JPS6237325B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method 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 this tool toward the rotation center of the processing surface, it is sufficient to detect the rotation center position of the processing surface and feed it back to the control of the tool rest. A satisfactory device for detecting the rotational center position of the machined surface has not yet been achieved.

This invention has been made in view of the above circumstances, and it is an object of the present invention to provide a rotation center position detection method that can easily and highly accurately detect the rotation center of a rotating surface by applying the laser Doppler method. This is the purpose.

Corresponding to this purpose, the method for detecting the rotation center position of a rotating object of the present invention uses an interference fringe measuring device having a phototube and a spectrum analyzer, an interference fringe generating device for laser Doppler, and a microscope,
The interference fringes for laser Doppler generated by the interference fringe generator for laser Doppler are imaged on the surface of the object to be measured by the microscope, and the reflected light from the surface of the object to be measured is transmitted to the phototube of the interference fringe measuring device. The Doppler signal frequency of the laser Doppler interference fringe on the surface of the object to be measured is measured by the spectrum analyzer through photoelectric conversion by the The present invention is characterized in that the position on the surface where the Doppler signal frequency becomes 0 is detected, and that position is set as the center of rotation of the surface.

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

In FIG. 1, reference numeral 1 denotes a rotation center position detection device used in the rotation center position detection method. The rotation center position detection device 1 includes an interference fringe generating device 2, a microscope 3, and an interference fringe measuring device 4. The interference fringe generating device 2 includes a laser generating device 5, and sequentially includes a mirror 6, a beam splitter 7, and two polarizers 8 in the traveling direction of the laser from the laser generating device 5.
a, 8b, another polarizer 9, and a lens 11. The two polarizers 8a and 8b are used to match the light quantities of the light fluxes F ₁ and F ₂ from the beam splitter 7, and the other polarizer 9 is used to match the light fluxes F 1 and F ₂ because the polarizers _8a and 8b are used. This is to match the difference in polarization state that occurs between the two. The microscope 3 is arranged with an objective lens facing the surface to be measured. The surface to be measured 12 is a finished surface of a workpiece, which rotates while being clamped by a chuck of a machine tool, and this is the object whose center of rotation position is to be detected by the device of the present invention. . The interference fringe measuring device 4 includes a phototube 13 and a spectrum analyzer 14.

The laser beam emitted from the laser generator 5 has its optical path changed by a mirror 6 and then enters a beam splitter 7, where it is split into two beams F ₁ and F ₂ . luminous flux
The light amount of F ₁ is adjusted by a polarizer 8a, the polarization is further adjusted by a polarizer 9, and then an image is formed at a focal point position 0 through a lens 11.

On the other hand, the light flux F ₂ is adjusted in light quantity by the polarizer 8b, and further polarized by the polarizer 9, and then
An image is formed at focal position 0 through lens 11. Therefore, these two light beams F ₁ and F ₂ overlap each other at the focal position 0, producing interference fringes.

The interference fringes at focal position 0 are projected onto the surface to be measured 12 through the microscope 3, but these interference fringes are scattered by minute irregularities on the rotating surface 12 to be measured, and the light is transmitted to the phototube 13. The photoelectrically converted electrical signal is analyzed by the spectrum analyzer 14.

As shown in _FIG .
2) When _{the scattered light is incident from the directions of -β and (π/2) +β and observed from the direction of π/2, the frequency of the scattered light from each direction is assumed to be 1.2 .} For example, V is the moving speed of the measured point, λ
As the wavelength, 〓 ₁ = 〓 ₀ + (Vsinβ/λ) 〓 ₂ = 〓 ₀ − (Vsinβ/λ) The Doppler signal frequency of the two-beam differential type LDV is _〓 = | λ, so by measuring this 〓, the velocity V of the point to be measured can be detected, and if the point where this velocity V=0 is found, the rotation center position of the surface to be measured 12 can be detected. In order to detect the point where the velocity V=0, interference fringes are measured as shown in FIG. In this case, the observation direction is perpendicular to the moving direction of the point to be measured.In this invention, the laser beam is irradiated only to a specific location, so for example, only when a Doppler shift occurs on the + side Since the signal is captured, a Doppler shift is observed in the resulting signal.

Note that the Doppler beat frequency can also be explained as follows.

The interval α of one period of brightness and darkness of the interference fringes occurring at the measurement position is α = 〓=V/α=2Vsinβ/λ, which agrees with the previously calculated 〓. In addition, in the detection operation as shown in FIG. 3, when it is desired to further simplify the measurement of interference fringes at multiple points in the X and Y directions on the surface to be measured 12, and when If nearby measurements are difficult due to the presence of pedestal components, interference fringes may be measured as shown in FIGS. 4 and 5. That is, the interference fringe generating device is configured so that four interference fringes A, A', B, and B' are generated on the XY coordinate axes on the surface to be measured 12. If four interference fringes A, A', B, and B' are formed simultaneously on the surface to be measured 12 in this way, the velocities of points B and B' on the The point where the speeds of points A and A' on the axis are equal can be detected as the rotation center position of the surface to be measured 12. In order to form such interference fringes A, A', B, 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. However, this multi-beam beam splitter can be constructed from a hologram subjected to multiple exposures, thereby simplifying the construction of the interference fringe generating device for laser Doppler. That is, FIG. 6 shows a rotation center position detection device 1a used in a rotation center position detection method according to another embodiment of the present invention. is a laser generator 5, a mirror 6, a mirror 6a, a lens 15, a lens 16, a hologram H, and a lens 1, which are arranged sequentially in the direction in which the laser from the laser generator 5 travels.
It consists of 7. The lenses 15 and 16 constitute a beam expander, and the laser beam is expanded to become a parallel beam of light, and then illuminates the hologram H.
Multiple object beams are reproduced from the hologram H,
The light passes through the lens 17 and is focused at the focal point 0' to form interference fringes.

The method for producing the hologram H functioning as a multi-beam beam splitter is as follows. That is, as shown in FIGS. 7 and 8, object beams 0 ₁ to 0 ₄ made up of four parallel light beams with different angles are used as reference beams R ₁ to R ₄ made up of four parallel light beams,
When recording on the hologram H, the hologram is divided into small blocks and the famous object light is recorded in each part. (Although it is possible to record the entire surface at once, this is to prevent contrast and unnecessary interference.) (1) First, the object beam O ₁ is recorded on the hologram H by the reference beams R ₁ and R ₂ . Record in blocks H ₁ and H ₂ .

Reference beam R ₁ illuminates block H ₁ , reference beam R ₂ illuminates block H ₂ , and object beam O ₁ illuminates both blocks H ₁ and H ₂ .

(2) Similarly, the object beam O ₂ is recorded in the blocks H ₃ and H ₄ by the reference beams R ₃ and R ₄ .

₍ 3) Next _, as _shown in _FIG .
Place the central ray of.

(4) As before, the object beam O ₃ is recorded in the blocks H ₁ and H ₄ by the reference beams R ₁ and R ₄ .

(5) Object beam O ₄ is recorded in blocks H ₂ , H ₃ by reference beams R ₂ , R ₃ .

Through these operations, the object beam O _{1 and}
O ₃ , object beams O ₁ and O ₄ were recorded in block H ₂ , object beams O _{2 and} O ₄ were recorded in block H 3, and object beams O ₂ and _{O 3 were} recorded in block H ₄ . Next, when reproducing these, as shown in Figure 9, a reference beam is placed on this hologram H.
When applying reference light R that includes R ₁ to R ₄ ,
Object light from the part where hologram H is made
_O1 to _O4 are played. At this time, since one object beam is holographically recorded by two reference beams, it is reproduced as two parallel beams. Therefore, four sets of parallel beams, two each, are reproduced.

By placing a lens 17 behind this, a set of parallel beams overlap at one point on the focal point to form interference fringes. Since there are four sets of beams, interference fringes are formed at four points. When dividing one beam of reference light into four beams, two parallel plane plates 18 and 19 may be used as shown in FIG.
As shown in Figure 1, two Kester prisms 21,
22 may be used. Note that it is also possible to omit the lens 17 by simultaneously recording the action of the lens 17 on the hologram. In producing the hologram H _b in this case, the hologram H _b is recorded behind the lens 17 as shown in FIG. 12, and the hologram H _b thus produced is replaced by the hologram H. In addition, as shown in FIG. 13, the reproduction light from the hologram H is recorded on the hologram H _c through the lens 17 using another reference light R ₅ , and the hologram H _c thus produced is used in place of the hologram H. do.

FIGS. 14 and 15 show Y=Oμm and Y of the surface to be measured, respectively, obtained by the measurement operation shown in FIG.
This is a graph of the measurement results obtained by scanning the position of =300μm in the X direction.The distance in the X direction and the Doppler signal frequency are proportional to each other, and the point where =O, that is, the center of rotation position, is successfully detected. You can confirm that

As is clear from the above description, according to the present invention, it is possible to obtain a rotation center position detection method that can easily detect the rotation center of a rotating surface with high accuracy.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing a rotation center position detection device used in a rotation center position detection method according to an embodiment of the present invention, FIG. FIG. 3 is an explanatory diagram showing the measurement site on the surface to be measured, FIG. 4 is a perspective explanatory diagram showing the interference fringe formation site in another embodiment, and FIG. 5 is an explanatory diagram showing the interference fringe formation site in another embodiment. An explanatory front view, FIG. 6 is an explanatory diagram showing the configuration of a rotation center position detection device used in a rotation center position detection method according to another embodiment of the present invention, and FIG. 7 is an explanatory diagram showing the manufacturing process of a multiple exposure hologram. , 8th
The figure is an explanatory diagram showing another manufacturing process of the multiple exposure hologram, FIG. 9 is an explanatory diagram showing the reproduction operation of the multiple exposure hologram, FIG. 10 is a perspective explanatory diagram showing an example of the reference beam division operation, and FIG. A perspective explanatory diagram showing another example of the reference beam splitting operation, FIG. 12 is an explanatory diagram showing the production operation of a hologram recording a lens effect, and FIG. 13 is an explanatory diagram showing the production operation of another hologram recording the lens effect. FIG. 14 is a graph showing the measurement results, and FIG. 15 is a graph showing the measurement results. 1, 1a...Rotation center position detection device, 2, 2b...
Interference fringe generator, 3... Microscope, 4... Interference fringe measuring device, 12... Surface to be measured, H, Ha, Hb, Hc... Hologram.

Claims (1)

[Claims] 1 Using an interference fringe measuring device having a phototube and a spectrum analyzer, an interference fringe generating device for laser Doppler, and a microscope, interference fringes for laser Doppler generated by the interference fringe generating device for laser Doppler are measured by the microscope. The reflected light from the surface of the object to be measured is photoelectrically converted by the phototube of the interference fringe measuring device, and then the light reflected from the surface of the object to be measured is converted into an image by the spectrum analyzer. measuring the Doppler signal frequency of the interference fringes for the laser Doppler, performing such measurements at a plurality of locations on the surface of the object to be measured to detect a position on the surface where the Doppler signal frequency becomes 0; A method for detecting a rotation center position of a rotating object, characterized in that a position is determined as the rotation center of the surface.