JPH0347737B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides high-precision images of two imaging parts set at positions separated by a certain distance, such as leads located on opposite sides of an LSI, using a single imaging means. The present invention relates to a method of imaging.

[Conventional technology]

A solid-state image sensor (hereinafter referred to as
Recently, it has become popular to use devices such as CCD (CCD) and image pickup tubes to inspect bent LSI leads, the shape of electronic components, and other circuit patterns. With these devices, the amount of information that can be captured is
The measurement resolution is determined by the number of pixels of the CCD and the number of scanning lines of the image pickup tube, so if the imaging field of view is increased, the measurement resolution will decrease, and if the image is taken at a high magnification to improve the measurement resolution, the field of view will be narrower. There is a problem of becoming. Therefore, when trying to obtain high-magnification images of two distant parts of a measurement target using these devices, each part is imaged while moving the measurement target or the imaging means, but it is necessary to use multiple imaging means. Positioned at each imaging site,
There is no choice but to simultaneously image two imaging regions.

[Problem that the invention seeks to solve]

However, in the method of moving the measurement target or the image means, the device configuration is complicated and
Since positioning requires a lot of time, there have been problems with work efficiency and consistency with other work processes placed before and after the process. Furthermore, although the method of providing a plurality of imaging means can shorten the measurement time, it inevitably increases the manufacturing cost, which is a factor in increasing the product price.

[Means for solving problems]

The present invention has been made in view of the current situation, and allows highly accurate imaging of two imaging regions separated from each other using a single imaging device without moving the measurement target or imaging means or increasing the number of imaging means. The purpose is to do something by means.

Generally, when obtaining high-precision images of the measurement target,
It is rarely necessary to obtain all images within each field of view in perfect condition, and in many cases, the purpose of quality inspection etc. cannot be achieved if high-precision images are obtained only of the important parts within each field of view. It will be done. The present invention has been completed by paying attention to this fact and considering that this object can be achieved by combining image information obtained from two fields of view using an equilateral prism.

A first invention that achieves this object is characterized in that an equilateral triangle is arranged in a direction perpendicular to a plane containing two imaged regions of the measurement target and at a position spaced a predetermined distance from a substantially midpoint between both imaged regions. The prism is positioned with one apex angle facing the intermediate point, and a scattering surface light source is placed on the opposite side of the measurement target to the side where the prism is located to illuminate the imaged area from behind in an oblique direction. The light that has passed through two different imaged areas is made to enter the two adjacent outer surfaces of the prism from the substantially normal direction of the sides, and after being totally reflected within the prism, a portion of both lights is reflected. Combining is performed while being superimposed, and the combined combined light is emitted to the outside of the prism from a side surface different from the light incident side, and the combined light is received by an imaging means disposed in front of the combined light in the direction in which the combined light travels. It is characterized by:

Furthermore, the gist of the second invention, which is an improvement on the first invention, is as follows:
In the first invention, a screen is interposed between the measurement object and the equilateral prism, and the illumination light source is a parallel light source, and the irradiation angle to the measurement object is changed to create a silhouette of the measurement object corresponding to each irradiation angle. This method is characterized in that an image is projected onto a screen twice, and each silhouette image is captured through an equilateral prism, similar to the first invention.

[Effect]

The present invention, which has such an optical system, uses a prism to combine images of two fields of view, that is, images of two imaged parts set at mutually distant positions on the measurement target, and removes unnecessary parts of the measurement target. Since only the necessary parts are synthesized at a close position, it is possible to capture images of two fields of view with a single imaging device without reducing the resolution.

〔Example〕

Next, details of the present invention will be explained based on illustrated embodiments. FIG. 1 is an explanatory diagram showing the entire optical system according to the present invention, and FIG. 2 shows the main parts thereof. 1
is the measurement target, 2a and 2b are illumination light sources, 3 is an equilateral prism, 4 is an imaging means, and the imaging means 4CCD
It is composed of an imaging means main body 5 and an objective lens 6 for image resolution. Measurement object 1 is actually an LSI, other electronic components, or even a circuit pattern printed on a transparent board, but here, to simplify the explanation, an arrow is placed at one end and a circle is placed at the other end. This will be explained using a straight line. The measurement object 1 is roughly divided into a left side 1a, a right side 1b, and a center 1c. The central portion 1c is a portion that does not need to be imaged, and corresponds to the mold portion when an LSI is selected as the measurement target.

An equilateral prism with an apex angle of 60° is placed at the bottom center of the measurement object 1, with the apex angle 7 directed toward the center of the measurement object, while an equilateral prism 3 with the measurement object 1 sandwiched therebetween is placed. On the sides, an illumination light source 2a that illuminates the left side 1a of the measurement object 1 and an illumination light source 2b that illuminates the right side 1b are arranged. The illumination light sources 2a and 2b are scattering surface light sources, and their arrangement positions are on the left side 1a, which is the imaging region.
The configuration is such that the transmitted light that has passed through the right side portion 1b is incident on the side surfaces 3a and 3b of the prism 3 from approximately the normal direction. Further, an imaging means 4 is arranged vertically below the prism 3 so that the distance from the prism 3 can be increased or decreased.

In the optical system having such a configuration, the light emitted from the illumination light source enters the imaging means body 5 through the following optical path and forms an image of the measurement target.

For example, light emitted from the illumination light source 2a illuminates the measurement object 1 from diagonally above, passes through the left side 1a of the measurement object 1, and then enters the side surface 3a of the prism 3 from a substantially normal direction. On the side surface 3a, there is a measurement object 1.
Of the light that irradiates the entire area, only the light that has passed through the left side 1a is incident, and the light that has passed through the center 1c from the right side of the left side 1a does not enter the prism 3.
Therefore, the central portion 1c is excluded from the imaging target.

Since the incident direction of the light entering the prism 3 from the side surface 3a is approximately the normal direction, the light passes through the side surface 3a without being refracted, travels straight through the prism 3, and enters the adjacent side surface 3b from inside the prism 3. do. The entrance angle at this time is about 60°, and the light incident at this angle is totally reflected, then passes through the bottom surface 3c of the prism 3 and exits the prism 3. The light exiting from the prism 3 is condensed by an objective lens 6 placed a certain distance away from the prism 3, and a silhouette image 1a' of only the left side 1a of the measurement object 1 is formed on the imaging means main body 5. It is something to do. Although the above description is about the optical path of the light rays emitted from the illumination light source 2a, the same optical path also holds true for the light emitted from the illumination light source 2b, so the imaging means main body 5 has a right side 1b formed by the illumination light source. silhouette image 1
b' and the silhouette image 1a' on the left side are partially overlapped 1
The image will be formed as d′. The image of the superimposed 1d' portion does not preserve the original shape of the measurement target, so it cannot be used as data for image analysis.
There is no problem if this part is excluded from the image analysis target. In other words, the method of the present invention is applied to a measurement object in which the part of the measurement object corresponding to the overlapping portion does not need to be measured.

By following such an optical path, the central part 1c of the measurement object 1 is excluded and only the silhouette images of the left side 1a and the right side 1b are combined by the prism 3, and the combined silhouette image is captured by the imaging means 4. As a result, images of two fields of view placed apart from each other can be captured by one imaging means.

In the present invention, in response to an increase or decrease in the size of the object to be measured, that is, an increase or decrease in the distance between the two fields of view, the illumination light sources 2a and 2b are moved horizontally, and the prism 3 and the imaging means 4 are moved up and down, as shown in FIG. Respond by moving. For example, when imaging the left side 1a and the right side 1b, the illumination light sources 2a, 2b, prism 3, and objective lens 6 are placed at the positions shown by solid lines in the figure, and the imaging means 4 is placed at the positions shown by broken lines in the figure. However, when the object to be measured becomes larger and the distance between the imaged areas increases and the imaged areas become the left side 1a' and the right side 1b', the illumination light sources 2a' and 2b' , prism 3', objective lens 6', and imaging means main body 5' are set so as to satisfy the arrangement relationship shown by imaginary lines in the figure.

That is, the left side portion 1a is affected by the irradiation light from the illumination light source 2a.
The illumination angle γ of the illumination light source 2a' to the left side 1a' is always set to be equal to the illumination angle γ' of the illumination light from the illumination light source 2a' to the left side 1a'.For this reason, the illumination light source is movable in the horizontal direction. ing. Furthermore, the prism 3 and the imaging means 4 are configured to be vertically movable, and the amount of movement is based on the fact that the incident light on the prism 3 always enters from the normal direction to each side surface 3a, 3b. The image capturing means 4 moves the objective lens 6 and the image capturing means main body 5 integrally to adjust their position so that the silhouette image formed on the image capturing means 4 has a constant size and is focused correctly. It is something to be adjusted. And the distance between the two fields of view L1
When the prism 3 is enlarged, the prism 3 is moved downward in the vertical direction, while the imaging means 4 is moved upward to reduce the distance L2 between the prism 3 and the imaging means 4, and a silhouette image of the object to be measured is displayed on the imaging means main body 5'. It forms an image. In this embodiment, the measurement target can be enlarged by moving the illumination light source horizontally, but even if the illumination light source remains fixed, the light emitting area of the illumination light source itself can be increased to accommodate the enlargement of the measurement target. I can do it.

Next, a case will be described in which the present invention is applied to a flat IC lead inspection device. The appearance of the flat IC9 to be measured is shown in Figure 4.
The structure is such that a plurality of lead pins 11 bent in a hook shape are provided around a flat mold part 10. Since the flat IC 9 has a large number of lead pins 11 arranged at narrow intervals, bending of the lead pins 11 may cause poor contact or short circuit when mounted on a board. Therefore, the bending test of the lead pin 11 is widely recognized as an extremely important test.

The lead pin 11 can be bent in the width direction x of the lead pin 11 and in the thickness direction y of the lead pin 11, but bending in the thickness direction y appears as a floating phenomenon of the lead pin when mounted on a board, causing poor contact, and Since bending in the width direction x causes the lead pins to come into contact with each other and short-circuiting the circuit, bending in either direction must be strictly inspected. As a method for simultaneously inspecting the bending of lead pins in the thickness direction y and the width direction
However, this embodiment applies the present invention to the above application to reduce the number of imaging means and shorten the inspection time.

FIG. 5 is an explanatory diagram showing the concept of this embodiment.
Immediately below the flat IC 9, an equilateral prism 3 with an apex angle of 60° is arranged so as to be vertically movable, and at a lower position spaced a certain distance from the prism 3, the direction of the light emitted from the bottom surface 3c of the prism 3 is arranged. A right angle prism 12 is arranged to change the direction. or,
A camera 14 associated with an objective lens 13 is disposed on the horizontal side of the right-angle prism 12 at a position where it can receive the light emitted from the right-angle prism 12. In this example, as the camera 14
Although a CCD is used, it is also possible to use an image pickup tube. The right angle prism 12, objective lens 13 and camera 14 are fixed on a mounting table 15,
These are configured to be able to move up and down integrally in the vertical direction while maintaining a distance from each other. The reason why the mounting table 15 is configured to be able to move up and down is to offset the change in the optical path length between the lead pin and the equilateral prism caused by the difference in the size of the flat IC 9. Although the direction is opposite, it is possible to set it equal to the vertical movement l2 of the equilateral prism 3 corresponding to the size of the flat IC 9. When set in this way, the distance between the mounting table 15 and the prism 3 is Vertical movement can be performed using a drive source. For example, the mounting table 15 and the prism 3
As shown in FIG. 6, the drive mechanism for simultaneously moving up and down is provided with a shaft body 18 having screw grooves 16 and 17 in a reverse screw relationship on both ends in the length direction, and the shaft body 18 has a gear 19. A prism support 21 for supporting the prism 3 is provided in the upper part of the shaft body 18 in relation to the screw groove 16, and a right angle prism 12, an objective lens 13 and A configuration in which a mounting table 15 supporting the camera 14 is provided in relation to the screw groove 17 is adopted. In the figure, reference numerals 22, 22, . . . indicate guide shafts for stably supporting the prism support stand 21 and the mounting table 15, which move up and down along the shaft body 18.

Diagonally above the flat IC 9, an illumination light source 2a,
2b is arranged so as to be movable in the horizontal direction. The left lead 11 is emitted from the illumination light sources 2a and 2b.
a, the irradiation angle γ of the light passing through the right lead 11b is set to about 30° so that the light after passing through the lead enters the side surfaces 3a and 3b of the prism 3 from the normal direction.

In order to detect lead bending of the flat IC 9 using the apparatus having the above configuration, the following procedure is performed.

The light transmitted through the left lead 11a and right lead 11b of the flat IC 9 is transmitted to each side 3 of the prism 3.
The illumination light sources 2a and 2b are moved horizontally, the prism 3 is moved up and down, and the mounting table 15 is moved up and down to form a silhouette image of the lead on the camera 14 so that the illumination light sources 2a and 3b are incident from the normal direction. let The horizontal movement distance of the illumination light sources 2a and 2b,
There is a certain relationship between the vertical movement of the prism 3 and the mounting table 15, and these three are moved in relation to each other. In particular, the elevation of the prism 3 and the mounting table 15 are controlled by the same driving source as shown in FIG.

The light emitted from the illumination light sources 2a and 2b enters the left lead 11a and the right lead 11b at an angle of approximately 30°, and then enters each side surface 3a and 3b of the prism 3 from the normal direction. The light incident on the side surfaces 3a, 3b travels straight through the prism 3 without being refracted, since the direction of incidence is perpendicular to the side surfaces 3a, 3b, and the light enters the opposing side surfaces 3b, 3a at an angle of approximately 60°. It enters the prism at the incident angle and undergoes total reflection, and the prism bottom surface 3c
The light is ejected from the prism 3 to the outside. The light emitted to the outside of the prism 3 has a left lead 11a and a right lead 11b.
contains the light that has passed through it in a synthesized state,
This light enters a right angle prism 12 located directly below the equilateral prism 3. Right angle prism 12
The light whose traveling direction has been converted to the horizontal direction is focused by the objective lens 13 and then focused by the camera 14.
Silhouette images of the left lead 11a and the right lead 11b are formed on the left lead 11a and the right lead 11b.

Since there are various sizes of flat ICs, the distance between the left lead and the right lead may be large as shown in the figure as left lead 11a' and right lead 11b', but in this case, the illumination light source and horizontal movement This can be easily handled by vertical movement of the equilateral prism and the mounting table.

FIG. 7 is a silhouette image of the lead taken by the camera 14. The silhouette image is left lead 1
Silhouette image A of 1a and silhouette image B of right lead 11b are synthesized in a partially overlapping state C', but only the silhouette images A' and B' on the tip side of the lead part are subject to inspection. So there is no problem.

A bend in the width x direction of the lead also appears as a bend in the width direction 11x in the silhouette image, while a bend in the thickness direction y of the lead is a shortening of the lead length 11
Since it appears as y, lead bending can be easily detected by image processing the silhouette image.

In this way, in the field of view of the camera 14, the silhouette image of the lead located on the opposite side is captured with the mold part interposed in between omitted.
Even when the imaging magnification is increased, the image does not protrude from the field of view, making it possible to obtain a high-magnification image of the lead.

If the above-described embodiment device is used, flat
Although normal IC tests can be carried out satisfactorily,
Next, an embodiment of the apparatus embodying the second invention, which is capable of more accurate measurement, will be disclosed.

As mentioned above, bending in the thickness direction y of the leads of flat IC9 appears as a shortening of the lead length in the silhouette image. If the lead is bent in the thickness direction y, the lengthening and shortening of the lead cancel each other out on the silhouette and no change appears in the position of the tip of the lead in the silhouette image. The problem is that it cannot be detected. This embodiment makes it possible to detect even such a special bend. What is shown in FIGS. 8 and 9 are conceptual diagrams of this embodiment. The figure shows the flat IC viewed from the side of the mold, and only the tip end of the lead is shown.
In this embodiment, in order to achieve the above problem, a screen 8 is provided between the flat IC 9 and the equilateral prism 3.
At the same time, a parallel light source is used as the illumination light source, and while changing the illumination angle θ, a silhouette image corresponding to each illumination angle θ is projected on the screen 8, and the same region is imaged twice. A method of capturing images was used. That is, in the embodiment described above, the silhouette images of the left lead and the right lead were directly captured by the camera, but in this embodiment, the silhouette images of the leads projected on the screen 8 were captured, and this imaging This is carried out twice while changing the irradiation angle θ, obtaining silhouette images corresponding to each irradiation angle, and detecting lead bending by comparing both silhouette images.

That is, as shown in FIG. 8, a screen 8 is placed at a certain distance t from the bottom surface of a large number of parallel leads 11, and the first time, parallel light is irradiated from vertically above (θ=90°) the flat IC 9. A silhouette image of the lead is projected onto the screen 8, and the silhouette image is captured through the prism 3. Next, the illumination light source is moved horizontally in a direction perpendicular to the length direction of the lead to irradiate parallel light from diagonally above the lead, and at this time a silhouette image is captured. The bending of the lead is detected by processing the images obtained by these two imaging operations. The bending of the lead can be detected from the images obtained by imaging twice as follows.

For example, when the irradiation angle of light in the oblique direction is θ, the pitch P and the float d between the leads 11 satisfy the following relational expression: L(θ)=1/sinθ(Psinθ−dcosθ).

(L(θ) is the screen 8 when the incident angle is θ.
This is the pitch of the projected image. ) When θ=90°, L(90)=P When θ=45°, L(45)=P−d Therefore, P=L(90) d=L(90)−L(45) Relational expression As shown in Figure 8, this relational expression is calculated by taking a projected image when the lead is illuminated from vertically above and a projected image when illuminating it at an incident angle of 45°. Image pitch L (90), L (45)
This means that if you measure the lead pitch P and float d, you can treat them as independent values. Note that the projected image is captured through an equilateral prism, similar to the first embodiment. In this way, according to this embodiment, it is possible to reliably detect bending and floating of the lead in the width direction simply by measuring the image pitch, and especially regarding the floating d, it is possible to detect the bending and floating of the lead in the width direction. Even if there is heat, it can be detected accurately. In this embodiment, the irradiation angle θ was set to 90° and 45° to facilitate calculation, but the irradiation angle θ can also be set to other angles.

As mentioned above, the lead inspection device started as an embodiment of the first invention and the second invention can be used alone,
It is also optional to incorporate it into a so-called mounting device used to automatically arrange electronic components onto a board.

In the above embodiment, the illumination light source is a flat IC.
Although the prism, camera, etc. are positioned at the bottom of the flat IC, it is of course possible to position the illumination light source at the bottom of the flat IC and the prism and camera at the top.

A lead inspection device with this configuration is a flat
A single camera can capture a high-magnification silhouette image of the leads located on the opposite side of the IC, excluding the mold part intervening between the leads, making it possible to reduce the number of cameras and improve lead inspection. This can contribute to lowering the cost of the device.
Moreover, since the leads on the opposite side can be inspected at the same time, inspection time can be shortened and inspection work can be made more efficient. Especially when combined with mounting equipment,
This eliminates wasted processing time between processes, which conventionally took longer to inspect the flat IC leads than it took to mount the flat IC on the board, making it possible to speed up the entire mounting process. becomes. Furthermore, since the apparatus of this embodiment can easily be used for testing flat ICs of different sizes, the apparatus can be applied to testing all kinds of flat ICs.

Furthermore, in the lead inspection device disclosed as the second embodiment, in addition to the effects of the first embodiment, bending of the lead pin in the width direction and thickness direction can be achieved by changing the pitch of the lead pin projected on the screen by changing the illumination angle. Since inspection can be performed by just measuring once, image processing becomes extremely easy. Moreover, according to the present device, even if there is variation in the length of the lead pins, floating of the lead pins can be reliably detected, so that the inspection of the lead pins becomes even more accurate.

〔Effect of the invention〕

According to the two-view imaging method disclosed as the first invention, images of imaged parts of the measurement target set apart from each other are combined by using a prism to exclude unnecessary parts between the two imaged parts. It becomes possible to obtain high-magnification images, and the imaging of two fields of view, which was conventionally done by using multiple imaging means or moving the imaging means, can now be performed with a single imaging means. . When the present invention is applied to various inspection devices, the inspection time can be significantly shortened because the imaging means does not have to be moved frequently, and the number of imaging means can also be reduced, which reduces the inspection equipment and manufacturing costs. It can also contribute to the reduction of

The present invention allows the prism to be moved up and down even when the distance between the parts to be imaged changes, such as the size of the measurement target.
That is, this can be handled by moving in a direction perpendicular to the plane containing the two imaged regions. Since the light that has passed through the imaged area is set to always enter the outer surface of the prism from the approximately normal direction, each The posture of the imaging target remains almost constant regardless of whether the distance between the imaging target parts is expanded or reduced. Therefore, the image obtained by the imaging means is not distorted and can always be measured with high precision. In addition, in the method of the present invention, since a silhouette image is captured by illuminating the imaged area from behind in an oblique direction, there is no reflection on the surface of the imaged area, and measurements can be performed without being affected by the surface condition of the imaged area. I can do it.

In addition, in the two-view imaging method disclosed as the second invention, a screen is interposed between the measurement target and the prism, and the silhouette image of the measurement target is projected twice on the screen while changing the irradiation angle to capture both silhouettes. Since the object to be measured is inspected by comparing the images, more accurate inspection becomes possible. In particular, when the second invention is applied to a flat IC lead inspection device, it becomes possible to accurately detect lead pitch and float even when there are variations in lead length, and perfect inspection can be performed.

[Brief explanation of drawings]

Figures 1 and 2 are principle diagrams of the first invention, Figure 3 is a principle diagram of an embodiment of the first invention, and Figure 4 is a flat diagram.
An external view of the IC, FIG. 5 is an explanatory diagram of an embodiment of the first invention, FIG. 6 is a simplified explanatory diagram showing an embodiment of the optical system moving mechanism in the first invention, and FIG. 7 is an imaged silhouette. FIGS. 8A and 8B are diagrams showing the principle of the second invention, and FIGS. 9A and 9B are explanatory diagrams showing silhouette images of the leads taken according to the second invention. 1: measurement object, 2: illumination light source, 3: equilateral prism, 4: imaging means, 5: imaging means main body, 6: objective lens, 7: vertex angle, 8: screen, 9: flat IC, 10: mold part, 11: Lead pin,
12: Right angle prism, 13: Objective lens, 14:
Camera, 15: Mounting table, 16: Spiral groove, 1
7: Spiral groove, 18: Shaft, 19: Gear, 20: Drive source, 21: Prism support, 22: Guide shaft.

Claims (1)

[Scope of Claims] 1. A method for imaging an imaging region included in two mutually separated fields of view of a measurement object, the method comprising: a direction perpendicular to a plane containing two imaging regions of the measurement object; An equilateral triangular prism is positioned at a predetermined distance from the approximate midpoint between the prisms, with one vertex of the prism facing toward the midpoint, and on the opposite side of the measurement target to the prism. A scattering surface light source is arranged to illuminate the imaged area from behind in an oblique direction, and the light that has passed through two different imaged areas is incident on two adjacent outer surfaces of the prism from a direction substantially normal to the outer surfaces. After being totally reflected within the prism, both lights are combined while partially superimposed, and the combined combined light is emitted to the outside of the prism from a side different from the incident side, and the combined light is A two-field imaging method in which combined light is received by an imaging means placed in front of it in the direction in which it travels. 2. In a method of imaging an imaged area included in two mutually separated fields of view of a measurement object, in a direction perpendicular to a plane containing the two imaged areas of the measurement object, and from approximately the midpoint between the two imaged areas. An equilateral triangular prism is positioned at a predetermined distance apart, with one apex of the prism facing the intermediate point, and a screen is interposed between the measurement target and the prism, and the prism is placed on the side of the prism with the measurement target in between. On the opposite side, a collimated light source that illuminates the imaged area from behind is arranged, and by changing the illumination angle of the parallel light source, a silhouette image of the imaged area is projected onto the screen twice, and each captured image is The light scattered on the bottom surface of the screen is made to enter the two adjacent outer surfaces of the prism from the direction of the normal to each side, and after being totally reflected within the prism, the light is combined by partially overlapping the two lights. A two-field imaging method in which the combined light is emitted to the outside of the prism from a side surface different from the light incident side, and the combined light is received by an imaging means disposed forward in the direction in which the combined light travels. .