JP2014055891A - Imaging lens and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging lens capable of easily imaging a subject in a plurality of directions at a low cost.SOLUTION: An imaging lens 7 used for imaging a subject 1 by imaging means 7 is configured so that a flat surface part 13 is provided on the surface on the side of the subject 1 of a lens body 12 and a convex part 18 is provided on the surface on the side of the imaging means 7 opposite to the flat surface part 13. The convex part 18 includes a plurality of inclined surfaces 19 inclined in directions different from each other and light made incident on the flat surface part 13 is emitted in parallel with each other from the plurality of inclined surfaces 19.

Description

  The present invention relates to an imaging lens used for imaging an object with an imaging unit, and an imaging apparatus including the imaging lens.

  For example, an inspection apparatus used for inspecting the presence or absence of a minute crack (hereinafter referred to as a crack) generated in a semiconductor wafer is known (see Patent Document 1). In this type of inspection apparatus, generally, a semiconductor wafer is irradiated with infrared light, the transmitted light is received by a camera, and displayed as an infrared image on a monitor. At this time, if there is a crack in the imaging range of the semiconductor wafer, the cracked portion is projected as a shadow in the image on the monitor.

  However, when imaging a semiconductor wafer from only one direction, as shown in FIG. 24, if the crack C is formed so as to be substantially parallel to the imaging direction D of the camera, the crack displayed on the monitor Since the shadow becomes very thin (the imaging width Z is about 1 μm, which is the same as the width W of the crack C), it is difficult to find the crack and there is a risk of missing the crack.

  For this reason, conventionally, in order to make it easier to find a crack, a method of imaging a semiconductor wafer from a plurality of directions by changing the direction of the camera or the direction of the semiconductor wafer has been proposed (see Patent Document 1).

JP 2006-184177 A

  However, there is a problem that the structure becomes complicated if the orientation of the camera and the semiconductor wafer can be changed. There is also a method of installing a plurality of cameras, but in this case, there is a problem that the cost is increased.

  Therefore, in view of such circumstances, the present invention intends to provide an imaging lens capable of easily imaging an object from a plurality of directions at low cost, and an imaging apparatus including the imaging lens. .

  The invention according to claim 1 is an imaging lens used for imaging an object with an imaging unit, wherein a flat surface portion is provided on a surface of the lens body on the object side, and the imaging on the side opposite to the flat surface portion is provided. A convex surface portion is provided on the surface on the means side, the convex surface portion has a plurality of inclined surfaces inclined in different directions, and light incident on the flat surface portion is emitted in parallel to each other from the plurality of inclined surfaces. It is composed.

  By using the imaging lens according to claim 1, light incident from the flat surface portion on the object side can be emitted in parallel to each other from a plurality of inclined surfaces of the convex surface portion on the opposite side. Images can be taken simultaneously from multiple directions.

  According to a second aspect of the present invention, in the imaging lens according to the first aspect, a central flat surface portion parallel to the flat surface portion is provided at the center of the convex surface portion.

  By providing a central flat surface portion parallel to the flat surface portion at the center of the convex surface portion, the object can be imaged from the direction parallel to the imaging direction of the imaging means via the central flat surface portion.

  A third aspect of the present invention is the imaging lens according to the first aspect, wherein a through-hole penetrating from the center of the convex surface portion to the center of the flat surface portion is formed.

  By forming a through hole penetrating from the center of the convex surface portion to the center of the flat surface portion, the object can be imaged from the direction parallel to the imaging direction of the imaging means through the through hole. In this case, the processing is easy and the manufacturing cost can be reduced.

  According to a fourth aspect of the present invention, in the imaging lens according to the third aspect, the through hole is reduced in diameter from the convex surface portion toward the flat surface portion.

  By reducing the diameter of the through hole from the convex surface portion toward the flat surface portion, it is possible to ensure a large range in which imaging can be performed via the inclined surface.

  The invention of claim 5 is an image pickup apparatus comprising an image pickup lens and an image pickup means for picking up an image of a surface of an object through the image pickup lens, and the image pickup lens is any one of claims 1 to 4. The imaging lens described in 1 is provided.

  When the imaging apparatus includes the imaging lens according to any one of claims 1 to 4, the object can be simultaneously imaged from a plurality of directions.

  A sixth aspect of the present invention is the imaging apparatus according to the fifth aspect, wherein the imaging means is a camera having a telecentric optical system.

  By using a camera equipped with a telecentric optical system as the imaging unit, the imaging unit is suitable for image processing.

  A seventh aspect of the present invention is the imaging apparatus according to the fifth or sixth aspect, wherein the imaging lens or the object passes through the center of the convex surface portion and around an axis parallel to the imaging direction of the imaging means. The imaging direction can be changed by rotating.

  By rotating the imaging lens or the object around the axis, imaging from more directions can be performed without increasing the number of inclined surfaces.

  According to the present invention, an object can be easily imaged simultaneously from a plurality of directions. As a result, it is not necessary to install a plurality of imaging means or change the orientation of the imaging means or the object, so that the configuration can be simplified and the cost can be reduced.

It is a figure which shows one Embodiment of the imaging device which concerns on this invention. 1 is a perspective view of an imaging lens according to a first embodiment of the present invention. It is a figure which shows the transmitted optical path of the imaging lens of 1st Embodiment. It is a figure which shows the image of the semiconductor wafer displayed on a monitor through the imaging lens of 1st Embodiment. It is a figure which shows the optical path difference in the case of imaging using the imaging lens of 1st Embodiment. It is a figure for demonstrating the characteristic of the imaging lens of 1st Embodiment. It is a figure for demonstrating the characteristic of the imaging lens of 1st Embodiment. It is a figure which shows the image of the semiconductor wafer displayed on a monitor at the time of forming a convex surface part in hexagonal pyramid shape. It is a figure which shows the example which formed the convex surface part in shapes other than a pyramid. It is a figure which shows the image of the semiconductor wafer displayed on a monitor via the imaging lens shown in FIG. It is a figure which shows the modification of the imaging lens of 1st Embodiment. It is a figure which shows the example which comprised the imaging lens so that rotation was possible. In the imaging lens of 1st Embodiment, it is a figure which shows the example of the various display screens displayed on a monitor when the shape of a convex-surface part is varied. It is a perspective view of the imaging lens of 2nd Embodiment of this invention. It is a figure which shows the example which formed the convex part in shapes other than a truncated pyramid. It is a figure which shows the transmitted optical path of the imaging lens of 2nd Embodiment. It is a figure which shows the image of the semiconductor wafer displayed on a monitor through the imaging lens of 2nd Embodiment. It is a figure for demonstrating the characteristic of the imaging lens of 2nd Embodiment. It is a figure for demonstrating the characteristic of the imaging lens of 2nd Embodiment. In the imaging lens of 2nd Embodiment, it is a figure which shows the example of the various display screens displayed on a monitor when the shape of a convex-surface part is varied. It is a perspective view of the imaging lens of 3rd Embodiment of this invention. It is a figure which shows the transmitted optical path of the imaging lens of 3rd Embodiment. It is a figure which shows the example which diameter-reduced the through-hole. It is a figure which shows the inspection method using the conventional semiconductor wafer inspection apparatus.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

FIG. 1 is a schematic configuration diagram of an inspection apparatus according to an embodiment of the present invention.
The inspection apparatus shown in FIG. 1 includes a movable table 2 as a support member that supports a semiconductor wafer 1, infrared irradiation means 3 that irradiates the semiconductor wafer 1 with infrared light, and an imaging apparatus 4 that captures an infrared image of the semiconductor wafer 1. And a monitor 5 for displaying the captured infrared image.

  The movable table 2 is configured to be movable in a horizontal direction and a vertical direction by a moving mechanism (not shown) so that the semiconductor wafer 1 can be disposed at an appropriate position. An infrared irradiation means 3 is disposed below the movable table 2, and infrared rays are irradiated upward from the infrared irradiation means 3. As the infrared irradiating means 3, one arbitrarily selected from known infrared light sources such as a halogen lamp can be applied.

  The imaging device 4 includes a camera 6 as imaging means, and an imaging lens 7 interposed between the semiconductor wafer 1 and the camera 6. The camera 6 includes a camera body 8 and a lens barrel 9 attached to the camera body 8. In the camera body 8, there is provided an image sensor 10 that converts an image formed via an optical system into an electrical signal. In addition, a telecentric lens 11 that is a telecentric optical system is provided in the lens barrel 9.

  Here, the telecentric optical system is an optical system designed such that the principal ray is parallel to the lens optical axis, and is an optical system particularly suitable for image processing. The telecentric optical system includes an object side telecentric optical system in which the chief ray is parallel to the lens optical axis only on the object side, an image side telecentric optical system in which the chief ray is parallel to the lens optical axis only on the image side, and the object side. There is a bilateral telecentric optical system in which the principal ray is parallel to the lens optical axis on both the image side and the image side. Among them, here, a telecentric optical system in which the principal ray is parallel to the lens optical axis at least on the object side, that is, an object side telecentric optical system or a bilateral telecentric optical system is used.

  When the semiconductor wafer 1 is irradiated with infrared light from the infrared irradiation means 3, the infrared light is transmitted through the semiconductor wafer 1, and an infrared image of the semiconductor wafer 1 is formed on the image sensor 10 through the imaging lens 7 and the telecentric lens 11. The The infrared image is converted into an electrical signal by the image sensor 10 and sent to the monitor 5. The infrared image of the semiconductor wafer 1 is displayed as a contrast image on the monitor 5 based on the electrical signal.

FIG. 2 is a perspective view of an imaging lens used in the inspection apparatus.
Hereinafter, based on FIG. 2, the structure of the imaging lens of 1st Embodiment of this invention is demonstrated.

  As shown in FIG. 2, the imaging lens 7 of the first embodiment has a lens body 12 made of a translucent member. A surface (lower surface in the drawing) disposed on the semiconductor wafer 1 side of the lens body 12 is a flat surface portion 13. On the other hand, a surface (upper surface in the drawing) disposed on the camera 6 side opposite to the flat surface portion 13 is a convex surface portion 18.

  In the configuration shown in FIG. 2, the convex surface portion 18 is formed in a quadrangular pyramid shape having four triangular inclined surfaces 19. Each inclined surface 19 is disposed so as to protrude from the lens body 12 toward the center of the convex portion 18 and is inclined in different directions.

FIG. 3 is a diagram illustrating a transmission optical path of the imaging lens according to the first embodiment.
As shown in FIG. 3, when the infrared light transmitted through the semiconductor wafer 1 is incident on the flat surface portion 13 of the imaging lens 7, it is refracted with the flat surface portion 13 as a boundary, and further on each inclined surface 19 of the convex surface portion 18 on the opposite side. Refraction is emitted. At this time, the infrared light emitted from each inclined surface 19 is emitted in parallel with each other toward the camera 6. Then, the infrared light emitted in parallel enters the telecentric lens 11 as it is, and is displayed as an infrared image on the monitor 5 via the image sensor 10.

FIG. 4 shows an image of the semiconductor wafer displayed on the monitor via the imaging lens of the first embodiment.
As shown in FIG. 4, the monitor screen has four triangular display sections H1 to H4, and images P1 to P4 of the semiconductor wafer are displayed for each display section H1 to H4. These images P <b> 1 to P <b> 4 are obtained by imaging a semiconductor wafer from above obliquely through four inclined surfaces of the imaging lens. Thus, by imaging a semiconductor wafer via an imaging lens having four inclined surfaces, the semiconductor wafer can be imaged simultaneously from four different directions. In FIG. 4, circled portions e1 to e4 in the images P1 to P4 indicate the same portions in the images P1 to P4.

FIG. 5 is a diagram illustrating an optical path difference when imaging is performed using the imaging lens of the first embodiment.
When the imaging lens of the first embodiment is used, the optical path difference ΔI between the transmitted light L1 transmitted through one end portion of the semiconductor wafer 1 and the transmitted light L2 transmitted through the opposite end portion is the transmitted light L1 in FIG. , L2 is the optical path difference from the incidence to the imaging lens 7 until it is emitted, and Ia is the optical path difference from the transmission light L1 and L2 from the imaging lens 7 to the incidence to the camera 6. It is represented by (1). In addition, in each optical path of the transmitted light L1 and L2 shown in FIG.

  ΔI = Ib−Ia (1)

  As described above, when the imaging lens of the first embodiment is used, the optical path difference ΔI includes the optical path difference Ib from when the transmitted lights L1 and L2 enter the imaging lens 7 to the exit, and the transmitted lights L1 and L2. It is obtained by the difference with the optical path difference Ia from the exit from the imaging lens 7 to the incidence on the camera 6.

  In FIG. 5, if the angle formed by a line perpendicular to the flat surface portion 13 of the imaging lens 7 and the optical axis when each of the transmitted lights L1 and L2 passes through the imaging lens 7, θ is the optical path difference ΔI. Can also be represented by the following formula (2).

  ΔI = (1 / cos θ−1) Ib Expression (2)

  Further, the optical path difference ΔI becomes smaller as the angle θ is smaller, that is, as the refractive index of the imaging lens 7 is smaller, so that blurring of the image can be suppressed.

The configuration using the imaging lens of the first embodiment has the following characteristics.
FIG. 6 is a diagram illustrating an optical path of light transmitted through the imaging lens of the first embodiment. In this figure, reference numerals Q1 to Q3 denote arbitrarily selected imaging points on the semiconductor wafer 1, reference numerals s1 to s3, and FIG. Reference numerals t1 to t3 indicate exit points where light from the imaging points Q1 to Q3 passes through the inclined surfaces 19 of the imaging lens 7 and exits.

  Here, in FIG. 6, assuming that the distances between the emission points s1 to s3 and t1 to t3 are A and B, and a and b, respectively, the relationship between the distances A and B, and a and b between the emission points is It is constant regardless of the orientation of the semiconductor wafer 1 with respect to the imaging lens 7. That is, A: B = a: b. As described above, in the configuration using the imaging lens of the first embodiment, the relationship between the distances between the emission points is constant regardless of the orientation of the semiconductor wafer 1 with respect to the imaging lens 7. Thus, it is possible to easily grasp the positional relationship of each image taken in correspondence with each other. For this reason, the calculation performed to correspond the position on each image becomes very simple.

In particular, in the configuration in which the imaging lens 7 has an even number of inclined surfaces 19, the following characteristics are further provided between images displayed via the inclined surfaces 19 facing each other.
For example, a type having four inclined surfaces 19 will be described as an example. Among images displayed through the inclined surfaces 19 facing each other in FIG. The same places e1 and e3 are arranged on the same straight line M orthogonal to the virtual line Y that is the axis of symmetry of the image display sections G1 and G3. Similarly, between the images P2 and P4 arranged opposite to each other in the vertical direction in the figure, the same portions e2 and e4 are the same straight line orthogonal to the virtual line X that is the axis of symmetry of the image display sections G2 and G4. N. Although not shown, the same applies to other configurations having an even number of inclined surfaces 19. As described above, it is also possible to specify the position on each image based on the characteristic that the same portion is arranged on a predetermined straight line between the images displayed via the inclined surfaces 19 facing each other. is there.

  In the above-described embodiment, the convex surface portion 18 is formed in a quadrangular pyramid shape, but the shape of the convex surface portion 18 is not limited to this. A triangular pyramid or other polygonal pyramids may be formed.

FIG. 8 shows an image of the semiconductor wafer displayed on the monitor when the convex surface portion is formed in a hexagonal pyramid shape.
In this case, since six inclined surfaces 19 constituting the convex surface portion 18 are provided, six images P1 to P6 obtained by imaging the semiconductor wafer from six directions are displayed on the monitor screen. Although not shown, when the convex surface portion 18 is formed in other polygonal pyramids, a plurality of images are displayed according to the number of inclined surfaces 19 of the convex surface portion 18.

Moreover, you may form the convex part 18 in shapes other than a pyramid.
For example, as shown in FIG. 9, the convex surface portion 18 may be configured to have a pair of inclined surfaces 19 that are inclined so as to protrude from the lens body 12 toward the intermediate portion from both end sides thereof. In this case, an image captured through each inclined surface 19 is as shown in FIG.

  Further, as shown in FIGS. 11A and 11B, a prismatic member (a rectangular parallelepiped) or a cylindrical member is cut a plurality of times from the middle of the side surface toward one end to form a pyramidal cut surface. Thus, the imaging lens 7 of the first embodiment may be created.

  By the way, as the number of the inclined surfaces 19 included in the convex surface portion 18 is larger, imaging from more than one direction is possible. However, there is a limit to increasing the number of inclined surfaces 19. On the contrary, when the number of the inclined surfaces 19 is increased, the range of each display section corresponding to each inclined surface 19 is reduced, or when the number of pixels of the camera 6 is determined, the pixels assigned to each image display section The number is relatively reduced and the resolution is lowered.

  Therefore, as shown in FIG. 12, the imaging lens 7 passes through the center of the convex portion 18 and is around an axis R parallel to the imaging direction of the camera 6 (or the light emission direction from the imaging lens 7 to the camera 6). By rotating the lens to the first position, it is possible to capture images from more directions without increasing the number of inclined surfaces 19.

  When it is desired to image the semiconductor wafer 1 from the entire circumference, the imaging lens 7 may be rotated by, for example, 360 °. However, it is not always necessary to rotate the imaging lens 7 by 360 °. Specifically, in the case of the convex portion 18 having n inclined surfaces 19, the rotation angle may be only 360 ° / n. For example, in the case of a quadrangular pyramid-shaped convex surface portion 18 having four inclined surfaces 19, the imaging lens 7 may be rotated by 360 ° / 4 = 90 °. In other words, by rotating the field of view equally divided into four by the four inclined surfaces 19 by 90 °, 4 × 90 ° = 360 ° imaging can be performed.

  On the other hand, if the imaging lens 7 is fixed and the semiconductor wafer 1 is rotated around the axis R, or both the imaging lens 7 and the semiconductor wafer 1 are rotated, all the same processing is performed. Imaging from the circumferential direction is possible. Further, the camera 6 may be rotated together with the imaging lens 7. In addition, when it is not necessary to obtain an image from the entire 360 ° circumference, a rotation angle may be set as appropriate.

FIG. 13 shows examples of various display screens displayed on the monitor when the shape of the convex surface portion is changed in the imaging lens of the first embodiment.
In each of FIGS. 13A to 13G, the size and shape of the entire display screen of the monitor are all displayed in the same size and shape for comparison. In each figure, a circular hatched portion indicates a maximum effective display range in which an imaging target object is displayed without protruding when the imaging lens is rotated in each display section in the display screen.

  In FIGS. 13A and 13B, two display sections are formed by providing two inclined surfaces facing each other on the convex portion, but the shapes of the display sections are different. Specifically, in (a), two rectangular display sections are formed by dividing the entire rectangular display screen by a line segment passing through the middle part of the pair of opposite sides. On the other hand, in (b), two triangular display sections are formed by dividing the same entire display screen by one diagonal line.

  Comparing (a) and (b), (b) is advantageous in that a larger maximum effective display range can be secured when the imaging lens is rotated than (a). On the other hand, (a) is advantageous in manufacturing because the shape of the imaging lens becomes simpler than (b).

  In (c) and (d), four display sections are formed by forming convex portions in a quadrangular pyramid shape. However, the display sections have different shapes. Specifically, in (c), four rectangular display sections are formed by dividing the entire display screen into two line segments that pass through the middle part of the two pairs of opposite sides. On the other hand, in (d), four triangular display sections are formed by dividing the entire display screen by two diagonal lines.

  Comparing (c) and (d), (c) is advantageous in that a larger maximum effective display range can be secured when the imaging lens is rotated than (d). On the other hand, (d) is advantageous in manufacturing because the shape of the imaging lens becomes simpler than (c).

  Further, (e) is a convex surface portion formed in a hexagonal pyramid shape and six display sections are formed, and (f) is a convex surface portion formed in an octagonal pyramid shape and eight display sections are formed. Is. As described above, increasing the number of inclined surfaces increases the direction in which imaging can be performed, but the area per display section decreases, so the range that can be displayed for each display section and the maximum effective display range when the imaging lens is rotated It tends to be smaller.

  In (g), the convex surface portion is formed in a triangular pyramid shape, and three display sections are formed. In this case, it is possible to ensure a large range that can be displayed for each display section and a maximum effective display range when the imaging lens is rotated. However, when forming an odd number of inclined surfaces such as a triangular pyramid or a equilateral pyramid on a lens body composed of an even number of sides such as a quadrangle when viewed in plan as in this example, the shape becomes complicated. It takes time to form a lens.

  As described above, the size and shape of the display section on the monitor screen vary depending on the number of inclined surfaces formed on the lens body and the manner of arrangement. Accordingly, the range that can be displayed for each display section and the maximum effective display range when the imaging lens is rotated are different, so it is necessary to select an imaging lens that is suitable for the type of imaging object and the purpose of imaging. Is preferred.

FIG. 14 is a perspective view of an imaging lens according to the second embodiment of the present invention.
The imaging lens 7 shown in FIG. 14 differs from the imaging lens 7 of the first embodiment described above in the shape of the convex surface portion 18. Specifically, a central flat surface portion 20 parallel to the flat surface portion 13 on the semiconductor wafer 1 side is provided at the center of the convex surface portion 18 of the imaging lens 7 shown in FIG. A plurality of inclined surfaces 19 that are inclined so as to protrude from the lens body 12 toward the central flat surface portion 20 are provided around the central flat surface portion 20. Here, although the convex surface part 18 is formed in the shape of a quadrangular pyramid as a whole, it can also be formed in other pyramid shapes. As shown in FIG. 15, in a configuration having two inclined surfaces 19 facing each other, a central flat surface portion 20 can be formed between the inclined surfaces 19.

FIG. 16 is a diagram illustrating a transmission light path of the imaging lens according to the second embodiment.
As shown in FIG. 16, the infrared light transmitted through the semiconductor wafer 1 enters from the flat surface portion 13 of the imaging lens 7 and exits from the inclined surfaces 19 and the central flat surface portion 20 of the convex surface portion 18. At this time, the infrared light emitted from each inclined surface 19 is refracted, and the infrared light emitted from the central flat surface portion 20 goes straight without being refracted, but the infrared light emitted from each inclined surface 19 and the central flat surface portion 20 is The beams are emitted in parallel with each other toward the camera 6. Then, the infrared light emitted in parallel enters the telecentric lens 11 as it is, and is displayed as an infrared image on the monitor 5 via the image sensor 10.

FIG. 17 shows an image of a semiconductor wafer displayed on a monitor via the imaging lens of the second embodiment.
Here, an image displayed when an imaging lens having a quadrangular frustum-shaped convex surface portion is used and an image displayed when an imaging lens having a hexagonal frustum-shaped convex surface portion is used are shown. .

  As shown in FIG. 17A, in the case of using an imaging lens having a quadrangular frustum-shaped convex surface portion, the monitor screen has a quadrangular display section H5 in the center and a trapezoid around it. Semiconductor wafer images P1 to P5 are displayed in the four display sections H1 to H4, respectively. The images P1 to P4 displayed in the four surrounding display sections H1 to H4 are obtained by imaging the semiconductor wafer from obliquely above through the inclined surfaces, and the image P5 displayed in the central display section H5 is The semiconductor wafer is imaged vertically from above (the direction parallel to the imaging direction of the imaging means) through the central flat surface portion.

  In addition, as shown in FIG. 17B, when an imaging lens having a hexagonal frustum-shaped convex surface portion is used, a hexagonal display section H7 at the center and a trapezoidal or pentagonal shape around the hexagonal display section H7. Semiconductor wafer images P1 to P7 are displayed in the six display sections H1 to H6, respectively. Also in this case, the images P1 to P6 displayed in the six surrounding display sections H1 to H6 are images of the semiconductor wafer imaged obliquely from above through the respective inclined surfaces, and are displayed in the central display section H7. The image P7 is an image of the semiconductor wafer taken from above through the central flat surface portion. In FIG. 17, the circled portions e1 to e7 in the images P1 to P7 indicate the same portions in the images P1 to P7.

  As described above, when the imaging lens of the second embodiment is used, in addition to an image obtained by imaging a semiconductor wafer from a diagonally upper side through a plurality of inclined surfaces, the semiconductor wafer is imaged from an upper vertical direction through a central flat surface portion. Images can be obtained simultaneously. In addition, according to the configuration of the second embodiment, it is possible to effectively utilize the vicinity of the center of the display screen by obtaining an image through the central flat surface portion.

The imaging lens of the second embodiment has the following characteristics.
In FIG. 18, an image P7 imaged through the central flat surface portion and an image P1 imaged through one of a plurality of inclined surfaces will be described as an example. The same image on these images P1 and P7. The places e1 and e7 are arranged on the same straight line K orthogonal to the boundary line between the display sections H1 and H7 displaying these images P1 and P7. Further, this relationship is established between the central flat surface portion 20 and all the inclined surfaces 19, and is established regardless of whether the number of the inclined surfaces 19 is an even number or an odd number.

  Further, in the configuration in which the imaging lens 7 has an even number of inclined surfaces 19, the same place is a predetermined straight line between images displayed via the inclined surfaces 19 facing each other, as described with reference to FIG. 7. There is a characteristic placed on top. As described above, the position on each image can be specified based on the characteristics of the imaging lens of the second embodiment.

  Further, as shown in FIG. 19, also in the imaging lens of the second embodiment, the distance between the emission points emitted from the inclined surface 19 and the central flat surface portion 20 regardless of the orientation of the semiconductor wafer 1 with respect to the imaging lens 7. The relationship is constant. That is, in FIG. 19, the emission points at which light from arbitrarily selected imaging points Q1 to Q3 on the semiconductor wafer 1 pass through the inclined surfaces 19 and the central flat surface portion 20 of the imaging lens 7 are denoted by reference numerals, respectively. s1 to s3, t1 to t3, and u1 to u3, and the distances between the emission points s1 to s3, t1 to t3, and u1 to u3 are A and B, a and b, and α and β, respectively. A: B = a: b = α: β. Therefore, even when an image is picked up using the imaging lens of the second embodiment, as in the first embodiment, the correspondence is used to specify the position on each image in correspondence with a simple calculation. It is possible.

  Although not shown in the drawing, in the configuration using the imaging lens of the second embodiment, as in the first embodiment, the imaging lens 7 and the semiconductor wafer 1 are rotated, and an imageable range is targeted. It is also possible to enlarge in the circumferential direction of the object.

FIG. 20 shows examples of various display screens displayed on the monitor when the shape of the convex surface portion is changed in the imaging lens of the second embodiment.
20A to 20G, for the purpose of comparison, the entire size and shape of the display screen of the monitor are all displayed in the same size and shape. In each figure, a circular hatched portion indicates a maximum effective display range in which an imaging target object is displayed without protruding when the imaging lens is rotated in each display section in the display screen.

  In FIGS. 20A and 20B, three display sections are formed by providing inclined surfaces on both sides of the central flat surface portion, but the shapes of the display sections are different from each other. Specifically, in (a), three rectangular display sections are formed by dividing the entire rectangular display screen by two line segments orthogonal to the pair of opposite sides. On the other hand, in (b), the same entire display screen is divided into two line segments parallel to the diagonal line, thereby forming two triangular display sections and one long hexagonal display section.

  Comparing (a) and (b), (b) is advantageous in that a larger maximum effective display range can be secured when the imaging lens is rotated than (a). However, in each of the examples (a) and (b), since the display section extends long, it is difficult to effectively utilize the entire display section particularly when the imaging lens is rotated.

  Further, (c) and (d) are formed by forming the convex surface portion in the shape of a quadrangular pyramid to form five display sections. In (c), the entire display screen is centered. Are divided by line segments drawn from the respective vertices of the rectangle toward the middle portion of each side of the display screen, thereby forming five display sections. On the other hand, in (d), the display screen is divided into five by dividing the entire display screen by a square arranged at the center and a line drawn from each vertex of the rectangle toward each vertex of the display screen. Forming one.

  Comparing (c) and (d), (c) is advantageous in that a larger maximum effective display range can be secured when the imaging lens is rotated than (d).

  Further, (e) is a convex surface portion formed in a hexagonal frustum shape and seven display sections are formed, and (f) is a convex surface portion formed in an octagonal frustum shape and nine display sections. Formed. As described above, increasing the number of inclined surfaces increases the direction in which imaging can be performed, but the area per display section decreases, so the range that can be displayed for each display section and the maximum effective display range when the imaging lens is rotated It tends to be smaller.

  In (g), the convex portion is formed in a triangular frustum shape and four display sections are formed. In this case, the ratio of the maximum effective display range during rotation in the entire display screen is reduced, which is inefficient.

FIG. 21 is a perspective view of an imaging lens according to the third embodiment of the present invention.
In this embodiment, the imaging lens 7 is formed with a through hole 17 that penetrates from the center of the convex surface portion 18 to the center of the flat surface portion 13. A plurality of inclined surfaces 19 that are inclined in different directions are formed around the through hole 17. Here, although the convex surface part 18 is the structure which has the four inclined surfaces 19, the number of the inclined surfaces 19 can also be 2 or 3 or 5 or more. Moreover, the cross-sectional shape of the through-hole 17 is not limited to a quadrangle, and may be formed in other polygons.

FIG. 22 is a diagram illustrating a transmission optical path of the imaging lens according to the third embodiment.
As shown in FIG. 22, the transmission optical path of the imaging lens of the third embodiment is basically the same as the transmission optical path of the imaging lens of the second embodiment shown in FIG. The difference is that in the second embodiment, the light passing through the central portion (central flat surface portion 20) of the imaging lens 7 goes straight through the lens, whereas in the third embodiment, the light passes through the central portion of the imaging lens 7. That is, the light to travel straightly travels through the space (the through hole 17) where there is no lens. However, since the transmitted light path is the same in either case, the image displayed on the monitor is the same.

  Therefore, even when the imaging lens of the third embodiment is used, as in the second embodiment, the semiconductor wafer is simultaneously imaged from a plurality of obliquely upward directions and vertically upward (a direction parallel to the imaging direction of the imaging means). Is possible. Also in the third embodiment, the positional relationship between the images and the imaging range have the same characteristics as in the second embodiment.

  As described above, the imaging lens of the third embodiment and the imaging lens of the second embodiment are the same in that the object can be imaged from diagonally upward and vertically upward, but in terms of manufacturability, the imaging lens of the third embodiment. The configuration is more advantageous. That is, the imaging lens of the second embodiment is troublesome because the central flat surface portion 20 must be formed at the center of the convex surface portion 18. Further, since the central flat surface portion 20 needs to be disposed so as to be parallel to the opposite flat surface portion 13, it is required to process the central flat surface portion 20 with high accuracy. On the other hand, in the case of the imaging lens according to the third embodiment, it is only necessary to form the through hole 17 at the center of the convex portion 18, so that there is an advantage that the processing is easy and the manufacturing cost can be reduced.

  Although not shown, in the configuration using the imaging lens according to the third embodiment, at least one of the imaging lens 7 and the semiconductor wafer 1 may be rotated as in the first embodiment.

  Further, as shown in FIG. 23, the through-hole 17 is formed in a straight shape as shown in FIG. 22 by reducing the diameter of the through-hole 17 from the upper convex surface portion 18 toward the lower flat surface portion 13. Compared to the case, the area of the flat surface portion 13 can be increased. Thereby, it is possible to ensure a large range in which the semiconductor wafer 1 can be imaged from the oblique direction via the inclined surface 19. On the other hand, when it is desired to ensure a large range in which the semiconductor wafer 1 can be imaged from vertically above, the through-hole 17 may be formed in a straight shape.

  As described above, according to the present invention, since a semiconductor wafer can be imaged simultaneously from a plurality of directions, it is easy to find a crack generated in the semiconductor wafer, and the possibility of missing a crack can be reduced. In addition, the semiconductor wafer can be easily imaged from a plurality of directions simply by passing an imaging lens having a plurality of inclined surfaces between the semiconductor wafer and the camera. As a result, it is not necessary to install a plurality of cameras or rotate the cameras, so that the configuration can be simplified and the cost can be reduced.

In addition, this invention is not limited to the above-mentioned embodiment, Of course, a various change can be added in the range which does not deviate from the summary of this invention.
In the above-described embodiment, the case where the imaging lens according to the present invention is applied to an inspection apparatus that inspects for cracks in a semiconductor wafer has been described as an example, but the present invention is also applied to an apparatus that inspects an object other than a semiconductor wafer. It is possible to apply the invention. Further, the imaging object is not limited to a translucent workpiece such as a semiconductor wafer, and may be a non-translucent workpiece. The present invention can also be applied to an imaging apparatus used for purposes other than inspection, such as observation, position recognition, or measurement.

1 Semiconductor wafer (object)
4 Imaging device 6 Camera (imaging means)
7 imaging lens 11 telecentric lens 12 lens body 13 flat surface portion 17 through-hole 18 convex surface portion 19 inclined surface 20 central flat surface portion

Claims (7)

An imaging lens used for imaging an object with an imaging means,
While providing a flat surface portion on the object side surface of the lens body,
Providing a convex surface portion on the surface on the imaging means side opposite to the flat surface portion,
The convex surface portion has a plurality of inclined surfaces inclined in different directions,
An imaging lens configured to emit light incident on the flat surface portion in parallel with each other from the plurality of inclined surfaces.   The imaging lens according to claim 1, wherein a central flat surface portion parallel to the flat surface portion is provided at the center of the convex surface portion.   The imaging lens according to claim 1, wherein a through-hole penetrating from a center of the convex surface portion to a center of the flat surface portion is formed.   The imaging lens according to claim 3, wherein the diameter of the through hole is reduced from the convex surface portion toward the flat surface portion. An imaging apparatus comprising an imaging lens and imaging means for imaging an object through the imaging lens,
An imaging apparatus comprising the imaging lens according to claim 1 as the imaging lens.   The imaging apparatus according to claim 5, wherein the imaging unit is a camera including a telecentric optical system.   The imaging lens or the object is configured to be able to change the imaging direction by rotating around the axis parallel to the imaging direction of the imaging means through the center of the convex surface portion. Imaging device.

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