the first and second imaging data. The presence / absence, shape, and the like are determined, and these results may be synthesized later to obtain the determination result for the entire surface.

Hereinafter, the present invention will be described in more detail with reference to Examples (Examples 1 to 2).
(Example 1)
Using the appearance inspection apparatus of FIG. 1, the surface shape of the optical element was inspected as follows.
The inspection object holding container used in this example is made of aluminum having a 10 mm plate with a through hole smaller than the diameter of the inspection object and subjected to black alumite treatment on the surface, and an optical element as the inspection object is predetermined. A hole with a diameter of 22 mm smaller than the diameter of the object to be inspected is opened at the center so that light from below can be transmitted through the optical element without being blocked by the holding container. ing.

In addition, below the object-holding container, a first ring illumination (product name: URG31-1000S) and a second ring illumination (product name: TRL100 × 52−, made by UTEC Co., Ltd.) are provided. 12W-4) are arranged and fixed so as to be 20 mm and 35 mm from the upper part of the inspection object of the inspection object holding container, respectively.
Further, as an image pickup means, a CCD camera (product name: CM-200MCL, manufactured by JAI) is 150 mm from the position of the upper surface of the inspection object holding container to the tip of the lens of the CCD camera above the inspection object holding container. Are arranged as follows.

A concave meniscus lens (diameter: 23.5 mm, effective diameter: 22 mm, front radius of curvature: 10 × 10 ¹⁰ mm, rear radius of curvature: −30 mm, refractive index: 1.85025, focal length: 35.2 mm). In addition, the curvature radius represented the convex surface as + and the concave surface as-in both the front surface and the rear surface.

Here, the front radius of curvature represents the radius of curvature of the optical surface on the ring illumination side, and the rear radius of curvature represents the radius of curvature of the optical surface on the CCD side. The focal length is L1, L1 = 1 / ((n-1) / (1 / r1-1 / r2)) where r1 is the front curvature radius, r2 is the rear curvature radius, and n is the refractive index. It is a value calculated by an approximate expression.

First, light was irradiated from below the object to be inspected by the first ring illumination, and image data of the object to be inspected that was irradiated with light by the image pickup means was acquired as first image data. Next, the first ring illumination is turned off, light is irradiated from below the object to be inspected by the second ring illumination, and the image data of the object to be inspected irradiated by the imaging means is used as the second image data. I got it.
For the obtained first and second imaging data, the magnitude of the reflection is judged, and from the second imaging data with a large reflection, the inner part of the reflection is the first imaging with a small reflection. From the data, the outside part of the reflection was extracted, and the extracted image data was synthesized to create determination data.

Furthermore, from the determination data, the portion where light is diffusely reflected and whitened is colored by image processing to make it stand out. In the image processing data obtained at this time, a dotted colored portion, a linear colored portion or the like was recognized as a defect, and the presence or absence, shape, etc. could be confirmed. Thereby, it is possible to determine whether the inspection object is good or bad in the presence of the defect.
Note that when the position of the ring illumination with respect to the object to be inspected was changed and examined together with the acquisition status of the imaging data, the first ring illumination position was set to 35, 40, and 45 mm as well. Imaging data was obtained.

(Example 2)
Using the appearance inspection apparatus of FIG. 1, the surface shape of the optical element was inspected as follows.
The inspection object holding container used in this example is made of aluminum having a 10 mm plate with a through hole smaller than the diameter of the inspection object and subjected to black alumite treatment on the surface, and an optical element as the inspection object is predetermined. A hole having a diameter of 28 mm smaller than the diameter of the object to be inspected is opened at the center so that light from below can be transmitted through the optical element without being blocked by the holding container.

In addition, below the inspected object holding container, a first ring illumination (product name: URG53-1000S, manufactured by U Technology Co., Ltd.) and a second ring illumination (product name: TRL125 × 77-, manufactured by ITEC System, Inc.). 12W-4) are arranged and fixed so as to be 21 mm and 36 mm from the upper part of the inspection object, respectively.
Further, as an image pickup means, a CCD camera (product name: CM-200MCL, manufactured by JAI) is 150 mm from the position of the upper surface of the inspection object holding container to the tip of the lens of the CCD camera above the inspection object holding container. Are arranged as follows.

A biconvex lens (diameter: 29.5 mm, effective diameter: 28 mm, front radius of curvature: 147.068 mm, rear radius of curvature: 26.294021 mm as an inspected object is placed on the inspected object holding container of the appearance inspection apparatus having such a configuration. , Refractive index: 1.58913, focal length: 37.8 mm).
Here, the front radius of curvature represents the radius of curvature of the optical surface on the ring illumination side, and the rear radius of curvature represents the radius of curvature of the optical surface on the CCD side. The focal length is L1, L1 = 1 / ((n-1) / (1 / r1-1 / r2)) where r1 is the front curvature radius, r2 is the rear curvature radius, and n is the refractive index. It is a value calculated by an approximate expression.

First, light was irradiated from below the object to be inspected by the first ring illumination, and image data of the object to be inspected that was irradiated with light by the image pickup means was acquired as first image data. Next, the first ring illumination is turned off, light is irradiated from below the object to be inspected by the second ring illumination, and the image data of the object to be inspected irradiated by the imaging means is used as the second image data. I got it.
For the obtained first and second imaging data, the magnitude of the reflection is judged, and from the second imaging data with a large reflection, the inner part of the reflection is the first imaging with a small reflection. From the data, the outside part of the reflection was extracted, and the extracted image data was synthesized to create determination data.

Furthermore, from the determination data, the portion where light is diffusely reflected and whitened is colored by image processing to make it stand out. In the image processing data obtained at this time, a dotted colored portion, a linear colored portion or the like was recognized as a defect, and the presence or absence, shape, etc. could be confirmed. Thereby, it is possible to determine whether the inspection object is good or bad in the presence of the defect.
As in Example 1, when the position of the ring illumination with respect to the object to be inspected was changed and the imaging data acquisition situation was examined, the position of the first ring illumination position was set to 20, 35, and 40 mm. Appropriate imaging data was also obtained.

  From the above, the appearance inspection apparatus and the appearance inspection method of the present invention do not need to change the inspection object and the position of the illumination many times even when the surface state of the inspection object is reflected. The surface condition can be evaluated stably with a simple operation.

  The appearance inspection method and the appearance inspection apparatus of the present invention are useful for evaluating the presence / absence, shape, etc. of defects in the surface shape of a light-transmitting product other than optical elements.

DESCRIPTION OF SYMBOLS 1 ... Appearance inspection apparatus, 2 ... Inspection object holding container, 3 ... 1st ring illumination, 4 ... 2nd ring illumination, 5 ... Imaging means, 6 ... Chamber, 50 ... Glass material

Claims (11)

A first light irradiating step of irradiating light from below with a first ring illumination on an inspection object having a curved surface shape on the surface;
A first imaging step of acquiring imaging data of the inspection object irradiated with light by the first light irradiation step by an imaging means disposed above the inspection object;
A second light irradiating step of irradiating the inspection object with light from below with a second ring illumination having a light incident angle different from that of the first ring illumination;
A second imaging step of acquiring imaging data of the inspection object irradiated with light by the second light irradiation step by the imaging means;
A visual inspection method characterized by comprising: A first light irradiating step of irradiating light having a curved shape on the surface with ring illumination from below;
A first imaging step of acquiring imaging data of the inspection object irradiated with light by the first light irradiation step by an imaging means disposed above the inspection object;
An illumination movement step of moving the ring illumination upward or downward to move to a position different from the first light irradiation step; and
After the illumination moving step, a second light irradiation step of irradiating the inspection object with light from below with the ring illumination;
A second imaging step of acquiring imaging data of the inspection object irradiated with light by the second light irradiation step by the imaging means;
A visual inspection method characterized by comprising:   Further, the magnitude of the reflection of the ring illumination is compared from the imaging data obtained in the first imaging step and the second imaging step, and in the imaging data with a small reflection, the data outside the reflection is The visual inspection according to claim 1, further comprising a step of creating determination data representing the surface state of the entire surface of the object to be inspected for each of the data inside the reflection in the imaging data having a large reflection of the illumination. Method.   The appearance inspection method according to claim 3, further comprising a surface shape determination step of determining presence / absence and shape of a defect of a surface shape of the inspection object from the determination data.   The inspection object is an optical element, and the position of the first ring illumination and the second ring illumination or the position before and after the illumination movement process of the ring illumination is within a range of ± 40 mm from the focus of the inspection object. The visual inspection method according to any one of claims 1 to 4. An inspection object holding means for holding an object having a curved surface on the surface so as not to prevent light irradiation from below,
A first ring illumination that irradiates the inspection object with light from below;
A second ring illumination that irradiates the inspection object with light from below so that an incident angle of light is different from that of the first ring illumination;
Imaging means for acquiring first imaging data of an inspection object irradiated with light by the first ring illumination and second imaging data of an inspection object irradiated with light by the second ring illumination When,
An appearance inspection apparatus characterized by comprising: An inspection object holding means for holding an object having a curved surface on the surface so as not to prevent light irradiation from below,
Ring illumination for irradiating light on the object to be inspected from below;
Illumination moving means for holding the ring illumination in a vertically movable manner;
Imaging for acquiring first imaging data before moving the ring illumination and second imaging data after moving as the imaging data of the object irradiated with light by the ring illumination. Means,
An appearance inspection apparatus characterized by comprising:   Further, the magnitude of the reflection of the ring illumination is compared from the first imaging data and the second imaging data, and in the imaging data with a small reflection, the data outside the reflection is compared with the imaging data with a large reflection. 8. An appearance inspection apparatus according to claim 6 or 7, further comprising determination data creating means for creating data for determination representing the surface condition of the entire surface of the object to be inspected, with the data inside the reflection being the object of inspection.   The appearance inspection apparatus according to claim 8, further comprising surface shape determination means for determining presence / absence and shape of a defect of a surface shape of the inspection object from the determination data.   The appearance inspection apparatus according to any one of claims 6 to 9, wherein a diameter of the first ring illumination and a second ring illumination or the ring illumination is larger than an effective diameter of the inspection object.   The appearance inspection apparatus according to claim 10, wherein a diameter of the first ring illumination is smaller than a diameter of the second ring illumination.

Images