JPS58167907A - Device for detecting central position of rotation of rotary body - Google Patents

Abstract

PURPOSE:To facilitate the separation of a pedestal component and a signal component, in the measurement of a part, whose rotary speed is slow, by detecting the center of the rotation of the rotary surface highly accurately by applying a laser doppler method. CONSTITUTION:Light from a laser generating device 5 is split into two luminous fluxes F1 and F2 by a beam splitter 7 through a mirror 6. The image of the luminous flux F1 is formed to a focal position 0 through polarizers 8a and 9. Meanwhile, the image of the luminous flux F2 is formed at the focal position 0 through a prism 10 and the polarizers 8b and 9. The interference fringes at the focal position 0 are projected on a plane to be measured 12. The interference fringes are dispersed by minute convex and concave parts on the plane to be measured 12. The light is transduced to electricity by a photoelectric tube 13 and analyzed by a spectrum analyzer 14.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for detecting the rotation center position of a rotating object. When performing ultra-precision finishing on a flat machined surface of a workpiece using a machine tool, the machined surface is usually attached to the machine tool and rotated, and a diamond bit, etc. attached to the tool post is inserted from the outer periphery of the machined surface. Proceed toward the center of rotation. In order to accurately move the tool tool toward the center of rotation of the machined surface, it is necessary to detect the rotation center position of the machined surface and feed it back to the control of the tool rest. The inventors of the present invention have previously developed a device for detecting the center of rotation of a body surface by applying the laser Doppler method. During the rotation of this newly developed rotating object: ◆The position detection device can easily detect the center of rotation of the rotating surface with high accuracy, but the rotational speed near the center of the rotating surface It would be even better if it were easier to separate the pedestal component and signal component in the slow part of the signal! It is considered embarrassing.

This invention was made in view of the above circumstances, and it is possible to easily and highly accurately detect the center of rotation of a rotating surface by applying the laser Doppler method, and is particularly useful for detecting the center of rotation of a rotating surface with low rotation speed. The object of the present invention is to provide a rotation center position detection unit that can easily separate the pedestal component and the signal component during measurement.

Corresponding to this purpose, the device for detecting the center position of one rotation of a rotating object of the present invention includes an interference fringe generating device for the two-beam method or differential beam method, a microscope, and an interference fringe measuring device. The laser top interference fringes generated by the laser top interference fringe generator are imaged on the surface of the object to be measured, and the interference fringe measuring device is configured to image the laser dots on the surface of the object to be measured. a horizontal prism is positioned in the optical path of one of the two beams in the two-beam method or the self-illumination method, and the thickness of the prism in the optical path is varied. The present invention is characterized in that the prism is configured to be movable in the following directions.

Hereinafter, details of the present invention will be explained with reference to the drawings showing one embodiment.

In FIG. 1, 1 is a rotation center position detection device. 1
The rotation center position detection scissors holder 1 includes an interference fringe generating holder 2, a microscope 3,
It is equipped with an interference fringe measuring device 4. Interference fringe generation @I12 includes a laser generator 5, and a mirror 6 and a beam splitter 7 in order in the direction of movement of the laser from the laser generator 5.
．． 2 polarizers 8a, 8b 1 other polarizer 9
, and a lens 11. What is particularly important is that a horizontal prism 10 is inserted between the beam splinter 7 and the polarizer 8b. This prism 1
0 is configured so that it can move in the direction in which its thickness changes. The two polarizers 8a and 8b- are used to match the light intensity of the light fluxes F, F2 from the beam splitter 7, and because the other polarizers 9j and polarizers sa and sb are used, the light fluxes are F, F+2. This is to match the difference in polarization state that has arisen. The microscope 3 is arranged with an objective lens facing the surface to be measured. The object to be measured 1i 112 is the finished surface of a workpiece, which is rotated while being clamped by a chuck of a machine tool, and this is the object whose center of rotation is to be detected by the apparatus of the present invention. The interference fringe measuring device 4 is equipped with a phototube 13° spectrum analyzer 14.

The laser beam emitted from the laser generator 5 has an optical path diverted by a mirror 6, and then enters the beam splitter 7, where the 2
The light beam is divided into two light beams F, , F2. The light flux F1 is made into a light quantity sni by a polarizer 8a, roughly adjusted in polarization by a polarizer 9, and then passes through a lens 11 to form an image at a four-focal position lIO.

゛, 7Ii direction light flux F is frequency modulated by the prism 10,
In the next step, the light quantity is determined by the polarizer 8b, the polarization is further adjusted by the polarizer 9, and then an image is formed at the focal point O through the lens 11. Therefore, these two luminous fluxes F, , F
2 overlap each other at the focal position O, resulting in interference fringes.

The interference fringes at this focal position O are projected onto the surface to be measured 12 through the microscope 3, but these interference fringes are scattered by minute irregularities on the rotationally moving object 1lli12, and the light is photoelectrically converted by the phototube 13. The electrical signal is analyzed by a spectrum analyzer 14.

21st! As shown in lI, the frequency 1.1. The light of
2) If it is incident from the direction of −β, (π/2)+β, then if ■ is the moving speed of the measured point and λ is the wavelength, '+-1(1+ (Vslnβ/λ))F2-F6(1
-(Vslnβ/λ)) Doppler signal frequency I of two-beam differential type LDV! f should be -1f, -zu, I-(2VS
ln β ) /λ, the velocity V of the measured point (one point) can be detected by measuring this factor,
Furthermore, by finding the point of cleanliness v-0, it is possible to detect the 54th center of one rotation of the surface to be measured 12. In order to detect the lid at a velocity v-0, as shown in FIG. 3, interference fringes are measured at multiple arbitrary points in the
and at multiple arbitrary points in the Y direction.

By the way, what should be noted here is the camellia flower on the prism 10. That is, the prism 10 does not exist, and
When the single rotation speed of the measured object 1112 is low, as shown in 4118, the signal component from the scattered light by the measured fli 12 is buried in the pedestal component, making it difficult to distinguish between the two. Therefore, in order to make this discrimination possible, a prism 10 is provided in the present invention.
As shown in Fig. 5, the prism 10 has a horizontal shape with two perpendicular surfaces S1 and S2 and a slope S3 with the prism apex angle e, and the material and the optical path length are changed by the prism 10, and the phase of the light beams F1 and F2 is changed. By changing the relationship and continuously increasing the thickness of the prism 10', the phase relationship also changes continuously, and therefore a difference occurs between the frequencies of the two light beams F2 and F2. Continuously changing the thickness of the prism 10 is performed by continuously moving the prism 10 in a direction parallel to the diagonal 1IiS3. In this case, the frequency difference Δf between the two luminous fluxes Fls F2 is expressed as follows: n is the refractive index of the prism 10, and Vd
is the rate of increase in the thickness of prism 10, vp is the rate of increase in the thickness of prism 10
If the moving speed is Δf, -(1-n, :, ) ・Vd/λVd
-vp -sin e Therefore, a frequency difference Δf occurs between the light beams F1 and F. At this time, the relationship between the Doppler signal frequency t of the two-beam differential type, D and V, and the rotational speed of the measured object l1i12 is f-2sinβ-f, -V/C-Δt0, where C is the speed of light.

In this way, the signal from the interference fringes may be used to measure the pedestal interference fringes as shown in FIG.

That is, the interference fringe generating device is configured so that two interference fringes A and B are generated on the XY seat axis on the surface to be measured 12. If t interference fringes A and B are formed simultaneously on the surface to be measured 12 in this way, by measuring them, the velocities at 8 points on the X axis and the Y
The surface to be measured 12 is searched for a point where the speed at point A on the axis is equal to the speed corresponding to the frequency shifted by the prism.
It can be detected as the rotation center position. By checking whether the frequency of the Doppler signal obtained with respect to the position of the frequency shifted by the prism has shifted higher or lower, the distance r to the center of the velocity axis can be calculated as r- It is given by v/ω. From the detection of points A and 8, the distances from points A and B in the V-axis and x-axis directions, respectively, are determined from the formula r', and the direction is determined from the sign of the velocity. In this case, it is necessary to measure the angular velocity ω of the rotating surface in advance at a position separated by light from the center of rotation. (If the problem is to detect a center position on the μ order as in the present invention, it is sufficient that the position at which the angular velocity ω is measured is several centimeters away from the center of rotation.)
The advantage of this method is that the detector does not have to be moved.

In order to form such interference fringes A and B, it is necessary to divide the laser beam to obtain the required number of multiple beams, and for this purpose, a multi-beam beam splitter is required, but this multiple beam The splitter can be constituted by a hologram subjected to multiple exposures, thereby simplifying the configuration of the interpolation fringe generating device for laser Doppler. That is, FIG. 7 shows a rotational center position detecting device 1a according to another embodiment of the present invention, which is composed of this rotational center and a lens 17. As shown in FIG. Prism 10 is used for the luminous flux F.
is inserted. Lenses 15 and 16 constitute a beam expander, and the laser beam is expanded to become parallel light, and then illuminates the hologram H. A plurality of object beams are reproduced from the hologram ''H, pass through the lens 17, and are focused at a focal point d&: to form interference fringes.

The method for producing the hologram H that functions as a multi-beam beam splitter is as follows. That is, (1) First, the object light 02 is focused on the reference beams R3 and R4.

(3) As before, the object beam is recorded in blocks H, , H4 by the reference beams R,,R,.

Through these operations, object light 04 was recorded in block H1, object light q1 was recorded in block H8, and object light 0□, 04 was recorded in block H4. Next, when playing these, please refer to section 10.1.
As shown in 1ai, a reference beam R is attached to this hologram H.
1, R8, and the object beam 02.04 from the part where the hologram H is made.
is played. In this case, the prism 10 is inserted only in the optical path of the reference beam R1.

At this time, since one object beam is recorded in the hologram by two reference beams, it is reproduced as two beams traveling in parallel. Therefore, it is assumed that two sets of parallel beams, two by two, are reproduced. Since there are two sets of beams, interference fringes are formed at two points.

Note that it is also possible to omit the lens 17 by simultaneously recording the action of the lens 17 on the hologram.

In this case, the hologram H is produced by recording the hologram H behind the lens 17 in FIG. 10, and replacing the hologram H with the hologram H thus produced. Further, the reproduction light from the hologram H is recorded on the hologram H through the lens 17 using another reference light R, and the hologram H' thus produced is used in place of the hologram H.

Next, when playing these, please refer to Figures 12 and 13.
As shown in the figure, Y-0 μm of the surface to be measured is measured by reference to hologram H.

This is a graph of the results of scanning and measuring the position of Y-300μ- in the X direction.The distance in the X direction and the Doppler signal frequency t are proportional to each other, and the point where f-0, that is, the rotation center position, is good. You can confirm that it is detected.

As is clear from the above explanation, according to the present invention, the rotation and center of the rotating surface can be detected easily and with high precision, and the pedestal component and signal component can be detected especially when the rotational speed of the surface to be measured is low. It is possible to use a rotation center position detection device that can easily distinguish between

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the configuration of a rotation center position detection device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram showing the incident angle of a light beam to an interference fringe forming area, and FIG. Fig. 4 is an explanatory diagram showing the measurement site, Fig. 4 is an explanatory diagram showing the signal component and pedestal component, Fig. 5 is an explanatory diagram showing the prism, Fig. 6N1
1 is an explanatory diagram showing interference fringes, and 10th Ill is an oblique I! diagram showing the reproduction operation of a multiple exposure hologram. An explanatory diagram, Fig. 11 is a side explanatory diagram showing the reproduction operation of a multiple exposure hologram, and Fig. 12 is an explanatory diagram.
The figure is a perspective explanatory view showing the reproduction operation of a hologram recording a lens effect, FIG. 13 is a side m* bright view showing a reproduction operation of a hologram recording a lens effect, and FIG. Figure 15 is a graph showing the measurement results. 1... Rotation center position detection @ stomach 2... Interference fringe generator 3... Microscope 4... Interference fringe measuring device
5... Laser generator 6... Mirror 7.
...Beam Figure 1 Figure 3 Figure 5 'Ari rb $to+=aSJIJ & Schiff 11? ll
Figure 6 Figure 7 4-' Figure 14 Figure 15 Procedural amendment (Yoshiiri) September 2, 1982. ? 1, Indication of the case Patent Application No. 61681 of 1988 2 Name of the invention Rotational center position detection device for rotating objects 3 Person making the amendment Relationship to the case Patent applicant Address 1-3 Kasumigaseki, Chiyoda-ku, Tokyo No. 1 (1
14) Name Makoto Ishizaka, Director of the Institute of Industrial Science and Technology
-4 Designated agent 〒305 5 Date of amendment order June 1, 1985 i”” B Figure 5 5 ■ Amount of shift in skin length
:Δf.

Claims (1)

[Claims] A beam method or a reference beam method is provided with a laser Doppler interference generating device, a chain copying mirror, and an interference fringe measuring device; The laser Doppler interference fringes on the surface of the object to be measured are measured by the interference fringe measuring device, and in the two-beam method or the reference beam method. A horizontal prism is positioned in the optical path of one of the two luminous fluxes, and the prism is configured to be movable in a direction in which the thickness of the prism in the optical path changes. A device for detecting the rotation center position of a rotating object.