JP2013238522A - Multifocal imaging apparatus - Google Patents

Abstract

An object of the present invention is to provide an optical measurement device using a multifocal image that can be measured while being mounted on an XY moving table.
SOLUTION: The focal plane is changed at high speed by a high-speed focal point moving mechanism using a rotating disk in which parallel plane transparent bodies having different thicknesses are arranged on the circumference, and the optical path of the objective lens system is bent 90 degrees by a mirror or a right-angle prism. The objective lens system is arranged so as to form an angle of 45 degrees with respect to the XY moving table moving axis, and the two-dimensional photoelectric converter is attached in a state inclined by 45 degrees.
[Selection] Figure 4

Description

  The present invention relates to a measuring device using light. In particular, the present invention relates to an increase in speed and compactness of an apparatus that performs various measurements using a plurality of images at different focal positions.

  For example, in order to measure the three-dimensional shape of the surface of an object, a plurality of image data with different focal positions are obtained, and this image data is input to an image processing apparatus to determine the local in-focus state of each image by image processing. The three-dimensional shape of each part of the object surface is specified from the focused state and the focal position of each image. At this time, the optical system used for inputting image data includes an imaging optical system and a two-dimensional photoelectric converter that photoelectrically converts and outputs an optical image formed by the imaging optical system. A plurality of image data having different focal positions are obtained by changing an optical distance between the image optical system and the object to be measured, that is, an optical path length.

  As means for changing the optical path length between the imaging optical system and the object to be measured, it is common to place the object to be measured on the Z-axis movement table and move the Z-axis movement table. However, the change in the optical path length due to the Z-axis moving table is to increase the accuracy when the object to be measured is large and heavy, or the jig for holding the object to be measured is heavy. Considering rigidity and the like, the Z-axis moving table itself is large and has a heavy weight. Therefore, high-speed and high-precision movement (change in optical path length) is not easy. In particular, when the optical system for inputting image data is a scanning optical system such as a laser scanning microscope, the focal position should not be changed during the scanning period. It was more difficult to move the Z-axis moving table, which has a large weight, at high speed and with high accuracy.

  In order to solve this problem, Patent Document 1 discloses a mechanism for optically changing the optical path length instead of the mechanical optical path length as described above by the same inventor as the present invention. The principle will be described with reference to FIG. When the parallel flat transparent body 503 is inserted into the optical path of the imaging optical system such as a microscope objective lens, the focal position changes with the change in the optical path length between the optical system and the object 103 to be measured. This amount of change can be controlled by the thickness of the parallel flat transparent body 503. Using this principle, parallel plane transparent bodies 503 having different thicknesses are arranged on the circumference of the disk 501, the circumference is brought to the optical axis position of the imaging optical system, and the disk 501 is continuously formed. , The focal position moves as the thickness of the parallel flat transparent body 503 changes. By moving the shutter of the two-dimensional photoelectric converter at the timing when each parallel plane transparent body 503 and the optical axis of the imaging optical system intersect with the timing sensor, stepwise focal movement can be realized at high speed and with high accuracy.

Japanese Patent Application No. 7-237947

  This mechanism has a simple structure and can realize high-speed and high-accuracy optical path length change. However, since the rotating disk is arranged perpendicular to the optical axis of the optical system, for example, a high-resolution high-resolution optical system or telecentric In the case of a wide-field high-precision optical system, etc., the total length of the optical system becomes very long, so if a rotating disk orthogonal to it is placed, the circumscribed rectangular space will be very large, leading to an increase in the scale of the device. Become.

  In addition, if the object to be measured is large and cannot be measured by a single measurement (one field of view), a measurement mechanism unit including an imaging optical system, a rotating disk, and a two-dimensional photoelectric converter (hereinafter simply referred to as a measurement mechanism unit) It is necessary to measure a plurality of times by changing the positional relationship between the object to be measured and the object to be measured using an XY axis moving table or the like. Those who have moved on the XY-axis moving table (hereinafter referred to as the measurement mechanism section moving type) have a higher degree of freedom in terms of the object to be measured, the method of introducing the measurement mechanism section to the measurement position, etc. Simplification of the entire device or improvement of throughput can be expected.

  However, when the measurement mechanism becomes larger as described above, not only a large XY-axis moving table is required, but also vibrations are likely to occur during movement, so measures such as increasing the rigidity of the optical system itself are required. It becomes larger and becomes less feasible.

  In view of such circumstances, the present invention is light and compact so that an apparatus for acquiring images at a plurality of focal positions at a high speed (hereinafter referred to as a multifocal imaging apparatus) can be used as a measurement mechanism unit moving type. The purpose is to provide.

To solve the above problem,
A moving table having at least one moving axis;
It consists of a measuring mechanism that can be mounted on the moving table or change the relative position with respect to the object to be measured along with the movement of the object moving table,
The measurement mechanism unit is a two-dimensional photoelectric converter capable of photoelectrically converting an optical image and outputting it as a two-dimensional image signal;
An image processing apparatus which receives an output image signal from the two-dimensional photoelectric converter and stores it as an image or performs various data processing;
An objective lens system having a structure in which an optical image of an object to be measured is formed on the photoelectric conversion surface of the two-dimensional photoelectric converter and the optical path is bent at least once;
A rotating plate having a rotating surface orthogonal to an optical axis (hereinafter simply referred to as an optical axis) in the object space of the objective lens system and rotating at a constant speed by a motor, and a circle intersecting the optical axis on the rotating plate A plurality of parallel plane transparent bodies having different thicknesses are arranged side by side on the circumference, and each time the parallel plane transparent bodies pass through the optical axis, a plurality of different focal positions are captured by the two-dimensional photoelectric converter. It consists of a focus movement mechanism that can obtain an image,
The multifocal imaging device is configured such that at least one of the moving axes of the moving table is parallel to the rotating plate rotation surface of the focus moving mechanism.
Furthermore, a plane formed by the rotation center axis of the rotating plate of the focal point moving mechanism and the optical axis (hereinafter referred to as a center plane) is an axis parallel to the rotating plate rotation surface of the moving axes of the moving table. Arranged parallel or orthogonal,
The objective lens system is arranged so that the optical path is bent 90 degrees in the middle of the optical axis and parallel to the rotation plane of the rotating plate and at an angle of 45 degrees with the center plane,
The two-dimensional photoelectric converter is attached with its two-dimensional coordinate axis inclined at 45 degrees with respect to the rotation plane of the rotating plate.

  By configuring as described above, the circumscribed rectangular space of the measurement mechanism section can be reduced, and since the center of gravity is lowered, it is advantageous for the force received with the acceleration / deceleration of the moving table, and the measurement mechanism section is compact. A movable multifocal imaging device can be realized.

It is the figure which showed the Example of this invention. It is a figure for demonstrating a prior art. It is the figure which showed one Example of the measurement mechanism part of this invention. It is the figure which showed the other Example of the measurement mechanism part of this invention. It is a figure for demonstrating a high-speed focus moving mechanism.

  In the following, embodiments that are considered to be the best for concrete implementation of the present invention will be described.

  First, an example of an embodiment embodying the present invention will be described with reference to FIGS.

  As an example of the measurement optical system, here, a case of a two-dimensional array type confocal optical system will be described with reference to FIG. This optical system includes a pinhole array 201 in which pinholes are two-dimensionally arranged, an illumination optical system 202 that illuminates the pinhole array 201, and illumination light that has passed through the pinhole array 201 to the object 103 to be measured. An objective lens system 204 that performs image projection and collects reflected light from the object 103 to be measured again, a quarter-wave plate 205 having a function of converting the polarization directions of illumination light and reflected light by 90 degrees, an objective A polarized beam splitter 206 having a function of bending the reflected light collected by the lens system 204 and passing through the pinhole array 201 again without returning to the illumination optical system 202, and reflected light passing through the pinhole array 201 into 2 The second objective lens system 208 that transmits the image to the two-dimensional photoelectric converter 207 and the output image signal of the two-dimensional photoelectric converter 207 are received and stored or image data Composed of the image processing apparatus 209 for performing management.

  This optical system is a so-called confocal optical system, and the reflected light passes through the pinhole array 201 only when the surface of the object to be measured 103 exists on the conjugate plane of the pinhole array 201 (hereinafter referred to as the focal plane 210). The characteristic is that when the light passes again and an output is obtained at the corresponding pixel of the two-dimensional photoelectric converter 207 and the surface of the object 103 to be measured is other than the focal plane 210, no output is obtained (the output value is small). And changing the relative position of the focal plane 210 with respect to the object to be measured 103 to obtain the position of the surface of the object to be measured 103 by obtaining the relative position with the largest output for each pixel of the two-dimensional photoelectric converter 207. The optical system can be specified for each pixel, that is, the surface shape can be measured.

  As a mechanism for changing the relative position of the focal plane 210 with respect to the object 103 to be measured, the mechanism shown in FIG.

  In such a confocal optical system for acquiring an image (hereinafter referred to as a confocal imaging system), it is necessary to use a telecentric optical system as the objective lens system 204, but the telecentric optical system sandwiches an aperture stop. The front lens group is divided into a front lens group and a rear lens group, and the total length is usually long. Therefore, as shown in FIG. 2, when the two-dimensional array type confocal optical system including the objective lens system 204 and the focal plane changing mechanism by the rotating disk 210 are combined, the circumscribed rectangular space becomes considerably large. End up.

  Therefore, the optical path is bent 90 degrees by a mirror or a right-angle prism before and after the aperture stop in the middle part of the objective lens system 204. As shown in FIG. 3, this makes it possible to significantly reduce the dimension (hereinafter referred to as the vertical direction) perpendicular to the rotation surface direction (hereinafter referred to as the horizontal direction) of the rotating disk 501. By bending 90 degrees, the optical system after the rear group of the objective lens system 204 can be disposed in the horizontal direction, and the spread in the vertical direction can be greatly suppressed. Furthermore, it can suppress that the whole size spreads in a horizontal direction by arrange | positioning so that it may overlap with the rotation disc 501. FIG.

  The polarizing beam splitter 206 bends the optical path of the optical system by 90 degrees. This bending direction can also be folded in a horizontal plane, and can overlap the rotating disk 501. Also, the illumination optical system 202 can be bent so as to overlap the rotating disk 501.

  By doing so, as shown in FIG. 1, the vertical size of the measurement mechanism unit 102 is significantly reduced and the center of gravity is lowered, which is advantageous in bending rigidity, and the measurement mechanism unit 102 is attached to the XY moving table 101. It can be attached and moved at high speed. The rigidity of each part can be reduced, and the apparatus can be reduced in size and cost.

  Since there is a motor 502 at the center of the rotating disk 501 and a support base for holding the motor 502 and the rotating disk 501 is required, it is usual to place an optical system near the center of the rotating disk 501. difficult. Therefore, as shown in FIG. 3, the optical system is arranged so as to avoid the center of the rotating disk 501.

  In this case, when the two-dimensional photoelectric converter 207 is attached to the optical system, a general attachment method in which the image coordinate axis direction of the two-dimensional photoelectric converter 207 is aligned with the horizontal and vertical directions is shown in FIG. Therefore, it is natural to align the XY moving table moving axis 302 with the coordinate axis direction of the measurement visual field 301.

  However, in this case, the position of the measurement visual field 301 is an unnatural position that is largely deviated from the measurement mechanism unit center line 302 (here, equal to the XY moving table moving axis 302). Further, when the clearance between the rotating disk 501 and the object 103 to be measured is small (when it is desired to obtain a high-resolution wide-field image, the NA of the objective lens system 204 cannot be set to a small value, and the rotating disk 501 In this case, the clearance between the rotating disk 501 and the object to be measured 103 is generally set to be small). 3 If the measurement visual field position is at the position of the measurement visual field 301, the position of the measurement visual field 301 is difficult to be visually recognized by the user (from the front direction with the Y-axis direction as the front-rear direction of the rear part 102 of the measuring instrument). If the size is large, it becomes almost impossible for the user to visually confirm the position of the measurement visual field 301, and the usability becomes extremely poor.

  Therefore, as shown in FIG. 4, the plane direction including the center line of the rotating disc 501 and the center line of the measurement visual field 301 is made parallel to the direction of the XY moving table moving axis 302 (usually the Y axis direction). . By doing in this way, the measurement visual field 301 can be arrange | positioned in the position which is easy to confirm.

  When the relationship between the XY moving table moving axis 302 and the measurement visual field 301 is as shown in FIG. 4, the optical path of the optical system includes the YZ axis plane of the XY moving table (that is, the center line of the rotating disk 501 and the central line of the measurement visual field 301). The shape is inclined by about 45 degrees with respect to the plane. In this case, when attaching the two-dimensional photoelectric converter 207 to the optical system is a general attachment method in which the image coordinate axis direction of the two-dimensional photoelectric converter 207 is aligned in the horizontal and vertical directions, as shown in FIG. The XY moving table moving axis 302 is inclined 45 degrees.

  If the image coordinate axis of the two-dimensional photoelectric converter 207 and the XY movement table moving axis 302 do not coincide with each other, it is difficult to handle for image data processing, and is determined by the size of the parallel flat transparent body 503 on the rotating disk 501 and the shape of the field of view 2 This is also not preferable from the viewpoint of the exposure time margin of the two-dimensional photoelectric converter 207. Therefore, the two-dimensional photoelectric converter 207 is attached to the optical system so that the image coordinate axis direction of the two-dimensional photoelectric converter 207 is inclined 45 degrees with respect to the horizontal and vertical directions. In this way, the image coordinate axis of the two-dimensional photoelectric converter 207 and the XY movement table moving axis 302 can be matched as shown in the measurement visual field 301b of FIG.

  In the above, the example of the two-dimensional array type confocal imaging system has been given as the measurement optical system, but the application range of the present invention is not limited to the two-dimensional array type confocal imaging system. A scanning confocal imaging system can be considered in the same way, and need not be a confocal imaging system. In the confocal imaging system, the output of the optical system itself indicates the in-focus state, but it is possible to calculate the in-focus state by image processing even for an image by a normal optical system. Can also be realized by a general imaging optical system that is not a confocal imaging system. Even in that case, the present invention is effective. Further, the present invention can be used in the same manner even when a high-resolution image is required for high-precision two-dimensional dimension measurement instead of surface shape measurement and a high-speed focusing mechanism is required. In addition, it can be applied to white interference surface shape measurement.

  In the above embodiment, the positional relationship is described in terms of parallel or orthogonal, or 90 degrees and 45 degrees, but it does not necessarily require strict conditions. If the purpose can be achieved even if there is a certain amount of error, it is within the scope of the present invention. For example, the optical path of the optical system is arranged in the direction of 45 degrees with respect to the Y axis of the XY moving table, and the two-dimensional photoelectric converter is mounted with an inclination of 45 degrees. Is possible.

  According to the present invention, a multi-focal imaging device with a moving measuring mechanism can be realized in a compact, low-cost or high-speed manner. As a result, it is considered that there is a great demand in the semiconductor industry where there are many parts that require high-speed and high-precision measurement using light.

DESCRIPTION OF SYMBOLS 101 XY movement table 102 Measuring mechanism part 103 to-be-measured object 201 Pinhole array 202 Illumination optical system 204 Objective lens system 205 1/4 wavelength plate 206 Polarizing beam splitter 207 Two-dimensional photoelectric converter 208 2nd objective lens system 209 Image processing apparatus 210 Focal plane 301 Measurement field of view 302 XY moving table moving axis 501 Rotating disk 502 Motor 503 Parallel plane transparent body

Claims (2)

In a measuring device using light,
A moving table having at least one moving axis;
It consists of a measuring mechanism that can be mounted on the moving table or change the relative position with respect to the object to be measured along with the movement of the object moving table,
The measurement mechanism unit is a two-dimensional photoelectric converter capable of photoelectrically converting an optical image and outputting it as a two-dimensional image signal;
An image processing apparatus which receives an output image signal from the two-dimensional photoelectric converter and stores it as an image or performs various data processing;
An objective lens system having a structure in which an optical image of an object to be measured is formed on the photoelectric conversion surface of the two-dimensional photoelectric converter and the optical path is bent at least once;
A rotating plate having a rotating surface orthogonal to an optical axis (hereinafter simply referred to as an optical axis) in the object space of the objective lens system and rotating at a constant speed by a motor, and a circle intersecting the optical axis on the rotating plate A plurality of parallel plane transparent bodies having different thicknesses are arranged side by side on the circumference, and each time the parallel plane transparent bodies pass through the optical axis, a plurality of different focal positions are captured by the two-dimensional photoelectric converter. It consists of a focus movement mechanism that can obtain an image,
The multi-focus imaging apparatus, wherein at least one of the moving axes of the moving table is arranged so as to be parallel to a rotating plate rotation surface of the focus moving mechanism. A plane formed by the rotation center axis of the rotating plate of the focal point moving mechanism and the optical axis (hereinafter referred to as a center plane) is parallel to an axis parallel to the rotating plate rotation surface of the moving axes of the moving table or Arranged orthogonally,
The objective lens system is disposed so that the optical path is bent 90 degrees in the middle of the optical axis, parallel to the rotation plane of the rotating plate and at an angle of 45 degrees with the center plane,
2. The multifocal imaging device according to claim 1, wherein the two-dimensional photoelectric converter is attached in a state in which the two-dimensional coordinate axis is inclined by 45 degrees with respect to the rotation plane of the rotating plate.