KR20090036510A - Three-dimensional shape measuring method - Google Patents

Abstract

A 3D shape measuring method is provided to acquire measurement data of the high precision by introducing the data are according to the surface shape to the fixed sampling pitch regardless of the tilt angle of the measured position. A 3D shape measuring method measures the shape of the measured object as the probe which is supported in order to be moved the Z-axis is scanned to the plane of measurement of the measured object according to route. The approximate circle is drawn as the surface shape of the measured object contacts around the cross point of the central line of the measured object. The sampling pitch(s, s') acquiring measurement data of the measured object is calculated from the radius of the approximate circle.

Description

Three-dimensional shape measurement method {THREE-DIMENSIONAL SHAPE MEASURING METHOD}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-dimensional shape measuring method which scans the surface of an object to be measured, such as an aspherical lens or an object, such as a metal mold, to perform shape measurement, roughness measurement, or the like of an object to be measured with high precision.

The use of a three-dimensional shape measuring apparatus has already been widely known as a method of scanning the surface of an object to be measured, such as an optical component or a mold, to accurately measure the shape of the object to be measured. In general, a three-dimensional shape measuring apparatus approaches a probe of a contact type or a non-contact type to an object to be measured, and controls the probe position along the measuring surface of the object while controlling the probe position so that both are approximately at a constant distance or approximately constant force. It moves to measure the shape of the measurement surface of the object under test.

As one of such three-dimensional shape measuring devices, a three-dimensional shape measuring device using a laser measuring instrument and a reference plane mirror is disclosed, for example, in Japanese Patent Laid-Open No. 2006-105717. This three-dimensional shape measuring apparatus will be described with reference to FIG. 9.

The three-dimensional shape measuring apparatus 20 is an atomic force that is movable in the X-axis direction, the Y-axis direction, and the Z-axis direction on the measurement surface 2a of the measurement target object 2 such as a lens provided on the stone tablet plate 1. The tip of the probe 5 is followed, and the shape of the measurement surface of the object 2 is measured. Here, the moving object 3 which is movable in the X-axis direction and the Y-axis direction via the X-stage 9 and the Y-stage 10 is placed in the stone panel 1 on which the object 2 is mounted. The Z-axis movable body 11 that is movable in the Z-axis direction is attached to the movable body 3, and the atomic force probe 5 is attached to the Z-axis movable body 11. Then, when the moving body 3 is moved in the X-axis direction and the Y-axis direction, the Z-axis moving body 11 and the atomic force probe 5 are moved in the Z-axis direction so that the measurement surface 2a of the measurement object 2 is moved. The atomic force probe 5 can be scanned in accordance with the shape of Fig. 2).

An X reference mirror 6, a Y reference mirror 7, and a Z reference mirror 8 are arranged on the stone platform 1 through the support, and the laser measuring optical system 4 is provided on the movable body 3. , The X coordinate of the probe 5 with respect to the X reference mirror 6, the Y coordinate of the probe 5 with respect to the Y reference mirror 7, and the Z reference mirror 8 by a known optical interference method. The Z coordinates of the probe 5 on the basis of.

The measurement procedure of the three-dimensional shape in such a three-dimensional shape measuring apparatus 20 is demonstrated below. First, the design information about the shape in the measurement surface 2a of the to-be-measured object 2 is input into the arithmetic processing apparatus attached to the 3D shape measuring apparatus 20. FIG. Next, the probe 5 is followed by a constant measurement pressure on the measurement surface 2a of the measurement target object 2, and the method of the measurement surface 2a is performed by the method described in JP-A-2-254307. Centering is done. Next, the probe 5 is subjected to surface scanning or pre-scanning in the two-dimensional direction (X-axis and Y-axis direction) or one-dimensional direction (X-axis direction or Y-axis direction) on the measurement surface 2a, and the height direction data. (Z) is calculated | required and the shape of the measuring surface 2a of the to-be-measured object 2 is measured.

When measuring the shape, a fixed fixed sampling pitch along the scanning direction of the probe 5 is set in advance, and measurement data is acquired for each sampling pitch. The scanning direction of the probe 5 here is a two-dimensional direction (X-axis and Y-axis direction) or a one-dimensional direction (X-axis direction or Y-axis direction), and is a movement distance on an X-Y plane. For example, in the case of pre-scanning in the one-dimensional direction only in the X-axis direction, measurement data is introduced for every predetermined value by the distance moved by the probe 5 in the X-axis direction.

As described above, when measuring the sampling pitch along the scanning direction of the probe 5 in advance, the measurement data is acquired at a constant sampling pitch regardless of the shape of the object 2 to be measured. In other words, even when measuring the measured object 2 having a shape near to a plane such as a mirror, for example, an inclined angle of the measurement surface such as a lens has an angle of more than 60 deg. (60 degrees). Even when the measurement object 2 is measured, it is introduced at the same (constant) sampling pitch.

However, in this case, when the measured object 2 having a shape near to a plane such as a mirror is measured, if the sampling pitch along the scanning direction of the probe 5 is fixed to a predetermined value, the sampling pitch along the surface shape Although the measurement data is acquired at regular intervals, the measurement target 2 has an angle of inclination of the measurement surface such as a lens exceeding 60 deg. When the sampling pitch fixed at a constant pitch in the advancing direction is replaced with the sampling pitch along the surface shape of the measurement target object 2, the tilt angle represented by the inclination of the surface shape of the measurement target object 2 with respect to the XY plane In practice, the three-dimensional sampling pitch to which the probe 5 moves changes, and the larger the inclination angle becomes, the larger the sampling pitch becomes.

For example, consider the case where a spherical surface having a radius R of 5 mm as shown in FIG. 10 is pre-scanned and measured in the X-axis direction. Here, when scanning by the probe 5, moving the moving body 3 to the 1-dimensional direction only in the X-axis direction, it will sample with equal pitch of s' = 0.1 mm with respect to the X-axis which is the advancing direction of the probe 5 here. Is set to s' = s1 '= s2' =…. Measurement data is acquired under the condition of = sn '. The pitch s1 along the surface direction can also be regarded as a pitch of approximately 0.1 mm in the vicinity where the inclination angle near the apex of the spherical surface to be measured 2 is relatively small. However, when moved 4.3 mm from the vertex in the X-axis direction, the inclination angle of the surface of the object to be measured is about 60 deg., And the sampling pitch sn 'at the position along the surface direction of the object 2 is measured. When the pitch sn is replaced, the pitch sn widens to 0.2 mm. This means that the pitch (movement amount) along the surface becomes wider as the inclination angle of the surface of the object to be measured 2 increases, and the object to be measured 2 has a deviation in the actual amount of movement of the probe 5. It is not desirable to measure the surface shape of.

As another method of determining the sampling pitch capable of coping with such a problem, a method of determining a parameter in accordance with the result of the determination of the surface state of the object under test is described in, for example, Japanese Patent Laid-Open No. 2005-345123.

Here, the surface state is at least one of the surface direction change rate, the radius of curvature, the roughness, and the wave of the surface of the object to be measured along the traveling direction of the probe, and the traveling speed of the probe in addition to the sampling pitch is determined according to the determination result of the surface state. By adjusting, it leads to shortening of measurement time or improvement of measurement precision.

In patent document 3, it is described that using the radius of curvature which is one of a surface state as a parameter which determines a sampling pitch. For example, when measuring a spherical surface in the X-axis direction by pre-scanning, the radius of curvature which is one of the said surface states is described. Considering the case where the sampling pitch is used as a parameter for determining the sampling pitch, since it always has a constant radius of curvature with respect to the X-axis direction, which is the direction in which the probe travels, the sampling pitch along the surface is made constant when the scan position is coordinated along the surface. It becomes possible to measure.

However, considering the case where a lens having an aspheric shape as shown in Fig. 11 is taken as an example and pre-scanned in the X-axis direction, it is difficult to obtain measurement data at a constant sampling pitch along the surface shape. This point is described below. The lens mentioned as this example is a lens which has an aspherical shape which is rotationally symmetrical with the normal line passing through the origin which is a vertex as a center axis, and has a diameter of 19 mm and a change amount of about 3.5 mm in the Z-axis direction. When the radius of curvature at each scanning position of this lens is found, as shown in Fig. 12, the radius of curvature is gradually changed, and the radius of curvature of the outer circumference is about 8 mm while the radius of curvature near the center is about 16 mm. It changes to half radius of curvature. Here, the horizontal axis in FIG. 12 has shown the position (coordinate) of the radial direction of the to-be-tested object which is aspherical. As shown in Fig. 13, the sampling pitch determined by the above method gradually changes depending on the radius of curvature from Rmin to Rmax, so that the radius of curvature far from the center is larger than the sampling pitch of the portion with the large radius of curvature close to the center. The sampling pitch of a small portion becomes small, making it difficult to acquire measurement data at a constant sampling pitch along the surface shape.

Here, in FIG. 13, when (1) Rmin = 8 mm, Rmax = 16 mm, sampling pitch Lmin = 0.1 mm, Lmax = 0.2 mm, and (2) Rmin = 8 mm, Rmax = 16 mm, In the case where the sampling pitch Lmin = 0.09mm and Lmax = 0.11mm are assumed, when the lens having the spherical shape shown in FIG. 11 is measured by pre-scanning in the X-axis direction, the sampling pitch is changed as shown in FIG. . By changing the setting of the sampling pitch, it is possible to measure in a shape close to the equal pitch, but it is difficult to obtain the measurement data at a constant sampling pitch along the surface shape.

As described above, in the conventional measurement method, the measurement object 2 having an aspherical shape in an optical component or a mold cannot be set to a constant sampling pitch along the surface shape of the measurement object 2, so that the measurement is performed with high accuracy. Acquiring data is difficult.

This invention solves the said subject and an object of this invention is to provide the three-dimensional shape measuring method which can acquire a measurement data with very high precision, even if an object to be measured has an aspherical shape.

In order to solve the above problems, the three-dimensional shape measuring method of the present invention measures the sampling pitch for acquiring measurement data at regular intervals along the surface shape of the object from the acquired shape information of the object to be measured, such as design data. The sampling pitch along the scanning direction of a probe is calculated so that data can be acquired, and measurement data is acquired using the sampling pitch determined based on the value.

That is, the measured object is measured at the position on the surface of the measured object centered on the point where the straight line drawn in the normal direction of the measuring surface of the measured object at each position on the scan obtained from the acquired shape information of the measured object intersects with the centerline of the measured object. A circle in contact with the surface shape of water is used as an approximate circle, and a sampling pitch for acquiring measurement data of the object to be measured is calculated from a radius of the approximated circle.

More specifically, as a method of calculating a sampling pitch for acquiring measurement data at regular intervals along the surface shape of the object under measurement from the acquired shape information of the object under measurement, such as design data, the object at each position scanned by the probe It is a method of calculating from the inclination angle of the surface shape of a workpiece and the radius of the approximation circle calculated | required approximately at the position. As a method for obtaining an approximation circle, a point where a normal crossing the origin of the measurement object, which can be known from the surface shape normal at each position scanned by the probe, and the design data of the measurement object intersect, is created. Thus, the circle contacting the surface shape at each position on the surface of the object to be measured is determined as an approximate circle. Using the radius of this approximation circle, the position which acquires a measurement data is calculated next, and the sampling pitch on the X-Y plane which is a scanning direction of a probe is sequentially determined from a calculation result. That is, the angle of the center angle is calculated so that the distance of the portion corresponding to the circular arc of the approximate circle is equal to the distance over the surface shape, and the next sample is moved from the surface position along the approximate circle by the predetermined distance based on the angle. The sampling pitch of the probe is obtained as the pitch point. Thus, the pitch along the surface shape of the object to be measured can be set to be constant.

According to the three-dimensional shape measuring method of the present invention, even when the object to be measured has an aspherical shape, data can be introduced at a constant sampling pitch along the surface shape regardless of the inclination angle of the measurement position, so that the measurement data can be obtained with high accuracy. can do.

Hereinafter, a three-dimensional shape measuring method according to an embodiment of the present invention will be described with reference to the drawings. In addition, since the structure of the three-dimensional shape measuring apparatus used for this three-dimensional shape measuring method is the same as that of the conventional three-dimensional shape measuring apparatus shown in FIG. 9, it abbreviate | omits description about this. In addition, the same code | symbol is attached | subjected to each component of a three-dimensional shape measuring apparatus.

The three-dimensional shape measuring method in this invention is demonstrated using the flowchart shown in FIG. First, the design information (including shape information) of the measurement target object 2, the speed along the XY axis direction, the operating conditions of the probe 5 such as the scanning range, the sampling pitch along the surface shape, etc. (Steps S1 to S3). Next, as a shape measurement predecessor, the probe 5 is followed by a constant measurement pressure on the measurement surface of the object 2 to be scanned based on the shape information such as the result of scanning the vicinity of the center of the object 2 and design data. Centering is then performed (step S4). After centering, shape measurement is performed. This shape measurement measures the movable body 3 which drives the X stage 9 and the Y stage 10 based on operating conditions, such as a preset speed, and supports the probe 5 so that a movement to a Z-axis direction is possible, XY axis | shaft. Direction (step S5). For this reason, the probe 5 moves to Z-axis direction following the shape change of the Z-axis direction of the to-be-measured object 2 (step S6). At this time, measurement data is acquired according to the sampling pitch set in advance in the coordinate values in the respective axial directions of the X, Y, and Z axes (steps S7, S8).

In the acquisition method of the measurement data at that time, after acquiring (input) design information of the measurement target object 2 (step S11), the surface shape of the measurement target object 2 is first measured before measurement. The sampling pitch for the distance traveled in the XY-axis direction, which is the travel direction of the probe, based on the sampling pitch s set as the pitch along the surface shape of the object to be measured (input S12). s '), the measurement data is acquired on the basis of the distance in which the probe 5 is moved in the XY axis direction based on s'.

Here, the sampling pitch replaced by the distance moved in the XY axis direction, which is the traveling direction of the probe 5 when the measurement data is set to be introduced at a constant sampling pitch s along the surface shape of the object 2 to be measured. The determination method of (s') is demonstrated. First, the method at the time of pre-scanning the probe 5 to the 1-dimensional direction only in the X-axis direction and obtaining measurement data is demonstrated.

As shown in FIG. 3, first, in order to determine the sampling pitch s' substituted for the distance moving in the XY axis direction, which is the travel direction of the probe 5, first, the distance over the surface shape of the object 2 to be measured. The inclination angle θ of the surface shape of the measurement object 2 calculated from the sampling pitch s set as the value, the acquired surface shape information of the measurement object 2 such as design data, and the tangential direction of the surface shape. Considers a case where the sampling pitch s' is obtained from a straight line. Here, the calculation method of the sampling pitch s' about the case where the probe 5 pre-scans and measures in the X-axis direction is demonstrated. Specifically, first, a tangent line is drawn at a predetermined position of the surface shape. Next, the position where the length of the tangent line is equal to the sampling pitch s is obtained from the tangent position toward the position where the next measurement data is obtained, and the movement distance of the probe 5 to this position is determined by the XY axis. It determines as sampling pitch s' substituted by the distance moved to the direction.

That is, when the amount of movement (sampling pitch) s' in the advancing direction at the position where the inclination angle of the measurement target object 2 is θ is calculated,

s' = s

The relationship is established.

From this equation, the sampling pitch s' along the travel direction can be set by simple calculation according to the inclination angle θ of the measurement target object 2.

However, when the sampling pitch s' is set by this equation, the acquired measurement data has a larger sampling pitch along the actual surface shape as the inclination angle of the measurement target object 2 becomes larger, and an error compared to the set sampling pitch. Becomes large. For example, consider a case where a spherical surface having a radius of 5 mm is measured. As a condition at this time, the case of the line scanning in only one direction along the X-axis direction is considered, and the case where the measurement is made by setting the sampling pitch along the surface shape to 0.1 mm is considered. As shown in Fig. 4, as the inclination angle θ becomes larger, the error of the actual sampling pitch s along the surface shape becomes larger, so that the sampling pitch (only with the inclination angle θ of the surface of the object 2 to be measured) Even when s') is determined, it is difficult to measure at equal pitch along the surface shape.

Therefore, in the three-dimensional shape measuring method of the present invention, in addition to calculating using the inclination angle θ of the surface of the measurement target object 2 (step S13), the surface contact is made in contact with the surface shape at a position where the tangent of the surface is drawn. The approximate circle is set, and the sampling pitch s 'substituted for the distance moved in the XY axis direction using the radius R' of the approximate circle is calculated (steps S14 to S16). As a result, the measurement (step S17) can be carried out at the same pitch.

This method will be described in more detail, and in this case as well, the case where the probe 5 is pre-scanned in the X-axis direction and measured will be described. As shown in Fig. 5, first, it calculates the inclination angle (θ _i) of the surface position (X _i, Z _i) from the shape information, such as design data of the measurement subject (2). It does not change with the said method so far. Next, a straight line in the normal direction is obtained by referring to the inclination angle θ _{i at the} surface positions X _i and Z _i . Moreover, the center line T of the to-be-measured object 2 passing through the origin of the to-be-measured object 2 is calculated | required, and the point where these two straight lines cross | intersect is created. Let this point be P _i (0, Z _0i ), and the surface of the object 2 to be measured at the surface position X _i , Z _i of the object 2 around the point P _i . Create a circle that you touch, and make this circle an approximation. Since the distance between the center point (P _i (0, Z _0i )) and the surface location (X _i , Z _i ) becomes the radius of the approximate circle (R _i '), R _i '

R _i '= X _i / sinθ _i

It can be calculated from It is assumed that this circle can approximate the shape of the object 2 to be measured, and the angle α is calculated so that the distance of the portion corresponding to the arc is equal to the sampling pitch set as the distance over the surface shape. . The sampling pitch s, the approximate circle radius R ', and the angle α have the following relationship.

s = R'α

On the basis of the angle α calculated in this way, the point X X _{+ 1} , Z of the next sample pitch is moved from the surface position X _i , Z _i by the distance s along the circle of the radius R '. _{i + 1} ) to obtain this value. Since this position is strictly different from the position on the surface of the object to be measured, the coordinate of X _i is set as a point to acquire measurement data next. In this case, the sampling pitch s' substituted for the distance moved in the XY axis direction

s' = X _{i +1} -X _i

By sequentially repeating this calculation, the sampling pitch s' substituted for the distance moved in the X-Y axis direction can be determined.

Here, the case where the lens which has an aspherical surface shape as shown in FIG. 11 is pre-scanned in the XX axis direction and measured as an example of the to-be-measured object 2 is considered. The lens mentioned as an example of the to-be-measured object 2 has the aspherical shape which rotated and contrasted about the normal line passing through the origin which is a vertex as a center axis. Since the normal 2 passing through the origin coincides with the central axis, the center of the approximate circle becomes (0, Z _0i ).

The surface coordinates (X _i, Z _i) is the one to think in the new coordinate of the approximate center of the circle (P _i) to the reference point _{(R i '· sinθ, R} i' · cosθ). Considering the rotation of the angle α with the origin of the approximate radius as the origin, the formula for the next sampling position is

Becomes Here, from the surface coordinates (X _{i + 1} ) derived from the above formula, the radius of curvature and the inclination angle of the approximate circle of the measurement target object 2 in the surface coordinates (X _{i + 1} ) are obtained as described above. Determine the next sampling position (X _{i + 2} ) based on the value. By repeating these calculations sequentially and converting them into pitches along the XY axis direction in advance, the measurement data can be obtained at equal pitch.

In this way, when determining the sampling pitch, it shows in FIG. 6, comparing with the conventional example about the error with the pitch along the aspherical surface shape. In this case, the lens having the aspherical surface shown in Fig. 11 is rotated symmetrically aspheric with a normal line passing through the origin, which is the vertex, as a target of the measurement target object 2, and has a diameter of 19 mm and a Z axis direction. The lens has a variation of about 3.5 mm. The scanning method of the probe 5 examined the case where line scanning of only one direction along the X-axis direction is performed. The conventional example (1) in FIG. 6 is a conventional method of acquiring measurement data for every sampling pitch by setting the sampling pitch along the X-axis direction which is the scanning direction of the probe 5 to a fixed value in advance, and setting the sampling pitch to 0.1. This is the result when measurement data is acquired by fixing to mm. Conventional example (2) is a method of acquiring measurement data while changing the sampling pitch from the radius of curvature of the surface of the object to be measured. The set values in FIG. 13 are set to Rmin = 8 mm, Rmax = 16 mm, and sampling pitch Lmin = 0.09. This is the result when measurement data was acquired when it set to mm and Lmax = 0.11mm. On the other hand, when setting the sampling pitch along the surface shape and measuring data is acquired after converting to the pitch along the XY axis direction by the above method, when measuring a lens having an aspherical shape, the error of the measurement data acquisition position is actually An error in the nanometer order is generated due to the above, but it can be seen that the measurement data can be obtained with high accuracy at a substantially constant pitch.

In addition, the description about the said measuring method is the case of the line scan measurement which scans the probe 5 only in 1 direction, such as moving the probe 5 parallel to an X axis, or moving the probe 5 parallel to a Y axis. As described above, other scanning methods are also applicable. First, as a 1st method, as shown to FIG.7 (a), (b), there exists a method of scanning a surface shape by repeating a measurement to a columnar shape. This measurement is an effective measuring method when measuring the measured object 2 which has a rotation symmetry axis parallel to the Z axis | shaft orthogonal to each other in the X-Y-axis direction, and has the shape rotationally symmetric about the axis. In this measurement, the probe 5 is moved to draw a circle around the axis of rotation symmetry, and the measurement data is acquired based on the preset sampling pitch. The sampling pitch set at this time is set so that the moving distance of the probe 5 in the XY axis direction becomes constant, or the sampling pitch is set so that the probe 5 divides the circle drawn by the trajectory moved in the XY axis direction. It may be a method. After the end of one round, the probe 5 moves by a certain amount along the normal direction of the circle drawn by the trajectory in which the probe 5 moves, and then the measurement data is acquired while scanning the trajectory of the probe 5 to draw the circle. The amount of movement along the normal direction of the circle drawn by the trajectory at which the probe 5 moves is referred to as a feed amount. After the probe 5 has moved by this feed amount, the X stage 9 and the Y stage 10 are moved to draw a circle around the origin as before.

In the case of this measurement, it sets along the surface shape of the to-be-measured object 2 by setting the feed amount according to the inclination angle by the method which computed the said sampling pitch as the feed amount which is a movement amount to the normal direction of the circle created at the time of a scan. You can set a constant feed amount.

As a specific method, a scan is performed in which a circle is started in the counterclockwise direction on the X-Y plane, starting from the + side on the X axis when the scanning point is scanned in the columnar shape. After the first round, the probe 5 is moved by the predetermined feed amount at the time when the probe 5 has moved to the X axis again, and scanning is started on the circumference from the + side on the X axis. In determining the starting point on the X-axis, the amount calculated from the inclination angle and the approximate circle of the measurement target object 2 is determined as the feed amount. In this case, for example, when a cross section is made in the XZ plane, when the measurement positions on the cross section are connected, the measurement data can be introduced at a constant sampling pitch along the surface shape as in the case where the stage moves only in the axial direction. .

Next, as a second method, for example, as shown in FIG. 8, the movement of the probe 5 is moved only in the X-axis direction in a fixed state in the Y-axis direction, and based on a preset sampling pitch. Acquire measurement data. When the measurement of the predetermined section is finished, the probe 5 is moved by a predetermined amount in the Y-axis direction. This movement amount is referred to as the feed amount. After that, the measurement is repeated by moving the probe 5 in the X-axis direction as before.

In this case, for example, in the case of Fig. 8, the cross section is created by the XZ plane passing through the line segment created at the time of scanning, and the inclination angle calculated on the cross section and the radius of the approximate circle are determined. The sampling pitch on the line segment can be determined.

In addition, about the feed amount at this time, you may determine the feed amount according to the inclination angle by the method which computed the said sampling pitch similarly to the 1st method of measuring in the said cylindrical shape.

In addition, although the case where the shape information of design data was used as acquisition design information was described in the said Example, it is not limited to this, You may use the information of the shape data obtained by measuring a to-be-measured object as acquisition design information.

The three-dimensional shape measuring method of the present invention can be used for surface roughness measuring instruments and the like in addition to the three-dimensional shape measuring apparatus.

1 is a flowchart illustrating a measuring method of a three-dimensional measuring method according to an embodiment of the present invention.

2 is a flowchart for determining a sampling pitch for acquiring measurement data at regular intervals along the surface shape which is an embodiment of the present invention.

FIG. 3 is a diagram schematically illustrating a method of converting a sampling pitch only by the inclination angle at each position of the object to be measured.

4 is a diagram showing an error amount of a sampling pitch generated when a spherical surface is measured by a method of converting the sampling pitch only by the inclination angle at each position of the object to be measured.

FIG. 5 is a diagram schematically illustrating a method of converting a tilt angle at each position of a measurement object and a sampling pitch from an approximate circle.

FIG. 6 is a diagram showing an error amount generated when an aspherical surface is actually measured by a method of converting an inclination angle at each position of a measurement target and a sampling pitch from an approximate circle.

7 (a) and 7 (b) are a perspective view and a plan view schematically illustrating a method of measuring a measurement target in a columnar shape, respectively.

8A and 8B are respectively a perspective view and a plan view schematically illustrating a method of repeatedly measuring the measured object in the X-axis direction while moving a certain amount of the measured object in the Y-axis direction.

9 is a perspective view illustrating a configuration example of a three-dimensional shape measuring device.

It is a figure which shows the sampling pitch at the time of acquisition of measurement data by the conventional three-dimensional shape measuring method.

11 is a perspective view of an example of a lens having an aspheric shape.

It is a figure which shows the change of the radius of curvature of the lens shown in FIG.

It is a figure which shows the relationship between the radius of curvature and a sampling pitch in the conventional method.

It is a figure which shows the relationship between the amount of movement of a probe, and a sampling pitch when various conditions shown in FIG. 13 are set.

Claims (6)

Scan the probe 5 supported by the movable body 1 driven in the X-axis direction and the Y-axis direction orthogonal to each other in the Z-axis direction along a predetermined path to the measurement surface 2a of the object to be measured 2. As a three-dimensional shape measuring method of measuring the shape of the measurement target object 2 by: The point where the straight line drawn in the normal direction of the measurement surface 2a of the measurement target object 2 at each position on the scan obtained from the acquired shape information of the measurement target object 2 and the center line of the measurement target object 2 intersect. A circle which is in contact with the surface shape of the measurement object 2 at a position on the surface of the measurement object 2 with respect to the center as an approximate circle, and the measurement data of the measurement object 2 is obtained from the radius of the approximation circle. A three-dimensional shape measurement method characterized by calculating a sampling pitch. The method of claim 1, wherein the angle of the center angle is calculated so that the distance of the portion corresponding to the circular arc of the approximation circle is equal to the distance over the surface shape, and a predetermined distance along the approximation circle from the surface position based on the calculated angle. The three-dimensional shape measuring method characterized by obtaining the sampling pitch of the probe (5) as the point of the next sample pitch as far as it went. The three-dimensional shape according to claim 1 or 2, wherein the acquired shape information of the measurement object used when setting the sampling pitch of the measurement data is shape information of the design data of the measurement object (2). How to measure. 3. The method according to claim 1, wherein the object to be measured has an aspheric shape. 4. The movement distance in the XY axis direction of the probe 5 which measures the shape of the to-be-measured object 2 while moving the probe 5 so that a circle may be drawn about the axis of rotation symmetry. The sampling pitch is set so that the constant becomes constant or the sampling pitch is set to equally divide the circle drawn by the trajectory moved by the probe (5) in the XY axis direction. As a measuring apparatus used when performing the three-dimensional shape measuring method of Claim 1 or 2. Stages 9 and 10 moving in the X-axis direction and the Y-axis direction that are horizontal and orthogonal to each other on the measuring table 1 on which the object to be measured 2 is installed; A Z-axis moving body 11 vertically moving in the Z-axis direction perpendicular to the X and Y axes; A probe 5 attached to the Z-axis moving body 11 to measure the surface of the object to be measured; And And measurement data introduction means for introducing coordinate values of the X, Y, and Z axes as measurement data.

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