JP3750259B2 - Image inspection / measurement equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image inspection / measurement apparatus that projects an inspection object onto an imaging device via an optical system, and inspects or measures the inspection object using the photoelectrically converted image signal.
[0002]
[Prior art]
An object to be inspected placed on a stage movable in the horizontal direction is projected onto an imaging device via an optical system, and the surface of the object to be inspected using an image signal obtained by photoelectrically converting the projected image. Image inspection / measurement devices for performing inspections and measurements are widely used. In such an image inspection / measurement apparatus, it is desirable to be able to change the magnification of the optical system in as wide a range as possible so as to be able to deal with inspection objects of various shapes and sizes.
[0003]
In particular, in order to inspect and measure the entire inspection object, and to inspect or measure a part of the inspection object with high accuracy, the inspection object can be projected with as wide a field of view as possible, that is, with a low magnification. There is a need for an optical system that can project an object to be inspected with as high a resolution as possible, that is, with a high magnification. For this purpose, a zoom optical system, a variable power optical system capable of switching an objective lens by a revolver or a turret is used for the optical system. In that case, the type of magnification obtained by the objective lens switching method is determined by the type of the mounted objective lens, and a magnification suitable for the object to be inspected may not be obtained. On the other hand, since the magnification can be continuously changed in the zoom optical system, the optimum magnification for the object to be inspected can be obtained.
[0004]
FIG. 4 is a general configuration diagram of such a zoom optical system. This zoom optical system is an example using an afocal zoom optical system. The objective lens 31 is provided below the zoom optical system 33. A light beam from the inspection object 32 is converted into parallel light by the objective lens 31, and the parallel light passes through the half mirror 43 and enters the zoom optical system 33. Then, the collimated light is obtained again from the upper lens 40 of the zoom optical system 33, and the object to be inspected is projected onto the imaging surface 35 by the imaging lens 34.
[0005]
In the zoom optical system 33, for example, the lens chambers 36 and 37 in which the variable magnification lenses 70 and 80 are accommodated for zoom magnification change are driven in the optical axis direction. Reference numerals 38a and 38b denote movement guide mechanisms for driving the lens chambers 36 and 37. The lens chambers 36 and 37 are moved in the optical axis direction by a positioning drive mechanism 39 with a predetermined relationship. Reference numeral 42 denotes a light source for epi-illumination with respect to the inspection object, and the light is reflected by the half lens 43 and applied to the inspection object 32.
[0006]
[Problems to be solved by the invention]
However, in the above zoom optical system, the zoom magnification ratio is practically limited to several times to 10 times at most. An objective lens in a zoom optical system should have a large numerical aperture with a short focal length in order to obtain a high resolution and a bright image at a high magnification, and a long focal length to secure a wide field of view at a low magnification. The reason for this limitation is that the contradictory conditions of being desirable must be realized with a common objective lens.
[0007]
However, in actual measurement or inspection, the initial positioning of the object to be inspected and the entire inspection are performed with a wide field of view at a low magnification, and then a high-precision or high-resolution inspection or measurement is performed with a high magnification and high resolution. It is necessary to. From a practical aspect, this zoom magnification ratio is desired to be about 100 times.
[0008]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image inspection / measurement apparatus having an optical system that has an enlargement ratio larger than that of the prior art and can obtain an optimum magnification.
[0009]
Furthermore, another object of the present invention is to provide an image inspection / measurement apparatus having a zoom optical system which can be reduced to 1 or minimum without requiring correction work accompanying a change in magnification, and which has a substantially large zoom ratio. There is.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an image inspection / measurement apparatus for inspecting or measuring an inspection object using an image signal of the inspection object imaged by an imaging apparatus via an optical system. The optical system includes: a first objective lens; a second objective lens having a shorter focal length and a larger numerical aperture than the first objective lens; the first objective lens and the second objective lens; And a zoom optical system that is provided between the imaging apparatus and changes an imaging magnification to the imaging apparatus.
[0011]
The first objective lens with optimum focal length and numerical aperture on the low magnification side is used exclusively for low magnification, and the second objective lens with shorter focal length and large numerical aperture optimum for high magnification is dedicated for high magnification. By using the zoom lens, it is possible to realize a substantially wider zoom magnification range.
[0012]
Furthermore, in another invention, in the image inspection / measurement apparatus for inspecting or measuring the inspection object using an image signal obtained by imaging the inspection object through the optical system, the optical system includes: A first optical system and a second optical system;
The first optical system is provided between a first objective lens and the first objective lens and the first imaging device, and changes an imaging magnification on the first imaging device. One zoom optical system,
The second optical system is provided between a second objective lens having a shorter focal length and a larger numerical aperture than the first objective lens, and between the second objective lens and the second imaging device. And a second zoom optical system for changing the imaging magnification on the second imaging device,
The zoom lens of the first zoom optical system and the zoom lens of the second zoom optical system are driven by the same drive mechanism.
[0013]
The low-magnification side optical system and the high-magnification side optical system each have an objective lens and a zoom optical system, and the focal length and numerical aperture of the objective lens are designed to be optimal values for low magnification and high magnification. By driving each zoom optical system by a common drive mechanism, the configuration can be simplified. Further, when the magnification varies across the variable magnification range of both optical systems, it can be smoothly performed only by moving the position of the inspection object to the focal position of each objective lens.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the technical scope of the present invention is not limited to the embodiment.
[0015]
FIG. 1 is an overall configuration diagram of an image inspection / measurement apparatus according to an embodiment of the present invention. A lens barrel 52 having a zoom optical system 53 provided with a low-magnification side zoom optical system and a high-magnification side zoom optical system is attached to the main body support portion 63. The main body support portion 63 is moved in the vertical direction by a vertical drive mechanism (not shown), and focusing is mainly performed. An inspection object (not shown) is placed on the stage surface 50 of the stage 51 that can move in the X-axis and Y-axis directions, which are horizontal directions perpendicular to each other. The stage 51 is provided with a horizontal drive mechanism (not shown), and the position of the object to be inspected or measured is moved into the field of view of the predetermined zoom optical system, and moved between the two zoom optical systems. Is done.
[0016]
Although not shown, the vertical drive mechanism and the horizontal drive mechanism each have a drive mechanism, a guide mechanism, and a position reading mechanism. These drive mechanisms are controlled by the control-side CNC drive unit and the position coordinate reading unit 62.
[0017]
The lens barrel 52 has objective lens storage portions 54 and 55 for the two zoom optical systems, respectively. The low-magnification side objective lens storage section 54 is located higher than the high-magnification side objective lens storage section 55. The objective lens on the low magnification side has a long focal length, while the objective lens on the high magnification side has a short focal length, so that the in-focus position of both zoom optical systems is almost the same as the stage surface by using the illustrated positional relationship. It is configured to match 50.
[0018]
Imaging devices 56 and 57 are provided at the upper ends of the respective zoom optical systems in the lens barrel 52. Images projected by the respective zoom optical systems are subjected to photoelectric conversion via the imaging devices 56 and 57, and the image signals are supplied to the image processing unit 60 on the control unit side via the cables 58 and 59. A monitor 64 is connected to the image processing unit 60, and an image is displayed according to the image signal. The correction calculation / operation unit 61 mainly performs conversion correction of the stage coordinates in the monitor screen when the object to be measured moves between the two zoom optical systems. Further, the correction calculation / operation unit 61 inputs an operation command including a magnification designation from the operator, and gives a control signal according to the operation command to the image processing unit 60, the CNC drive unit, and the position coordinate reading unit 62. Further, a correction calculation is performed in accordance with the magnification change in the zoom optical system. These will be described in detail later.
[0019]
FIG. 2 is a detailed configuration diagram of the lens barrel 52. The lens barrel 52 is provided with the optical system 10 on the high magnification side and the optical system 20 on the low magnification side. In the optical system 10 on the high-magnification side, an objective lens 11 having a short focal length and a large numerical aperture (NA) is provided in the objective lens storage portion 55. Therefore, the objective lens 11 is suitable for inspection / measurement with high magnification and high resolution. On the other hand, in the low-magnification side optical system 20, the objective lens 21 having a long focal length suitable for observation with a low magnification and a wide field of view is provided in the objective lens storage portion 54. The objective lenses 11 and 21 are provided at positions corresponding to the focal lengths, and the in-focus positions 12 and 22 are located at substantially the same height. In order to achieve such a configuration, a relay lens 46 is inserted into the optical system 10 on the high magnification side. By aligning the in-focus positions, the magnification can be switched between the low-magnification side optical system 20 and the high-magnification side optical system 10 simply by moving the stage according to the distance L between them. Since the focusing operation after switching is unnecessary or minimal, the operability at the time of changing the magnification exceeding the magnification region of each zoom optical system is not impaired.
[0020]
The high-magnification side optical system 10 and the low-magnification side optical system 20 respectively have zoom optical systems 13 and 23 having the same configuration. The zoom optical system 13 includes, for example, variable power lenses 71 and 81 that move in the vertical direction between the lenses 141 and 142. Further, the zoom optical system 23 on the low magnification side also includes, for example, variable power lenses 72 and 82 that move in the vertical direction between the lenses 241 and 242. The variable magnification lenses 71 and 72 are accommodated in the same lens chamber 7, and the variable magnification lenses 81 and 82 are also accommodated in the same lens chamber 8, respectively.
[0021]
The lens chambers 7 and 8 are driven by a common positioning drive mechanism 9 and a common movement guide mechanism 6a, 6b so as to have a predetermined positional relationship by a drive signal from the CNC drive unit 62. Accordingly, the zoom optical systems 13 and 23 on the high magnification side and the low magnification side are similarly driven by the drive signal and controlled to the same zoom magnification. Then, the magnifications of the optical systems 10 and 20 are determined from the zoom magnification and the magnifications of the objective lenses 11 and 21, respectively.
[0022]
The light beams that have passed through the respective optical systems via the imaging lenses 14 and 24 provided on the upper sides of the respective zoom optical systems 13 and 23 are converted into image pickup surfaces 15 such as CCD elements of the image pickup devices 56 and 57, respectively. 25 is projected.
[0023]
In the embodiment shown in FIG. 2, the zoom optical system is based on an afocal zoom optical system. The movement guide mechanisms 6a and 6b are configured by a mechanism with very little mechanical play and hysteresis so that the optical axis shift can be sufficiently suppressed as the lens chambers 7 and 8 are driven during zooming. For example, a preload type finite orbit ball race or roller race is used. Similarly, in order to ensure the reproducibility of the magnification with respect to the driving during zooming, for example, a preload type driving mechanism and a positioning mechanism with extremely little mechanical play and hysteresis are used.
[0024]
The vertical epi-illumination is performed by reflecting the light from the common light source 42 by the half mirrors 43 and 44 and irradiating the inspection object through the objective lenses 11 and 21, respectively.
[0025]
In this embodiment, for example, if the zoom ratio of the zoom optical systems 13 and 23 is about 10 times, the zoom range of the optical system 20 on the low magnification side is about 0.5 to 5 times, and the high magnification side When the zooming range of the optical system 10 is about 5 to 50 times, when two optical systems are used, the zooming range is 0.5 to 50 times as a whole, and the zooming ratio is about 100.
[0026]
As yet another example, by setting the zoom range to partially overlap between the low-magnification side optical system 20 and the high-magnification side optical system 10, at the boundary of the zoom range between both optical systems. The operability can be improved. For example, the optical system 20 on the low magnification side is 0.5 to 5 times, and the optical system 10 on the high magnification side is 4 to 40 times. In another example, a special use is possible by omitting between the magnification range on the low magnification side and the magnification range on the high magnification side. For example, the low magnification side is 0.5 to 5 times, and the high magnification side is 50 to 500 times. It is set according to each application and type of inspection object. Such setting is mainly performed by appropriately selecting the focal length f of the objective lenses 11 and 21.
[0027]
In addition, since the optimum objective lenses 11 and 21 are provided on the low-magnification side and the high-magnification side, respectively, a bright and high-resolution image can be projected on the imaging surface over a wide zoom range.
[0028]
In the zoom optical system, various corrections are required by using the positioning drive mechanism 9 and the movement guide mechanisms 6a and 6b. In general, it is necessary to correct the magnification by zooming and to correct the coordinates by optical axis deviation. That is, the lens chambers 7 and 8 are driven and moved to predetermined positions in accordance with zooming, so that the respective magnifications are changed. However, a slight shift occurs with respect to the position of the desired magnification due to the shift by the drive mechanism or the guide mechanism. Therefore, for example, for each arbitrary number of magnifications, a correction table for the magnification corresponding to the drive position is created in advance using an inspection object having a reference pattern, or a correction table for the drive position that becomes the set magnification is created. . When inspecting or measuring an actual inspection object, magnification correction or drive position correction is performed with reference to the correction table.
[0029]
Further, the correction of the coordinates due to the optical axis shift is performed on the image pickup device such as a CCD by shifting the optical axes of the variable power lenses 71, 81, 72, and 82 in the respective optical systems 10 and 20 with the driving of the lens chamber. This is necessary because the position of the projected image differs slightly for each magnification. Therefore, in the same manner as described above, a correction table for the coordinate position is created in advance for each arbitrary number of magnifications using an inspection object having a reference pattern. The coordinate correction table is used at the time of actual inspection or measurement.
[0030]
In general, when an arbitrary position on the monitor screen is determined, from the stage coordinates (Xs, Ys) and the coordinates (Xm, Ym) on the screen, the coordinates (Xo, Yo) of the position are B,
(Xo, Yo) = (Xs, Ys) + (Xm + Δx, Ym + Δy) / (B + ΔB). ΔB is a correction value of the magnification due to the drive position deviation, and (Δx, Δy) is a correction value of the coordinates due to the optical axis deviation.
[0031]
In the embodiment of the present invention, in order to expand the magnification range, the optical system 20 on the high magnification side and the optical system 10 on the low magnification side are provided side by side. Therefore, it is necessary to move the inspection object between the optical systems 10 and 20 at the time of actual inspection or measurement. In that case, the stage 51 is moved by a distance L between both zoom optical systems. In this case, for example, the position of the stage 51 differs by a distance L, but the coordinates of the inspection object in the inspection or measurement are corrected by the CNC driving unit and the position coordinate reading unit 62 so as to have the same value.
[0032]
For example, when a magnification is input from the magnification input device 61a provided in the operation unit 61 of FIG. 1, it is necessary to move the target portion of the inspection object to a position facing the zoom optical system corresponding to the magnification. . If the movement between both zoom optical systems is the movement of the distance L in the X-axis direction, the stage coordinates (Xs, Ys) in the above equation are converted as (Xs ± L, Ys) as the distance L moves. Is done.
[0033]
FIG. 3 is a detailed configuration diagram of a lens barrel according to another embodiment of the present invention. In this example, the zoom optical system 13 is provided in common on the high magnification side 10 and the low magnification side 20. Then, one of the lights from the objective lenses 11 and 21 is selected and enters the common zoom optical system 13. FIG. 3 shows a state in which light from the low-magnification side objective lens 21 is selected. Light from the objective lens 21 is reflected by the mirrors 44 and 43 and enters the zoom optical system 13. Light from the objective lens 11 on the high magnification side is blocked by the mirror 43 and does not enter the zoom optical system 13. When the light from the high-magnification side objective lens 11 is selected, the mirror 43 is retracted in the direction perpendicular to the paper surface by a driving device (not shown), and the light from the high-magnification side objective lens 11 directly enters the zoom optical system 13. Incident. The light from the low-magnification objective lens 21 travels straight after being reflected by the mirror 44, and therefore does not enter the zoom optical system 13. The light on the side not selected is preferably blocked by a shutter (not shown) so that stray light does not enter the zoom optical system 13. In this example, the cost can be reduced by providing a common zoom optical system.
[0034]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain a large zoom magnification ratio substantially from several tens of times to 100 times or more. Therefore, in the operation process of the image inspection / measurement device, when searching for initial positioning and detection points, the inspection object is captured at a low magnification that realizes a wider field of view, and when performing inspection or measurement, a higher magnification may be used. The inspection object can be captured with high resolution (accuracy). Thereby, the workability of inspection or measurement can be greatly improved and the accuracy can be increased.
[0035]
Furthermore, by setting the position of the objective lens on the high-magnification side and the low-magnification side so that the in-focus positions match, along with the movement between the optical system on the high-magnification side and the optical system on the low-magnification side Each of them does not require focusing work and has high operability.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an image inspection / measurement apparatus according to an embodiment of the present invention.
FIG. 2 is a detailed configuration diagram of a lens barrel that is an embodiment of the present invention.
FIG. 3 is a detailed configuration diagram of a lens barrel according to another embodiment of the present invention.
FIG. 4 is a general configuration diagram of a zoom optical system.
[Explanation of symbols]
6a, 6b, 9 Drive mechanism 10 High magnification side optical system 11 Objective lens 13 High magnification side zoom optical system 20 Low magnification side optical system 21 Objective lens 23 Low magnification side zoom optical system

Claims (5)

In an image inspection / measurement apparatus that inspects or measures an inspection object using an image signal of the inspection object imaged by an imaging device via an optical system,
The optical system includes: a first objective lens; a second objective lens having a shorter focal length and a larger numerical aperture than the first objective lens; the first objective lens and the second objective lens; An image inspection / measurement apparatus, comprising: a zoom optical system that is provided between the imaging apparatus and changes an imaging magnification to the imaging apparatus. In an image inspection / measurement apparatus for inspecting or measuring the inspection object using an image signal obtained by imaging the inspection object through an optical system,
The optical system has a first optical system and a second optical system,
The first optical system is provided between a first objective lens and the first objective lens and the first imaging device, and changes an imaging magnification on the first imaging device. One zoom optical system,
The second optical system is provided between a second objective lens having a shorter focal length and a larger numerical aperture than the first objective lens, and between the second objective lens and the second imaging device. And a second zoom optical system for changing the imaging magnification on the second imaging device,
An image inspection / measurement apparatus, wherein the zoom lens of the first zoom optical system and the zoom lens of the second zoom optical system are driven by the same drive mechanism. In claim 1 or 2,
A relay lens between the second objective lens and the second zoom optical system, wherein the object side focal plane of the second optical system is substantially flush with the object side focal plane of the first optical system; An image inspection / measuring device further comprising: In claim 1, 2 or 3,
It further has a stage on which the object to be inspected is placed and movable in the horizontal direction,
A predetermined position of an object to be inspected placed on the stage is moved to a position facing the first optical system or the second optical system according to a magnification input from a magnification input device. Image inspection / measurement equipment. In claim 4,
When the predetermined position of the object to be inspected is moved between a position facing the first optical system and a position facing the second optical system, within the display screen displaying the captured image An image inspection / measurement apparatus that converts the stage coordinate value of the image by the amount of movement.

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