JPH1138299A - Method for adjusting cofocal optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate adjustment of the alignment and to execute the alignment with good accuracy. SOLUTION: A reflection object for alignment, such as a concave mirror 25, which is arranged in the position where the object to be measured is ought to exist and of which the contour plane in a direction perpendicular to the optical axis is not one and which plane is formed into a specified shape, is irradiated with the light from an arrayed spot light sources of the cofocal optical system. The reflected light thereof is observed or measured and the alignment of the optical system is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adjustment method for performing alignment between a projection pinhole array of a confocal optical system and a lens group.

[0002]

2. Description of the Related Art The above-mentioned confocal optical system is used as a measuring device for precisely measuring the surface shape (height) of an object, and includes a system using a beam splitter and a system using a hologram.

FIG. 1 shows a confocal optical system using a beam splitter. Light emitted from a light source 1 is transformed into parallel light by a condenser lens 2, and is projected two-dimensionally into a light emitting pinhole array. 3, the light is emitted as a two-dimensional array of point light sources. In the figure, only one optical path is shown as an example.

After passing through the beam splitter 4, the emitted light is condensed on the measured object 6 by the first and second lens groups 5a and 5b. Then, the reflected light passes through the lens groups 5a and 5b in the opposite direction, is reflected by the beam splitter 4, and is projected on the light-receiving pinhole array 7 conjugate with the light-projecting pinhole array 3. A detector array 8 is arranged behind the light receiving pinhole array 7 and detects the intensity of light passing through the light receiving pinhole array 7.

At this time, when the light projected on the measured object 6 is focused on the surface of the object, the amount of light passing through the light receiving pinhole array 7 is maximized. By moving 5) in the Z direction (optical axis direction), the surface shape of the measured object 6 in the range where light is projected can be measured. If this is scanned in the X and Y directions, a wider range can be measured.

In a conventional alignment procedure in a confocal optical system using this beam splitter, first, as shown in FIG. 2, light from a light source 1 is irradiated, and a beam splitter 4 and first and second lens groups are irradiated. The alignment of 5a and 5b is adjusted. At this time, CC below the second lens group 5b
An imaging device such as a D camera 9 is arranged, and adjustment is performed while observing the image.

[0007] Next, as shown in FIG.
Is disposed, that is, the plane mirror 10 is disposed at the focal position of the second lens group 5b so that the reflected light is uniform and the output becomes maximum when passing through the light receiving pinhole array 7. , The light receiving pinhole array 7 and the detector array 8 are aligned. A technique for performing alignment by disposing a plane mirror at the position of the measured object 6 is described in JP-A-6-109958.

FIG. 4 shows a confocal optical system using a hologram.
When the hologram 13 becomes parallel light via the reference light 12b and enters the hologram 13 as reference light in an oblique direction, the hologram 13 diffracts the light equivalent to a point light source emitted from each pinhole position of the pinhole array 14 into the reference light. Play by doing.

The reproduced light is projected onto the object 6 to be measured by the second lens group (objective lens) 15b, reflected by the second lens group (objective lens), transmitted through the first lens group 15a and the hologram 13, and is reflected by the first lens group 15a via pinhole array 1
Focus on 4 In this figure, light at one pinhole position is represented as a representative.

The confocal optical system using the hologram also uses the pinhole array 14 when the light projected on the object 6 to be measured focuses on the surface of the object, similarly to the system using the beam splitter. Since the amount of light passing therethrough is maximized, the second lens group 15b is moved in the Z direction, and the light that has passed through the pinhole array 14 at this time is detected by the detector array 18 via the relay lenses 17a and 17b. By detecting, the surface shape of the measured object 6 in the range where the light is projected can be measured.

FIG. 5 shows how a hologram 13 of a confocal optical system using the hologram is exposed.
The light source 11 'is a coherent light source such as a laser,
Wavefront splitting is performed by the beam splitter 19, and the light becomes the light source of the reference light and the object light of the hologram 13. Light source 1
In the case where the light of 1 ′ shows the characteristic of linearly polarized light, the first 1 /
The polarization direction of the linearly polarized light is rotated by rotation of the two-wavelength plate 20a, and a polarization beam splitter is used as the beam splitter 19, thereby setting the intensity ratio of the division to a desired value.

The reference light and the object light split by the beam splitter 19 are converted into first, second and third and fourth magnifying lenses 2.
The images are enlarged by 1a, 21b, 21c, and 21d and are incident on the hologram 13 and the pinhole array 14, respectively. The light transmitted through the pinhole array 14 is diffracted by each pinhole and becomes light equivalent to a point light source.
Is converted into parallel light by the lens group 15a, and is incident on the hologram 13 as object light. By adjusting the second and third half-wave plates 20b and 20c, the polarization directions of the reference light and the object light are set to desired directions (generally the same direction), and the hologram exposure is performed. Preparation is completed.

In a confocal optical system using this hologram, the measurement accuracy is reduced unless the distance and angle between the optical elements are accurately adjusted. Therefore, the beam splitter described above is conventionally used for the alignment. This was performed by the same means as the confocal optical system.

[0014]

However, precise alignment cannot be performed only by the conventional alignment method in the confocal optical system, and the measurement accuracy of the confocal optical device cannot be sufficiently improved. This is because the degree of freedom of the pinhole array is extremely large, but alignment must be performed for all of the multiple pinholes. This is because it is difficult to determine which state is optimal when comparing this with a numerical value of the intensity of the light amount on a plane surface reflected by the plane mirror.

Further, after the alignment has been performed to some extent, even if the pinhole array is moved by a small amount, the amount of light incident on the detector array does not change so much, and final fine adjustment cannot be performed. Nevertheless, when the lens is actually moved in the Z direction, the accuracy of the alignment has a significant effect on the accuracy of the measurement, and an accurate alignment method has been required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and provides a method of adjusting a confocal optical system in which adjustment for alignment can be easily performed and alignment can be performed very accurately. It is intended for.

[0017]

In order to achieve the above-mentioned object, a method for adjusting a confocal optical system according to the present invention comprises the steps of: receiving light from an array of point light sources in a confocal optical system; A concave mirror, etc. placed at the position where the measurement object should be
It is necessary to irradiate a reflective object for alignment whose surface is not a single level surface perpendicular to the optical axis and that the surface has a fixed shape, and observe or measure the reflected light to align the optical system. I made it.

The confocal optical system converts the light from the light source into an array of point light sources using a light projecting pinhole array, transmits each light of the point light source through a beam splitter, and measures the light through a lens group. The object is focused and irradiated, and the reflected light passes through the lens group, is reflected by the beam splitter, and is received by the detector array via the light receiving pinhole array installed at a position conjugate with the light projecting pinhole array. Confocal optical system.

The confocal optical system converts the light from the light source into parallel light and irradiates the hologram as reference light from an oblique direction. The reference light determines whether or not a point light source using a pinhole array exists. Such a light is reproduced by a hologram, the reproduced light is focused on the object to be measured through a lens group, and the reflected light is passed through a pinhole array through the lens group. This is a confocal optical system that receives light at a detector array.

The light from the light source is formed into an array of point light sources by a light projecting pinhole array, and each light of the point light source is transmitted through a beam splitter and focused and irradiated on an object to be measured via a lens group. In a confocal optical system, the reflected light passes through a lens group, is reflected by a beam splitter, and is received by a detector array via a light receiving pinhole array installed at a position conjugate to the light projecting pinhole array. For alignment, where there is not one concave surface such as a concave mirror, etc. in the direction perpendicular to the optical axis, and the surface is fixed, without the light receiving pinhole array. Of the optical system, and the reflected light is observed or measured to adjust the alignment of the optical system except for the light receiving pinhole array.

According to the present invention, the deviation of the alignment of the confocal optical system can be intuitively grasped by the reflected light from the reflecting object for alignment, and the adjustment for adjusting the alignment is facilitated. . In addition, according to the present invention, alignment can be performed very accurately.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. 6 to 20 show a case where the present invention is applied to a confocal optical system using a beam splitter.
The components of these components are the same as those described in the above-described related art, and thus description thereof will be omitted.

In FIG. 6, the beam splitter 4
The alignment of the first and second lens groups 5a and 5b is performed in the same manner as in the conventional example shown in FIG. This is done in advance by making adjustments.

In this state, the concave mirror 25 is arranged near the converging point of the second lens group 5b instead of the object 6 to be measured, and light is emitted from the light source 1. Thereby, the light corresponding to each pinhole of the light projecting pinhole array 3 is focused on the surface of the concave mirror 25 by the second lens group 5b. FIG. 7 shows how each light is condensed on the surface of the concave mirror 25, and FIG. 8 shows how light is reflected by the concave mirror 25 and enters the light receiving pinhole array 7 via the beam splitter 4. At this time, assuming that the concave mirror 25 is arranged so that the focal plane of the second lens group 5b is located at the middle of the concave depth of the concave mirror 25, in FIG. However, since the reflected light intersects before the light receiving pinhole array 7 in FIG. 8, the output of this portion A of the detector array 8 becomes small.

In the peripheral portion C, light is reflected by the surface before the focal point, and the reflected light is blocked by the light receiving pinhole array 7 as shown in FIG. Becomes smaller.

On the other hand, in FIG.
In this case, since focusing is performed on the surface of the concave mirror 25, almost the entire amount of light passes through the light receiving pinhole array 7, and the output of this portion of the detector array 8 increases.

Therefore, an image obtained when the output of the detector array 8 is taken out to a monitor or the like at this time is as shown in FIG. The portion B indicated by the dotted points in the figure is a bright place, and the other places A and C are dark. Thus, the inner circle and the outer circle of the bright portion B are concentric and parallel, and the light receiving pinhole array 7 and the detector array 8 are aligned with the brightness being bright.

On the other hand, an example in which the above-mentioned alignment is not matched will be described below. FIG. 12 shows a case where the boundary between the bright portion B and the dark portions A and C is blurred as shown in FIG. 10 or a case where the inner circle and the outer circle are largely asymmetrically shifted as shown in FIG. This is the case, for example, when a part of a circle is broken.

In an actual apparatus, a more complicated pattern is formed due to a combination of light interference and the like. However, as shown in FIG. 9, alignment is always performed so that the detected image is concentric and the boundary is clear. What is necessary is just to match.

According to this method, the misalignment of the alignment can be known not by a multipoint numerical value but by a pattern. Therefore, it is easy to find an optimum alignment of the light receiving pinhole array 7 with respect to the detector array 8. Alternatively, an image when the alignment is optimal may be registered in a memory or the like in advance, and the image may be compared with the current image by image processing. This makes it possible to automate the alignment operation. Further, if the intensity of the light transmitted through the light receiving pinhole array 7 is measured not only by the image pattern but also by the photodetector, the alignment accuracy is further improved.

FIG. 13 shows another embodiment, in which a relay lens 26 is arranged between the light receiving pinhole array 7 and the detector array 8. This is used when the pitch between the detector array 8 and the light receiving pinhole array 7 is different or when the detector array 8 cannot be closely attached due to the structure of the detector array 8.

In this apparatus, first, a detector array (not necessarily the same as that used for the confocal optical system)
The light-receiving pinhole array 7 is arranged at a position indicated by a dotted line behind the light-receiving pinhole array 7 and the alignment of the light-receiving pinhole array 7 is adjusted with respect to the reflected light from the concave mirror 25 in the above-described procedure.
Thereafter, the detector array 8 is arranged at the position indicated by the solid line,
A relay lens 2 is provided between the light receiving pinhole array 7
If the detector array 8 is aligned with the light passing through the pinholes of the light receiving pinhole array 7, the entire alignment can be accurately adjusted.

Although the alignment adjustment described so far is performed with the second lens group 5b stationary at a certain point, in actual measurement, the second lens group 5b or the concave mirror ( Even if the second lens group 5b or the concave mirror 25 is moved in the Z-axis direction in order to move the object (measurement object) 25 in the Z-axis (optical axis) direction and to set the position where the maximum amount of light is detected to the surface height of the object. You have to make sure that the alignment is correct.

To do this, the second lens group 5b or the concave mirror 25 is moved in the Z-axis direction to
Check the image shown in 2. At this time, FIG.
As shown in (b), the second lens group 5b or the concave mirror 25 keeps the image concentric at any position in the Z direction (FIG. 14 (a)) or at another position (FIG. 14 (b)). If it is, the alignment is correct.

By the way, up to now, the concave mirror 25 has been used as the reflecting mirror.
However, as shown in FIG. 15, a convex mirror 25a having a spherical surface may be used instead of the concave mirror 25 as shown in FIG. If the curved surface is accurate, a cylinder or a cylinder can be used. In this case, as shown in FIG. 16, the alignment in only one direction is confirmed, and the deviation in the other direction can be separated. This method is effective when the direction of the misalignment is not known.

As another embodiment, a mold 27 having a conical (or conically concave) shape as shown in FIG.
May be arranged instead of the object to be measured. Each of the concave mirror 25 and the convex mirror 25a described above may be replaced with a mold (object) having the same shape. In this case, there is no problem simply by reducing the total amount of reflected light.

Similarly, in addition to the above shapes, the shape of the reflecting object for alignment is triangular pyramid (a), square pyramid (b), cylindrical (c) as shown in FIGS. 18 (a) to 18 (h). ), A half cylinder (d), an inclined surface in one direction (e), a V-shaped inclined surface (f), a spherical surface (g), an inclined surface (h) in which a plane mirror is inclined in one direction, and the like. In short, the contour plane (cross section in the Z-axis direction)
Is not a single plane, that is, not a plane perpendicular to the Z axis, and the plane should always have a constant shape. It is even better if the shape is regular like triangles and squares,
If the shape of the contour surface is circular, it can be confirmed whether or not alignment is performed in all directions.

In the above embodiment, the alignment of the light projecting pinhole array 3 and the lens groups 5a and 55b is adjusted by a CCD camera below the second lens group 5b as in the prior art shown in FIG. 19, the concave mirror 25 can be arranged in place of the CCD camera 9 and adjusted as shown in FIG. In this case, the concave mirror 25 is
If the image is observed by the detector 8 by irradiating light, the light projecting pinhole array 3 and the lens groups 5a and 5b are adjusted so that the image becomes concentric as shown in FIG.

Next, FIG. 21 shows an embodiment in which the present invention is applied to a confocal optical device using the hologram 13 shown in FIGS. When the exposure step of the hologram 13 shown in FIG. 5 is completed and the relay lenses 17a and 17b and the detector array 18 are arranged instead of the magnifying lenses 21c and 21d, the concave mirror 25 is placed at the position where the measured object 6 is arranged. (Alignment object) is arranged, and alignment is performed in the same manner as that using the beam splitter.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a confocal optical system using a beam splitter.

FIG. 2 is an explanatory diagram showing an adjustment method using a CCD camera.

FIG. 3 is an explanatory diagram showing a conventional adjusting method of a confocal optical system using a beam splitter.

FIG. 4 is an explanatory diagram showing a confocal optical system using a hologram.

FIG. 5 is an explanatory diagram showing an exposure state of a hologram of a confocal optical system using a hologram.

FIG. 6 is an explanatory diagram showing a method for adjusting a confocal optical system using a beam splitter according to the present invention.

FIG. 7 is an explanatory diagram showing an irradiation state of light when a concave mirror is placed at a position of an object to be measured.

FIG. 8 is an explanatory diagram showing a state where light is incident on a light-receiving pinhole array and a detector array when alignment is performed.

FIG. 9 is a diagram showing an alignment image when alignment is performed.

FIG. 10 is a diagram showing an alignment image when alignment is not performed.

FIG. 11 is a diagram showing an alignment image when alignment is not performed.

FIG. 12 is a diagram showing an alignment image when alignment is not performed.

FIG. 13 is an explanatory diagram showing a method of adjusting an apparatus in which a relay lens is arranged in front of a detector array.

14A and 14B are diagrams showing a change in an alignment image when a lens group or a concave mirror is moved in the Z-axis direction.

FIG. 15 is an explanatory diagram showing an adjustment method using a convex mirror according to the present invention.

FIG. 16 is a diagram showing an alignment image in an adjustment method using a cylinder according to the present invention.

FIG. 17 is a perspective view showing an example in which a reflecting object has a conical shape.

18 (a), (b), (c), (d), (e),
(F), (g), (h) is a perspective view showing another example of a reflective object.

FIG. 19 is an explanatory diagram showing a method for adjusting a lens group and a light projecting pinhole array according to the present invention.

FIG. 20 is a diagram showing an alignment image without a light receiving pinhole array.

FIG. 21 is an explanatory diagram showing a method of adjusting a confocal optical system using a hologram.

[Explanation of symbols]

1, 11, 11 ': Light source 2: Condenser lens 3: Projection pinhole array 4, 19: Beam splitter 5a, 5b, 15c, 15d: Lens group 6: Object to be measured 7: Light receiving pinhole array 8, 18: Detector array 9 CCD camera 10 Planar mirror 12 a, 12 b, 21 a, 21 b, 21 c, 21 d Magnifying lens 13 Hologram 14 Pinhole array 17 a, 17 b, 26 Relay lens 20 a, 20 b, 20 c 1/2 wavelength Plate 25: concave mirror 25a: convex mirror

Claims (4)

[Claims] In a confocal optical system, light from an array of point light sources is arranged at a position where an object to be measured should be.
Alignment of the optical system by irradiating a reflective object for alignment, such as a concave mirror, which does not have one contour surface in the direction perpendicular to the optical axis, and whose surface has a fixed shape, and observing or measuring the reflected light And a method for adjusting a confocal optical system. 2. A confocal optical system converts light from a light source into an array of point light sources using a light projecting pinhole array, transmits each light of the point light source through a beam splitter, and measures the light through a lens group. The object is focused and irradiated, and the reflected light passes through the lens group, is reflected by the beam splitter, and is received by the detector array via the light receiving pinhole array installed at a position conjugate with the light projecting pinhole array. 2. The method for adjusting a confocal optical system according to claim 1, wherein the confocal optical system is a confocal optical system. 3. A confocal optical system converts light from a light source into parallel light and irradiates the hologram as reference light from an oblique direction, and by this reference light, it is as if a point light source by a pinhole array exists. Hologram, reconstructed light is focused on the object to be measured via a lens group, and the reflected light is passed through a pinhole array via the lens group to detect this light. 2. The method for adjusting a confocal optical system according to claim 1, wherein said confocal optical system is a confocal optical system for receiving light in a detector array. 4. A light from a light source is converted into an array of point light sources by a light projecting pinhole array, and each light of the point light source is transmitted through a beam splitter, and focused and irradiated on an object to be measured via a lens group. In a confocal optical system, the reflected light passes through a lens group, is reflected by a beam splitter, and is received by a detector array via a light receiving pinhole array installed at a position conjugate with the light projecting pinhole array. Alignment without a light receiving pinhole array, where the object to be measured is located at the position where the object should be located, such as a concave mirror, etc. A method of adjusting a confocal optical system, comprising irradiating a reflective object for use with a subject and observing or measuring the reflected light to adjust the alignment of a portion of the optical system other than the light receiving pinhole array.