JP2001066121A - Surface shape measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the surface shape of a large-sized measuring object at high speed with a simple and low-cost formation, by providing optical interference measuring means on each partial region, and by installing the optical interference measuring means fixedly relative to the placed position of the measuring object. SOLUTION: Parallel light outputted from a light source 1 is trisected by a mirror 2, and enlarged by a floodlight lens system 3, and thereafter irradiated toward a measuring object P. A part of parallel light irradiated from the floodlight lens system 3 is transmitted through a reference plane 4 and reflected on the back the measuring object P, and two kinds of parallel light having different optical lengths is synthesized again, and interference fringes are generated at that time. Synthesized reflected light is reduced by a light-receiving lens system 5 and thereafter reaches a light-receiving part 7 through a mirror 6, and the interference fringes are observed thereon. This measuring device Z1 has only one light-receiving part 7, therefore at the time of actual measurement, an illumination switching means, such as a shutter or the like, is installed, for example, on a part of the floodlight lens system 3, and measurement of each partial region is executed successively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface shape measuring apparatus using an interferometer, and more particularly to a surface shape measuring apparatus for measuring a large-area measuring object by dividing it into a plurality of partial regions.

[0002]

2. Description of the Related Art Conventionally, when measuring the surface shape of a measuring object such as a plane or a spherical surface, a reference light such as a light reflected from a reference plane and a light reflected from the surface of the measuring object interfere with each other. A so-called interferometer, which measures the surface shape of the object to be measured based on the interference fringes obtained by the measurement, is widely used. By the way, in recent years, the size of the above-mentioned measuring object has been increasing, and the use of a large-sized interferometer has been used for such a large measuring object. The projecting part of the interferometer must meet strict requirements for the parallelism, intensity unevenness, and coherence of the illuminating beam, but it is more difficult to meet those requirements as the lens diameter increases. This is because the cost becomes enormous. Therefore, when targeting a large measurement object, the measurement area is divided into a plurality of partial areas having overlapping parts, and each is measured with a small interferometer, and the shape data obtained for each partial area is obtained. Then, a method of obtaining the shape of the entire measurement region by synthesizing the overlapping portions so as to match each other has been performed. For example, JP-A-10-160
No. 428 discloses a method in which a measurement object or an interferometer is fixed on a multi-axis stage as a driving mechanism, and measurement is performed for each partial area while moving the interferometer with respect to the measurement object. There has been proposed a method of performing a combining process by fitting shape data of each partial region using components and the like as parameters.

[0003]

However, in a measuring apparatus using a driving mechanism as described above, the final accuracy of image synthesis depends on the repetition error of the driving mechanism. In order to perform the above, it is necessary to use a stage having a high-precision driving mechanism. However, there has been a problem that the production of such a high-precision stage is technically difficult and very expensive.
In addition, there is also a problem that it takes a long time to perform the measurement due to the mechanical operation by the drive mechanism during the measurement. Furthermore, since each partial area is measured while moving the interferometer using the drive mechanism, it is necessary to perform high-precision fitting processing to correct errors related to the drive mechanism every time image synthesis is performed. There are also problems such as the time being longer and the need for using a high-performance computer for performing large-scale operations at high speed. The present invention has been made in view of the above circumstances, and has as its object to provide a simple and low-cost apparatus configuration and a surface shape capable of measuring the surface shape of a large measuring object at high speed. It is to provide a measuring device.

[0004]

In order to achieve the above object, the present invention provides a method for measuring an object to be measured based on interference fringes obtained by interfering reflected light from the surface of the object to be measured with a predetermined reference light. By means of optical interference measurement means for measuring the surface shape of an object,
A surface for measuring the surface shape of the object to be measured for each of a plurality of partial regions having overlapping portions and synthesizing the obtained surface shape information for each of the partial regions to obtain the surface shape of the entire object to be measured In the shape measuring device, each of the partial areas is provided with one of the optical interference measuring means, and each of the optical interference measuring means is fixedly installed with respect to the mounting position of the object to be measured. The surface shape measuring apparatus is characterized by the following. With such a configuration, expensive equipment such as a high-precision drive mechanism is not required, and the device configuration can be simplified. Furthermore,
Since no mechanical operation is involved in the measurement, the measurement time can be reduced as compared with the conventional technology. In addition, since there is no error for each measurement such as a repetition error in a measuring device using a conventional drive mechanism, when combining the surface shape data for each partial area, each part determined at the time of installation or adjustment of the device is used. Combination processing can be performed with a small amount of computation using spatial transformation processing such as movement / rotation of shape data, and quick measurement can be performed using a computer with general performance.

Further, if the optical interference measuring means is constituted by an oblique incidence interferometer, it is possible to project light in a relatively free direction and at an angle to an object to be measured. It is easy to dispose them while avoiding excessive interference. Also,
If the light receiving side optical systems of the plurality of grazing incidence interferometers are integrated into one, and the light projecting side optical systems of the respective grazing incidence interferometers are arranged toward the integrated one light receiving side optical system, the light receiving It is possible to reduce the cost by using only one side optical system, and to remove the influence of the difference in the optical system on the light receiving side and the like. Further, since the light projecting directions of the respective light projecting side optical systems are different, it is possible to make the incident angles to the object to be measured the same without physical interference, thereby making the fringe sensitivity of each optical system uniform. On the other hand, even if the plurality of grazing incidence interferometers are arranged so as to surround the measurement object, the fringe sensitivity of each optical system can be made uniform by making all the incident angles to the measurement object the same without physical interference. It is. At this time, for example, when the measurement object is circular, if the interferometers are arranged at an equal angle around the measurement object, the overlapping portion of each partial region can be widely secured, and a plurality of partial regions can be secured. Since they overlap at the same position, it is possible to perform the processing of synthesizing the surface shape data for each partial area with high accuracy.

[0006]

Embodiments and examples of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention. The following embodiments and examples are mere examples embodying the present invention, and do not limit the technical scope of the present invention. Here, FIG. 1 is a schematic configuration diagram of a surface shape measuring apparatus Z1 according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of a shape data synthesizing process for each partial area, and FIG. 3 is an example of the present invention. FIG. 4 is a schematic configuration diagram of a surface profile measuring device Z2, and FIG. 4 is a surface profile measuring device Z3 according to an embodiment of the present invention.
FIG.

[0007] Surface profile measuring apparatus Z1 according to the present embodiment.
Are, as shown in FIG. 1, a light source 1, mirrors _2a , _2b , 2
_c (2 _a and 2 _b are half mirrors, 2 _c is a total reflection mirror), light projecting lens system 3, reference plane 4, light receiving lens system 5
Mirrors _6a , _6b , _6c ( _6a , _6b are half mirrors,
Reference numeral _6c denotes a total reflection mirror, and a plurality of (three in FIG. 1) oblique incidence interferometers (an example of optical interference measuring means) including a light receiving unit 7. The light source 1 and the light receiving unit 7 are common to each interferometer. ), The optical paths from the light projecting side optical system to the light receiving side optical system are parallel to each other in plan view, and the respective visual fields A,
B and C are fixedly installed on the measurement object P such that they have overlapping portions. Here, the overlapping portion between each of the visual fields and the measurement object P is a partial region measured by each interferometer. In the upper part of FIG. 1, the light projecting lens system 3 and the light receiving lens system 6 in the three interferometers seem to physically interfere with each other. However, in this measuring apparatus Z1, an oblique incidence interferometer is used. Therefore, for example, by making the angle of incidence of the interferometer having the field of view B different from that of the other two, physical interference with each other can be avoided.

The parallel light output from the light source 1 is reflected by a mirror 2
After being divided into three parts and enlarged by the light projecting lens system 3, the light is irradiated toward the measurement object P. A part of the parallel light emitted from the light projecting lens system 3 passes through the reference plane 4 and is reflected on the surface of the measuring object P, and another part is reflected on the reference plane 4 (predetermined part). Reference light) and two types of parallel light having different optical distances are combined again, and at this time, interference fringes are generated. The combined reflected light is reduced by the light receiving lens system 5 and reaches the light receiving unit 7 via the mirror 6, where interference fringes are observed. Main measuring device Z
In 1, since there is only one light receiving unit 7, in actual measurement, for example, an illumination switching unit such as a shutter is provided in a part of the light projecting lens system 3, and measurement of each partial area is sequentially performed.
Of course, three light receiving sections 7 may be provided to simultaneously measure the shapes of three partial areas. When the shape data of each partial area is obtained as described above, an image combining processing unit (not shown) combines the shape data of each partial area. FIG. 2 is an explanatory diagram of the synthesis processing of the shape data for each partial area. The upper diagram in FIG. 2 shows partial shape data on a certain line in the vertical direction (the vertical direction in the upper diagram in FIG. 1) of the measurement target P. Since there are two types of shape data in each of the overlapping regions, fitting is performed on the two types of shape data using, for example, the least squares method, and the partial shape is set so that the two types of shape data match in the overlapping region. If the data is moved / rotated and synthesized, the entire shape data as shown in the lower diagram of FIG. 2 can be obtained.

Here, in the present measuring apparatus Z1, since the shape measurement for each partial area is performed by a plurality of interferometers fixedly mounted on the measuring object P, a measuring apparatus using a conventional driving mechanism is used. Does not occur for each measurement, such as the repetition error in. Therefore, the fitting processing of the shape data for each partial area described above need only be performed at the time of installation or adjustment of the apparatus. At the time of normal measurement, spatial conversion such as movement / rotation of each partial shape data obtained by the fitting processing is performed. Since the synthesis processing can be performed with a small amount of calculation using the processing, quick measurement can be performed even with a computer having general performance. In addition, this measuring device Z1
The configuration is such that the shape measurement for each of the three partial areas on the measurement object is performed individually by three systems of grazing incidence interferometers that are fixedly installed on the measurement object. No expensive equipment such as a drive mechanism is required, and the device configuration can be simplified. Furthermore, since no mechanical operation is involved in the measurement, the measurement time can be further reduced as compared with the prior art.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Surface profile measuring apparatus Z1 according to the above embodiment
When the oblique incidence interferometer is used as described above, the degree of freedom in the arrangement of the light-emitting side optical system and the light-receiving side optical system is high, and therefore, various modifications of the device configuration are possible. Two cases that are particularly effective among the modifications will be described. In the surface shape measuring device Z2 shown in FIG. 3, a plurality of sets (three sets in FIG. 3) of the light projecting side optical system are prepared similarly to the measuring device Z1, and light is projected onto the measuring object P from different directions. Is installed as follows. The light receiving side optical system is integrated into one for the plurality of light projecting side optical systems. Each of the parallel light beams emitted and reflected from the plurality of light projecting side optical systems toward the measurement object P is projected onto a translucent screen 11 to form interference fringes. This interference fringe is reflected on the screen 1
1 is reduced by the lens 5 from the back side and is observed by the light receiving unit 7. Also in the case of the present measuring apparatus Z2, in actual measurement, for example, an illumination switching means such as a shutter is provided in a part of the light projecting lens system 3, and measurement of each partial area is sequentially performed. With the above-described configuration, the number of lens systems on the light receiving side can be reduced to one, so that the cost can be reduced and the influence of the difference in the optical systems on the light receiving side can be eliminated. . In addition, since the light projecting directions of the light projecting side optical systems are different, it is possible to make the incident angles to the measurement object P all the same without physical interference, and to make the fringe sensitivity of each optical system uniform.

In the surface profile measuring apparatus Z3 shown in FIG. 4, a plurality of oblique incidence interferometers (four in FIG. 4) each having a single projecting side optical system and a single light receiving side optical system are prepared. The optical system is arranged so as to surround the measurement object P, and the optical systems are arranged at equal angles. According to this configuration, although the number of optical systems is increased as compared with the measuring apparatus Z2 shown in FIG. 3, a wide overlapping portion of each partial region can be secured, and a plurality of partial regions overlap at the same position. Therefore, it is possible to perform the shape data synthesizing process with high accuracy. Further, similarly to the measuring apparatus Z2, it is possible to equalize the fringe sensitivities of the respective optical systems by making all incident angles to the measuring object P the same without physical interference.

In the above example, the grazing incidence interferometer, which is the most practical in constructing the apparatus, is used. Of course, other interferometers are used so that each interferometer does not physically interfere. It goes without saying that they may be arranged.

[0013]

As described above, according to the present invention, the surface shape of the object to be measured is measured based on the interference fringes obtained by causing the reflected light from the surface of the object to interfere with the predetermined reference light. Measuring the surface shape of the object to be measured for each of a plurality of partial regions having overlapping portions with each other, and synthesizing the obtained surface shape information for each of the partial regions, thereby obtaining the entire object to be measured. A surface shape measuring device for acquiring the surface shape of the object, wherein each of the partial areas is provided with one of the optical interference measuring means, and each of the optical interference measuring means is fixed to a mounting position of the object to be measured. Since it is configured as a surface shape measuring device characterized by being installed in a special manner, expensive equipment such as a high-precision driving mechanism is not required, and the device configuration can be simplified. Further, since no mechanical operation is involved in the measurement, the measurement time can be reduced as compared with the conventional technology. In addition, since there is no error for each measurement such as a repetition error in a measuring device using a conventional drive mechanism, when combining the surface shape data for each partial area, each part determined at the time of installation or adjustment of the device is used. Combination processing can be performed with a small amount of computation using spatial transformation processing such as movement / rotation of shape data, and quick measurement can be performed using a computer with general performance.

Further, if the optical interference measuring means is constituted by an oblique incidence interferometer, it is possible to project light in a relatively free direction and at an angle to an object to be measured. It is easy to dispose them while avoiding excessive interference. Also,
If the light receiving side optical systems of the plurality of grazing incidence interferometers are integrated into one, and the light projecting side optical systems of the respective grazing incidence interferometers are arranged toward the integrated one light receiving side optical system, the light receiving It is possible to reduce the cost by using only one side optical system, and to remove the influence of the difference in the optical system on the light receiving side and the like. Further, since the light projecting directions of the respective light projecting side optical systems are different, it is possible to make the incident angles to the object to be measured the same without physical interference, thereby making the fringe sensitivity of each optical system uniform. On the other hand, even if the plurality of grazing incidence interferometers are arranged so as to surround the measurement object, the fringe sensitivity of each optical system can be made uniform by making all the incident angles to the measurement object the same without physical interference. It is. At this time, for example, when the measurement object is circular, if the interferometers are arranged at an equal angle around the measurement object, the overlapping portion of each partial region can be widely secured, and a plurality of partial regions can be secured. Since they overlap at the same position, it is possible to perform the processing of synthesizing the surface shape data for each partial area with high accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a surface shape measuring device Z1 according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a process of synthesizing shape data for each partial area.

FIG. 3 is a surface profile measuring apparatus Z2 according to an embodiment of the present invention.
FIG.

FIG. 4 is a surface profile measuring apparatus Z3 according to an embodiment of the present invention.
FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light source 2 ... Mirror 3 ... Projection lens system 4 ... Reference plane 5 ... Light receiving lens system 6 ... Mirror 7 ... Light receiving part 11 ... Screen P ... Measurement object

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroyuki Takamatsu 1-5-5 Takatsukadai, Nishi-ku, Kobe City, Hyogo Prefecture Inside Kobe Research Institute, Kobe Steel Ltd. (72) Inventor Koji Yoneda Takatsuka, Nishi-ku, Kobe City, Hyogo Prefecture 1-5-5 Kobe Steel Works, Ltd. Kobe Research Institute, Kobe Research Institute F-term (reference) QQ18 QQ31

Claims (4)

[Claims] 1. An optical interference measuring means for measuring the surface shape of the object to be measured based on interference fringes obtained by interfering reflected light from the surface of the object to be measured with a predetermined reference light,
A surface for measuring the surface shape of the object to be measured for each of a plurality of partial regions having overlapping portions and synthesizing the obtained surface shape information for each of the partial regions to obtain the surface shape of the entire object to be measured In the shape measuring device, each of the partial areas is provided with one of the optical interference measuring means, and each of the optical interference measuring means is fixedly installed with respect to the mounting position of the object to be measured. Surface profile measuring device characterized by the above-mentioned. 2. The surface profile measuring apparatus according to claim 1, wherein said optical interference measuring means is a grazing incidence interferometer. 3. The light receiving side optical systems of the plurality of oblique incidence interferometers are integrated into one, and the light projecting side optical systems of each of the oblique incidence interferometers are directed toward the integrated one light receiving side optical system. 3. The surface profile measuring device according to claim 2, wherein the surface profile measuring device is arranged in an inclined manner. 4. A surface profile measuring apparatus according to claim 2, wherein said plurality of oblique incidence interferometers are arranged so as to surround said object to be measured.