JP7516201B2 - Inspection Equipment - Google Patents

Description

An embodiment of the present invention relates to an inspection device.

Many mass-produced products undergo visual inspection before shipping. In particular, for small, round samples such as screw heads and bottle mouths, it is preferable to inspect the sample from above in order to simplify and miniaturize the inspection equipment.

Such inspection equipment captures images of the sample from all sides at an angle, extracts the area of the surface to be inspected from the acquired images, and inspects for defects, etc. through image processing. In inspections performed in this way, it is important to reduce the load of image processing and speed up the inspection.

Petr Zavyalov, "3D Hole Inspection Using Lens with High Field Curvature", Measurement Science Review. Vol.15, No.1 (2015).

The problem that this invention aims to solve is to provide an inspection device that reduces the load of image processing.

The inspection device of the embodiment includes a double-telecentric optical system, an imaging element on which an optical image of a sample is formed by the double-telecentric optical system, a first mirror having a plurality of reflective surfaces arranged inwardly around the optical axis of the double-telecentric optical system and reflecting a plurality of light beams emitted from the sample at an angle to the optical axis, and a second mirror having a plurality of reflective surfaces arranged inwardly around the optical axis and reflecting the light beams and directing them to the imaging element at an angle to the optical axis. The reflective surfaces of the first mirror and the reflective surfaces of the second mirror are arranged in a relative positional relationship in which the chief ray emitted from the surface to be inspected of the sample and the chief ray incident on the imaging element are symmetrical.

FIG. 1 is a diagram showing an inspection device according to an embodiment. FIG. 2 is a diagram showing an inspection optical system in the inspection apparatus according to the embodiment. FIG. 3 is a diagram showing an inspection optical system in an inspection device according to a comparative example. FIG. 4 is a conceptual diagram of a double-telecentric optical system. FIG. 5 is a perspective view showing a schematic configuration example of a regular octagonal cylindrical mirror. FIG. 6 is a perspective view showing a schematic configuration example of a regular octagonal pyramid mirror. FIG. 7 is a diagram showing the movement of the chief ray with respect to the positional displacement of the sample. FIG. 8 is a diagram showing the movement of the incident position on the light receiving surface of the image sensor relative to the movement of the chief ray. FIG. 9 is a diagram showing an image acquired by the inspection optical system according to the embodiment shown in FIG. 2 for a sample whose center is located on the optical axis. FIG. 10 illustrates an image acquired by the inspection optics according to the embodiment shown in FIG. 2 for a sample that is off-center from the optical axis. FIG. 11 is a diagram in which the image depicted by the two-dot chain line in FIG. 10 has been shifted in accordance with the deviation of the sample from the optical axis. FIG. 12 is a diagram showing an image acquired by the inspection optical system according to the comparative example shown in FIG. 3 for a sample whose center is located on the optical axis. FIG. 13 is a diagram showing an image acquired by the inspection optical system according to the comparative example shown in FIG. 3 for a sample whose center is offset from the optical axis. FIG. 14 is a diagram in which the image depicted by the two-dot chain line in FIG. 13 has been moved in accordance with the deviation of the sample from the optical axis.

The inspection device according to the embodiment will be described below with reference to the drawings. In the drawings, the same components are indicated with the same reference symbols, and repeated explanations will be omitted. The drawings are schematic or conceptual.

FIG. 1 is a diagram showing an inspection apparatus 10 according to an embodiment. The inspection apparatus 10 inspects a sample S. For example, the inspection apparatus 10 inspects the sample S for defects. The inspection apparatus 10 inspects the inspection target surface of the sample S for defects. The inspection target surface of the sample S is the side surface Sa of the sample S. The defects include scratches, chips, stains, discoloration, attachment of foreign matter, etc.

The inspection device 10 includes an inspection optical system 20, an image processing unit 60, a judgment unit 70, a display unit 80, and a conveyor 90.

The conveyor 90 has, for example, an endless belt 92 and a pair of drive rollers 94 that rotate the endless belt 92. The conveyor 90 transports the sample S placed on the endless belt 92.

The inspection optical system 20 is disposed above the conveyor 90. The inspection optical system 20 captures an image of a specific imaging area on the conveyor 90 from all sides at an angle to obtain an image. When the sample S is positioned on the lower conveyor 90, the inspection optical system 20 captures an image of the sample S from all sides at an angle.

The image processing unit 60 cuts out an image of the area of the surface of the sample S to be inspected from the image of the sample S captured by the inspection optical system 20. The image processing unit 60 also supplies the cut-out image to the judgment unit 70.

The determination unit 70 determines whether or not there is a defect in the image of the area of the surface to be inspected that is supplied from the image processing unit 60. For example, the determination unit 70 determines whether or not there is a defect using an image processing technique that utilizes AI. The determination unit 70 also supplies the determination result to the display unit 80.

The display unit 80 displays the presence or absence of defects on the inspection target surface of the sample S according to the judgment result supplied from the judgment unit 70.

Next, the inspection optical system 20 in the inspection device 10 will be described in detail with reference to FIG. 2. FIG. 2 is a diagram showing the inspection optical system 20.

The inspection optical system 20 includes an illuminator 22, a first mirror unit MU1, a bilateral telecentric optical system TOS, a second mirror unit MU2, and an image sensor 38.

The illuminator 22 is disposed near the endless belt 92 that transports the sample S. The first mirror unit MU1 is disposed between the endless belt 92 and the double-telecentric optical system TOS. The image sensor 38 is disposed on the optical axis A of the double-telecentric optical system TOS. The second mirror unit MU2 is disposed between the double-telecentric optical system TOS and the image sensor 38.

The illuminator 22 illuminates an imaging area on the endless belt 92 that extends around the optical axis A of the double-telecentric optical system TOS. When the sample S is located within the imaging area, the illuminator 22 illuminates the sample S. For example, the illuminator 22 includes a ring-type illuminator. The ring-type illuminator illuminates the sample S located on the optical axis A, for example, evenly from all around. The illumination light irradiated to the sample S is reflected or scattered by the sample S.

The double-telecentric optical system TOS forms an optical image of an object present within the imaging region. When a sample S is positioned within the imaging region, the double-telecentric optical system TOS forms an optical image of the sample S.

The image sensor 38 has a light receiving surface 38a that receives light. An optical image is formed on the light receiving surface 38a by a double telecentric optical system TOS. The image sensor 38 generates an image by converting an optical image of an object present in the imaging area into an electrical signal of a corresponding image. When a sample S is located in the imaging area, the image sensor 38 generates an image of the sample S.

The first mirror unit MU1 reflects the incident light beam parallel to the optical axis A of the double-telecentric optical system TOS and guides it to the double-telecentric optical system TOS. The second mirror unit MU2 reflects the light beam that has passed through the double-telecentric optical system TOS at an angle to the optical axis A of the double-telecentric optical system TOS and guides it to the image sensor 38.

The double-telecentric optical system TOS includes an objective lens 28, an imaging lens 32, and an aperture stop 30. The objective lens 28, the imaging lens 32, and the aperture stop 30 are arranged coaxially. In other words, the objective lens 28, the imaging lens 32, and the aperture stop 30 are all rotational or rotationally symmetric bodies with the optical axis A as their central axis. The central axes of the objective lens 28, the imaging lens 32, and the aperture stop 30 coincide with the optical axis A.

The objective lens 28 and the imaging lens 32 are positioned so that their focal points coincide. The aperture stop 30 is positioned at the focal point of the objective lens 28 and the imaging lens 32. The aperture stop 30 adjusts the beam diameter of the light passing through.

The first mirror unit MU1 includes a primary mirror (first mirror) 24 and a secondary mirror (third mirror) 26. The second mirror unit MU2 includes a primary mirror (fourth mirror) 34 and a secondary mirror (second mirror) 36.

On the path of light from the imaging area through the bilateral telecentric optical system TOS to the imaging element 38, the primary mirror 24 is located between the imaging area and the bilateral telecentric optical system TOS, the secondary mirror 26 is located between the primary mirror 24 and the bilateral telecentric optical system TOS, the primary mirror 34 is located between the bilateral telecentric optical system TOS and the imaging element 38, and the secondary mirror 36 is located between the primary mirror 34 and the imaging element 38.

The primary mirror 24 has multiple reflective surfaces arranged inwardly around the optical axis A of the double-telecentric optical system TOS. The secondary mirror 26 has multiple reflective surfaces arranged outwardly around the optical axis A of the double-telecentric optical system TOS. The primary mirror 34 has multiple reflective surfaces arranged outwardly around the optical axis A of the double-telecentric optical system TOS. The secondary mirror 36 has multiple reflective surfaces arranged inwardly around the optical axis A of the double-telecentric optical system TOS.

The primary mirror 24, the secondary mirror 26, the primary mirror 34, and the secondary mirror 36 are arranged coaxially on the optical axis A of the double-telecentric optical system TOS.

The multiple reflective surfaces of the primary mirror 24, the multiple reflective surfaces of the secondary mirror 26, the multiple reflective surfaces of the primary mirror 34, and the multiple reflective surfaces of the secondary mirror 36 are the same in number and correspond to each other. That is, a light beam reflected by one reflective surface of the primary mirror 24 is then reflected by one corresponding reflective surface of the secondary mirror 26, then reflected by one corresponding reflective surface of the primary mirror 34, and then reflected by one corresponding reflective surface of the secondary mirror 36.

For example, the primary mirror 24 comprises a regular octagonal cylindrical mirror having a reflective surface on the inner circumferential surface, the secondary mirror 26 comprises a regular octagonal pyramid mirror having a reflective surface on the outer circumferential surface, the primary mirror 34 comprises a regular octagonal pyramid mirror having a reflective surface on the outer circumferential surface, and the secondary mirror 36 comprises a regular octagonal cylindrical mirror having a reflective surface on the inner circumferential surface.

The inner diameter of the regular octagonal cylindrical mirror of the primary mirror 24 is larger than the outer diameter of the sample S. The outer diameter of the regular octagonal pyramid mirror of the secondary mirror 26 is smaller than the inner diameter of the regular octagonal cylindrical mirror of the primary mirror 24. The outer diameter of the regular octagonal pyramid mirror of the primary mirror 34 is smaller than the inner diameter of the regular octagonal cylindrical mirror of the secondary mirror 36. The inner diameter of the regular octagonal cylindrical mirror of the secondary mirror 36 is larger than the outer dimensions of the image sensor 38. For example, in projection onto a plane perpendicular to the optical axis A, the secondary mirror 26 is located inside the primary mirror 24, and the primary mirror 34 and the image sensor 38 are located inside the secondary mirror 36.

Figure 5 shows an example of the configuration of a regular octagonal cylindrical mirror. As shown in Figure 5, the regular octagonal cylindrical mirror has a cylindrical exterior shape with a regular octagonal through hole, the primary mirror (first mirror) 24 has a reflective surface 24a on its inner circumferential surface, and the secondary mirror (second mirror) 36 has a reflective surface 36a on its inner circumferential surface.

Figure 6 shows an example of the configuration of a regular octagonal pyramid mirror. As shown in Figure 6, the regular octagonal pyramid mirror has an external shape of a regular octagonal pyramid, the secondary mirror (third mirror) 26 has a reflective surface 26a on the outer circumferential surface, and the primary mirror (fourth mirror) 34 has a reflective surface 34a on the outer circumferential surface.

The number of reflective surfaces of the primary mirror 24, secondary mirror 26, primary mirror 34, and secondary mirror 36 is not limited to this. The primary mirror 24, secondary mirror 26, primary mirror 34, and secondary mirror 36 may have an appropriate number of reflective surfaces surrounding the optical axis A of the double-telecentric optical system TOS. In other words, the primary mirror 24 and secondary mirror 36 may comprise regular polygonal cylindrical mirrors, and the secondary mirror 26 and primary mirror 34 may comprise regular polygonal pyramid mirrors.

For the sake of convenience, the following description will be given assuming that the sample S is located within the imaging region. In other words, the description will be given assuming that the sample S exists on the optical axis A of the double-telecentric optical system TOS. Also, consider a collection of light rays, i.e., a light beam, that are reflected in order by the primary mirror 24, the secondary mirror 26, the primary mirror 34, and the secondary mirror 36. In other words, the light rays from the sample S include light rays that do not enter the primary mirror 24 and light rays that deviate along the way and do not reach the imaging element 38, but such light rays will not be taken into consideration.

The illumination light irradiated from the illuminator 22 to the sample S is reflected or scattered by the sample S. A part of the light reflected or scattered by the sample S is incident on the primary mirror 24. The primary mirror 24 reflects the light beam incident obliquely to the optical axis inward and guides it to the secondary mirror 26. The secondary mirror 26 reflects the light beam reflected by the primary mirror 24 parallel to the optical axis A of the double-telecentric optical system TOS and guides it to the double-telecentric optical system TOS. The light beam passing through the double-telecentric optical system TOS is incident on the primary mirror 34. The primary mirror 34 reflects the incident light beam outward and guides it to the secondary mirror 36. The secondary mirror 36 reflects the light beam reflected by the primary mirror 34 inward and guides it obliquely to the optical axis to the image sensor 38. An optical image of the sample S is formed on the light receiving surface 38a of the image sensor 38.

Now, with reference to Figures 7 and 8, the relative positional relationship between the reflecting surface of the primary mirror (first mirror) 24 and the reflecting surface of the secondary mirror (second mirror) 36 will be described. In this description, of the light beams emitted from the sample S, passing through the first mirror unit MU1, the bilateral telecentric optical system TOS, and the second mirror unit MU2, and incident on the image sensor 38, the light beams emitted from the inspection target surface of the sample S, i.e., the side surface Sa, will be considered. Furthermore, attention will be paid to the chief ray L of the light beam emitted from the side surface Sa of the sample S. Figure 7 shows the chief ray L emitted from the side surface Sa of the sample S. Figure 8 shows the chief ray L incident on the image sensor 38.

As shown in FIG. 7, the inclination angle of the principal ray L with respect to the normal line to the side surface Sa of the sample S is defined as θ. For convenience, the inclination angle θ is referred to as the emission angle of the principal ray L. Also, as shown in FIG. 8, the inclination angle of the principal ray L with respect to the normal line to the light receiving surface 38a of the image sensor 38, i.e., the incidence angle, is defined as η.

The reflecting surface of the primary mirror 24 and the reflecting surface of the secondary mirror 36 are arranged in the following relative positional relationship. The chief ray L emitted from the side surface Sa of the sample S shown in FIG. 7 is symmetrical to the chief ray L incident on the image sensor 38 shown in FIG. 8. In more detail, as shown in FIG. 8, the angle of incidence η of the chief ray L with respect to the light receiving surface 38a of the image sensor 38 is equal to the complement angle θ of the exit angle θ of the chief ray L at the side surface Sa of the sample S, i.e., π/2-θ.

In other words, the reflecting surfaces of the primary mirror 24 and the secondary mirror 36 are arranged so that the chief ray L emitted from the side surface Sa of the sample S at an emission angle θ, as shown in FIG. 7, is incident on the light receiving surface 38a of the image sensor 38 at an incident angle equal to the complement of the emission angle θ, i.e., π/2-θ, as shown in FIG. 8.

In the above explanation, an example was described in which the primary mirror 24 and the secondary mirror 36 are configured as regular octagonal cylindrical mirrors. That is, an example was described in which the reflective surfaces of the primary mirror 24 and the secondary mirror 36 are parallel to the optical axis A of the double-telecentric optical system TOS. However, this is not limited to this. The reflective surfaces of the primary mirror 24 and the secondary mirror 36 may be inclined with respect to the optical axis A of the double-telecentric optical system TOS. It is sufficient that the reflective surfaces of the primary mirror 24 and the secondary mirror 36 satisfy the relative positional relationship described above.

Next, the basic characteristics of a double-telecentric optical system will be described with reference to Figure 4. Figure 4 is a conceptual diagram of a double-telecentric optical system.

The double-telecentric optical system 40 comprises an objective lens 42, an aperture stop 44, and an imaging lens 46. The rear focal point of the objective lens 42 and the front focal point of the imaging lens 46 coincide with each other, and the aperture stop 44 is located at this point. A sample S is located at the front focal point of the objective lens 42, and an image sensor 48 is located at the rear focal point of the imaging lens 46. Light from the sample S is collected by the objective lens 42, passes through the aperture stop 44, and is imaged by the imaging lens 46 onto the image sensor 48.

In such a double-telecentric optical system 40, the chief ray of each light beam with a predetermined divergence angle emitted from each point on the sample S is parallel to the optical axis A both between the sample S and the objective lens 42 and between the imaging lens 46 and the image sensor 48. Therefore, even if the position of the sample S or the image sensor 48 changes, the imaging magnification of the double-telecentric optical system 40 does not change.

Now, as a comparative example, the inspection optical system 20C will be described with reference to FIG. 3. FIG. 3 is a diagram showing the inspection optical system 20C according to the comparative example. Simply put, the inspection optical system 20C has a configuration in which the second mirror unit MU2 is omitted from the inspection optical system 20.

Below, with reference to Figures 7 to 14, we will explain the differences between the image acquired by the inspection optical system 20 according to this embodiment and the image acquired by the inspection optical system 20C according to the comparative example.

First, referring to FIG. 7, the movement of the principal ray L caused by the positional displacement of the sample S will be described. Consider the principal ray L emitted from the side surface Sa of the sample S at an emission angle θ. This corresponds to imaging the side surface Sa of the sample S from diagonally above at an angle of θ with respect to the normal line to the side surface Sa. In other words, the light beam of the principal ray L emitted from each point on the side surface Sa of the sample S is focused to one point on the light receiving surface 38a of the image sensor 38 by the double telecentric optical system TOS. As a result, an optical image of the side surface Sa is formed on the light receiving surface 38a of the image sensor 38.

Figure 7 shows the movement of the chief ray with respect to the positional displacement of the sample S. In Figure 7, the sample S whose center is located on the optical axis A is drawn with a two-dot chain line. The chief ray L emitted from the side surface Sa of the sample S at this time is drawn with a two-dot chain line. Furthermore, the sample S that is shifted horizontally to the right by Δ relative to the sample S drawn with the two-dot chain line is drawn with a solid line. The chief ray L emitted from the side surface Sa of the sample S at this time is also drawn with a solid line.

When the sample S is displaced by Δ in the horizontal direction parallel to the paper surface of FIG. 7 with respect to the sample S depicted by the two-dot chain line, the optical path length from the side surface Sa to the image sensor 38 changes, but because the optical image of the side surface Sa is formed by the double-telecentric optical system TOS, the magnification of the optical image of the side surface Sa on the light receiving surface 38a of the image sensor 38 does not change. However, as is clear from FIG. 7, the optical path of the chief ray L emitted from each point on the side surface Sa moves in parallel by d = Δ sin θ with respect to the positional displacement of Δ.

Although not shown in FIG. 7, consider a sample S that is displaced by Δ in the horizontal direction perpendicular to the plane of the paper in FIG. 7 with respect to the sample S depicted by the two-dot chain line. In this sample S, the optical path length from side surface Sa to the image sensor 38 does not change, and it is clear that the optical path of the chief ray L emitted from each point on side surface Sa moves in parallel by Δ in response to the positional displacement of Δ.

In this way, when imaging the side surface Sa of the sample S from an oblique direction, even if the sample S is shifted in position by the same amount, the amount of movement of the chief ray L changes depending on the direction of the shift.

In the comparative inspection optical system 20C shown in FIG. 3, such a change in the amount of movement of the principal ray L, which depends on the direction of the positional shift of the sample S, affects the optical image formed on the light receiving surface 38a of the image sensor 38.

Figures 12 to 14 show images I3 and I4 acquired by the inspection optical system 20C according to the comparative example shown in Figure 3. Figure 12 shows image I3 acquired for a sample S whose center is located on the optical axis A. Figures 13 and 14 show image I4 acquired for a sample S whose center is shifted from the optical axis A.

In images I3 and I4 in Figures 12 to 14, the images S3 and S4 of sample S are drawn with solid lines. Also, for convenience, in image I4 in Figures 13 and 14, the image S3 of sample S in image I3 in Figure 12 is drawn superimposed with a two-dot chain line. In image I4 in Figure 13, the image S3 of sample S in image I3 in Figure 12 is drawn in the same position. On the other hand, in image I4 in Figure 14, the image S3 of sample S in image I3 in Figure 12 is drawn translated so as to overlap as much as possible with the image S4 of sample S in image I4.

Images I3 and I4 in Figures 12 to 14 each include images S3 and S4 of eight samples S. The images S3 and S4 of the eight samples S are images corresponding to optical images formed by a light beam passing through the eight reflecting surfaces of the primary mirror 24 and the secondary mirror 26, respectively.

In image I3 of FIG. 12, the images S3 of the eight samples S all have the same shape. Furthermore, the images S3 of the eight samples S are positioned rotationally symmetrically. The center of rotational symmetry is located at the center of image I3.

On the other hand, in the image I4 in FIG. 13 and FIG. 14, the center of the image S4 of the eight samples S is off center of the image I4, as can be seen from FIG. 13. In FIG. 14, the image S4 of the eight samples S does not completely overlap with the image S3 of the eight samples S. In detail, the two outermost images S4 on the left and right, which are located in the center of the top and bottom, completely overlap with the image S3, but the other images S4 do not completely overlap with the image S3. As can be seen from this, the images S4 of the eight samples S do not all have the same shape. Furthermore, the amount of movement of the images S4 of the eight samples S relative to the image S3 of the eight samples S is also different for each one. This is the effect of the amount of movement of the principal ray L changing depending on the direction of the positional shift of the sample S.

In the inspection optical system 20C according to the comparative example shown in FIG. 3, the chief ray L of the light beam that passes through the primary mirror 24 and the secondary mirror 26 is both perpendicularly incident on the light receiving surface 38a of the image sensor 38. As described above, the amount of movement of the chief ray L caused by the misalignment of the sample S differs depending on the direction of the misalignment of the sample S. For this reason, the optical images of the eight samples S are not all formed with the same shape for samples S whose centers are off from the optical axis A. For this reason, the images S4 of the eight samples S in image I4 do not all have the same shape.

The image processing unit 60 cuts out images of the side surface S3a and S4a regions of the images S3 and S4 of the sample S from the images I3 and I4 acquired by the inspection optical system 20C. As shown in FIG. 12, when the images S3 of the eight samples S all have the same shape and are positioned rotationally symmetrically, it is relatively easy to cut out the image of the side surface S3a region. This is because the process of cutting out the image of one side surface S3a region can also be applied to the images S3 of other samples S, for example, by rotating the cut-out region around the central axis of rotational symmetry.

In contrast, as shown in Figures 13 and 14, when the images S4 of the eight samples S are not all the same shape, cutting out the image of the region of the side surface S4a is inevitably complicated. This is because the process of cutting out the image of one region of the side surface S4a cannot be easily applied to the images S4 of the other samples S. Therefore, cutting out the image of the region of the side surface S4a of the image S4 of the sample S for the image I4 in Figures 13 and 14 takes a lot of time, and the load of image processing by the image processing unit 60 is large.

Next, an image acquired by the inspection optical system 20 according to this embodiment will be described with reference to FIG. 8. FIG. 8 is a diagram showing the movement of the incident position on the light receiving surface 38a of the image sensor 38 in response to the movement of the principal ray L caused by the positional deviation of the sample S.

As described with reference to Fig. 7, the amount of movement d of the chief ray L due to the positional shift of the sample S by the shift amount Δ in the horizontal direction parallel to the paper surface of Fig. 7 is d = Δ sin θ. In the inspection optical system 20 according to this embodiment, as shown in Fig. 8, the chief ray L reflected by the reflecting surface of the secondary mirror 36 is incident on the light receiving surface 38a of the image sensor 38 at an incident angle η. The incident angle η is the complement angle of θ, and η = π/2 - θ. Therefore, the amount of movement of the incident position on the light receiving surface 38a of the image sensor 38 relative to the movement of the chief ray L due to the positional shift of the sample S is M Δ, where M is the optical magnification of the double-telecentric optical system TOS.

In other words, with respect to a positional shift of the sample S in a horizontal direction parallel to the paper surface of FIG. 7, the incident position of the chief ray L on the light receiving surface 38a of the image sensor 38 moves by MΔ in a horizontal direction parallel to the paper surface of FIG.

As described above, the amount of movement of the chief ray L due to the positional shift of the sample S by the amount of shift Δ in the horizontal direction perpendicular to the paper surface of Fig. 7 is Δ in the horizontal direction perpendicular to the paper surface of Fig. 7. Therefore, the amount of movement of the incident position of the chief ray L on the light receiving surface 38a of the image sensor 38 is MΔ in the horizontal direction perpendicular to the paper surface of Fig. 8.

For this reason, in the inspection optical system 20 according to this embodiment, the amount of movement of the incident position of the principal ray L on the light receiving surface 38a of the image sensor 38 is a constant value MΔ with respect to the positional shift of the shift amount Δ of the sample S, regardless of the direction of the positional shift. This means that all of the eight optical images of the sample S formed by the inspection optical system 20 have the same shape.

Figures 9 to 11 show images I1 and I2 acquired by the inspection optical system 20 according to the present embodiment shown in Figure 2. Figure 9 shows image I1 acquired for a sample S whose center is located on the optical axis A. Figures 10 and 11 show image I2 acquired for a sample S whose center is shifted from the optical axis A.

In images I1 and I2 in Figures 9 to 11, the images S1 and S2 of the sample S are drawn with solid lines. Also, in image I2 in Figures 10 and 11, the image S1 of the sample S in image I1 in Figure 9 is drawn superimposed with a two-dot chain line for convenience. In image I2 in Figure 10, the image S1 of the sample S in image I1 in Figure 9 is drawn in the same position. On the other hand, the image S1 of the sample S in image I1 in Figure 9 can be completely superimposed with the image S2 of the sample S in image I2 in Figure 11 by translation, but for convenience of illustration, in image I2 in Figure 11, the image S1 of the sample S in image I1 in Figure 9 is drawn adjacent to the image S2 of the sample S in image I2.

Images I1 and I2 in Figures 9 to 11 each include images S1 and S2 of eight samples S. The images S1 and S2 of the eight samples S correspond to optical images formed by light beams passing through the eight reflecting surfaces of the primary mirror 24, the secondary mirror 26, the primary mirror 34, and the secondary mirror 36, respectively.

In image I1 of FIG. 9, the images S1 of the eight samples S all have the same shape. Furthermore, the images S1 of the eight samples S are positioned rotationally symmetrically. The center of rotational symmetry is located at the center of image I1.

On the other hand, in image I2 in FIG. 10, the center of image S2 of the eight samples S is offset from the center of image I2. Also, from FIG. 11, it can be seen that image S1 of the eight samples S can be completely overlapped with image S2 of the eight samples S by translation.

In other words, the images S1 of the eight samples S and the images S2 of the eight samples S all have the same shape, only their central positions are different. This is because the amount of movement of the chief ray L does not depend on the direction of the positional shift of the sample S.

The image processing unit 60 cuts out images of the side surface S1a, S2a regions of the images S1, S2 of the sample S from the images I1, I2 acquired by the inspection optical system 20. In both images I1, I2, the images S1, S2 of the eight samples S all have the same shape and are positioned rotationally symmetric. Therefore, for example, the process of cutting out an image of one side surface S1a region can also be applied to the images S1, S2 of the other samples S by rotating the cut-out region around the central axis of rotational symmetry. This makes it easier to cut out images of the side surface S1a, S2a regions. This significantly reduces the image processing load on the image processing unit 60.

In other words, this embodiment provides an inspection device 10 with a reduced image processing load.

In the embodiment, an example configuration has been shown in which the first mirror unit MU1 includes a primary mirror 24 and a secondary mirror 26, and the second mirror unit MU2 includes a primary mirror 34 and a secondary mirror 36. However, the configuration of the first mirror unit MU1 and the configuration of the second mirror unit MU2 are not limited to this. The configuration of the first mirror unit MU1 and the configuration of the second mirror unit MU2 may be changed as appropriate as long as the primary mirror (first mirror) 24 and the secondary mirror (second mirror) 36 satisfy the relative positional relationship described above, and the first mirror unit MU1 and the second mirror unit MU2 perform their original functions.

For example, the secondary mirror 26 and the primary mirror 34 may be omitted, and the primary mirror 24 and the secondary mirror 36 may satisfy the relative arrangement relationship described above, with the primary mirror 24 reflecting the light beam parallel to the optical axis A, and the secondary mirror 36 directly reflecting the light beam that has passed through the double-telecentric optical system TOS. Conversely, in addition to these mirrors 24, 26, 34, and 36, other optical elements may be appropriately added.

In addition, while an example configuration has been shown in which the double telecentric optical system TOS includes an objective lens 28, an imaging lens 32, and an aperture stop 30, the present invention is not limited to this, and other optical elements may be added as appropriate in addition to these optical elements.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

10...inspection device, 20...inspection optical system, 22...illuminator, MU1...first mirror unit, 24...primary mirror, 26...secondary mirror, TOS...telecentric optical system on both sides, 28...objective lens, 30...aperture stop, 32...imaging lens, MU2...second mirror unit, 34...primary mirror, 36...secondary mirror, 38...imaging element, 38a...light receiving surface, 60...image processing unit, 70...determination unit, 80...display unit, 90...conveyor, 92...endless belt, 94...drive roller, S...sample, Sa...side surface.

Claims (8)

An inspection apparatus for inspecting a sample based on images captured obliquely from all around the sample, comprising:
A double telecentric optical system;
an imaging element on which an optical image of the sample is formed by the double telecentric optical system;
a first mirror having a plurality of reflecting surfaces arranged inwardly around an optical axis of the double-telecentric optical system, the first mirror reflecting a plurality of light beams emitted from the sample obliquely with respect to the optical axis;
a second mirror having a plurality of reflective surfaces arranged inwardly around the optical axis, which reflects the light beam and guides it obliquely to the optical axis to the image sensor, the reflective surfaces being arranged with respect to the reflective surfaces of the first mirror in a relative arrangement relationship in which a chief ray emitted from an inspection target surface of the sample and a chief ray incident on the image sensor are symmetrical;
An inspection device comprising: The inspection device according to claim 1, wherein the reflecting surface of the first mirror and the reflecting surface of the second mirror are arranged so that a chief ray emitted from the surface to be inspected is incident on the imaging element at an angle of incidence equal to a complement of the angle of emergence of the chief ray. a third mirror having a plurality of reflective surfaces arranged outwardly around the optical axis, which reflects the light beam reflected by the first mirror parallel to the optical axis and guides the light beam to the double-telecentric optical system; and
3. The inspection apparatus according to claim 1, further comprising: a fourth mirror having a plurality of reflective surfaces arranged inwardly around the optical axis, the fourth mirror reflecting the light beam that has passed through the double-telecentric optical system and directing it to the second mirror. the first mirror comprises a regular polygonal cylindrical mirror having the reflecting surface on an inner peripheral surface thereof,
4. The inspection device according to claim 1, wherein the second mirror comprises a regular polygonal cylindrical mirror having the reflecting surface on an inner circumferential surface. the first mirror comprises a regular octagonal cylindrical mirror having the reflective surface on an inner peripheral surface thereof,
The inspection device according to claim 4 , wherein the second mirror comprises a regular octagonal cylindrical mirror having the reflective surface on an inner peripheral surface thereof. The double telecentric optical system is
An objective lens;
an imaging lens arranged coaxially with the objective lens and arranged so as to coincide with a focal point of the objective lens;
an aperture diaphragm arranged coaxially with the objective lens and the imaging lens and arranged at a focal position of the objective lens and the imaging lens;
6. An inspection device according to claim 1, comprising: The inspection device according to any one of claims 1 to 6, further comprising a ring-shaped illuminator that illuminates the sample from all sides. an image processing unit that cuts out an image of a region of the inspection target surface of the sample from the image generated by the imaging element;
a determination unit for determining the presence or absence of a defect in an image of the region of the inspection target surface;
The inspection device according to claim 1 , further comprising a display unit that displays a result of the determination by the determination unit.