JPH10232121A - Angle-measuring equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and positively apply measurement rays to the desired position of an object to be measured and to simultaneously measure all angle components of three degrees of freedom being sufficient for describing the posture of a rigid body completely. SOLUTION: In an angle-measuring instrument 1 that is constituted to guide parallel beams emitted from a light source 2 outside the measuring instrument 1 by a beam splitter 3, pass rays entering the measuring instrument 1 again after being reflected on the surface of an object 4 to be measured through a convex lens 5, measure the angle of an object 4 to be measured by obtaining position information on the focusing surface of the convex lens 5, another beam splitter 6 for dividing a light path into two portions is arranged at the rear of the convex lens 5, for example CCD cameras 7 and 8 are arranged at positions where the real image of the object 4 to be measured at the rear part from the focusing position of the convex lens 5 and the focusing position of the convex lens 5, and the real image of the object 4 to be measured that is formed at a rear position from the focusing position of the convex lens 5 is utilized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angle measuring device for measuring the posture of an object to be measured from a position away from the object by using light.

[0002]

2. Description of the Related Art As an angle measuring instrument for measuring the posture of an object to be measured from a remote position using light, a light from a pinhole or the like or a laser beam is incorporated as a light source, and a parallel beam to the object to be measured. There is a device generally called an autocollimator that emits a (measurement light beam) and measures the inclination of reflected light therefrom.

[0003]

However, when a conventional autocollimator is used in a practical measurement system, it may be very difficult to reliably emit the emitted light beam to a desired location on the object to be measured. . In particular, when there are many reflectors around the measured object and on the optical path,
It is difficult to specify the position where the light beam emitted from the autocollimator hits. Further, even when the light beam to be used is not a visible light beam, or when it cannot be used with sufficient intensity and cannot be identified by the naked eye, it is difficult to specify the position where the light beam emitted from the autocollimator hits. Further, generally, to describe the posture of a rigid body, three quantities (three degrees of freedom) are required, as typified by Euler angles, but the angle that can be measured by an autocollimator is two degrees of freedom. In other words, although only two inclination angles are measured by the autocollimator, another angle information is required in addition to this in order to describe the posture of the rigid body in the three-dimensional space.

[0004] It is an object of the present invention to provide an angle measuring instrument which can easily and surely apply a measuring light beam to a desired position of an object to be measured. It is a further object of the present invention to provide an angle measuring instrument capable of simultaneously measuring all the angular components having three degrees of freedom which are sufficient to completely describe the posture of a rigid body.

[0005]

In order to achieve the above object, an angle measuring instrument according to the present invention guides a parallel light beam emitted from a light source to the outside of the measuring instrument by a beam splitter, and reflects the parallel light beam on the surface of an object to be measured. In the angle measuring device configured to measure the angle of the object to be measured by obtaining the positional information on the focal plane of the convex lens, the light beam entering the measuring device again passes through the convex lens. In addition to the positional information on the surface (information obtained by converting the angle of the reflected light from the measured object into an image forming position on the focal plane), information on the real image of the measured object formed at a position behind the focal position of the convex lens is obtained. It is characterized by having obtained.

[0006]

FIG. 1 shows an embodiment of an angle measuring device according to the present invention. The angle measuring device 1 includes a light source 2 that emits a parallel light beam, a beam splitter 3 that guides the parallel light beam from the light source 2 to the outside of the measuring device 1, and a measuring device 1 that reflects on the surface of an object 4 to be measured and returns. And a beam splitter 6 disposed behind the convex lens 5 and two CCD cameras 7 and 8. One CCD camera 7 is placed at the focal point of the convex lens 5, and the other CCD camera 8 is placed at a position where a real image of the measured object 4 that is farther from the convex lens 5 than its focal length is formed. The position of the CCD camera 8 for the real image is preferably variable when the position of the measured object 4 is likely to change greatly, so that it can be adjusted so as to obtain a real image within the range of the desired measurement position. A focusing function may be provided by inserting an appropriate lens system.

The operation of the angle measuring device having the above configuration will be described with reference to FIG. As shown in FIG. 2A, the parallel light emitted from the light source 2 is guided to the outside of the measuring device 1 by the beam splitter 3, reflected on the surface of the object 4 to be measured, and reenters the measuring device 1. Then, by the action of the convex lens 5, an image is formed on the light receiving surface of the CCD camera 7 placed at the focal position. The operation up to this point is exactly the same as that of a normal autocollimator. However, in the angle measuring device 1 shown in the drawing, another beam splitter 6 is inserted between the convex lens 5 and its focal position. As shown in FIG.
The light emitted from can be observed on another axis. That is, the real image of the measured object 4 is observed by placing the second CCD camera 8 at an appropriate position farther from the convex lens 5 than its focal length. Thus, the beam splitter 6 is inserted, and the second CCD for real image observation is placed on the same optical axis as the first CCD camera 7 for autocollimation.
The parallel light emitted from the light source 2 has the shape of the beam spot illuminated on the reflection surface even if the reflection surface of the measured object 4 is a perfect mirror having no irregular reflection component. Can be observed as a real image. Observing the spot of the beam used for measurement in the real image of the measured object 4 as described above is extremely useful for reliably irradiating the beam to a desired position of the measured object 4. Further, from the real image of the measured object 4, it is possible to measure the rotation angle (1 degree of freedom) about the optical axis of the angle measuring device 1 and the displacement in a plane perpendicular to the optical axis (2 degrees of freedom). . That is, along with the measurement of the tilt angle (two degrees of freedom) of the object to be measured by the autocollimation image, the position in the optical axis direction (one degree of freedom) out of six degrees of freedom necessary and sufficient for describing the posture and position of the rigid body. The amount of five degrees of freedom excluding can be measured.

In addition, in the conventional autocollimator, it is necessary to visually check the state of the light beam hitting the object to be measured, and there is a limit to reducing the power of the light beam used for measurement. On the other hand, in the angle measuring device described above, the position of the beam impinging on the object to be measured can be observed by a CCD camera having much higher sensitivity than the naked eye, so that the power of the light beam emitted toward the object to be measured can be reduced. .

The beam splitters 3 and 6 include plate beam splitters, cube beam splitters, and the like.
There is no particular limitation as long as the beam can be split into transmitted light and reflected light, and a cube beam splitter is preferable from the viewpoint of reducing the occurrence of double images. The beam splitters 3 and 6 shown in FIG. 1 are of a cubic shape having a structure in which two prisms are bonded so that reflection and transmission are 1: 1.

As the light source 2, a commercially available semiconductor laser module adjusted to emit a parallel light beam is preferable, but a light source using a pinhole, which has been widely used in an autocollimator, may be used. . Also, as for the convex lens 5, an appropriate combination lens may be used similarly to a conventional autocollimator.

In the example shown in FIG. 1, CC is used to detect an image.
Although the D cameras 7 and 8 are used, a 4-division sensor or the like may be used for an autocollimation image.
In this case, since the position information of the light spot is directly obtained, there is an advantage that relatively complicated post-processing such as image processing is not required, and at the same time, the reflection between the measured object 4 and the angle measuring device 1 is obtained. When the body is present, there is a risk that a plurality of light spots are generated in the field of view and a large error is generated. For observation of real images, CCD
Instead of a camera, an appropriate eyepiece may be provided so that observation can be made directly with the eyes.

Appropriate filters are provided on the entrance sides of the CCD cameras 7 and 8 so as to reduce the influence of the state of light in the measurement environment to be used and to obtain an image with small noise. In addition, installing an ND filter or the like on the exit side of the light source 2 and reducing the power of the light beam incident on the object to be measured means reducing the effect of the light beam used for the measurement on the object to be measured, such as an increase in temperature. Leads to.

As described above, in this example, another beam splitter 6 is placed behind the convex lens 5 so that an actual image of the object to be measured can be simultaneously observed in addition to the autocollimation image, and an angle measuring device is used. The optical axis is divided into two inside 1 so that simultaneous measurement can be performed at two points having different optical path lengths from the convex lens 5. Further, in this example, the CCD cameras 7 and 8 are arranged at the focal position of the convex lens 5 and at a position behind the focal point where a real image of the measured object can be obtained. However, when it is not always necessary to perform the measurement at the same time, or when the image distortion is particularly disliked, for example, the beam splitter 6 may be omitted, and the automatic collimation image and the real image may be switched by a mechanical switching operation. In this case, there are a method of changing the position of the CCD camera, and a method of installing a removable lens between the CCD camera and the convex lens.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example in which the angle measuring device of the present invention is applied to a superconducting magnetic levitation experiment system will be described with reference to FIG. In this superconducting magnetic levitation experiment system, a funnel-shaped floating body 11 is placed in a cryostat cooled with liquid helium, and there is a request to measure the position and attitude of the floating body 11 when it floats.

An interferometer 12 is placed in a cryostat to measure the vertical displacement of the floating body 11,
The vertical displacement (one degree of freedom) of the corner cube prism 13 mounted on the floating body 11 can be measured.
In addition, a ring-shaped flat mirror 14 is mounted to measure the inclination angle of the floating body 11, and conventionally, a beam of an autocollimator is applied to the flat mirror 14 to
(Two degrees of freedom) was measured. However,
With many reflectors such as optical interferometer optics and cryostat optical windows in a narrow and deep cryostat (diameter 6 cm, depth about 1 m), it is difficult to reliably hit the flat mirror 14 with light rays. there were. Therefore, when the angle measuring device 1 according to the present invention is applied, it is possible to easily and reliably hit the light beam to the flat mirror 14, and furthermore, the rotation angle around the vertical axis (one degree of freedom) and the displacement in the horizontal plane (two degrees of freedom) ) Can be measured, and together with the measurement of vertical displacement (one degree of freedom) by the light wave interferometer, all six degrees of freedom necessary and sufficient for complete description of the posture and position of the rigid body can be measured. .

In this embodiment, a stabilized He—Ne laser (wavelength: about 633 nm) is used as a light source 15 for the interferometer 12 used for measuring the vertical displacement of the corner cube prism 13. The light returns to the receiver 16 through the illustrated path. On the other hand, as the light source 2 of the angle measuring device 1, a semiconductor laser module (wavelength: about 670) incorporating a collimating lens system is used.
nm). And the beam from the light source 2
The filters 18, 19, and 20 are appropriately arranged so that the power can be reduced to about 10 μW by the ND filter 17 and good images can be obtained by the two CCD cameras 7, 8. In addition, He- which enters the angle measuring instrument 1
Light from the Ne laser is reduced by the high-pass filter.

The focal length of the convex lens 5 used in the angle measuring device 1 of this embodiment is 200 mm, and the diameter is 20 mm.
The beam splitter 3 for changing the angle of the light beam from the light source 2 has a transmittance of 90% and a reflectance of 10%. The reason for using the beam splitter having such a large transmittance is to minimize the intensity of the light beam applied to the object to be measured and to obtain images of a sufficient amount of light with the CCD cameras 7 and 8.

FIG. 4A shows an autocollimation image obtained by the first CCD camera 7, and FIG. 4B shows a second CC image.
2 shows a real image of the measured object obtained by the D camera 8.
In the figure, reference numeral 21 denotes a light spot formed by reflected light from the flat mirror 14. Reference numeral 22 denotes an image formed on the flat mirror 14 by the light beam emitted from the light source 2, reference numeral 23 denotes an image of the flat mirror 14, and reference numeral 24 denotes an image of the corner cube prism 13.

The obtained image is analyzed by image processing based on an appropriate algorithm. In this embodiment, images from the two CCD cameras 7 and 8 were synthesized by a mixer (“Multiviewer MV-10” manufactured by Howay Co., Ltd.) and then recorded on a video deck equipped with an RC time code function. After that, 640 × 480 pixels, 8
The image was taken into a personal computer at bit gradation and image processing was performed. With respect to the autocollimation image, after extracting a component equal to or more than an appropriately determined threshold value, weighted averaging was performed to obtain the center of the light spot. The standard uncertainty was 0.05 mrad and the resolution was 0.001 mrad. For the real image, three straight lines were combined so as to form an angle of 60 ° with each other, the angle of the combination of the straight lines, the center position, and the real image were matched, and the rotation around the vertical axis and the displacement in the horizontal plane were obtained. . The real image was previously sharpened by differential processing. As a matching method, an algorithm was used in which points closer to the combination of straight lines were weighted and added for all pixels, and a position (angle and center position) at which the sum was maximized was determined. The standard uncertainty in the rotation angle measurement about the vertical axis was 5 mrad, and the resolution was 0.1 mrad.

As for the image processing method, an appropriate algorithm may be set in accordance with an actually obtained image. Alternatively, when a high degree of accuracy is not required, it may be performed visually.

Further, in this embodiment, the angle measuring device 1 and the interferometer 12 for measuring the vertical displacement are installed independently of each other. is there.

[0022]

As described above, according to the angle measuring device of the present invention, it is possible to easily and surely hit the measuring light beam at a desired position on the measured object. Further, it has become possible to simultaneously measure all the angular components having three degrees of freedom which are sufficient to completely describe the posture of the rigid body.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of an angle measuring device of the present invention.

FIG. 2 is a diagram for explaining the operation of the angle measuring device according to the present invention.

FIG. 3 is a diagram for explaining an embodiment of the present invention.

FIG. 4 is a diagram for explaining an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Angle measuring device 2 Light source 3 Beam splitter 4 Object to be measured 5 Convex lens 6 Beam splitter 7 First CCD camera 8 Second CCD camera 11 Floating body 12 Interferometer 13 Corner cube prism 14 Flat mirror 15 Light source 16 Receiver 17 ND filter 18, 19, 20 Filter 21 Light spot 22 Real image of light ray 23 Image of flat mirror 24 Image of corner cube prism

Claims (2)

[Claims] 1. A parallel light beam emitted from a light source is guided to the outside of a measuring device by a beam splitter, and a light beam reflected on the surface of an object to be measured and incident on the measuring device again passes through a convex lens. In an angle measuring device configured to measure the angle of an object to be measured by obtaining position information on a focal plane, in addition to the positional information on the focal plane of the convex lens, the measured object can be located at a position behind the focal position of the convex lens An angle measuring device wherein information of a real image of an object is obtained. 2. Arranging another beam splitter, which divides the optical path into two parts, behind the convex lens, in addition to the positional information on the focal plane of the convex lens, the object to be measured which can be located at a position behind the focal position of the convex lens. The angle measuring device according to claim 1, wherein information of a real image is obtained.