JPH09280819A - System for measuring accuracy of rotation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the radial motions and angular motion of a revolving shaft with high accuracy. SOLUTION: This system has a mirror 10 which has a central region (a) and peripheral region (b) varying in focal lengths from each other, an optical sensor 11 which detects the out-of-focus of laser beams and a processing device 17 which calculates the accuracy of rotation of the revolving shaft A from the output of the optical sensor 11. Namely, the laser beams c1 , c2 reflected in the respective regions (a), (b) of the mirror 10 are so adjusted as to be respectively condensed to the centers of the different quadrisected photodiodes 13a, 13b in a state where the main axis is still. The radial motions at the respective condensing points are calculated from the outputs of the respective quadrisected photodiodes 13a, 13b. Further, the ratio of the differences between both radiation motions with respect to the difference in the distances from the respective regions (a), (b) of the mirror 10 to the respective condensing points is calculated as the angular motion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotation accuracy measuring system suitable for measuring the rotation accuracy of rotation of a rotary shaft, particularly the rotation accuracy of a spindle of a machine tool or the like.

[0002]

2. Description of the Related Art The rotation accuracy of a spindle of a machine tool is usually
It is defined as the degree of movement of the axis of the spindle that adversely affects machining accuracy, that is, three error motions of axial motion, angular motion and radial motion. Now, generally, of the three error motions, radial motion and angular motion have a dominant effect on machining accuracy, and the remaining axial motion has only a secondary effect in machining except for end face machining. It is known not to give. That is, the angular motion and the radial motion are more important in relation to the processing accuracy. Now, the angular motion and the radial motion are usually calculated based on the displacement amount of the reference object fixed to the end of the main shaft due to the rotation of the main shaft. Specifically, the following two methods are known.

The first method uses a member 111 that holds two master balls 110a and 110b, which are reference objects and have a small shape deviation (sphericity), as shown in FIG.
This is a method for simultaneously detecting the radial motion amount and the angular motion amount of the spindle A (Yoshiaki Kakino, "Rotation Accuracy of Machine Tool Spindles", Journal of the Japan Society of Mechanical Engineers, Vol. 83, No. 742, 198).
0, 9, 1172). Specifically, the member 111 is fixed to the spindle end A ₁ so that the two master spheres 110a and 110b are located in a line on the axis B of the spindle, and the master spheres 110a and 110b are rotated by the rotation of the spindle A. The displacement amount is detected by the capacitance displacement meters 112a and 112b, respectively. Then, the displacement amounts Ra (θ) and Rb (θ) of the master spheres 110a and 110b detected as a function of the rotation angle θ of the main axis are displayed in polar coordinates, and this is taken as the radial motion at the positions of the master spheres 110a and 110b. . Furthermore, each master ball 1
After calculating the difference (Ra (θ) −Rb (θ)) between the displacement amounts Ra (θ) and Rb (θ) at the positions of 10a and 110b, the distance s between the centers of the two master balls 110a and 110b is calculated as described above. The ratio ((Ra (θ) −Rb (θ)) / s) of the difference between the displacement amounts is calculated. Then, the ratio (tangent of the deflection angle of the axis B of the main axis A) calculated here is displayed in polar coordinates, and this is set as the angular motion of the main axis A.

The second method uses a lightweight and thin concave mirror 71 as a reference object as shown in FIG.
This is a method of detecting the radial motion of the main axis A by utilizing the fact that the focal point e of the laser light c reflected by the object moves according to the radial motion of the main axis A (K.Mitui, et.al.
Development of an Optical Measuring Method for Rad
ial Spindle Error, Proc.of the 7th Int.Precision E
ngineering Seminar, 1993, 506). Specifically, in the state where the main axis A is stationary, the laser light c emitted from the laser diode 70 passes through the collimator lens 73, the beam expander 74, the beam splitter 76, and the objective lens 75, and is then reflected by the concave mirror 71. After reflection, the optical system of FIG. 10 is adjusted so as to focus on the central portion of the four-division photodiode 77 via the objective lens 75 and the beam splitter 76. Then, based on the difference in the amount of light detected by each element of the four-division photodiode 77 as the main axis A rotates, the focus e of the laser light c reflected by the concave mirror 70 on the light-receiving surface of the four-division photodiode 77. The amount of defocus from the center is calculated. The defocus amount calculated as a function of the rotation angle θ of the main axis is displayed in polar coordinates R (θ), and this is taken as the radial motion at the position of the center of curvature of the concave mirror 70.

[0005]

The first method has the advantage that it is possible to detect both radial motion and angular motion, but on the other hand, the following two methods are mainly used. It has a drawback that the measurement accuracy often decreases depending on the cause. The reasons why the measurement accuracy of the second method is lowered include (1) attachment of the reference object 110 (that is, the weight of the reference object 111 and each master ball 1 from the axis B of the main axis).
The influence of the eccentric center of gravity or the like caused by the deviation of 10a and 110b) causes the main axis A to bend and to steadily swing.
(2) The output of the capacitance displacement meter fluctuates due to the influence of electrical noise from the motor, the control device, and the like.

On the other hand, the second method has a drawback that it is not possible to detect both radial motion and angular motion, but on the other hand, the spindle A
A reference object that is difficult to bend (light and thin concave mirror 7
The use of 0) and the adoption of an optical measurement system that is less susceptible to electrical noise have the advantage that more reliable measurement can be performed.

Therefore, the present invention provides a rotation accuracy measuring system having the advantages of the first method and the advantages of the second method, that is, the radial motion and the angular motion of the spindle that have a dominant influence on the machining accuracy. It is an object of the present invention to provide a rotation accuracy measuring system capable of detecting with high accuracy.

[0008]

In order to solve the above-mentioned problems, the present invention is a rotation accuracy measuring system for measuring the rotation accuracy of a rotating shaft, wherein the rotating shafts are fixed to the rotating shaft and have different focal lengths. A reflection means having two reflection areas,
Illumination means for irradiating the two reflection areas with illumination light, and detection for detecting the displacement amount from a predetermined position of each condensing point where the illumination light reflected by the two reflection areas condenses. And a radial motion amount of the rotation axis at the position of each condensing point based on the displacement amount of each condensing point of the illumination light reflected by the two reflection areas detected by the detecting unit. At the same time, as the angular motion amount of the rotation axis, a calculation means for calculating a ratio of a difference between the calculated radial motion amounts at the positions of the respective focal points to a difference between the distances from the respective reflection regions to the respective condensing points. And as the rotation accuracy of the rotation axis, the smaller of the angular motion amount calculated by the calculating means and the radial motion amount at the position of each condensing point is smaller. Also provides rotational accuracy measuring system, characterized by an output means for outputting the one of the radial motion amount.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below as an example with reference to the accompanying drawings, when it is applied to detection of rotational accuracy of a spindle of a machine tool.

First, the configuration of the system according to the present embodiment will be described with reference to FIG.

This system comprises a mirror 10, which is a reference object fixed to the spindle end A ₁ , an optical sensor 11 for detecting a laser beam c reflected by the mirror 10, and an optical sensor 1.
Processing device 17 for calculating the rotation accuracy of the spindle A from the output of 1
It is composed of The location of the optical sensor 11 need not be particularly limited. For example, if the optical sensor 11 is installed on the tool post, the optical sensor for the spindle A can be used by using the tool post moving mechanism. The positioning of 11 can be performed smoothly.

Next, the structure of the mirror 10 shown in FIG. 1 will be described with reference to FIG.

On the surface of the mirror 10, spherical regions a and b having different curvatures are formed, and one region b is formed so as to surround the other region a. Therefore, the light c illuminating the mirror 10 is reflected by each of the areas a and b, and then is positioned by the areas a and b of the mirror 10 in a conjugate relationship with the light source position (infinity in FIG. 4). Focus on ₁ and E ₂ , respectively. That is, mirror 1
The light c reflected by each of the areas a and b of 0 is focused on two different positions E ₁ and E ₂ determined by the focal lengths of the areas a and b, respectively.

Next, the optical system of the optical sensor 11 shown in FIG. 1 will be described.

The optical sensor 11 includes a laser diode 12 for irradiating the laser light c for illuminating the mirror 10, a four-division photodiode 13a for detecting the laser light c ₁ reflected by the central area a of the mirror 10, and a mirror 10. and a quadrant photodiode 13b for detecting the laser beam c ₂ reflected by the peripheral region b of. Specifically, the optical sensor 1
In the optical system of No. 1, the laser beam c emitted from the laser diode 12 is transmitted through the collimator lens 14, the beam expander 15 and the objective lens 18 in the state where the main axis A is stationary, and the central region of the mirror 10 is obtained. After being reflected by a and the peripheral region b, each four-division photodiode 13 is passed through the objective lens 18, the beam splitter 16, and the beam splitter 19 which divides the incident light into transmitted light and reflected light.
The light receiving surfaces of a and 13b are adjusted to collect light.
That is, the laser light c reflected by the central region a of the mirror 10
₁ is focused at the center O ₁ of the light receiving surface of one of the four-divided photodiodes 13a (see FIG. 3), and the laser beam c ₂ reflected by the peripheral region b of the mirror 10 is the other of the four-divided photodiodes 13a. The light is condensed at the center O ₂ of the light receiving surface of 13b (see FIG. 4).

By the way, since the focal lengths of the respective regions a and b are determined in consideration of the matters described later, the laser light c ₁ reflected by the central region a having a short focal length is in front of the 4-division photodiode 13b. The light is then diverged after being condensed at 1, and the light receiving surface of the four-division photodiode 13b is always illuminated uniformly as shown in FIG. That is, the four elements 1 arranged on the light receiving surface of the four-divided photodiode 13b
The outputs of 3b ₁ , 13b ₂ , 13b ₃ and 13b ₄ are not affected by the laser light c ₁ reflected by the central region a having a short focal length. Therefore, the elements 13b ₁ , 13b ₂ , 13b ₃ , arranged on the light receiving surface of the four-division photodiode 13b,
The laser beam c ₂ reflected by the peripheral region b is output to the output 13 b _4.
The difference corresponding to the movement amount of the spot e ₂ 'of That is, the laser beam c ₂ reflected in the peripheral region b is based on the difference between the outputs of the elements 13b ₁ , 13b ₂ , 13b ₃ , 13b ₄ arranged on the light-receiving surface of the 4-division photodiode 13b.
This means that the amount of movement of the spot e ₂ 'at the focus point of can be calculated. The amount of movement of the spot e ₂ 'here is the amount of movement from the center O ₂ of the light receiving surface of the four-divided photodiode 13b.

Further, the laser beam c ₂ reflected by the peripheral region b having a long focal length illuminates the outside of the light receiving surface of the four-division photodiode 13a as shown in FIG. That is, 4
Four elements 1 arranged in the divided photodiode 13a
The outputs of 3a ₁ , 13a ₂ , 13a ₃ and 13a ₄ are not affected by the laser light c ₂ reflected by the peripheral region b having a long focal length. Therefore, the four-division photodiode 13a
Each element 13a ₁ , 13a ₂ , 13a arranged on the light receiving surface of
Differences appearing in the outputs of ₃ and 13a ₄ according to the movement of the spot e ₁ ′ of the laser light c ₁ reflected in the central area a. That is, the laser beam c ₁ reflected in the central region a is based on the difference between the outputs of the elements 13a ₁ , 13a ₂ , 13a ₃ and 13a ₄ arranged on the light receiving surface of the four-division photodiode 13a.
It means that the movement amount of the spot e ₁ ′ at the light condensing point can be calculated. The amount of movement of the spot e ₁ 'here is the amount of movement from the center O ₂ of the light receiving surface of the four-divided photodiode 13b.

Here, matters to be considered when determining the focal lengths of the above-mentioned areas a and b will be described.

Laser beams c ₁ and c ₂ reflected by the areas a and b
Are incident on the light receiving surfaces of the four-divided photodiodes 13a and 13b as described with reference to FIGS. 3 and 4, respectively, the focal length of the central region a and the focal length of the peripheral region b of the mirror 10 are Rather than independently
The relationship with the area of the light-receiving surface of each of the four-divided photodiodes 13a and 13b must be taken into consideration. That is, if the difference between the focal lengths of the central region a and the peripheral region b of the mirror 10 is smaller than a predetermined value, the laser light c ₁ reflected by the central region a of the mirror 10 is reflected by the light receiving surface of the four-division photodiode 13b. Illuminate only a part or the peripheral area b of the mirror
The laser light c ₂ reflected by the
This causes inconvenience such as incidence on the light receiving surface of 3a. On the contrary, if the difference between the focal lengths of the central region a and the peripheral region b of the mirror 10 is excessively large, the optical system of the optical sensor 11 becomes large, which is not preferable.

Therefore, when determining the focal length of the central region a and the focal length of the peripheral region b of the mirror 10, each of the four-divided photodiodes 13 is arranged so as not to cause the above inconvenience.
It is necessary to take into consideration the relationship with the area of the light receiving surface of a and 13b.

This is the end of the description of the optical system of the optical sensor 11 shown in FIG.

Next, the calculation processing of the rotation accuracy of the spindle A performed by the processing device 17 will be described.

First, according to the following procedure, each element 13 arranged on the light receiving surface of the four-divided photodiode 13a.
_{a 1, 13a 2, 13a 3} , the output of 13a ₄ S _1, S _2,
The radial motion amount R ₁ at the position of the 4-division photodiode 13a is calculated based on S ₃ and S ₄ .

That is, according to the following equation, each element 13a ₁ arranged on the light receiving surface of the four-division photodiode 13a,
Differences Vx and Vy of the outputs of 13a ₂ , 13a ₃ and 13a ₄ are calculated respectively.

[0025]

[Equation 1]

[0026]

[Equation 2]

In this embodiment, the difference Vx and Vy calculated by the equations 1 and 2 and the 4-division photodiode 1 are used.
Since the measurement target is a range in which the movement amount of the spot e ₁ ′ of the laser light c _{1 on} the light receiving surface of 3a is linear, the difference Vx and Vy calculated by the mathematical formulas 1 and 2 are respectively divided into four divided photos. The amount of movement of the spot e ₁ 'of the laser light c _{1 on} the light receiving surface of the diode 13a in the XY directions can be calculated.

Further, similarly to the second method described in the section of the prior art, the rotation angle θ of the main axis A detected by the encoder (not shown) and the spot e ₁ 'at the condensing point of the laser beam c ₁ The polar coordinate display is created by associating it with the amount of movement of, and this is taken as the radial motion R ₁ (θ) at the position of the four-divided photodiode 13a. Further, using the well-known minimum area center method to calculate the radius difference from the polar coordinate display,
This is defined as the radial motion amount R ₁ that quantifies the radial motion R ₁ (θ) at the position of the four-divided photodiode 13a.

In accordance with the same procedure, the radial motion R ₂ (θ) and the radial motion amount R _{2 at} the position of the other four-divided photodiode 13b are also calculated.

After the radial motions R ₁ (θ) and R ₂ (θ) at the positions of the four-divided photodiodes 13a and 13b are calculated according to the above procedure, the angular motion of the spindle A is further followed according to the following procedure. Motion k
(θ) and the angular motion amount K are calculated.

That is, similarly to the second method described in the section of the prior art, each of the four-divided photodiodes 13a and 13a.
Radial motion difference at position b (R ₁ (θ)
-R ₂ (θ)) is calculated, and the difference in the radial motion with respect to the difference in the distance from the spindle end A ₁ to both the four-divided photodiodes 13a and 13b (R ₁ (θ) -R ₂ (θ)). (Representing the tangent of the deflection angle of the axis of the main axis A) is calculated. Then, the ratio calculated here is displayed in polar coordinates, and this is set as the angular motion K (θ) of the main axis A. Further, the radius difference is calculated from the polar coordinate display using the well-known minimum area center method, and this is used as the angular motion amount K that quantifies the angular motion K (θ) of the main axis A. The difference in distance from the spindle end A ₁ to each of the four-divided photodiodes 13a and 13b (that is, from the spindle end A ₁ to the laser beams c ₁ and c _{2 respectively).}
Is the difference between the distances E ₁ and E _{2 where}
It can be calculated from the distance between the objective lens 18 and the objective lens 18, the focal lengths of the regions a and b of the mirror 10, and the focal length of the objective lens 18.

In the above calculation process, the spindle end A ₁
If a well-known process for correcting an error that occurs in the output of the optical sensor 11 due to the mounting failure of the mirror 10 with respect to the above is applied, more appropriate angular motion K (θ) and radial motion R ₁ (θ), R ₂ (θ) can be calculated.

As described above, according to the rotation accuracy measuring system, the radial motion R ₁ (at the two positions different in distance from the spindle end A ₁ required for calculating the angular motion K (θ)). θ) and R ₂ (θ) can be detected. That is, according to the present rotation accuracy measuring system, the radial motions R ₁ (θ) and R ₂ (θ) and the angular motion K (θ) required for evaluating the rotation accuracy of the spindle are provided.
And can be obtained together.

Further, as compared with the first method described in the section of the prior art, the present rotation accuracy measuring system uses an optical sensor which is not easily affected by electric noise from a motor, a control device and the like, and , A reference object that does not easily deform the main axis A (that is, a thin mirror that is lightweight and that does not easily cause an eccentricity)
Since, is used, highly accurate measurement can be performed.

Therefore, referring to the radial motions R ₁ (θ) and R ₂ (θ) and the angular motion K (θ) obtained by such a rotation accuracy measuring system, the rotational motion of the spindle can be evaluated more properly. You can The rotation accuracy measuring system is not limited to the main shaft of the machine tool, but can also measure radial motion and angular motion of a rotating body having an appropriate axis as a rotation center.

In the present embodiment, each of the regions a, so that the central region a has a shorter focal length than the peripheral region b.
Although the curvature of the spherical shape of b is appropriately determined, conversely, the curvature of the spherical shape of each of the regions a and b is set so that the peripheral region b has a shorter focal length than the central region a. You may decide. However, also in this case, each focus of the laser light reflected by each of the areas a and b and each of the four-division photodiodes 13
It is necessary to properly adjust the positions of the four-divided photodiodes 13a and 13a so that the positions a and 13a have the above-described positional relationship.

In addition, each four-division photodiode 13a,
Since 13b may be arranged at a position where the laser beams c ₁ and c ₂ reflected by the respective regions a and b of the mirror 10 are condensed, for example, the laser beam reflected by the respective regions a and b of the mirror 10 is provided. to position E _1, E ₂ where c _1, c ₂ is first condensed each quadrant photodiode 13a, may be arranged to 13b.

By the way, the reference object used in this rotation accuracy measuring system is the focal length of the central area a ₂ and the peripheral area b _2.
2, the mirror 10 does not necessarily have to have two spherical regions a and b having different curvatures as shown in FIG. For example, as shown in FIG. 5, a mirror having a central region a ₁ and a peripheral region b ₁ each having a paraboloidal shape with different curvatures, or as shown in FIG. It may be a reflective zone plate having b. Since it is relatively easy to create a parabolic mirror having a long focal length, as shown in FIG. 7, each laser beam c reflected by each area a ₁ and b ₁ of the mirror of FIG. It is possible to condense ₁ and c ₂ at appropriate positions that do not cause any inconvenience in the arrangement of the four-division photodiodes 13a and 13b. Therefore, if the mirror of FIG. 5 is used as a reference object, the objective lens (18 of FIG. 1) used when using the mirror 10 of FIG. 2 is unnecessary, and the optical system of the optical sensor 11 is
A more compact structure can be achieved. FIG.
Compared with the optical system of No. 2, there is an advantage that there are few parameters that affect the measurement sensitivity (of course, the parameters that affect the measurement sensitivity in the optical system of FIG. 8 include the focal length of the objective lens). . Therefore, the use of the reference object shown in FIG. 5 is suitable when the measurement space is limited. On the other hand, since the focal lengths of the regions a and b of the reflection type zone plate of FIG. 6 are determined only by the regularity of the intervals of the ring zones, the degree of freedom in designing the shape and thickness of the reflection type zone plate is large. Therefore, it is possible to flexibly deal with the case where the size, weight, etc. of the reference object that can be attached to the spindle A are limited. When the reflective zone plate of FIG. 6 is used as the reference object, the configuration of the optical system of the optical sensor 11 when the mirror 10 of FIG. 2 is used as the reference object is changed as shown in FIG. No need.

It is desirable that the reference object of any type is set to the focal length of each area in consideration of the measurement space.

Further, in the present embodiment, each laser light c ₁ , c ₂
In order to detect the amount of movement of the spots e ₁ 'and e ₂ ' at the focal point of
a and 13b are used, but after removing the beam splitter 19, the two four-division photodiode detectors 13
As a substitute for a and 13b, a four-division photodiode 13
A CCD camera may be arranged at the position a. In this case, the radial motion R ₁ (θ) and the angular motion K (θ) may be detected based on the image captured by the CCD camera (see FIG. 9). That is, the center o of the image of the spot e ₁ 'at the condensing point of the laser light c _{1
After 1} detects the distance moved from a predetermined position on the image, the distance is associated with the rotation angle θ of the main axis A and displayed in polar coordinates, which is the radial motion R ₁ (θ) at _one predetermined position. And On the other hand, the spot e of the laser beam c ₂
After detecting the distance at which the center o ₂ of the approximate circle of the ₂ ′ image moves from a predetermined position on the image, a predetermined coefficient (geometry from the objective lens 18 to the laser beam c ₂
To the position of the CCD camera from the objective lens 18), and then the polar coordinates are displayed in association with the rotation angle θ of the main axis A. This is the radial motion at the other predetermined position. Let R ₂ (θ). Further, from the two radial motions R ₁ (θ) and R ₂ (θ), the angular motion K (θ) of the spindle A is calculated as in the case described above.

Alternatively, two quadrant photodiodes 1
CCD cameras may be arranged at the positions of 3a and 13b, respectively. In this case, the laser light c ₁ reflected by the central area a of the reference object is detected from the image captured by the CCD camera arranged at the position of the one of the four-divided photodiodes 13a.
The amount of movement of the center o ₁ of the image of the spot e ₁ 'at the condensing point is obtained, and from the image taken by the CCD camera arranged at the position of the other four-division photodiode 13b, in the peripheral area b of the reference object. The amount of movement of the center of the image of the spot e ₂ 'at the condensing point of the reflected laser light c ₂ is obtained, and the radial motions R ₁ (θ) and R ₂ (θ) at two different positions according to the procedure described at the beginning. And the angular motion K (θ) of the main axis A may be calculated.

[0042]

According to the rotation accuracy measuring system of the present invention, it is possible to detect both radial motion and angular motion. In addition, this rotation accuracy measurement system uses an optical measurement system that is not easily affected by electrical noise from the motor, control device, etc., and is a reference object (that is, lightweight and deviated Since a thin mirror that does not cause a heart easily is used, more accurate measurement can be performed.

Therefore, by referring to the radial motion and the angular motion obtained by such a rotation accuracy measuring system, the rotary motion of the spindle can be evaluated more appropriately.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a system according to an embodiment of the present invention.

FIG. 2 is a diagram for explaining an example of a shape of a reference object in FIG.

FIG. 3 is a diagram for explaining a laser beam that illuminates a division detection unit of one of the four-division photodiodes in FIG.

FIG. 4 is a diagram for explaining a laser beam that illuminates a division detection unit of the other four-division photodiode in FIG.

FIG. 5 is a diagram for explaining an example of the shape of a reference object according to the present invention.

FIG. 6 is a diagram for explaining an example of the shape of a reference object according to the present invention.

7 is a diagram showing a configuration of a system according to an embodiment of the present invention when the reference object of FIG. 5 is used.

8 is a diagram showing a configuration of a system according to an embodiment of the present invention when the reference object of FIG. 6 is used.

FIG. 9 is a diagram showing an image of laser light taken by a CCD camera which is a substitute for a four-division photodiode.

FIG. 10 is a diagram for explaining an optical system of a conventional measurement system.

FIG. 11 is a diagram for explaining a measurement system of a conventional measurement system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Mirror which is a reference object 11 ... Optical sensor 12 ... Laser diode 13a of optical sensor 11, 13b ... Four division photodiode 14 ... Collimator lens 15 ... Beam expander 16 ... Beam splitter 17 ... Processing device 18 ... Objective lens 19 ... Beam splitter

Claims (7)

[Claims] 1. A rotation accuracy measuring system for measuring the rotation accuracy of a rotating shaft, comprising: a reflecting means fixed to the rotating shaft and having two reflecting regions having different focal lengths; Illuminating means for irradiating the illuminating light for illuminating, detecting means for respectively detecting a displacement amount from a predetermined position of each condensing point where the illuminating light reflected by the two reflection areas is condensed, and the detecting means. The radial motion of the rotation axis at the position of each converging point is calculated based on the displacement amount of each converging point of the illumination light reflected by the two reflection areas detected in As an angular motion, a calculator for calculating the ratio of the difference in the radial motion at the calculated position of each condensing point to the difference in the distance from each reflection region to each condensing point. A step, and as the rotation accuracy of the rotation axis, an output unit that outputs the angular motion amount calculated by the calculation unit and at least one radial motion of the radial motions at the positions of the respective focal points. A rotation accuracy measuring system characterized by comprising. 2. The rotation accuracy measuring system according to claim 1, wherein one of the two reflection areas has a reflection area disposed around a reflection area of the other reflection area. Each condensing point of the illumination light reflected by
A rotation accuracy measuring system, wherein the rotation accuracy measuring system is located on the axis of the rotation shaft. 3. The rotation accuracy measuring system according to claim 1, wherein the two reflection areas are formed by spherical mirror surfaces having different curvatures. 4. The rotation accuracy measurement system according to claim 1, wherein the two reflection areas are formed of reflection type zone plates. 5. The rotation accuracy measurement system according to claim 1, wherein the two reflection areas are formed by parabolic mirror surfaces having different curvatures. . 6. The rotation accuracy measuring system according to claim 1, 2, 3, 4, or 5, wherein the detection means is provided at each position of each condensing point of the illumination light reflected by the two reflection areas. It is provided with four-division photodiodes arranged and means for detecting the amount of displacement of each condensing point of the illumination light from the normal position in accordance with the amount of light detected by each of the four-division photodiodes. Rotation accuracy measurement system. 7. The rotation accuracy measuring system according to claim 1, 2, 3, 4, or 5, wherein the detection means captures an image of each spot of the illumination light reflected by the two reflection areas. Photographing means, and means for respectively detecting a movement amount from a predetermined position of an image of each spot of the illumination light photographed by the photographing means as a displacement amount of each condensing point of the illumination light from a normal position. A rotation accuracy measuring system comprising: