JPH09170918A - Form measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the measurement of a form of a to-be-measured surface with inclination more than a specified angle (for example, 25 deg.) even with the use of a displacement gage which cannot measure an object if an angle of inclination of the to-be-measured surface such as an optical probe, etc., is over a specified value (e.d. 250), in a simple structure and method. SOLUTION: This device is provided with a stage 1 which is allowed to move in at least two direction of X and Y axes, length measuring means 4 and 5 measuring its displacement, displacement measuring means 2 and 3 detecting the position in at least two measuring axis directions, and a coordinate reference globe 10. At this time, the displacement measuring means 2 and 3 are so assigned as to be inclined relatively by the angle smaller than the allowance inclination angle, and a to-be- measured surface and the coordinate reference globe 10 are measured in the same measuring coordinate system with the displacement measuring means 2 and 3, respectively, and, based on the measurement result of each displacement measuring means 2 and 3, each measuring coordinate is so coordinate-transformed that the center of curvature of the coordinate reference globe 10 is made the same point, for jointing the measured data of the to-be-measured surface. By this device, even the form of the to-be-measured surface with inclination more than 25 deg. is easily measured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for measuring the shape of an aspherical lens or the like by a photo-tactile method, and relates to a shape measuring apparatus applicable to a three-dimensional shape measuring apparatus.

[0002]

2. Description of the Related Art In measuring the shape of an aspherical lens,
The development of a measuring machine that has both sufficient accuracy and high versatility has been a difficult problem. For example, contact probe (probe)
The 3D shape measuring instrument equipped with has problems such as inferior measurement accuracy and leaving scratches on the surface to be measured. When measuring with an interferometer based on the principle of interference of light waves, those with a large amount of aspherical surface can be measured. It was impossible. For surface roughness measurement and shape measurement of objects with a small inclination angle, the contour shape is measured in Cartesian coordinates using an optical probe that focuses the light beam on the surface to be measured and measures the surface shape from the reflected light beam. The measuring machine is non-contact,
The accuracy is also obtained and it is useful.

[0003]

Therefore, JP-A-60-1 is used.
Extensions have been made to use this system for shape measurement, such as the one disclosed in 69707. However, the allowable width of the tilt angle of the optical probe alone is currently ± 2.
The angle is up to about 5 °, and there is a problem that a surface having a large inclination angle cannot be measured. With a measuring machine that uses polar coordinates to measure by rotating the surface to be measured and the optical probe relatively,
The position of the center of rotation and the strict radius of gyration cannot be obtained accurately, and there is a problem that it is significantly disadvantageous in the evaluation of the shape after conversion to the Cartesian coordinate system as compared with the measurement in Cartesian coordinates.

There is also a measuring method that combines polar coordinate measurement and Cartesian coordinate measurement, such as the one disclosed in Japanese Patent Publication No. 6-29715, but the number of operating parts increases, the device becomes large, and accuracy and cost are low. There is a problem that it is disadvantageous to.

The present invention has been made in view of the above circumstances, and in the shape measuring apparatus according to the first aspect of the present invention, while the measurement accuracy is maintained, the measured angle is much larger than the inclination angle allowed by one displacement sensor. The purpose is to enable surface shape measurement.

Further, in the shape measuring apparatus according to the second aspect of the present invention, it is an object to shorten the measuring time of the object to be measured excluding the measuring time of the reference glass ball.

Further, in the shape measuring apparatus according to the third aspect, it is an object of the present invention to reduce the cost by measuring with a sensor for one displacement.

Further, in the shape measuring apparatus according to the fourth aspect, an object is to reduce an error due to Abbe's principle.

[0009]

In order to achieve the above object, the present invention provides a stage movable in at least two axial directions of X and Y, a length measuring means for measuring its displacement, and at least two measuring axes. The displacement measuring means for detecting the position in the direction and the coordinate reference sphere, and the displacement measuring means are arranged relatively inclined by an angle smaller than the respective allowable inclination angles, and the displacement measuring means The surface to be measured and the coordinate reference sphere are measured in the same measurement coordinate system, and the measurement coordinates obtained by the displacement measuring means are converted into coordinates so that the centers of curvature of the coordinate reference spheres are at the same point. It has a means for connecting the measurement data of the surface to be measured.

Further, all of the length measuring means and the displacement measuring means are fixed to one member having a high rigidity, which is sufficiently less affected by thermal expansion than the measurement accuracy. It is a thing.

Further, a stage movable in at least two axis directions of X and Y, a length measuring means for measuring the displacement thereof, a displacement measuring means for detecting a position in the measuring axis direction, and the displacement measuring means for the stage. Is provided with a rotating means for rotating in a plane parallel to the XY plane and a coordinate reference sphere, and further, the rotating means relatively rotates the displacement measuring means at an angle smaller than the allowable inclination angle. Measure the surface to be measured and the coordinate reference sphere in the same measurement coordinate system two or more times, and translate each measurement coordinate system so that the center of curvature of the coordinate reference sphere is at the same point based on the measurement results. It has a means for connecting the measurement data of the surface to be measured.

Further, the rotating means is configured to rotate about a measurement point of the displacement measuring means as a center.

With the above structure, the measurement data of the surface to be measured is adjusted so that the center of curvature of the coordinate reference sphere is at the same point based on the two measurement results of the surface to be measured and the coordinate reference sphere in the same measurement coordinate system. Therefore, even if the measurement is performed within the range of the tilt angle allowed by one displacement sensor (displacement measuring means), the shape measurement of the surface to be measured having a tilt angle of 25 ° or more maintains high measurement accuracy. Can be done.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment. That is, in FIG. 1, two types of the same type are mounted on the XY table 1 as a stage capable of movement control in two axial directions of X and Y on the surface plate.
Displacement sensors 2 and 3 as one displacement measuring means are attached at angles slightly smaller than the respective allowable inclination angles and inclined in opposite directions. Further, laser length measuring machines 4 and 5 as two length measuring means for measuring displacements of the X axis and the Y axis are attached, and displacements with respect to the X and Y axis reference mirrors 6 and 7 respectively attached to the surface plate. To measure. The object to be measured 8 having the surface to be measured is attached to the surface plate via the jig 9 with a position adjusting function. A reference glass sphere 10 as a coordinate reference sphere is attached near the object to be measured.

First, the displacement sensor 2 on one side is used to measure the surface to be measured of the object 8 to be measured within the range of the inclination angle allowed by the sensor 2. Next, without resetting the displacement outputs of the laser length-measuring machines 4 and 5, the reference glass ball 1 is used in the same measurement coordinate system.
0 is similarly measured. This order may be reversed before and after. This is measurement [1].

Next, measurement is performed using the other displacement sensor 3. The measurement procedure is the same. First, the surface to be measured of the object to be measured 8 is measured, and then the reference glass ball 10 is measured. This is measurement [2]. At this time, it is important that the laser measurement long term is 4, 5
Is to continuously measure the surface to be measured and the reference glass ball 10 in the same measurement coordinate system without resetting the displacement output. The measurement loci of measurement [1] and [2] are shown in FIG.

As the processing of the measurement data, first, the center position of the reference glass sphere 10 in each of the measurement coordinate systems is obtained from the measurement results of the respective reference glass spheres 10.
The reliability of the measurement accuracy can be easily increased to the required accuracy by giving a sufficient number of measurement points. Since the X and Y axes of the coordinate systems of measurement [1] and measurement [2] are parallel to each other with sufficient accuracy, the center of the reference glass sphere 10 of measurement [2] is the reference glass sphere of measurement [1]. Coordinate conversion is performed on the measured value of the object to be measured 8 in the measurement [2] so as to coincide with the center of 10. As a result, the measurement data of measurement [1] and measurement data of measurement [2] are connected with high accuracy. The measurement need not be performed twice, and may be performed three times or more. However, in this case, the allowable angle is narrowed, so that it is possible to use three or more sensors having good performance in the measurement axis direction and divide the measurement into several times to perform the measurement in the same procedure.

Further, not only the displacement sensors 2 and 3 as the displacement measuring means and the XY table 1 as the stage for fixing the laser length measuring machines 4 and 5 as the length measuring means, but also the object to be measured 8 and the reference are used. If the jig 9 with a position adjusting function for holding the glass sphere 10 is also made of a member having a low coefficient of thermal expansion and a sufficiently high rigidity, for example, a ceramic or a low expansion glass material, the reliability of the entire measuring device is improved. As a result, it is possible to reduce the number of measurement points of the reference glass ball 10 that is originally formed as a reference, and it is possible to shorten the measurement time of the object to be measured as a whole.

FIG. 3 shows a second embodiment. In the second embodiment, the displacement sensor 1 as one displacement measuring means.
The second embodiment is the same as the first embodiment except that it is attached to the XY table 1 via a jig 13 with a rotating function as a rotating means. The jig 13 with a rotating function is installed so as to rotate in a plane parallel to the XY table as a stage.

In the second embodiment, the displacement sensor 12 is relatively rotated and fixed by the jig 13 with a rotating function at an angle smaller than the allowable tilt angle, and then the object 8 to be measured is measured. The surface and the reference glass ball 10 are measured. Next, similarly, the displacement sensor 12 is relatively rotated and fixed at an angle smaller than the allowable tilt angle, and similarly, the measured surface of the measured object 8 and the reference glass ball 10 are measured. It is measured at least twice in the same measuring coordinate system. During measurement, only the X and Y axes operate. Then, although this is repeated several times, the subsequent steps are the same as in the first embodiment, and therefore will be omitted. In the second embodiment, there is one displacement sensor as the displacement measuring means, and since the measurement can be performed with this one displacement sensor, the cost can be reduced as compared with the first embodiment.

FIG. 4 shows a third embodiment. In the third embodiment, the displacement sensor 1 as one displacement measuring means.
5 is attached to the XY table 1 via an arc-shaped jig 16 having a rotation function, and is rotated about a measurement point of the displacement sensor 15 (one point of the measured surface of the object 8 to be measured) as an approximate center. It has become. The extension of the light beams of the laser length measuring machines 4 and 5 is set so as to roughly pass through the focal point. Other configurations are the same as those of the second embodiment, and the measurement procedure is also the same as that of the second embodiment.

In the third embodiment, the displacement sensor 1
Even if the setting of 5 is changed, the number of measurement points becomes almost one, and the optical axes of the laser length measuring machines 4 and 5 can be roughly aligned with each other. This means that the length of the object to be measured to be measured and the standard scale (moving position of the moving corner cube of the interferometer) must be in the same straight line, and the error is a measurement error. The error due to the principle of is reduced, and the measurement accuracy can be improved.

[0023]

As described above, according to the shape measuring apparatus according to the first aspect of the present invention, the shape of the surface to be measured which greatly exceeds the inclination angle allowed by one displacement sensor while maintaining the measurement accuracy. Can measure.

According to the shape measuring apparatus of the second aspect of the present invention, the time for measuring the reference glass ball is excluded, and the measuring time for the object to be measured is shortened.

According to the shape measuring apparatus of the third aspect of the present invention, the measurement can be performed by using one displacement sensor, and the cost is reduced.

Further, according to the shape measuring apparatus of the fourth aspect of the present invention, even if the setting of the displacement sensor is changed, the number of measuring points becomes almost one, and the optical axes of the laser length measuring machines can be roughly aligned with each other. it can. Therefore, the error due to the Abbe principle can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of a first embodiment according to the present invention.

FIG. 2 is an explanatory diagram showing a measurement trajectory according to the present invention.

FIG. 3 is a schematic plan view of a second embodiment according to the present invention.

FIG. 4 is a schematic plan view of a third embodiment according to the present invention.

[Explanation of symbols]

 1 XY table (stage) 2,3 Displacement sensor (displacement measuring means) 4,5 Laser length measuring machine (length measuring means) 6 X-axis reference mirror 7 Y-axis reference mirror 8 Measured object 9 Position adjustment function Tool 10 Reference glass sphere (coordinate reference sphere) 12 Displacement sensor (displacement measuring means) 13 Jig with rotation function (rotating means) 15 Displacement sensor (displacement measuring means) 16 Jig with arc-shaped rotation function (rotating means)

Claims (4)

[Claims] 1. A stage movable in at least two X, Y axis directions, a length measuring means for measuring the displacement thereof, a displacement measuring means for detecting positions in at least two measurement axis directions, and a coordinate reference sphere. Further, the displacement measuring means is arranged relatively inclined by an angle smaller than the respective allowable tilt angles, and the displacement measuring means causes the surface to be measured and the coordinate reference sphere to be in the same measurement coordinate system. Based on the result of measurement by each displacement measuring means, it has a means for connecting the measurement data of the surface to be measured by coordinate conversion of each measurement coordinate so that the center of curvature of the coordinate reference sphere becomes the same point. A shape measuring device characterized in that 2. The length measuring means and the displacement measuring means are all fixed to one member having a high rigidity and being less affected by thermal expansion than the measurement accuracy. The shape measuring device according to claim 1. 3. A stage movable in at least two axis directions of X and Y, a length measuring means for measuring the displacement thereof, a displacement measuring means for detecting a position in the measuring axis direction, and the displacement measuring means for the stage. Is provided with a rotating means for rotating in a plane parallel to the XY plane and a coordinate reference sphere, and further, the rotating means relatively rotates the displacement measuring means at an angle smaller than the allowable inclination angle. Measure the surface to be measured and the coordinate reference sphere in the same measurement coordinate system two or more times, and translate each measurement coordinate system so that the center of curvature of the coordinate reference sphere is at the same point based on the measurement results. A shape measuring device having means for connecting measurement data of a surface to be measured. 4. The shape measuring device according to claim 3, wherein the rotating means rotates about a measurement point of the displacement measuring means as a center.