JPH10332601A - Inspection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inspection apparatus by which a very small object can be inspected while its small slope is being illuminated by a method wherein at least one out of a plurality of movable mirrors is arranged in the optical path of illumination light. SOLUTION: One pair of mirrors 24, 26 are arranged between an objective lens 12 and an object 22, to be inspected, in such a way that one out of them can be moved. Then, an illumination luminous flux from the lens 12 is reflected by the mirror 26 and, in succession, by the mirror 24. The axis of the luminous flux is tilted with reference to the axial line of the lens 12, and the luminous flux is vertically incident on the object 22, to be inspected, which is arranged obliquely with reference to the axial line of the lens 12. Consequently, its reflected luminous flux is reflected by the mirrors 24, 26, and it is image-formed on an imaging element. On the other hand, when the mirror 26 is moved to the outside from the region of the illumination luminous flux from the lens 12, the illumination luminous flux is vertically incident on the object 22, to be inspected, which is arranged vertically to the axial line of the lens 12. Its reflected luminous flux is image-formed on the imaging element, and the image in the horizontal part of the object 22 to be inspected can be observed. In addition, the mirrors 24, 26 are returned to the optical path, the object 22 to be inspected is observed from an obliquely upper part, and the image of its tilted part can be observed in the same manner as the horizontal part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical inspection apparatus,
For example, the present invention relates to an inspection apparatus suitable for inspecting a pattern of a printed wiring board using an imaging camera or the like.

[0002]

2. Description of the Related Art In recent years, as electronic devices have become higher in density, printed circuit boards inside electronic devices have been actively developed as a structure having a multilayer thin film pattern for high-density wiring. In the manufacturing process of such a printed circuit board, a pattern inspection for detecting a secondary defect such as a chip of a wiring pattern, a disconnection or a short circuit is indispensable.

[0003] This inspection is no longer visually perceptible to an operator as the wiring pattern becomes finer. Therefore, there is a strong demand for the development of an inspection apparatus capable of performing a high-speed automatic inspection without contacting an object. In the manufacture of a printed circuit board, a conventional inspection apparatus for inspecting a pattern formed on the surface thereof is an apparatus combining a microscope and an imaging element, that is, an objective lens, an imaging lens, an imaging camera, Was included.
Further, the inspection device includes a vertical coaxial epi-illumination device, and illumination light is emitted from a light source such as a halogen lamp to the inspection object through a beam splitter and an objective lens. The illumination light reflected by the inspection object passes through an objective lens, a beam splitter, an imaging lens, and the like, and is imaged on an image sensor such as a CCD camera. Image processing is performed on the image thus formed, and a defect inspection such as chipping of the pattern, disconnection or short circuit is performed.

FIG. 22 shows an inspection apparatus for performing vertical coaxial epi-illumination.
Is shown in In FIG. 22, illumination light 1 is an objective lens 2
Irradiates the inspection target 3 through the inside of the cylinder. FIG.
Indicates an inspection apparatus using dark-field illumination. In the dark field illumination, a plurality of light sources (only one is shown) 4 are arranged around the objective lens 2, and irradiate the inspection target 3 at an angle inclined with respect to the axis of the objective lens 2, and are reflected by the inspection target 3. Illumination light is incident on the objective lens 2.

[0005]

Since there is an object to be inspected for a pattern which is a metal having a thickness of several tens of μm, the inspection surface slightly rises toward the end of the product, and the inspection surface is broken 3 ′ in FIG. May be inclined with respect to a horizontal plane perpendicular to the axis of the inspection apparatus. When vertical coaxial epi-illumination is performed when the inspection surface 3 ′ is inclined, the illumination light applied to the inspection target 3 through the inside of the cylinder of the objective lens 2 is irradiated with the objective lens as indicated by a broken arrow. 2 and the inspection becomes difficult.

In the case where the inspection surface 3 'is inclined, FIG.
Illumination from multiple directions using dark field illumination shown in 3,
It may be convenient to perform an inspection. However, for a target having an inclined surface as shown in the figure, ordinary dark-field illumination is effective. However, when the inclination angle of the inspection surface 3 'is small (within 10 degrees with respect to the horizontal), the ordinary dark-field illumination is effective. There is a problem that the inspection surface 3 'cannot be illuminated by dark-field illumination. In other words, if the inclination angle of the inspection surface 3 ′ is small, it is necessary to arrange the light source 4 very close to the objective lens 2 so as to generate the illumination light 5, for example, but arrange the light source 4 at such a position. It is difficult. In order to solve the problem, it is conceivable to install a small illumination such as an LED in the angle where the illumination cannot be performed.However, from the size of the space between the objective lens and the object and the size of the small illumination such as the LED, Many LEDs cannot be installed in this part, and only a small amount of light can be obtained as compared with coaxial epi-illumination.

An object of the present invention is to provide an inspection apparatus capable of inspecting a small object while illuminating a small inclined surface of the object.

[0008]

SUMMARY OF THE INVENTION An inspection apparatus according to the present invention includes an objective lens, an imaging lens, an image pickup device, and an illumination device which passes through the inside of a cylinder of an objective lens toward an inspection object below the objective lens. Illumination means for irradiating light, the illumination means comprises a plurality of mirrors arranged in the optical path of the illumination light,
The present invention is characterized in that an inspection object below the objective lens can be subjected to vertical coaxial epi-illumination, and an inspection object below the objective lens can be illuminated obliquely from above.

In the above configuration, by arranging a plurality of mirrors in the optical path of the illumination light for performing the vertical coaxial epi-illumination, the angle of the illumination light is changed to irradiate the inspection object below the lens, and The illumination light reflected by the object to be inspected can be made to enter the cylinder of the objective lens, so that the object to be inspected having an inclined surface can be inspected. By changing the arrangement of a plurality of mirrors, vertical coaxial epi-illumination can be performed.

The following configuration can be adopted in addition to the above configuration. At least one of the plurality of mirrors is preferably movably arranged. Thus, when observing the image of the horizontal portion of the inspection object, the plurality of mirrors are removed from the optical path, and observation using vertical coaxial incident illumination can be performed. Preferably, a transparent plate is inserted into the optical path of the illumination light. In the case of obliquely upward illumination, when the optical path length is different from that of the vertical coaxial epi-illumination, and the focus cannot be achieved, a transparent plate such as a glass plate is inserted into the optical path of the obliquely upward illumination for focusing.

Preferably, the plurality of mirrors are arranged so as to be rotatable with respect to the optical axis of the illumination light. It is preferable to acquire an image for one rotation at every fixed rotation angle and compare corresponding points on the image. The plurality of mirrors may be arranged between the objective lens and the inspection object or between the objective lens and the imaging lens.

Further, according to another feature of the present invention, the inspection apparatus according to the present invention comprises an objective lens, an image forming means, an image pickup device, and illumination light directed toward an object under the objective lens. Illuminating means for illuminating a horizontal portion and an inclined portion of the object under the objective lens, the illumination device including a light source and a filter disposed below the objective lens. It is characterized by.

[0013]

FIG. 1 is a diagram showing an apparatus 10 for inspecting a wiring pattern of a printed circuit board according to the present invention. The inspection apparatus 10 includes an objective lens 12, an imaging lens 14,
It includes an image sensor 16 such as a CCD camera and a vertical coaxial epi-illumination device. The vertical coaxial epi-illumination device includes an illumination light inlet 18 provided at an intermediate portion of a tube of the device, and a beam splitter 20 provided at an intermediate portion of the tube of the device. Illumination light is introduced from a light source (not shown) such as a halogen lamp into an illumination light introduction port 18 as shown by an arrow L, and is then bent downward by a beam splitter 20 to pass through the cylinder of the objective lens 12 so that the objective lens 12 Is irradiated toward the inspection object 22 located below. The illumination light applied to the inspection object 22 is reflected by the inspection object 22, passes through the objective lens 12, passes through the beam splitter 20, and the imaging lens 14, and
An image is formed on the image sensor 16. The imaging device 16 is connected to an image processing device (not shown), and performs a defect inspection such as chipping, disconnection, or short circuit of a wiring pattern of a printed circuit board, which is the inspection object 22.

In FIG. 1, the inspection apparatus 10 further includes a plurality of mirrors 24, 2 arranged in the optical path of the illumination light.
6 inclusive. In the example of FIG. 1, a pair of mirrors 24, 2
6 is arranged between the objective lens 12 and the inspection object 22. At least one of the pair of mirrors 24 and 26 is disposed so as to be movable, and the inspection object 2 below the objective lens 12.
2 can perform vertical coaxial epi-illumination, and can illuminate the inspection object 22 below the objective lens 12 from obliquely above.

FIG. 2 shows a case where the object 22 under the objective lens 12 is illuminated obliquely from above by using a pair of mirrors 24 and 26. A pair of mirrors 24, 26
Are both arranged obliquely with respect to the axis of the objective lens 12 so that the illumination light flux exiting from the pupil of the objective lens 12 can pass between the ends of the pair of mirrors 24 and 26 closer to the objective lens 12. Are located in The mirror surface of the first mirror 24 faces downward, and the mirror surface of the second mirror 26 faces upward. Accordingly, the illuminating light flux exiting from the pupil of the objective lens 12 is reflected by the mirror surface of the second mirror 26, goes to the mirror surface of the first mirror 24, is reflected by the mirror surface of the first mirror 24, and Go to the inspection object 22.

The optical axis of the luminous flux of the illuminating light traveling toward the inspection object 22 is inclined with respect to the axis of the objective lens 12, and thus the inspection object 2 which is arranged to be inclined with respect to the axis of the objective lens 12.
2 is perpendicularly incident. Therefore, the luminous flux of the illumination light reflected by the inspection object 22 is reflected on the mirror surface of the first mirror 24 and further reflected on the mirror surface of the second mirror 26, contrary to the time of incidence, as shown in FIG. The light passes through the beam splitter 20 and the imaging lens 14 as shown, and is imaged on the image sensor 16.

FIG. 3 shows a case where vertical coaxial epi-illumination is performed. In this case, the pair of mirrors 24 and 26 are removed from the optical path and are not used. The second mirror 26 is the objective lens 12
Is moved in the direction perpendicular to the axis of the objective lens 12, and is moved out of the region of the illumination light beam emerging from the pupil of the objective lens 12. The first mirror 24 does not need to be moved since the first mirror 24 is at the boundary of the area of the illumination light beam emerging from the pupil of the objective lens 12. However, the first mirror 24 can also be moved.

The illumination light beam emitted from the pupil of the objective lens 12 has its optical axis parallel to the axis of the objective lens 12 and vertically enters the inspection object 22 arranged perpendicular to the axis of the objective lens 12. Accordingly, in this case, the luminous flux of the illumination light reflected by the inspection object 22 under the vertical coaxial incident illumination passes through the beam splitter 20 and the imaging lens 14 shown in FIG. You. Thus, the image of the horizontal portion of the inspection object 22 can be observed. Further, by returning the pair of mirrors 24 and 26 to the optical path (FIG. 2), the inspected object 22 is observed from obliquely above the inspected object 22, and the image of the inclined portion of the inspected object having the inclination is converted into the image of the horizontal portion. Can be observed as well.

FIG. 4 shows a case in which the obliquely upward illumination and the vertical coaxial incident illumination have different optical path lengths and are out of focus. That is, in the case of obliquely upward illumination, the optical path of the illumination light is bent, so that the optical path length in a direction parallel to the axial direction of the objective lens 12 is shorter than the optical path length in the case of vertical coaxial incident illumination. Therefore, if the inspection object 22 is supported at a fixed position by the obliquely upward illumination and the vertical coaxial illumination, the focus will not be adjusted in any case.

FIG. 5 shows an example in which the transparent plate 28 is inserted into the optical path of the illumination light in the case of obliquely upward illumination. Transparent plate 2
Numeral 8 has an effect of increasing the optical path length in a direction parallel to the axial direction of the objective lens 12. FIG. 6 shows the case of vertical coaxial epi-illumination. In this case, the transparent plate 28 is moved out of the optical path. Thereby, the optical path length in the direction parallel to the axial direction of the objective lens 12 can be made equal between the obliquely upward illumination and the vertical coaxial epi-illumination. Also comes into focus.

FIGS. 7 and 8 are views showing modified examples of FIGS. 5 and 6. FIG. In this example, the transparent plate 28 has a first portion 28a and a second portion 28b having different refractive indexes. As shown in FIG. 7, in the case of obliquely upward illumination, the transparent plate 28
Is used. As shown in FIG. 8, in the case of vertical coaxial epi-illumination, the first portion 28a of the transparent plate 28 is used. Thereby, the optical path length in the direction parallel to the axial direction of the objective lens 12 can be made equal between the obliquely upward illumination and the vertical coaxial incident illumination, and
Even if 2 is supported at a fixed position, focus will be achieved in any case. In the examples of FIGS. 5 and 6, even if the transparent plate 28 having an appropriate refractive index is not provided, the refractive index can be adjusted by configuring as shown in FIGS. Further, in the examples of FIGS. 7 and 8, an example in which the first portion 28 a and the second portion 28 b have different refractive indices has been described, but the first portion 28 a and the second portion 28 b have different thicknesses. It may be.

FIG. 9 shows an example in which a pair of mirrors 24 and 26 are rotatably arranged with respect to the optical axis of illumination light (the axis of the objective lens 12). Then, an image for one rotation is obtained for each fixed rotation angle. In FIG. 9, for example, a pair of mirrors 24 and 26 are irradiated with illumination light from a diagonally upper direction indicated by an arrow A to the inspection object 22.
4 and 26 are rotated by 90 degrees to irradiate the inspection object 22 with illumination light from obliquely above indicated by arrow B, and then the pair of mirrors 24 and 26 are rotated by 90 degrees to obliquely inspect from above indicated by arrow C The illumination device 22 is configured to irradiate illumination light, and then rotate the pair of mirrors 24 and 26 by 90 degrees to irradiate the inspection object 22 with illumination light from obliquely above indicated by an arrow D. For example, as a result of forming an image using vertical coaxial epi-illumination, if it is found that there is an inclined portion 22a in a substantially horizontal inspection object 22, which of the inclined portions 22a is inclined? If you don't know,
Thus, it may be necessary to perform image acquisition while rotating the pair of mirrors 24 and 26.

FIG. 10 is a diagram showing a case where an image is acquired by using vertical coaxial epi-illumination and obliquely upward illumination. The hatched area is, for example, a part that appears in the image.
(A) is an image obtained by performing vertical coaxial epi-illumination. (B), (C), and (D) are images obtained by performing obliquely upward illumination in the directions of arrows B, C, and D in FIG. 9, for example. (E) is a diagram in which corresponding points are compared from all these images, and a portion of a matching image is extracted. From this image, even if there is an inclined area, it can be determined that this part is truly a part of the pattern.

Further, an image is obtained by vertical coaxial epi-illumination, a tilt angle of the object to be inspected is predicted from the image, and the plurality of mirrors are adjusted so as to meet conditions for obtaining an image from the tilt direction and angle. May be operated to perform image acquisition. FIGS. 11 and 12 show a second embodiment of the present invention. The inspection device 10 includes an objective lens 12, an imaging lens 14, an image sensor 16 such as a CCD camera, and a vertical coaxial epi-illumination device. The vertical coaxial epi-illumination device includes an illumination light inlet 18 and a beam splitter 20.
And The inspection device 10 further includes a plurality of mirrors 24 and 26 arranged in the optical path of the illumination light. In the example of FIGS. 11 and 12, the intermediate part 30 of the device between the objective lens 12 and the beam splitter 20 is
And a pair of mirrors 24, 2
6 is located in this intermediate part 30.

When the intermediate portion 30 is at the position shown in FIG. 11, the illumination light emitted downward from the beam splitter 20 is reflected by the second mirror 26, and then reflected by the first mirror 24, and is reflected by the objective lens. The inspection object 22 can be illuminated obliquely from above through the light source 12.
When the intermediate portion 30 is at the position shown in FIG. 12, the illumination light emitted downward from the beam splitter 20 can directly illuminate the inspection object 22 vertically.

In the above example, the mirrors 24 and 26 are formed as flat mirrors.
Can also be formed as curved mirrors. Alternatively, two or more mirrors 24 and 26 may be used instead of a pair. FIG. 13 shows the mirror 2
It is a figure which shows the example in which one of 4 and 26 was formed as a curved mirror. The first mirror 24 is a flat mirror as in the previous example, while the second mirror 26 is formed as an umbrella-shaped mirror with the central portion of the cone open. (B) is a plan view of the second mirror 26 of (A). The first mirror 24 is disposed inside the second mirror 26 and performs a reflection function between the first mirror 24 and an opposing portion of the second mirror 26. First
By arranging the mirror 24 at the illustrated position, obliquely upward illumination can be performed, and by moving the first mirror 24, vertical coaxial epi-illumination can be performed. The first mirror 24 is disposed inside the second mirror 26 so as to be rotatable about the axis of the objective lens 12, and can perform image acquisition at several rotational angle positions as described above.

FIG. 14 shows an example in which the first mirror 24 is also formed as a curved mirror. The first mirror 24 has a mirror surface on the convex surface side, and the second mirror 26 has a mirror surface on the concave surface side. This makes it possible to correct the curvature of the image when only the second mirror 26 is a curved mirror. FIG. 15 shows the first mirror 24.
Is a plane mirror, and the second mirror 26 is formed as a pyramid-shaped umbrella-shaped mirror whose central portion is open.
(B) is a plan view of the second mirror 26 of (A). In this case, while rotating the first mirror 24, an image can be obtained in a state where the first mirror 24 and the plane portion of the second mirror 26 face each other.

FIGS. 16 to 18 show a third embodiment of the present invention. Also in this example, the inspection apparatus includes an objective lens 12, an imaging lens 14, an imaging device 16 such as a CCD camera, and an illumination device, as in the example of FIG. The illuminating device includes an annular light source 40 disposed below the objective lens 12 around the axis of the objective lens 12, and a filter 42 disposed between the objective lens 12 and the light source 40. The filter 42 has a configuration in which a hole is formed in a perfect diffusion plate, and reflects light on the surface of a portion having no hole and transmits light at the portion of the hole. The light source 40 is slightly larger than the filter 42 and emits illumination light toward the filter 42. The illumination light reflected by the filter 42 irradiates the inspection object 22 with light obliquely at various angles.

The illumination light reflected on the horizontal portion of the inspection object 22 passes through the filter 42 and reaches the imaging lens 14 and the image pickup device 16, so that an image can be formed almost in the same manner as in the case of vertical coaxial illumination. . The illumination light reflected by the inclined portion of the inspection object 22 also passes through the filter 42 and passes through the imaging lens 14.
Then, the image reaches the image sensor 16, and the image can be formed almost in the same manner as in the case of the obliquely upward illumination. According to this example, since the light source 40 does not need to be disposed immediately below the objective lens 12, a sufficient installation space can be secured below the objective lens 12. In addition, instead of the filter 42 having a configuration in which holes are formed in the perfect diffusion plate, a filter in which holes are formed in the hologram may be used. Instead of the annular light source 40, a plurality of small light sources arranged around the axis of the objective lens 12 may be used.

FIG. 19 is a view showing an example in which a small concave mirror is formed as a filter 42 on a transparent plate such as glass by vapor deposition. Light reflects off the concave mirror at various angles and transmits through the non-concave mirror. FIG. 20 is a diagram showing an example in which a small microlens is embedded as a filter 42 in a reflection type diffusion plate. Light is reflected at various angles in a portion without a microlens and transmitted through a microlens portion.

FIG. 21 is a diagram showing still another embodiment of the present invention. In this embodiment, a hologram 44 is arranged between the objective lens 12 and the inspection object 22 instead of the mirrors 24 and 26 in the configuration for performing the vertical coaxial epi-illumination of FIG. When passing through the hologram 44, the illumination light coming from above the objective lens 12 is diffused into zero-order diffused light, primary diffused light, and the like. When the inspection object 22 is arranged horizontally, the inspection object 22 can be vertically illuminated coaxially, and when the inspection object 22 below the objective lens is inclined. In addition, mainly the 0th-order diffused light reflected by the inspection object 22 enters the objective lens 12, and the same illumination as the obliquely upward illumination can be performed.

[0032]

As described above, according to the present invention,
It is possible to obtain an inspection apparatus that can inspect while illuminating a small inclined surface of a minute object.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a case where illumination is performed from obliquely above in the configuration of FIG. 1;

FIG. 3 is a diagram showing a case where vertical coaxial epi-illumination is performed in the configuration of FIG. 1;

FIG. 4 is a diagram illustrating an example in which an optical path length is different between obliquely upward illumination and vertical coaxial illumination.

FIG. 5 is a diagram illustrating an example in which a transparent plate is inserted into an optical path of illumination light when performing oblique upward illumination.

FIG. 6 is a view showing a state where the transparent plate of FIG. 5 is moved when performing vertical coaxial epi-illumination.

FIG. 7 is a view showing a modification of the transparent plate of FIG. 5;

FIG. 8 is a view showing a state where the transparent plate of FIG. 7 is moved.

FIG. 9 is a diagram illustrating an example in which a mirror is arranged rotatably with respect to an optical axis.

FIG. 10 is a diagram illustrating an example in which an image is acquired using vertical coaxial epi-illumination and a plurality of obliquely upward illuminations.

FIG. 11 is a diagram showing a second embodiment of the present invention.

FIG. 12 is a view showing a state where an intermediate portion in FIG. 11 has been moved.

FIG. 13 is a diagram illustrating an example of a curved mirror.

FIG. 14 is a diagram showing a modification of FIG.

FIG. 15 is a diagram illustrating an example of a pyramid-shaped mirror.

FIG. 16 is a diagram showing a third embodiment of the present invention.

FIG. 17 is a diagram illustrating the filter of FIG. 16;

FIG. 18 is a diagram showing the light source of FIG.

FIG. 19 is a diagram showing a modification of the filter of FIG. 16;

FIG. 20 is a diagram showing a modification of the filter of FIG. 16;

FIG. 21 is a view showing another embodiment of the present invention.

FIG. 22 is a diagram illustrating a conventional technique.

FIG. 23 is a diagram illustrating a conventional technique.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Inspection apparatus 12 ... Objective lens 14 ... Image forming lens 16 ... Image sensor 18 ... Illumination light inlet 20 ... Beam splitter 22 ... Inspection object 24, 26 ... Mirror 28 ... Transparent plate 30 ... Intermediate part 40 ... Light source 42 ... Filter 44 ... Hologram

Claims (7)

[Claims] An object lens, an imaging lens, an imaging element, and illumination means for irradiating illumination light toward an inspection object below the objective lens through a cylinder of the objective lens. The illuminating means includes a plurality of mirrors arranged in the optical path of the illuminating light, and can perform vertical coaxial epi-illumination on the object under the objective lens, and can obliquely illuminate the object under the objective lens. An inspection device characterized in that it can be illuminated from above. 2. The inspection apparatus according to claim 1, wherein at least one of the plurality of mirrors is movably arranged. 3. The inspection apparatus according to claim 1, wherein a transparent plate is inserted into an optical path of the illumination light. 4. The inspection apparatus according to claim 1, wherein the plurality of mirrors are arranged rotatably with respect to an optical axis of the illumination light. 5. The inspection apparatus according to claim 4, wherein an image for one rotation is acquired at every fixed rotation angle, and corresponding points on the images are compared. 6. The inspection apparatus according to claim 1, wherein the plurality of mirrors are arranged between the objective lens and the inspection object or between the objective lens and the imaging lens. 7. An objective lens, imaging means, an image pickup device, and illumination means for irradiating illumination light toward an object under the objective lens, the illumination means being provided below the objective lens. An inspection apparatus comprising: an arranged light source and a filter; and capable of illuminating a horizontal portion and an inclined portion of an inspection object below an objective lens.