JP2002341252A - Image acquiring device and image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the resolution of an optical system of an image processor which processes an image obtained by photographing a body to be measured. SOLUTION: An objective 3 which constitutes the optical system 7 of an image acquiring device 2 photographing the body 8 to be measured is increased in NA by having power twice as large as the power with which a visual field including all measurement object places on the body 8 to be measured can be obtained. A relay lens 8 has ×0.5 power and includes a desired range of an image formed on a CCD 6a by reducing the size of the formed image. The resolution is increased by making the NA large, so the optical system 7 has the high resolution without making the visual field narrow.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image acquisition apparatus provided with an optical system for forming an image on an image sensor, and an image processing apparatus incorporating the image acquisition apparatus. Specifically, the resolution of an optical system is improved by providing an objective lens having a magnification higher than a magnification for obtaining a desired field of view and an intermediate lens having a magnification for reducing an image. .

[0002]

2. Description of the Related Art A CCD (charge) is used as an imaging device.
An image processing apparatus incorporating an image acquisition apparatus using a coupled device and an objective lens used in a metal microscope or a tool microscope is an I
By acquiring an image of an object to be measured such as a C package and performing image processing, it is used for, for example, recognizing a vertex as a measurement target portion on the object to be measured and positioning the object to be measured. I have.

Conventionally, the resolution of image processing depends on the number of pixels of a CCD, and has a resolution of 760 × 510. This is due to the widespread use of algorithm processing such as halftone (gray processing), and the data of 1/100 of one pixel has come out, and the resolution has increased 100 times, that is, the resolution of 76000 × 51000. In recent years, with the spread of digital TV standard cameras and corresponding image processing, 112000 × 9600
Some have a resolution of zero.

On the other hand, as for the resolution of the objective lens, if the resolution on the image processing side is about 760 × 510, the objective lens side is superior at any magnification. However, when the resolution on the image processing side is 100 times the resolution, or even 112,000 × 96000, the resolution of the objective lens cannot keep up with this. If the resolution on the image processing side exceeds the resolution of the objective lens, the performance of the image processing apparatus will not be improved unless the resolution of the objective lens is increased. Therefore, it is necessary to increase the resolution of the objective lens.

[0005]

The resolution of an objective lens improves as the numerical aperture (NA) increases. However, when an objective lens having the same magnification and a large NA is manufactured, the objective lens is different from a commonly distributed objective lens.

[0006] When the magnification of the objective lens is increased, the objective lens has a large NA, that is, a high resolution. However, since the viewing angle is narrowed, it is not possible to obtain an image of a portion to be measured on the object at once. For this reason, it is necessary to relatively move the object to be measured and the image acquisition device to acquire the image several times, and it takes a long time for processing, and there is a problem that efficiency is low.

The present invention has been made in order to solve such a problem, and provides an image acquisition apparatus capable of improving resolution without reducing the field of view, and an image processing apparatus incorporating the image acquisition apparatus. The purpose is to do.

[0008]

According to the present invention, there is provided an image acquisition apparatus having an optical system for forming an image on an image sensor, wherein the optical system has an objective having a magnification higher than a magnification for obtaining a desired visual field. An intermediate lens having a lens and a magnification for reducing an image is provided between the objective lens and the image sensor.

In the above-described image acquisition apparatus according to the present invention,
The NA is increased by setting the magnification of the objective lens higher than the magnification for obtaining a desired visual field. Then, since the image formed on the image sensor is reduced by the intermediate lens, a desired field of view can be obtained without lowering the NA. Therefore, an optical system with high resolution can be provided without narrowing the field of view and without using an expensive objective lens with low magnification and high NA.

An image processing apparatus according to the present invention is an image processing apparatus for processing an image of an object to be measured obtained by an image obtaining apparatus having an optical system for forming an image on an image pickup device. And an intermediate lens having a magnification higher than that for obtaining a desired field of view and an intermediate lens having a magnification for reducing an image is provided between the objective lens and the imaging element.

In the above-described image processing apparatus according to the present invention,
The NA is increased by setting the magnification of the objective lens of the image acquisition device higher than the magnification for obtaining a desired visual field. Then, since the image formed on the image sensor is reduced by the intermediate lens, a desired field of view can be obtained without lowering the NA. As a result, the resolution of the optical system is improved without reducing the field of view, so that the resolution of the optical system can catch up with the improvement of the resolution on the image processing side, and image processing can be performed using a more accurate image. It becomes possible.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an image acquiring apparatus according to the present invention and an image processing apparatus incorporating the image acquiring apparatus. That is, FIG. 1 is a schematic configuration diagram of the image processing apparatus of the present embodiment.

The image processing apparatus 1 processes an image acquired by the image acquiring apparatus 2. First, the configuration of the image acquiring apparatus 2 will be described. The image acquisition device 2 includes an objective lens 3, a lens barrel 4, a relay lens 5 as an example of an intermediate lens, a CCD camera 6, and the like.

The objective lens 3 is composed of a lens group 3a formed by combining about ten lenses of various shapes in order to improve the performance such as aberration. The objective lens 3 has a magnification higher than a magnification required to obtain a desired visual field. The objective lens 3 is attached to a CCD camera 6 via a lens barrel 4 having a predetermined length. The CCD camera 6 includes a CCD 6a as an example of an image sensor, and an interface for outputting data acquired by the CCD 6a to the outside.

The relay lens 5 includes an objective lens 3 and a CCD.
It is attached to the lens barrel 4 so as to be located on the optical axis between 6a. The relay lens 5 has a magnification for reducing an image formed on the CCD 6a. The relay lens 5 is composed of one convex lens or a combination of about two convex lenses in order to form an image of the transmitted light by the CCD 6a.

In the image acquisition device 2 of the present embodiment, the CCD 6a is formed by the objective lens 3 and the relay lens 5 described above.
The optical system 7 forms an image on the optical system. Note that another lens may be added to the optical system 7 for the purpose of correcting aberrations and the like.

The image acquisition device 2 faces the objective lens 3.
X-Y table 9 on which the DUT 8 to be photographed is set
Is provided. The XY table 9 is moved in the X and Y directions by a mechanism such as a ball screw and a motor (not shown).
It has a structure that can move horizontally in any direction.

The image processing device 1 is connected to the above-described image acquisition device 2 by a signal line 10. CCD camera 6
Is sent to the image processing apparatus 1 through the signal line 10 and subjected to image processing to output position data and the like. Then, based on the output position data and the like, the DUT 8 is measured.
The measurement of the distance between the above measurement target locations and the positioning of the device under test 1 for mounting elements are performed when the device under test 1 is, for example, an IC package.

The resolution of image processing in the image processing apparatus 1 conventionally depends on the number of pixels of the CCD 6a,
The resolution was × 510. This is due to the spread of algorithm processing such as halftone (gray processing), which is 1/100 of one pixel.
Data comes out, 76000 × 51000
, Or higher.

FIG. 2 is an explanatory view showing the relationship between the field of view of the objective lens and the size of the object to be measured. The objective lens 3 of the image acquisition device 2 according to the present embodiment will be described below with reference to FIGS.
And the relationship between the magnification of the relay lens 5 will be described. First,
A description will be given of a configuration excluding the relay lens 5 from the image acquisition device 2 shown in FIG. Assuming that the distance between the objective lens 3 and the object 8 is the same, the field of view is wide when the magnification of the objective lens 3 is low, and the field of view is narrow as the magnification increases, and the obtained image is enlarged. It is assumed that two vertices P1 and P2 on one diagonal line are measurement points on the DUT 8 having a square planar shape. And the size of the DUT 8 is
When the DUT 8 is located at a predetermined distance from the objective lens 3, as shown in FIG.
The size is such that both the two points P1 and P2 of the measurement target portion on the DUT 8 are included in the visual field Q obtained at the viewing angle in the case of the magnification. On the other hand, in the field of view R obtained at a field angle when the magnification of the objective lens 3 is 10 times, as shown in FIG. It is possible to capture either one of these.

The higher the NA of a lens, the higher the resolution (resolution) of the lens. However, the NA of a commonly distributed objective lens 3 is almost determined with respect to the magnification. The NA of the objective lens 3 increases as the magnification increases. Therefore, here, the magnification of the objective lens 3 is 1 more than when the magnification is 5 times.
When the magnification is 0, the NA is larger, and from the viewpoint of the resolution, the magnification of the objective lens 3 is more preferably 10 times.

However, when the magnification of the objective lens 3 is 10
Since the field of view R in the case of the magnification is narrower than the field of view Q in the case of the magnification of 5 times, the two vertices P1 and P2 of the measurement target portion on the object 8 are measured.
Cannot be captured at once.

For this reason, first, the position of the DUT 8 with respect to the visual field R is shown by a solid line in FIG. 2 (b) such that one vertex P1 of the two points to be measured enters the visual field R. An image including this vertex P1 is acquired as the position indicated by. Next, the DUT 8 is measured using the XY table 9 described with reference to FIG.
2B, or the image acquisition device 2 side is horizontally moved by a mechanism (not shown) so that the position of the DUT 8 with respect to the field of view R is adjusted so that the other vertex P2 enters the field of view R in FIG. An image including this vertex P2 is acquired as a position indicated by a broken line in ()). It is necessary to repeat such an operation several times until a required image is obtained, and to combine the obtained images by calculation.

As described above, when the magnification of the objective lens 3 is higher than the size of the DUT 8, one DUT 8 is moved while the DUT 8 and the image acquisition device 2 are relatively moved. Needs to be shot several times, which takes time to process.

Generally, the XY table 9 is horizontally moved by a mechanism using a ball screw.
As the positioning accuracy is increased, the lead amount is reduced, so that the time required to move the device under test 8 by a predetermined amount becomes longer. Therefore, the time required to divide one object under test 8 into several shots increases with the improvement in accuracy and becomes inefficient.

On the other hand, if the magnification of the objective lens 3 is 5 times, the entire surface of the object 8 enters the visual field Q, and the two points P1, P1 Since the image of P2 can be acquired, the magnification of the objective lens 3 is more preferably 5 times from the viewpoint of the viewing angle.

However, the NA of a commonly distributed objective lens 3 is almost determined in accordance with the magnification thereof, and a sufficient resolution cannot be obtained with an ordinary five-times objective lens 3.

Here, the viewing angle of the objective lens 3 is generally about twice as large as the viewing angle at the indicated magnification. For example, with a 10 × objective lens, a viewing angle equivalent to the viewing angle of a 5 × objective lens is ensured.
A range equivalent to the field of view of a double objective lens can be captured.

In the image acquisition device 2 of the present embodiment, since a five-fold objective lens is desirable as the viewing angle, the objective lens 3 has a ten-fold viewing angle equivalent to that of the five-fold objective lens. Use an objective lens. Since the obtained image is enlarged by the 10 × objective lens 3, the 0.5 × relay lens 5 is inserted. This allows
The image formed on the CCD 6a is reduced to a size equivalent to an image obtained with a 5 × objective lens. Therefore, although the 10 × objective lens 3 is used, the viewing angle and the size of the image are equivalent to those of the 5 × objective lens.

On the other hand, since the NA is 10 times the objective lens 3, it is larger than the usual 5 times objective lens. Since the relay lens 5 only reduces the image, the insertion of the relay lens 5 does not lower the NA. Therefore, by combining the objective lens 3 having a magnification of 10 times and the relay lens 5 having a magnification of 0.5 times, the NA of the objective lens is increased by 10 times, and the viewing angle is equivalent to the case of using the objective lens having a magnification of 5 times. The optical system 7 can be obtained.

Since the NA can be increased even when the magnification is low, it is possible to provide the image acquisition device 2 having a high resolution of the optical system 7 without reducing the field of view. By incorporating the image acquisition device 2 having such a high resolution of the optical system 7 into the image processing device 1, the resolution of the optical system 7 can catch up with the resolution of the image processing side. When the resolution of the optical system 7 is improved, the obtained image data becomes more accurate and closer to the device under test 8.

The image processing apparatus 1 performs image processing using more accurate image data, and outputs, for example, position data. This makes it possible to perform highly accurate positioning and the like by utilizing the resolution of the image processing side.

Since the magnification of the optical system 7 can be kept low, a large field of view can be obtained. Therefore, the measured object 8
Alternatively, a plurality of locations to be measured on the DUT 8 can be photographed at once without moving the image acquisition device 2, and the processing speed can be improved.

Here, in the present embodiment, the objective lens 3
Although the description has been made with the magnification of 10 times, the present invention is not limited to this. In other words, the objective lens 3 having a magnification of 2N times has a viewing angle equivalent to that of an objective lens having a magnification of N times.
It is possible to use an N-times objective lens 3. Since the NA is proportional to the magnification, it is desirable to use a 2N-times objective lens 3.

An optical system using an N-times objective lens requires 2
The fact that it is desirable to use an N-times objective lens 3 means that a relay lens 5 must be used in order to obtain a desired range of visual field.
Is preferably 0.5 times. If the magnification of the relay lens 5 is smaller than 0.5, vignetting occurs in an image obtained due to a viewing angle, which is not preferable.

If the magnification of the objective lens 3 is smaller than 2N times under the condition that the size of the object 8 to be measured is the same and the image size to be acquired is the same, the magnification of the relay lens 5 is 0.5 times. Need to be larger, but N
Since A is lowered, when priority is given to improvement in resolution, it is desirable to use a 2N-times objective lens 3 and a 0.5-times relay lens 5 in an optical system in which an N-times objective lens is used.

It should be noted that a 2N-times objective lens 3, for example, a magnification of 10 in the present embodiment is 10 times that of an N-times objective lens.
The 2 × objective lens 3 is not expensive compared to the 5 × objective lens. Further, the relay lens 5 includes a CCD 6a
Since only the size of the image to be formed is reduced, it can be realized by a combination of one convex lens or about two convex lenses. Therefore, the cost of the relay lens 5 can be reduced. Therefore, the optical system 7 having a visual field in a desired range and a large NA can be provided at low cost.

The relay lens 5 is manufactured and incorporated so as to form an image on the CCD 6a.
When the magnification of the objective lens 3 is changed by changing the size of the lens, the replacement of the relay lens 5 is not necessary, only the replacement of the objective lens 3. Therefore, one type of relay lens 5 can be widely distributed and can be provided at a lower cost.

[0039]

As described above, according to the image acquisition apparatus of the present invention, in an image acquisition apparatus having an optical system for forming an image on an image sensor, a magnification higher than a magnification for obtaining a desired visual field is used as the optical system. And an intermediate lens having a magnification for reducing an image is provided between the objective lens and the image pickup device.

In the above-described image acquisition apparatus according to the present invention,
The NA is increased by setting the magnification of the objective lens higher than the magnification for obtaining a desired visual field. Then, since the image formed on the image sensor is reduced by the intermediate lens, a desired field of view can be obtained without lowering the NA. Therefore, an optical system with high resolution can be provided without narrowing the field of view.

When an objective lens having a low magnification and a high NA is used, the objective lens becomes expensive.
Since it is not necessary to use such an objective lens having a low magnification and a high NA, a desired visual field can be obtained and an optical system having a high resolution can be provided at low cost.

The image processing apparatus according to the present invention incorporates the image acquisition apparatus with the improved resolution of the optical system as described above, and thereby improves the resolution of the optical system without narrowing the field of view. Since the resolution of the optical system can catch up with the improvement of the resolution on the image processing side, it becomes possible to perform image processing using a more accurate image.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image processing apparatus according to an embodiment.

FIG. 2 is an explanatory diagram showing a relationship between a field of view of an objective lens and a size of an object to be measured.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image processing apparatus, 2 ... Image acquisition apparatus, 3 ...
・ Objective lens, 4 ・ ・ ・ Barrel, 5 ・ ・ ・ Relay lens,
6 ... CCD camera, 6a ... CCD, 7 ... optical system, 8 ... DUT, 9 ... XY table

Claims (5)

[Claims] 1. An image acquisition apparatus comprising an optical system for forming an image on an image sensor, wherein said optical system includes an objective lens having a magnification higher than a magnification for obtaining a desired visual field and a magnification for reducing an image. An image acquisition apparatus, comprising: an intermediate lens provided between the objective lens and the image sensor. 2. The lower limit of the magnification of the relay lens is 0.5.
2. The image acquisition apparatus according to claim 1, wherein the number is doubled. 3. An apparatus according to claim 1, wherein an upper limit of a magnification of the objective lens is twice as large as a magnification for obtaining a desired visual field.
The image acquisition device according to the above. 4. An image processing apparatus for processing an image of an object to be measured acquired by an image acquisition device having an optical system for forming an image on an image sensor, wherein a desired field of view is obtained as the optical system of the image acquisition device. An image processing apparatus comprising: an objective lens having a magnification higher than a magnification; and an intermediate lens having a magnification for reducing an image is provided between the objective lens and the imaging element. 5. The magnification of the objective lens is twice as large as a magnification for obtaining a field of view including all measurement target points on the object to be measured, and the magnification of the relay lens is 0.5. The image processing apparatus according to claim 4, wherein