JP6526465B2 - Roundness measuring device - Google Patents

Description

  The present invention relates to an improved technique of a roundness measuring apparatus for measuring the roundness of the inner circumferential surface of a workpiece to be measured.

  For example, as a roundness measuring apparatus for measuring the roundness of the inner circumferential surface of the workpiece to be measured, the workpiece to be measured is rotated to measure the distance between the rotation center axis of the workpiece to be measured and the inner circumferential surface; It is known to calculate the roundness from the result (see, for example, Patent Document 1).

  In this type of roundness measuring device, in order to improve the measurement accuracy of roundness, it is necessary to accurately align the rotation center axis of the workpiece to be measured with the axis line of the inner peripheral surface of the workpiece to be measured. Although essential, this alignment is very time consuming and labor intensive. Therefore, it has been difficult to conduct an exhaustive inspection of the roundness of a large number of measured workpieces.

  On the other hand, for example, Patent Document 2 proposes a roundness measuring device that measures the roundness of the inner peripheral surface without rotating the workpiece to be measured. The roundness measuring apparatus comprises: light irradiating means for illuminating the inner peripheral surface of the workpiece to be measured; imaging means for imaging the inner peripheral surface to form image data; and the inner periphery based on the image data And computing means for computing the roundness of the surface.

JP, 2009-257887, A JP, 2008-209380, A

  However, the inner surface of the workpiece to be measured of the roundness measuring device of Patent Document 2 must have a bottomed cylindrical surface. This is because this roundness measuring device causes the light to be irradiated as a straight beam of a diameter smaller than the inner diameter of the workpiece to be measured and is incident on the back of the inner peripheral surface of the workpiece to be measured, and an image by the light reflected on the bottom surface The image of the Therefore, this roundness measuring device can not measure a work such as a pipe having a cylindrical surface without a bottom surface. Moreover, since this roundness measuring device picks up the image by the light reflected by the bottom surface, it can only measure the roundness around the opening of the inner peripheral surface of the workpiece to be measured. For this reason, this roundness measuring device can not measure the roundness, the degree of cylindricity, and the degree of coaxiality of the inner peripheral surface of the workpiece to be measured. That is, the roundness measuring apparatus of Patent Document 2 still leaves room for improvement as the roundness measuring apparatus.

  SUMMARY OF THE INVENTION In view of the above-described circumstances, the present invention has a technical object to enable 100% inspection without requiring an axis alignment operation in a roundness measuring apparatus and to enable measurement of even a pipe-like work or the like.

  The roundness measuring apparatus according to the present invention, which was devised to solve the above problems, comprises: a light irradiating means for illuminating the cylindrical inner peripheral surface of the workpiece to be measured; and an image by imaging the inner peripheral surface A reference axis extending in the direction of the axis of the inner circumferential surface, in a roundness measuring device comprising an imaging means for forming data, and a computing means for computing the circularity of the inner circumferential surface based on the image data. And, first moving means for moving the light emitting means illuminating the inner circumferential surface along the direction of the reference axis along the direction of the reference axis, and the imaging along the direction of the reference axis A second moving means for moving the means is provided, and the light emitting means and the imaging means are configured to move while maintaining a constant distance. Here, the “reference axis extending in the direction of the axis of the inner peripheral surface” includes a reference axis inclined with respect to the direction of the axis of the inner peripheral surface (the same applies hereinafter). Moreover, the definition and display of roundness conform to JIS B 0621: 1984.

  According to this configuration, since the roundness of the inner peripheral surface is calculated based on the image data of the inner peripheral surface, there is no need to rotate the workpiece to be measured. Therefore, alignment work can be made unnecessary. Therefore, since the time required to measure the roundness can be shortened, 100% inspection of the workpiece to be measured becomes possible.

  In addition, the light irradiation means that illuminates the inner peripheral surface moves inside the inner peripheral surface, and the light irradiation unit and the imaging unit move while maintaining a certain distance, so even a pipe-like work is a perfect circle. The degree can be measured. In addition, cylindricity and coaxiality can also be measured.

  Also, if the inner peripheral surface to measure roundness is included in the field of view of the imaging means, measure roundness regardless of where the axis of the workpiece to be measured is in the direction perpendicular to the reference axis be able to. Therefore, it is not necessary to perform positioning in the direction perpendicular to the reference axis with respect to the workpiece to be measured with high accuracy.

  In the above configuration, when viewed in the direction along the reference axis, the light emitting unit may simultaneously radiate light radially.

  With this configuration, it is possible to obtain image data of the inner peripheral surface in a short time as compared with the case where the light irradiation unit scans light and irradiates the inner peripheral surface.

  In the above configuration, a connection member may be provided to connect the light emitting unit and the imaging unit, and the second moving unit may double as the first moving unit.

  With this configuration, the light emitting means and the imaging means can maintain a constant distance by the connecting member, and the second moving means can also serve as the first moving means, so that the manufacturing cost can be reduced. In addition, it is easy to introduce the light irradiation means inside the inner peripheral surface while maintaining a fixed distance from the opening at one end of the inner peripheral surface. Therefore, even in the case of the workpiece to be measured in which one end of the inner peripheral surface is closed, the roundness can be easily measured.

  In the above configuration, the calculation means may correct the roundness based on an inclination angle of the axis with respect to the reference axis.

  With this configuration, it is possible to accurately measure the roundness even when the axis of the inner peripheral surface is inclined with respect to the reference axis.

  In the above configuration, the calculation means may calculate the tilt angle based on the position of the axis on a different surface of the vertical surface with respect to the reference axis.

  With this configuration, the inclination angle can be easily calculated.

  In the above configuration, the position of the axis may be calculated based on the position of the axis of the cylindrical inner circumferential surface of the master work with respect to the position on the vertical plane with respect to the reference axis. .

  With this configuration, it is possible to measure the roundness more accurately.

  As described above, according to the present invention, in the roundness measuring apparatus, it is possible to perform 100% inspection without the need for the axis alignment operation, and also to measure even non-contact, pipe-like workpieces and the like. In addition to the roundness, the inner diameter, the cylindricity, and the coaxiality can also be measured simultaneously.

It is a schematic partial cross section side view showing a roundness measuring device concerning an embodiment of the present invention. (A) is a schematic plan view of a periphery of a light irradiation means, (B) is a schematic side view of a periphery of a light irradiation means. It is the schematic which shows the image data formed of an imaging means, Comprising: When (A) is not inclined with respect to the reference axis of the to-be-measured workpiece | work, (B), the to-be-measured workpiece's axis line is a reference axis When it is inclined to the It is the schematic which shows the state in which the shadow of the connection member appeared in image data, (A) is a case where there are three connection members, (B) is a case where there are four connection members. It is the schematic which shows the example of a two-dimensional display of the deviation by a display means. It is a schematic longitudinal cross-sectional view which shows the state which the axis line of to-be-measured workpiece | work inclines with respect to a reference axis. It is a table | surface which shows the specific example of the value of a coordinate. It is a graph of the data of FIG. It is the schematic which shows the example of a three-dimensional display of the deviation or radius by a display means.

  Hereinafter, an embodiment for carrying out the present invention will be described based on the drawings.

  FIG. 1 is a schematic partial cross-sectional side view showing a roundness measuring apparatus 1 according to an embodiment of the present invention. The workpiece to be measured W measured by the roundness measuring apparatus 1 has an inner peripheral surface Wa having a cylindrical surface shape. The workpiece W to be measured is disposed such that the axis Wb of the inner circumferential surface Wa is in the vertical direction. In the present embodiment, the workpiece W to be measured is a circular tubular body, but as long as it has a cylindrical surface-shaped inner peripheral surface, for example, the cross section of the outer surface may be polygonal.

  The roundness measuring apparatus 1 is based on the light irradiator 2 for illuminating the inner circumferential surface Wa of the workpiece W to be measured, the imaging device 3 for imaging the inner circumferential surface Wa to form image data, and the image data Operation means 4 for calculating the roundness or the like of the inner peripheral surface Wa, moving means 5 as a second moving means for moving the imaging means 3, and support means 6 for supporting the workpiece W to be measured The display means 7 for displaying the roundness calculated by the calculation means 4 is the main component.

  The roundness measuring device 1 also includes a reference axis A extending in the direction of the axis Wb of the inner circumferential surface Wa. The reference axis A is a virtual axis which is a reference at the time of measurement of roundness, and corresponds to a Z axis of coordinates described later. The (extension) direction of the reference axis A is the vertical direction.

  The moving unit 5 is configured to move the moving unit 5b along the guide unit 5a by being controlled by a control unit (not shown), and is configured by, for example, a single-axis robot. The light irradiation means 2 and the imaging means 3 are connected by a connecting member 8, and the imaging means 3 is fixed to the moving part 5b. By the connection of the connecting member 8, the moving means 5 doubles as a first moving means for moving the light emitting means 2.

  At the time of measurement of roundness etc., the light irradiation means which illuminates the inner circumferential surface Wa along the direction of the reference axis A by moving the moving portion 5b along the guide portion 5a. 2 moves. Then, the imaging means 3 moves along the direction of the reference axis A while maintaining a constant distance with respect to the light emitting means 2.

  In the support means 6 such as the mounting table, a concave portion 6a on which the workpiece W to be measured is mounted is formed. The recess 6 a has a circular flat bottom surface (support surface 6 b) for supporting the lower end surface Wc of the workpiece W to be measured and a cylindrical side surface 6 c for positioning the workpiece W to be measured. The support surface 6 b is a surface perpendicular to the reference axis A, and the center of the support surface 6 b is on the reference axis A.

  It is very difficult to align the axis Wb of the workpiece W to be measured and the center of the support surface 6b. This is because it is necessary to provide a gap G between the side surface 6c of the recess 6a and the outer peripheral surface of the workpiece W to enhance productivity, and to facilitate the installation work of the workpiece W. is there.

  At the time of measurement of roundness etc., the light irradiation means 2 irradiates the light L to the inner peripheral surface Wa. More specifically, the light emitting means 2 emits the light L along the direction perpendicular to the reference axis A in the direction from the reference axis A toward the inner circumferential surface Wa. Therefore, the light L is irradiated only to the part (inner peripheral surface Wa1) of the predetermined position in the reference axis A direction in the inner peripheral surface Wa. The light L is a laser light in the present embodiment, but the light L is not limited to this as long as it can be imaged by the imaging unit 3.

  As shown in FIG. 2A, when viewed in the direction along the reference axis A, the light emitting means 2 simultaneously radiates light L toward all directions in a radial manner. Further, as shown in FIG. 2B, the light irradiation means 2 includes a laser light emitting part 2a, a prism 2b for reflecting the laser light La emitted from the laser light emitting part 2a, and a laser light emitting part 2a. It has a colorless and transparent cylindrical body 2c connecting the prism 2b.

  The imaging means 3 images the inner circumferential surface Wa (Wa1) irradiated with the light L to form image data, and is formed of, for example, a CCD camera. The center of the field of view of the imaging means 3 is on the reference axis A.

  The light L irradiated from the light irradiator 2 toward the inner circumferential surface Wa (Wa1) strikes the inner circumferential surface Wa (Wa1) and is reflected. Therefore, in the image data formed by the imaging means 3, as shown in FIG. 3A, the bright part B based on the reflected light is formed in a ring shape.

  The computing means 4 computes the roundness of the inner circumferential surface Wa (Wa1) based on the image data formed by the imaging means 3, and is constituted of, for example, a microcomputer, a personal computer or the like. Next, the calculation method of the calculation means 4 will be described.

  In the image data shown in FIG. 3A, the outer peripheral edge Ba of the bright portion B is considered to be a position where the inner peripheral surface Wa (Wa1) actually exists. Therefore, first, the position of the center of gravity of the circle formed by the outer peripheral edge Ba is determined, and the position of the center of gravity is made the position of the center C of the circle formed by the outer peripheral edge Ba (the center of the inner peripheral surface Wa1). Then, the distance (measured value R of the radius) from the position of the center C to the outer peripheral edge Ba is measured from a predetermined circumferential direction position (0 °) up to 360 ° at every predetermined angle. Then, the difference between the maximum value and the minimum value of the actual radius R is calculated as the degree of roundness.

  Further, a value obtained by subtracting a design value (reference value) of the radius of the inner circumferential surface Wa from the measured radius actual value R is calculated as a deviation.

  In addition, all the radius actual value R for 360 degrees at this time are recorded, and can be utilized as two-dimensional shape data. This can be used as three-dimensional inner diameter data in consideration of the reference axis A (Z axis) direction.

  By repeating the image data formation by the series of image pickup means 3 and the calculation of the calculation means 4 at predetermined pitches in the direction of the reference axis A, roundness and roundness at predetermined pitches in the direction of the reference axis A can be obtained. Calculate the deviation. More specifically, each of the portions Wa1, Wa2, Wa3,... Wa (N-2), Wa (N-1), Wa N at positions at predetermined pitches in the reference axis A direction on the inner peripheral surface Wa. Calculate roundness etc.

  The calculated roundness and deviation are displayed on the display means 7 such as a monitor. When displaying the deviation at a predetermined position in the direction of the reference axis A, for example, as shown in FIG. 5, a true circle E (the deviation at all circumferential positions is 0) as a reference is drawn. On the other hand, the deviation F for each circumferential position is displayed (two-dimensional display). Furthermore, as shown in FIG. 9, the deviation or the actual radius R at the position of each predetermined pitch in the reference axis A direction can be three-dimensionally displayed as a bird's-eye view of a cylinder. In this case, the area Pa with a small deviation (close to a perfect circle), the area Pb with a large deviation (far from a perfect circle), and the area Pc with a deviation between the area Pa and the area Pb are displayed in different colors it can. As the color coding, for example, the area Pa can be green, the area Pb can be red, and the area Pc can be yellow.

  In addition, obtain cylindricality that is three-dimensional roundness from each roundness of the inner circumferential surfaces Wa1, Wa2, Wa3, ... Wa (N-2), Wa (N-1), and WaN. And may be displayed on the display means 7. Also, the center C (C1, C2, C3... C (N-2), each of the inner peripheral surfaces Wa1, Wa2, Wa3, ... Wa (N-2), Wa (N-1), and WaN. The degree of coaxiality can be calculated from C (N-1), CN), and this may be displayed on the display means 7.

  Further, as described above, the roundness measuring apparatus 1 calculates the roundness and the deviation for each predetermined pitch in the direction of the reference axis A, but the predetermined pitch can be arbitrarily small. For example, if the deviation is accurately measured to form plane shape data, and this plane shape data is three-dimensionally formed at 1/100 mm pitch, three-dimensional shape data can be obtained. It can be applied as an original shape measuring machine. Of course, even in this case, the measurement pitch is not limited to 1/100 mm pitch, and may be further reduced to 1/1000 mm pitch, 1 / 10,000 mm pitch, or roughly 1/10 mm pitch. It can measure by pitch.

  In order to stabilize the positional relationship between the light emitting unit 2 and the imaging unit 3, it is preferable to arrange three or more connecting members 8 at equal intervals in the circumferential direction of the reference axis A. However, if the connecting member 8 is a non-transparent material, it blocks the reflected light from the inner peripheral surface Wa, so as shown in FIG. S occurs. As shown in FIG. 4A, in the case where three connecting members 8 are arranged at equal intervals in the circumferential direction, three radii can not be measured due to the lack S of the bright portion B, and three connecting members 8 can not be measured. The diameter D of can not be determined.

  On the other hand, as shown to FIG. 4 (B), when the connection member 8 is arrange | positioned four at equal intervals in the circumferential direction, the radius which can not be measured due to the notch S of the bright part B is There are four, but since the four unmeasurable four radii correspond to two diameters D, the number of unneeded diameters D is two. Therefore, in the case where it is assumed that the diameter D is to be determined by the roundness measuring device 1, it is preferable that four connecting members 8 be arranged at equal intervals in the circumferential direction. Here, for the sake of easy understanding, although it is described that one radius can not be measured due to the lack S1 of the bright portion B, strictly speaking, the size of the lack S and the radius The number of radii that can not be measured varies depending on whether it is measured.

  By the way, if the axis Wb of the inner circumferential surface Wa of the workpiece W to be measured is coaxial or parallel to the reference axis A, theoretically the above-mentioned calculation can obtain an accurate roundness, but as shown in FIG. When the axis Wb of the inner circumferential surface Wa is inclined with respect to the reference axis A, an accurate roundness can not be obtained only by the above-described calculation.

  This is because the roundness of the inner circumferential surface Wa has to be measured in a cross section in the direction perpendicular to the axis Wb of the inner circumferential surface Wa of the workpiece W to be measured, while the measurement by the roundness measuring apparatus 1 This is because the roundness of the inner circumferential surface Wa is measured based on the cross section (image data) in the direction perpendicular to the reference axis A.

  For this reason, when it is detected that the axis Wb of the inner circumferential surface Wa is inclined with respect to the reference axis A, the computing means 4 calculates the axis Wb of the inner circumferential surface Wa with respect to the reference axis A. The roundness may be corrected based on the inclination angle θ.

  The fact that the axis Wb of the inner circumferential surface Wa is inclined with respect to the reference axis A can be detected from the result of finding the coaxiality. For example, in FIG. 6, the inclination angle θ between the reference axis A and the straight line connecting the center C1 of the inner circumferential surface Wa1 and the two points of the center CN of the inner circumferential surface WaN is the reference axis of the axis Wb of the inner circumferential surface Wa. Detected as a slope to A.

  Next, a method of correcting the roundness on the basis of the inclination angle θ of the axis Wb of the inner peripheral surface Wa with respect to the reference axis A will be described with reference to a specific example.

  As a specific example, consider the case where a level (height) of 0 mm to 400 mm in the direction of the reference axis A is measured at a predetermined pitch (1 mm in this case).

  First, measure the master work MW. The master work MW is a work formed for correction, and the cross section of the inner circumferential surface Wa is substantially circular, and the axis Wb is substantially perpendicular to the lower end face Wc. ing. The calculation means 4 obtains the position of the center C of the cross section of the inner circumferential surface Wa of the master work MW in the same manner as described above, for every 1 mm between 0 mm and 400 mm in the direction of the reference axis A.

  Specifically, as shown in FIG. 7, with the reference axis A as the Z axis of coordinates, the position (Xm, Ym) of the center C of the transverse cross section (cross section perpendicular to the Z axis) of the inner circumferential surface Wa is calculated. And remember. For easy understanding, in this specific example, the coordinates (Xm, Ym) of the center C of the cross section of the inner circumferential surface Wa of the master work MW are all (0.00, 0.00).

  Next, the workpiece W to be measured is measured. The calculation means 4 positions the center C of the cross section (the cross section perpendicular to the Z axis) of the inner peripheral surface Wa of the workpiece W to be measured in the same manner as described above every 0 mm to 400 mm in the direction of the reference axis A Ask for

  Then, a value obtained by subtracting the value (0.00, 0.00) of the XY coordinates of the center C of the master work MW from the value of the XY coordinates of the center C obtained is calculated, and the coordinates of the center C of the workpiece W to be measured It stores as (Xw, Yw).

  That is, in this case, the calculation means 4 is the axis Wb of the inner peripheral surface Wa of the work W to be measured with respect to the position on the vertical plane (XY coordinate plane or plane parallel to this) with respect to the reference axis A (Z axis). The position (Xw, Yw) of the center C) is calculated based on the position (Xm, Ym) of the axis Wb (center C) of the cylindrical inner circumferential surface Wa of the master work MW.

  As shown in FIG. 7, (Xw, Yw) = (− 1.00, 0.00) at Z = 0, and (Xw, Yw) = (1.00, 0.00) at Z = 400. ). Since the value of Yw is 0.00 at Z = 0 and Z = 400, the axis line Wb of the workpiece W to be measured is inclined with respect to the reference axis A (Z axis) on the XZ coordinate plane. It is FIG. 8 which showed this calculation result as a graph. As can be understood from FIG. 8, assuming that the inclination angle of the axis Wb with respect to the reference axis A (Z axis) is θ, tan θ = 2.00 / 400, so the inclination angle θ = arctan (2.00 / 400). The inclination angle θ is calculated from this equation.

That is, here, the calculation means 4 is the axis line Wb (center C) of the work W to be measured on a different plane of a plane perpendicular to the reference axis A (Z axis) (XY coordinate plane or plane parallel thereto). The inclination angle θ is calculated based on the position (Xw, Yw) of

  When the axis Wb of the work W to be measured is inclined with respect to the reference axis A (Z axis) on the XZ coordinate plane, the work W to be measured formed by the imaging means 3 as shown in FIG. 3 (B) The bright portion B of the image data of the inner circumferential surface Wa has an elliptical shape having a major axis in the X-axis direction. As can be seen from the relationship shown in FIG. 6, assuming that the radius in the X-axis direction to be determined is Rr, the radius Ra in the X-axis direction calculated based on the image has a relationship of Rr = Ra × cos θ. The radius Rr is determined from the angle θ and the radius Ra. The roundness can be determined from the radius Rr in the same manner as described above. As a result, the calculating means 4 corrects the roundness based on the inclination angle θ of the axis Wb of the workpiece W to be measured with respect to the reference axis A (Z axis).

  The roundness measuring apparatus 1 configured as described above can receive the following effects.

  Since the roundness etc. of the inner peripheral surfaces Wa1, Wa2,... WaN are calculated based on the image data by the reflected light around the inner peripheral surfaces Wa1, Wa2,. There is no need to rotate W. Therefore, alignment work can be made unnecessary. Then, the light irradiator 2 moves inside the inner circumferential surface Wa, and can pick up an image by the reflected light of each portion of the inner circumferential surfaces Wa1, Wa2,. Thereby, the roundness can be measured based on this image, and furthermore, the cylindricity and the coaxiality which can be said to be a solid version of the roundness can be measured. In addition, since the light emitting unit 2 and the imaging unit 3 move while maintaining a constant distance, the image of the inner circumferential surface Wa imaged by the imaging unit 3 has a constant size. That is, there is no change in the size of the image due to the change in the distance between the light irradiation means 2 and the imaging means 3. In addition, by correcting the roundness based on the inclination angle θ of the axis Wb of the inner circumferential surface Wa with respect to the reference axis A, the measurement accuracy of the roundness is improved.

  In addition, if the inner circumferential surface Wa to be measured for roundness is included in the field of view of the imaging means 3, the axis Wb of the workpiece W to be measured is true regardless of where the axis Wb is perpendicular to the reference axis A. The degree of circularity can be measured. Therefore, it is not necessary to position the workpiece W in a direction perpendicular to the reference axis A with high accuracy.

  The present invention is not limited to the above embodiment, and various modifications are possible within the scope of the technical idea thereof. For example, in the above embodiment, the workpiece W to be measured is disposed such that the axis Wb is in the vertical direction, and the light irradiation unit 2 and the imaging unit 3 move along the vertical direction. The measurement workpiece W may be disposed so that the axis Wb is in the horizontal direction, and the light irradiation unit 2 and the imaging unit 3 may be configured to move in the horizontal direction.

  Moreover, in the said embodiment, although the light irradiation means 2 and the imaging means 3 maintained the fixed distance by connection by the connection member 8, even if not connected, the light irradiation means 2 and the imaging means 3 are fixed. I wish I could maintain the distance of For example, separately from the moving means 5 (second moving means) for moving the imaging means 3, a first moving means for moving the light irradiating means 2 is provided, and the light irradiating means 2 and the imaging means 3 are respectively It may be introduced from the opening on the opposite side of the measurement work W and moved synchronously at the time of measurement.

  Further, the positional relationship between the laser beam emitting portion 2a and the prism 2b in the light emitting means 2 of the above embodiment may be reversed.

  In the above embodiment, when the calculation means 4 corrects the roundness based on the inclination angle θ, the position (Xw, Yw) of the workpiece W to be measured is referred to as the position (Xm, Ym) of the master work MW. It was calculated. However, the present invention is not limited to this, and the position (Xw, Yw) of the workpiece W to be measured is set to the master work MW even if the arithmetic means 4 does not correct the roundness based on the inclination angle θ. It may be calculated based on the position (Xm, Ym) of.

1 Roundness measuring apparatus 2 Light irradiation means 3 Imaging means 4 Calculation means 5 Moving means A Reference axis L Light MW Master work W Workpiece to be measured Wa Inner surface Wb Axis θ Inclination angle

Claims (5)

Light irradiation means for illuminating the cylindrical inner peripheral surface of the workpiece to be measured, imaging means for imaging the inner peripheral surface to form image data, and perfect circle of the inner peripheral surface based on the image data In the roundness measuring device provided with the operation means for calculating the degree,
A reference axis extending in the direction of the axis of the inner circumferential surface;
First moving means for moving the light emitting means illuminating the inner peripheral surface along the direction of the reference axis on the inner side of the inner peripheral surface;
And second moving means for moving the imaging means along the direction of the reference axis,
The light emitting means and the imaging means are configured to move while maintaining a constant distance ,
The calculation means calculates the position of the axis with respect to the position on the vertical plane with respect to the reference axis, with reference to the position of the axis of the cylindrical inner peripheral surface of the master work. measuring device.   The roundness measuring apparatus according to claim 1, wherein when viewed in a direction along the reference axis, the light emitting means simultaneously radiates light.   The roundness measuring apparatus according to claim 1 or 2, further comprising a connecting member that connects the light emitting unit and the imaging unit, and the second moving unit doubles as the first moving unit.   The roundness measuring apparatus according to any one of claims 1 to 3, wherein the calculation means corrects the roundness based on an inclination angle of the axis with respect to the reference axis.   5. The roundness measuring apparatus according to claim 4, wherein the calculation means calculates the inclination angle based on the position of the axis on different ones of the vertical planes with respect to the reference axis.