JPH0587542A - Method and device for measuring curved surface - Google Patents

Abstract

PURPOSE:To obtain the method and device capable of measurement of surface precision and surface shape on an aspheric surface having various revolving shafts, not to mention BTS type and KTS type toroidal faces. CONSTITUTION:The device consists of a light source 1, an objective lens 6, a face to be measured 7a formed to rotate an arbitrary curve AB around a revolving shaft 12, a reference face 6a and an advance base 13 scanning the measurement face to be measured 7a in paralell to the revolving shaft 12, the coherent light of the light source 1 is applied to be converged on the revolving shaft 12 through the objective lens 6 and an image of interference fringes is formed on an area sensor 10. Furthermore the face to be measured 7a is scanned in paralell to the revolving shaft 12 and the aperture of the objective lens without eclipsing circumferential light is found from the trace of an interference fringes found on the whole face.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toroidal surface, a cylindrical surface, a conical surface or the like, which is generally an aspherical surface (including both coaxial and non-coaxial) having an axis of rotation. It is related to the technology of measuring.

[0002]

2. Description of the Related Art An optical scanning optical system used in a laser beam printer, a laser facsimile or the like is generally composed of an anamorphic optical system using a cylindrical lens, a toroidal lens or the like in order to correct a surface tilt of a polygon mirror. It Since the cylindrical surface can be considered as a special toroidal surface, the term "toroidal surface" in this specification includes a cylindrical surface unless otherwise specified.

These lenses are required to have a surface accuracy of about 0.1 μm in order to increase the density and uniformity of the dots formed on the photoconductor. From such a background, it is necessary to measure the toroidal surface or the like with high accuracy below the wavelength.

In general, a laser interferometer is widely known as a device for measuring a surface with high accuracy. This interferometer can measure a plane or a spherical surface, but an aspherical surface such as a toroidal surface. Can't be measured.

Therefore, the applicant of the present invention is the Japanese Patent Application No. 2-1.
No. 26659 proposes a method of measuring the toroidal surface shown in FIGS. 11 (a) and 11 (b).

In FIG. 1, reference numeral 1 denotes a light source, which is a gas laser or semiconductor laser having high coherence. 2a,
Reference numeral 2b is a beam expander for expanding a narrow luminous flux from the light source 1 to an appropriate size. 3 is a spatial filter, which cuts off unnecessary light such as ghost light and reflected light. An optical isolator 4 is a beam splitter 4a, λ /
It has four plates 4b and a reflecting surface 4c.

The light beams expanded by the beam expanders 2a and 2b reach the toroidal surface 7a as the surface to be measured of the subject 7 through the objective lens 6. This toroidal surface 7
Although a has main radial lines AB and CD orthogonal to each other at the apex, one of these main radial lines CD is used as a generatrix, and this is formed by rotating this along the other main radial line AB. CD
That is, the G main diameter line is referred to as a G main diameter line, and the main diameter line AB orthogonal to the G main diameter line is referred to as an R main diameter line.

The final surface of the objective lens 6 is a reference surface 6a as a semi-transparent mirror, and the center of curvature thereof is arranged at a position substantially coincident with the finished curvature center of the G main diameter line (CD) of the toroidal surface 7a. To be done. Further, the reference surface 6a or the toroidal surface 7a is arranged so as to be slightly shiftable and / or tiltable in the XZ cross section.

Then, a part of the light incident on the objective lens 6 is reflected by the reference surface 6a, and the rest of the light is transmitted to irradiate the toroidal surface 7a and is reflected.

Reference numeral 8 denotes a rotary base for fixing the subject 7, which has a rotary shaft that coincides with the center of curvature of the R main diameter line (AB) of the toroidal surface 7a, and is driven by a DC servo motor or stepping motor (not shown). The toroidal surface 7a, which is the surface to be measured, can be scanned along the R main radius line.

The coherent light beams reflected by the reference surface 6a and the toroidal surface 7a are returned and superposed on the incoming optical path, and the reference surface 6a.
The spherical surface and the toroidal surface 7a cause interference with the slit-shaped measurement portion or the measurement cross section shown in FIG. 12 which is parallel to the G main diameter line which can be regarded as substantially parallel, and the interference fringes 11 pass through the reflection surface 4c of the optical isolator 4. An image is formed on the image sensor 10 by the focusing lens 9.

When the rotary table 8 is rotated along the R main radius line, the surface shape and surface accuracy of the entire toroidal surface 7a can be measured.

[0013]

By the way, as described above, the toroidal surface has a short bus bar (G main diameter line) and a long R main diameter line orthogonal to the so-called donut type or normal type (hereinafter referred to as In addition to the type "NTS", there is a barrel type (hereinafter referred to as "BTS") or a saddle type (hereinafter referred to as "KTS") having a long main line and a short R main diameter line.

Then, the above measuring method is applied to the BTS type and the K type.
When applied to the TS type toroidal surface, it is necessary to increase the diameter of the reference surface 6a in accordance with the busbar (G main diameter line),
The interference optical system becomes very expensive. Therefore, a method is conceivable in which the toroidal surface 7a is rotated by 90 ° and is placed sideways so that interference fringes are generated in parallel with the R main diameter line and scanning is performed along the G main diameter line. By doing so, it is not necessary to increase the diameter of the reference surface 6a. However, when the measurement portion is scanned along the G main radius line, the radius of curvature of the measurement cross section changes with the change scan, and therefore cannot be simply applied. Also,
The same applies to the measurement of conical surfaces and other aspherical surfaces having various axes of rotation.

The present invention is intended to solve this problem, and it is possible to measure the surface accuracy and surface shape of not only BTS type and KTS type toroidal surfaces but also aspherical surfaces having various rotation axes. The purpose is to propose.

[0016]

In order to achieve the above-mentioned object, the present invention irradiates coherent light from the same light source on a surface to be measured and a reference surface which is a reference, and a reference reflected from both surfaces. In a method for measuring surface accuracy by superimposing a wave and a test wave to form interference fringes, the coherent light is rotated by an objective lens on a measured surface formed by rotating an arbitrary curve around a rotation axis. A process of forming an interference fringe by irradiating so as to focus on the axis, and a relative scanning between the light source and the surface to be measured so that the focusing point of the coherent light moves along the rotation axis. And a step of sequentially forming interference fringes on the entire surface to be measured, and a step of obtaining a locus of the interference fringes on the image plane of the objective lens and obtaining a required entrance pupil diameter of the objective lens from the locus. It is configured.

The measured surface is a toroidal surface,
Note that the process of obtaining the entrance pupil diameter should be done on the image plane of the objective lens.
Maximum length of interference fringes (d_MAX) And the maximum distance from the optical axis
Separation (H_MAX) And the following equation D ≧ {(2H_MAX)²+ D_MAX ²}^1/2 Calculate the required diameter D of the image plane from the
Required entrance pupil diameter D _NMay be obtained.

Further, a step of calculating the moving distance (H) of the interference fringes from the optical axis from the equation of the arbitrary curve and the translation amount (h) on the rotation axis due to the scanning, and thus calculated. Or a step of moving the line sensor provided on the image plane according to the moving distance (H), or
It is preferable that an area sensor is provided in place of the line sensor, the position of the interference fringe imaged on the area sensor is calculated, and the data of the interference fringe is taken in along the calculated position.

Further, when the surface to be measured is a toroidal surface, two or more different positions (h1,
h2, ...), an image of the interference fringes is formed on the screen, the length (d) of the interference fringe image and the distance (H) from the optical axis thereof are obtained, and the following equation H = fh / {h ² + (R-ro) ² } ^1/2 d = fW / [R- {h ² + (R-ro) ² } ^1/2 ] where: f: focal length of objective lens W: sub-scan of measured surface Radius of curvature (R) in the main scanning direction from the measurement width along the direction to the toroidal surface
And a configuration for calculating the radius of curvature (ro) in the sub-scanning direction,
It is also possible to monitor the shape formed by superimposing the interference fringes formed by the scanning step and to compare with the theoretical shape to correct the setting deviation.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. The apparatus of the present invention is shown in FIGS. 1 (a) and 1 (b), but since it has the same configuration as that shown in the conventional example as a whole, the configuration will be described focusing on the differences. First, the measured surface 7a to be measured by the present invention is formed by rotating an arbitrary curve (including a straight line) around the rotation axis 12, and is not limited to the toroidal surface of BTS or KTS, but a conical surface. , Gourd-shaped surface,
FIG. 1 illustrates the BTS toroidal surface, although it includes the like. The measured surface 7a shown in this example is formed by rotating an arc (G main diameter line) around the rotation axis 12 as an arbitrary curve. It should be noted that the G and R main diameter lines are reversed from those of the subject 7 of the conventional example in FIG.

The next difference is that the rotary table 8 used in the conventional example is not provided, and a translation table 13 is provided instead. The translation table 13 holds the subject 7 and scans it in parallel with the rotary shaft 12. This translation table 13
Are driven by a DC servo motor, a stepping motor, or the like (not shown). The image formation position detection device 14 and the calculation device 15 will be described later.

FIG. 2 is a diagram showing the interrelationship between the toroidal surface 7a of the BTS, the reference surface 6a and the rotary shaft 12, where O is the intersection of the center of the subject 7 and the rotary shaft 12, and O'is the G main diameter. The center of curvature of the line is shown. The reference surface 6a moves with respect to the toroidal surface 7a due to the movement of the translation table 13, but the moving state is exemplarily shown at three positions, namely, upper, middle, and lower.
Further, the center of curvature O ″ of the reference surface 6a always overlaps the rotation axis 12, and the coherent light emitted from the objective lens 6 is also irradiated so as to be focused on this point O ″.

Similar to the previous application, the coherent light from the light source 1 is reflected by the reference surface 6a and the measured surface 7a,
Of the coherent light reflected by the surface 7a to be measured, the light rays involved in the formation of the interference fringes are the light rays in which the incident light path and the reflected light path overlap, and as shown by the arrows at the three positions in FIG. Is a ray heading for a point O'as the center of curvature of the G main radius line. This light ray coincides with the optical axis of the objective lens 6 when the optical axis of the reference surface 6a passes through the point O, but when the reference surface 6a scans from the point O to h, this light ray will also be reflected. It will be moved by H'from the optical axis of.

The reference wave reflected by the reference surface 6a and the measured surface 7a and the detected wave are superimposed on each other, causing interference on the measurement section parallel to the R main diameter line as described above, and the interference fringes are generated by the focusing lens 9. An image is formed on the area sensor 10. This measurement cross section is scanned in the direction of the rotation axis 12, but since the focus point is always on the rotation axis 12 as shown in FIG. 2, it is possible to always perform scanning in a focused state.

FIG. 3 shows the interference fringes 11 formed on the area sensor 10 when the measured surface 7a is a BTS toroidal surface. Here, an interference fringe when the optical axis of the reference surface 6a and the center of the subject 7 coincide with each other is 11a, and an interference fringe when the reference surface 6a scans from the point O by a distance h is 11b. BT
In the case of S, the radius of curvature of the measurement cross section is the largest at the center of the subject 7 and becomes smaller toward both ends, so that the reference surface 6
The central angle of the arc parallel to a becomes larger toward both ends, and as a result, the length of the image of the interference fringe is shortest at the central portion and becomes longer toward both ends. Therefore, the length of the interference fringe 11a at the central portion is set to do, and the length of 11b when the scanning amount is h is set to d. On the other hand, the amount of movement of the interference fringe 11a from the optical axis is 0, and the amount of movement of 11b is H corresponding to H'in FIG. The image forming position detecting means 14 of FIG. 1 described above is composed of a two-dimensional CCD, and can detect the values of d and H for each interference fringe by measuring the output of each element.

FIG. 4 shows the interference fringes 11 on the area sensor 10 as in FIG. 3, but in FIG. 1, when the translation table 13 is scanned along the rotation axis 12 to both ends h _{MAX of the} surface 7a to be measured. The interference fringes formed at both ends of the measured surface 7a are shown. The length of the interference fringes at these ends is the maximum length d _MAX . The amount of movement from the optical axis at this time is
It is H _MAX .

The locus of the interference fringe drawn until the scanning amount reaches from 0 to h _MAX falls within the rectangle surrounded by 2H _MAX × d _MAX in FIG. Therefore, the diameter D of the area sensor required to form the interference fringes on the entire surface to be measured is obtained from the following equation: D ≧ {(2H _MAX ) ² + d _MAX ² } ^1/2 (1) be able to.

Then, from the value of D and various conditions of the measurement optical system, it is possible to calculate the desired diameter D _N of the entrance pupil without vignetting of ambient light. The calculation by the equation (1) and the calculation of D _N from D are performed by the calculation device 15 of FIG. 1 described above.

When the surface 7a to be measured is a surface formed by rotating an arbitrary curve other than the toroidal surface around the rotation axis 12, the translating table 13 is scanned and the area sensor 1 is scanned as described above.
The locus of the interference fringe 11 drawn on 0 is obtained, and D is calculated from the locus.
And D _N can be obtained. In any case, a screen is provided instead of the area sensor 10 and the above-mentioned D _N can be calculated by actually measuring the interference fringes on the screen.

By the way, the measurement of the image 11 of the interference fringes only needs to be possible in the longitudinal direction along the bright and dark fringes, so that the area sensor 10 can be replaced by a line sensor. However, in that case, the interference fringes that move by scanning must be constantly imaged on the narrow line sensor.

The device shown in FIG. 5 is an embodiment made from this point of view, and is a device capable of moving the line sensor 101 in synchronization with the movement of the interference fringes. This is similar to the device shown in FIG.
Drive device 1 capable of moving the line sensor 101 back and forth in the Z-axis direction
6, a moving distance calculating device 17 for calculating the moving amount (H) of the interference fringes from the scanning amount h, and a scanning amount detecting device 18 for detecting the scanning amount h of the translation table 13 are added.

The operation of this apparatus will be described below. The procedure until the formation of the interference fringes at the center of the surface 7a to be measured is the same as in the above-described embodiment. After that, first, the translation table 13 is driven to scan the distance h in the main scanning direction (direction of the rotary shaft 12).
The scanning amount detecting device 18 obtains the scanning amount h by this scanning and inputs it to the moving distance calculating device 17. The moving distance calculation device 17 calculates the moving amount H in the image plane of the interference fringe image 11 from the value of h and the radii of curvature R and r _{0 of the} G and R main diameter lines stored in advance by the following equation. calculate. ^{H = fh / {h 2 +} (R-ro) 2} 1/2 ...... (2) Here f: Enter a focal length value of the H of the objective lens driving device 16, the drive unit 16
Moves the line sensor 101 in the z-axis direction by the amount of H. In this way, the interference fringes 11 can always be imaged on the line sensor.

The above equation (2) is for the toroidal surface of the BTS, but an arbitrary curve (including a straight line) can be applied to the rotary shaft 1
A curved surface obtained by rotating around 2 can be similarly applied by deriving an expression corresponding to the above expression (2) from the expression of the arbitrary curve.

On the other hand, instead of the line sensor 101, when an area sensor composed of a two-dimensional CCD that covers the entire moving range of interference fringes as shown in FIG. 6A is used,
Measurement can be performed without being affected by the movement of the interference fringes 11, but it is necessary to capture data for all lines of A1, A2, A3 ...

Therefore, H is obtained from the above equation (2), and the position where the interference fringes are imaged is calculated to be, for example, the line of Ax as shown in FIG. Instead of the driving device 16 of FIG. 5 for controlling the scanning position, a reading position control device may be provided (not shown) to instruct reading of the Ax line.

FIGS. 7 (a) and 7 (b) are diagrams for explaining a method of obtaining an unknown radius of curvature of the G and R main diameter lines in the measurement of the toroidal surface. Reference numeral 19 is a curvature radius calculation device, 20
Indicates a display that displays interference fringes. When scanning the surface to be measured with coherent light, the scanning amount h1, h of 2 or more is appropriately set.
2, the image forming position detecting device 14 measures the lengths d1 and d2 of the interference fringes at that time and the moving amounts H1 and H from the optical axis.
Ask for 2. When this value is input to the radius-of-curvature calculation device 19, the device calculates these values by the following equations (2) and (3), H = fh / {h ² + (R-ro) ² } ^1/2 ... … (2) d = fW / [R- {h ² + (R-ro) ² } ^1/2 ] …… (3) where W: Substitute for the width of the measured surface in the Z-axis direction (Fig. 1). Then, the simultaneous equations are solved to obtain R and ro.

In the measuring method of the present invention, the rotary shaft 12
It is important that the scanning direction is parallel to the scanning direction. If the rotation axis of the subject 7 is not parallel to the scanning direction and there is an angular deviation of Δα as shown in FIG. 8, if the measured surface 7a is a toroidal surface close to an ideal state, then interference fringes will occur. Can be done as shown in Figs. 9 (a) and 9 (b). That is, when the objective lens 6 reaches the position shown in the upper part of FIG. 8, the reference surface 6a and the measured surface 7a are farther than the parallel distance, and the interference fringes are as shown in FIG. 9 (a). In addition, the image is not formed at the regular position indicated by the dotted line, but is formed as an image longer than the regular image and further away from the optical axis as indicated by the solid line. On the other hand, when the objective lens 6 comes to the position shown in the lower part of FIG. 8, the reference surface 6a and the measured surface 7a are closer than the distance in the case of being parallel, so the interference fringes are as shown in FIG. In addition, the image is not a regular position indicated by a dotted line but a short image approaching the optical axis indicated by a solid line.

FIG. 10A is a diagram showing the loci of the interference fringes 11 by superimposing the interference fringes from FIGS. 8A to 8B on the display 20 of FIG. 7B. The locus of the interference fringe is Z
It is asymmetric with respect to the axis. From the above, if the rotation axis 12 and the scanning direction are not parallel and there is an angle deviation of Δα, it will be mistakenly recognized that the measured surface 7a is distorted. Therefore, this asymmetric state is displayed on the display 20.
By monitoring the above and correcting the position of the subject 6 so as to be symmetrical as shown in FIG. 10B, Δα can be corrected.

The above correction is performed on both sides of the same scanning amount h.
For the point, the length d of the interference fringe and the movement amount H from the optical axis may be detected, and the position of the subject 7 on the translation table 13 may be corrected so that they are equal. Even if the measured surface 7a is a surface created by rotating an arbitrary curve around the rotation axis and is not symmetrical like a toroidal surface, the equation of the arbitrary curve is known. If so, H and d corresponding to the scanning amount h can be obtained in advance, so that Δα can be corrected by comparing this value with the actual locus of the interference fringes.

[0040]

As described above, the surface shape and surface accuracy of an aspherical surface (including both coaxial and non-coaxial) generally having a rotation axis, such as a toroidal surface, a cylindrical surface, and a conical surface. According to the invention of claim 1, 2 or 7,
By measuring the position and size of the interference fringes that change with translation, it is possible to know the diameter of the entrance pupil and thus the necessary aperture of the objective lens, and to avoid vignetting of ambient light when forming the interference fringes. Can be prevented.

According to the invention of claims 3, 4 or 8 and 9,
Since the line sensor can always be aligned with the image formation position of the interference fringes and the position of the reading line of the two-dimensional CCD sensor can be known in advance, the measurement time can be shortened.
According to the inventions of claims 5 and 10, when the surface to be measured is a toroidal surface, the radii of curvature of the G and R main radial lines can be obtained. According to the inventions of claims 6 and 11, it is possible to easily correct the deviation of the parallelism between the rotation axis used to create the surface to be measured and the translation direction.

[Brief description of drawings]

FIG. 1 is a diagram showing the configuration of a measuring apparatus of the present invention, in which (a) is x
-Y plane view, (b) are xz plane views.

FIG. 2 is a diagram illustrating a state where a light beam forming an interference fringe is deviated from an optical axis of a reference surface by scanning with a translation table in the measurement of the BTS surface.

FIG. 3 is a diagram showing interference fringes formed on a screen.

FIG. 4 is a diagram showing a range of movement of interference fringes for obtaining a required entrance pupil diameter.

FIG. 5 is an xy plan view of an example in which a line sensor is used as a detector for interference fringes.

FIG. 6 is a diagram showing data acquisition when detecting interference fringes on a two-dimensional CCD. (A) is the case where the entire data is acquired each time, and (b) is the movement amount H calculated from the scanning amount h. The case where the position of the interference fringe is known and only the data of that line is captured is shown.

FIG. 7A is a diagram illustrating a method of obtaining a radius of curvature of a G, R main diameter line of a toroidal surface by scanning a surface to be measured, and FIG. It is a block diagram of the apparatus which calculates | requires a radius of curvature.

FIG. 8 is a diagram showing a state where there is a deviation of Δα between the scanning direction of the translation table and the rotation axis.

9 (a) and 9 (b) are diagrams for explaining the image formation state of interference fringes when there is a deviation of Δα.

FIG. 10 is a diagram showing a locus of interference fringes that move by scanning with a translation table, where (a) shows a case where there is a setting deviation on the surface to be measured, and (b) shows a case where there is no setting deviation.

FIG. 11 is a configuration diagram of an apparatus for measuring a toroidal surface described in the prior application, (a) is an xy plane view, and (b) is an xz plane view.

FIG. 12 is a diagram showing interference fringes formed on an image sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 light source 6 objective lens 6a reference surface 7 subject 7a measured surface 11 interference fringes 12 rotation axis 13 translation table 14 imaging position detection device 15 calculation device 16 drive device 17 moving distance calculation device 18 scanning amount detection device 19 curvature radius calculation apparatus

Claims (11)

[Claims] 1. Coherent light from the same light source is applied to a surface to be measured and a reference surface as a reference, and a reference wave and a test wave reflected from both surfaces are superposed to form interference fringes to improve surface accuracy. In the measuring method, an interference fringe is formed by irradiating the surface to be measured formed by rotating an arbitrary curve around a rotation axis so that the coherent light is focused on the rotation axis by an objective lens. Steps: Relative scanning is performed between the light source and the surface to be measured so that the focal point of the coherent light moves along the rotation axis, and interference fringes are sequentially formed on the entire surface to be measured. A method of measuring a curved surface, comprising: a step of obtaining a locus of interference fringes on an image plane of an objective lens; and a step of obtaining a required entrance pupil diameter of the objective lens from the locus. 2. The surface to be measured is a toroidal surface,
The step of finding the entrance pupil diameter is the maximum length of the interference fringes on the image plane of the objective lens.
(D_MAX) And the maximum movement distance from the optical axis (H_MAX) And
Therefore, the following equation D ≧ {(2H_MAX)²+ D_MAX ²}^1/2 Calculate the required diameter D of the image plane from the
Required entrance pupil diameter D _NIs a process that requires
The method for measuring a curved surface according to claim 1, which is a characteristic. 3. Coherent light from the same light source is applied to a surface to be measured and a reference surface as a reference, and a reference wave and a test wave reflected from both surfaces are superposed to form interference fringes to form a curved surface. In the method for measuring, a surface to be measured formed by rotating an arbitrary curve around a rotation axis is irradiated with the coherent light so as to be focused on the rotation axis via an objective lens, Forming an image of interference fringes formed by superimposing the wave to be detected on the line sensor, and scanning the focal point of the coherent light along the rotation axis to sequentially form interference fringes on the entire surface to be measured. A step of calculating the moving distance (H) of the interference fringe from the optical axis from the equation of the arbitrary curve and the translation amount (h) on the rotation axis by the scanning, and the moving distance thus calculated. (H) and moving the line sensor. Curved measurement methods characterized by and. 4. An area sensor is provided instead of the line sensor, the position of an interference fringe imaged on the area sensor is calculated from the moving distance (H), and the data of the interference fringe is fetched along the calculated position. The curved surface measuring method according to claim 3, wherein 5. When the surface to be measured is a toroidal surface, two or more different positions (h1, h2, and h2) in the scanning step.
The image of the interference fringes of (...) is formed on the screen, the length (d) of the interference fringes image and the distance (H) from the optical axis thereof are obtained, and the following equation H = fh / {h ² + ( R-ro) ² } ^1/2 d = fW / [R- {h ² + (R-ro) ² } ^1/2 ] where f: focal length of objective lens W: sub-scanning direction of measured surface Radius of curvature (R) in the main scanning direction from the measurement width along the toroidal surface
And a radius of curvature (ro) in the sub-scanning direction is calculated. 6. The method further comprises the step of monitoring the trajectory of the interference fringes formed by superimposing the interference fringes formed by the scanning step and comparing them with a theoretical shape to correct the setting deviation. The method for measuring a curved surface according to any one of claims 1 to 4. 7. Coherent light from the same light source is used as a base surface for measurement.
It irradiates the reference surface and the reflection surface from both sides.
Superimpose the reference wave and the test wave to form interference fringes and measure the curved surface.
In the measuring device, hold the toroidal surface as the measured surface, and
Translation table that scans in parallel with the rotation axis used for its creation
And an objective for irradiating the rotating shaft so that the coherent light is focused.
The lens, the area sensor provided at the position where the image of the interference fringes is formed, and the distance of movement of the interference fringes on the area sensor from the optical axis.
An image forming position detecting device for measuring the distance (H) and the length (d), and an image forming position detecting device for detecting the image forming position of the objective lens.
Maximum length of interference fringe (d_MAX) And maximum movement from the optical axis
Distance (H_MAX) And the following equation D ≧ {(2H_MAX)²+ D_MAX ²}^1/2 Calculate the required diameter D of the image plane from the
Required entrance pupil diameter D _NAnd a computing device that calculates
A curved surface measuring device characterized in that 8. A curved surface by irradiating coherent light from the same light source on a surface to be measured and a reference surface as a reference, and superimposing a reference wave and a detected wave reflected from these both surfaces to form interference fringes. In a device for measuring, the toroidal surface as the surface to be measured is grasped, and the translation table for scanning the surface to be measured in parallel with the rotation axis used for its creation, and the translation amount (h) by the translation table. A scanning amount detection device for detecting, an objective lens for irradiating the rotation axis of the surface to be measured so that the coherent light is focused, a line sensor provided at the image forming position of the interference fringes, and an equation for the arbitrary curve And the translation amount (h),
A curved surface measuring device comprising a moving distance calculating device for calculating a moving distance (H) of the interference fringe from the optical axis and a driving device for moving the line sensor in accordance with the calculated distance (H). .. 9. A control for providing an area sensor in place of the line sensor, and for instructing a reading position of the area sensor according to a moving distance (H) of the interference fringe image instead of a driving means for moving the line sensor. The curved surface measuring apparatus according to claim 8, further comprising a device. 10. Coherent light from the same light source is applied to a measured surface and a reference surface serving as a reference, and the reference wave and the detected wave reflected from both surfaces are superposed to form interference fringes to form a curved surface. In the device for measuring, the toroidal surface as the surface to be measured is grasped and the translation table that scans the surface to be measured in parallel with the rotation axis used to create it, and the axis of rotation of the surface to be measured causes interference. The objective lens that irradiates the light so that it converges, the area sensor that is provided at the imaging position of the interference fringes, and the movement distance (H) and the length (d) from the optical axis of the interference fringes on the area sensor. And an image forming position detecting device for measuring the position, and two or more different positions (h1, h) in the scanning process.
2, ...) from the length (d) of each interference fringe and its distance from the optical axis (H), the following equation H = fh / {h ² + (R-ro) ² } ^1/2 d = fW / [R- {h ² + (R-ro) ² } ^1/2 ] where, f: focal length of the objective lens, W: main scanning direction on the toroidal surface depending on the measurement width along the sub-scanning direction of the surface to be measured. Curvature radius (R) and a curvature radius calculation device for calculating a curvature radius (ro) in the sub-scanning direction. 11. The curved surface measuring apparatus according to claim 7, further comprising a screen displaying a locus of interference fringes formed by the scanning step.