JP2001056217A - Optical element shape measuring method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the two-dimensional absolute shape of an optical element and to accurately compute the optical performance of the whole mirror frame unit by measuring the three-dimensional coordinates of an optical element or a mold by a three-dimensional measuring means, and obtaining shape from the obtained measured data. SOLUTION: Coordinates of one or more points on reference parts 7, 8 of a holder 3 are measured first simultaneously with an optical element 2 to be detected. Then the coordinates of one or more points on the surface of the optical element 2 are measured by a three-dimensional measuring apparatus 1. Then, the shape relative to a reference plane is subjected to a transformation based on the measured data of the reference parts 7, 8. At this time, the manufacturing error of the holder 3 is corrected using holder shape measured data. The obtained surface shape data are converted in the point sequence as they are into a surface shape or converted into a surface shape by applying the point sequence to a certain function. The obtained measured data is converted into a surface shape error and the measured shape error is compared with the result of applying the surface shape error data to a function representing the error data, and the difference is two-dimensionally or three- dimensionally displayed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring the shape of an optical element, and more particularly, to a method for measuring an absolute shape of an optical element or a mold used for manufacturing the optical element by plastic molding or glass molding. And the device.

[0002]

2. Description of the Related Art Since the surface shape of an optical element such as a lens or a prism greatly affects the performance of an optical system, measurement of an absolute surface shape is an important issue in quality control in a manufacturing process of the element. As a method for measuring the surface shape of an optical element, an interferometer is conventionally used, but the interferometer is a relative comparison with a reference surface and cannot measure an absolute shape.

[0003] As a method of measuring the absolute shape,
A stylus-type scale is commercially available, but it mainly measures cross-sectional shapes orthogonal to each other. Since it is difficult to measure the surface shape in two dimensions, it is not possible to correctly measure an asymmetric surface shape of the optical element. Also, the mold had the same problem.

On the other hand, there is a three-dimensional measuring device as a device capable of measuring the three-dimensional coordinates of a sample surface with high accuracy. However, since the device generally does not have an absolute coordinate system, an absolute shape cannot be measured. There is.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the prior art, and has as its object to provide a three-dimensional structure for a part of a member for holding an optical element which is a test object. An optical element shape measuring method in which a portion serving as a coordinate reference of a measuring machine is provided, and this portion is measured simultaneously with the shape of the optical element, and the obtained measurement value is converted into coordinates with respect to the reference to determine the absolute shape of the optical element. And an apparatus.

[0006]

According to the present invention, there is provided a method and apparatus for measuring the shape of an optical element according to the present invention, comprising: a three-dimensional coordinate measuring means for measuring three-dimensional coordinates of an optical element or a mold as an object; A method for obtaining a shape from measurement data obtained by a dimensional coordinate measuring means.

In this case, it is desirable to determine the eccentricity of the optical element by the eccentricity measuring means. At that time, an optical method can be used as the eccentricity measuring means of the optical element.

In the present invention, three-dimensional coordinate measuring means for measuring three-dimensional coordinates of an optical element to be inspected, and means for applying measurement data obtained by the three-dimensional coordinate measuring means to a function representing a shape. Therefore, for example, a part serving as a coordinate reference of the three-dimensional measuring means is provided in a part of a member for holding an optical element, which is a test object, and this part is measured simultaneously with the shape of the optical element. The absolute shape of the optical element can be determined by converting the measured values to coordinates with respect to the reference.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) FIG. 1 shows a basic configuration diagram of the present invention. This device includes a three-dimensional measuring machine 1 for measuring three-dimensional coordinates, a lens, an aspherical lens, a mirror,
A test optical element 2 such as an aspherical mirror, a holder 3 for holding the same, and a data processing unit 4 for obtaining a shape from measurement data
It is composed of

In general, since the three-dimensional measuring machine 1 does not have an absolute coordinate system of the apparatus itself, a coordinate reference is provided externally to obtain the absolute shape of the optical element 2 to be measured, and the measured data is coordinated with respect to the reference. Need to be converted to

Therefore, in the present invention, 3
A portion serving as a coordinate reference of the dimension measuring machine 1 is provided.

FIG. 2 is a diagram showing a cross section of the holder 3 used in the present measuring apparatus and the optical element 2 to be inspected arranged in the holder 3. Here, the portion serving as the coordinate reference is provided on the holder 3 at the upper flat portion 7 including the test surface (upper surface in the drawing) of the test optical element 2 and at the end of the upper flat portion 7. This is an edge portion 8.

FIG. 4 is a diagram showing a flow of a procedure when measuring the shape of the optical element 2 to be measured using the holder 3 as shown in FIG. First, in step 13, a reference portion of the holder is measured. In this step 13, the test optical element 2 is
, The coordinates of one or more points of the reference portions 7 and 8 of the holder 3 are simultaneously measured by the three-dimensional measuring machine 1 together with the optical element 2 to be measured.

The next step 14 is to measure the shape of the optical element 2 to be inspected.
It is measured by the dimension measuring machine 1.

Based on the measured data of the reference portions 7 and 8 of the holder 3, the shape measurement data of the test optical element 2 thus obtained is converted into a shape with respect to a reference surface in step 15.

Here, since the manufacturing error of the holder 3 serving as the coordinate reference affects the measurement accuracy of the shape, as shown in FIG. The concentricity of the edge portion 8 with the center 11 and the surface 7 of the holder 3
The parallelism 12 of the receiving surface of the optical element and the parallelism 12 of the optical element are measured in advance by a three-dimensional measuring device or the like, and stored in step 16 as holder shape measurement data.

When the shape is converted into the shape with respect to the reference plane in step 15, by correcting the manufacturing error of the holder 3 using the holder shape measurement data in step 16, the shape measurement error is reduced. .

It is to be noted that the optical element 2 to be measured is rotated by 180 ° around the center 10 in the holder 3 for measurement, and an average value of the measured values before rotation is obtained. The measurement error due to the error is canceled, and the measurement accuracy can be improved.

At this time, if the deviation is larger than the data measured before the rotation, it is considered that the optical element 2 in the holder 3 is not settled properly, so it is better to measure again.

Next, the surface shape data obtained in this way may be a surface shape as it is as a point sequence, or a surface shape by applying the point sequence to a certain function. Such functions include polynomials, power series, Zernike polynomials, spline functions, point sequence interpolation, and the like.

The measured data thus obtained is converted into a difference from the design surface shape, that is, a surface shape error. In step 17, fitting to a function representing a surface shape error is performed. As the function, for example, a Zernike polynomial may be used. In other cases, a spline function, or interpolation of a polynomial or point sequence data may be used. .

Here, in step 18, the measured shape error data is compared with the result of fitting to the function representing the surface shape error data to confirm the degree of matching, and the difference is determined in two or three dimensions. If it can be displayed, if a problem occurs during measurement, it can be confirmed on the spot. If the degree of matching is good, the two-dimensional absolute shape of the test optical element 2 is determined in step 19.

The above method can be applied to a mold.

Here, the eccentricity of the optical element 2 or the mold is
Although it may be obtained from the shape measurement data, since the accuracy is generally insufficient, it is better to perform the measurement by another method such as using an eccentricity measuring device. As an example of the eccentricity measuring device, an interferometer, an optical or contact type measuring device may be used, but for example, a method disclosed in Japanese Patent Application Laid-Open No. 9-222380 or the like can be used for accurate measurement. Hereinafter, this measuring device will be briefly described.

FIG. 7 shows an eccentricity measuring machine. In this eccentricity measuring machine, a test aspheric lens 121 is supported in a rotatable rotary holder 122, and a light beam emitted from a point light source of the visible semiconductor laser 101 is transmitted through a projection lens 103 of an incident optical system. The light enters the spherical surface 120. The reflected light reflected by the aspherical surface 120 forms an image by an image forming lens 102 of the observation optical system (in this case, the image forming lens 102 is shared with the projection lens 103), and the microscope objective lens 105 and the zoom lens The image is captured on the CCD camera 107 through the magnifying optical system 106 and observed.

In this eccentricity measuring machine, the mirror 111 is rotatable in the X1 direction so that the position and direction of the light beam incident on the aspherical surface 120 can be changed. 141 is the horizontal direction X as a whole
2 can be moved. In addition, a mechanism is provided so that the visible semiconductor laser 101 can move in the up-down direction X3 in order to change the reflection magnification at the aspheric surface 120. In order to adjust the focus of the spot image of the reflected light beam to be observed, a CCD camera 107, a zoom lens 106,
The triangular prism 134 and the microscope objective lens 105 are configured to be integrally movable in the left-right direction X4.

Using this eccentricity measuring instrument, two degrees of freedom for determining the eccentricity of the aspherical surface (the deviation δ from the reference axis of the aspherical surface top and the inclination ε of the aspherical surface with respect to the reference axis) are determined by the vertical incidence method. And two oblique incidence methods. The normal incidence method is a measurement method for observing a reflected light beam near the top of the aspheric surface almost parallel to the aspheric axis as shown in FIG. 7A, and the oblique incidence method is shown in FIG. 7B. As described above, this is a measurement method in which an incident light beam is made to enter the surface of the aspherical surface substantially perpendicularly at an angle to the aspherical axis, and the reflected light beam is observed.

(Second Embodiment) In the first embodiment, in order to measure the two-dimensional absolute shape of the optical element, a method of providing a coordinate reference to a holder for holding the optical element is shown in FIG. In addition, if the coordinates of the outer periphery of the optical element 2 or the mold are measured by the three-dimensional measuring device 1, it is not necessary to provide a coordinate reference for the holder. Here, the eccentricity of the optical element 2 may be obtained from the measured shape data, but it is more preferable to measure the eccentricity by using an eccentricity measuring device, as in the first embodiment, since the accuracy is improved.

Third Embodiment Although the first and second embodiments are examples of measuring the shape of an optical element alone, there is a case where it is desired to evaluate the optical performance of the entire optical system including the optical element to be tested. .

In the flow chart of FIG.
In step 20, the optical performance of the lens barrel unit is calculated based on the two-dimensional absolute surface shape of the optical element (procedure 18) obtained in the embodiment and the second embodiment. As a scale representing the optical performance, for example, MTF is used.

Here, in order to correctly calculate the optical performance of the lens barrel unit, the inter-plane eccentricity data (procedure 21) of the optical element measured by the eccentricity measuring machine described in the first embodiment is required. Further, generally, each optical element incorporated in the lens barrel unit is decentered, which causes a decrease in optical performance. Therefore, it is necessary to measure the eccentricity of each optical element in the lens frame with a built-up eccentricity measuring instrument and calculate the optical performance including the obtained built-up eccentricity data (procedure 22).

As the assembled eccentricity measuring instrument, for example, an assembled eccentricity measuring instrument as shown in FIG. 8 may be used (OPTRONICS (1995) No. 3, 120-).
121). A laser beam from a semiconductor laser 201 as a light source is measured by an optical system for measurement 202 and a beam splitter 204.
Are sequentially projected onto the center of curvature of each surface of the lens 203 to be measured via the
07, the eccentricity is measured by image processing in the arithmetic processing unit 210 and position detection. At this time, since the measured lens 203 is not rotated, the beam splitter 204 is not rotated.
The reference axis setting optical system 20 using the image rotator 205 on the extension of the optical axis of the measurement optical system 202 divided by
6 and rotating the image rotator 205,
The spot image of the light beam reciprocating in the reference axis setting optical system 206 rotates on the image plane of the CCD 207. The center of rotation serves as a reference for eccentricity. A spot image rotating on the image plane is captured at four points on the rotation trajectory, and these positions are obtained. By calculating the shake amount of the spherical image on each surface of the lens 203, the assembled eccentricity data is obtained.

The measuring method and measuring apparatus of the present invention
It can be used not only for measurement of optical elements such as lenses and prisms, but also for measurement of a mold for integrally molding the optical elements. That is, with reference to FIG. 9 which shows a simplified cross section of a mold of integral molding, an optical element such as a lens which is integrally molded is:
A resin or glass medium is put between the molds 6a and 6b, and pressed to produce. Therefore, the accuracy of the shape of the lens surface depends to some extent on the surface shape of the molds 6a and 6b. Therefore, similarly to the optical element, it is necessary to correctly measure the shape of the mold. Therefore, by using the measuring method and the measuring apparatus of the present invention, the two-dimensional absolute shape of the mold can be measured.

An example is shown in FIGS. FIG.
FIG. 2 is a cross-sectional view in which the optical device mold 6 is disposed in the holder 3 using the measuring apparatus according to the first embodiment of the present invention. The configuration, operation, and effects are the same as those of the first embodiment, and the same reference numerals as those of the first embodiment are shown, and the description thereof is omitted.

FIGS. 11 and 12 show a second embodiment of the present invention.
It is sectional drawing which showed the measuring method of the type | mold using the measuring method of an Example. FIG. 11 shows a case where the coordinate reference is on the side surface 211 of the mold, and FIG. 12 shows a case where the coordinate reference is on the upper surface 212 of the mold. In any case, a holder is not required, and the apparatus can be simplified.

The optical element shape measuring method and apparatus of the present invention described above can be configured, for example, as follows.

[1] There are three-dimensional coordinate measuring means for measuring three-dimensional coordinates of an optical element or a mold as a test object, and means for obtaining a shape from measurement data obtained by the three-dimensional coordinate measuring means. Characteristic shape measuring method and apparatus.

[2] The shape measuring method and apparatus according to the above item 1, wherein the eccentricity of the optical element or the mold is obtained by an eccentricity measuring means.

[3] The above-mentioned item 2 characterized in that an optical method is used as the eccentricity measuring means of the optical element or the mold.
The shape measuring method and apparatus according to the above.

[4] A three-dimensional coordinate measuring means for measuring the three-dimensional coordinates of an optical element or a mold to be inspected, and the three-dimensional coordinates are provided on a part of the member holding the optical element or the mold. An optical element or a mold holding member provided with a portion serving as a coordinate reference of the measuring means, and one or more points of the coordinate reference portion on the optical element or the mold holding member provided by the three-dimensional coordinate measuring means. 3. The shape measuring method and apparatus according to claim 1 or 2, wherein the coordinates of (1) and one or more points on the test optical element or the mold are measured.

[5] A three-dimensional coordinate measuring means for measuring the three-dimensional coordinates of the optical element or the mold as the object to be inspected, and the three-dimensional coordinates are provided on a part of the member holding the optical element or the mold. An optical element or a mold holding member provided with a portion serving as a coordinate reference of the measuring means, and one or more points of the coordinate reference portion on the optical element or the mold holding member provided by the three-dimensional coordinate measuring means. And the coordinates of one or more points on the test optical element or mold, and the coordinates of one or more points on the test optical element or mold, the optical element or mold holding member. 5. The shape measuring method and apparatus according to the above 2 or 4, wherein a difference between a result of conversion into coordinates with respect to the above coordinate reference and a design value of the shape of the test optical element or the mold is applied to a function.

[6] The shape measuring method and apparatus according to the above item 2, 4 or 5, wherein a Zernike polynomial is used as a function representing the surface shape.

[7] The above-mentioned item 2, wherein the optical element or the type to be inspected is an aspherical lens or a type thereof.
The shape measuring method and apparatus according to 4 or 5.

[8] The shape of the optical element to be measured is obtained based on the value obtained by measuring the coordinates of the outer periphery of the optical element or the mold by the three-dimensional coordinate measuring means. The shape measuring method and apparatus according to the above.

[0045]

[9] The shape measuring method and apparatus according to the above item 2, further comprising means for displaying a two-dimensional or three-dimensional display of a measurement data sequence of the optical element or the mold obtained by the three-dimensional coordinate measuring means.

The present invention includes the following optical performance evaluation method and apparatus.

[10] Three-dimensional coordinate measuring means for measuring the three-dimensional coordinates of the optical element to be inspected, and the coordinates of the three-dimensional coordinate measuring means on a part of the member holding the optical element to be inspected. An optical element holding member provided with a reference portion, wherein the coordinates of one or more points of the coordinate reference portion on the optical element holding member are determined by the three-dimensional coordinate measuring means; Measuring the coordinates of one or more points on the element, converting the coordinates of the one or more points on the test optical element into coordinates with respect to a coordinate reference on the optical element holding member, Fitting the difference between the design value of the shape of the optical element and the design value to a function, and determining the optical performance of the entire optical system including the test optical element based on the shape of the test optical element obtained from the function. Optical performance evaluation method and apparatus.

[11] The optical performance evaluation method and apparatus according to the above [10], wherein the eccentricity of each optical element in the lens frame holding the test optical element is obtained by eccentricity measuring means.

[12] The optical performance evaluation method and apparatus according to the above item 10 or 11, wherein a Zernike polynomial is used as a function representing the surface shape.

[13] The optical performance evaluation method and apparatus according to the above [10] or [11], wherein the test optical element is an aspherical lens.

[14] The above-mentioned 10 or 1 wherein the shape of the optical element to be measured is obtained based on the value obtained by measuring the coordinates of the outer peripheral portion of the optical element to be measured by the three-dimensional coordinate measuring means.
2. The optical performance evaluation method and apparatus according to 1.

[0052]

As is apparent from the above description, according to the optical element shape measuring method and apparatus of the present invention, the two-dimensional absolute shape of the optical element can be measured, and the optical performance of the entire lens frame unit can be accurately calculated. can do.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of an apparatus for performing an optical element shape measuring method of the present invention.

FIG. 2 is a diagram showing a cross section of a holder used in the optical element shape measuring apparatus of the present invention and a test optical element disposed therein.

FIG. 3 is a diagram showing concentricity and parallelism of a reference portion of a holder.

FIG. 4 is a diagram showing a flow of a measurement procedure of the first embodiment.

FIG. 5 is a diagram showing a state of measurement including an outer peripheral portion of an optical element in a second embodiment of the present invention.

FIG. 6 is a diagram showing a flow of a measurement procedure of the third embodiment.

FIG. 7 is a diagram for explaining a vertical incidence method and an oblique incidence method using an eccentricity measuring instrument.

FIG. 8 is a configuration diagram of an example of an assembled eccentricity measuring device.

FIG. 9 is a diagram showing a simplified cross section of an integrally molded mold.

FIG. 10 is a cross-sectional view in which a mold of an optical element is arranged in a holder using the measuring apparatus according to the first embodiment of the present invention.

FIG. 11 is a cross-sectional view illustrating a method for measuring a mold using the measurement method according to the second embodiment of the present invention.

FIG. 12 is a cross-sectional view illustrating a method for measuring a mold using the measurement method according to the second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 3D measuring device 2 ... Optical element to be examined 3 ... Holder 4 ... Data processing part 6, 6a, 6b ... Mold 7 ... Upper plane part (reference part) 8 ... Edge part (reference part) 10 ... Holder Center of surface receiving optical element 11 Center of edge of holder 12 Parallelism between surface of holder and receiving surface of optical element 13-22 Procedure 101 Visible semiconductor laser 102 Imaging lens 103 Projection lens 105: Microscope objective lens 106: Zoom lens 107: CCD camera 111: Mirror 115: Beam splitter 120: Aspheric surface 121: Aspheric lens to be tested 122: Rotating holder 141: Upper part of the eccentricity measuring machine 134: Triangular prism 201: Semiconductor laser 202: Optical system for measurement 204: Beam splitter 203: Lens to be measured 205: Image rotator 206: Reference Setting the optical system 207 ... CCD 208 ... monitor television 209 ... CRT 210 ...... processing unit 211 ... reference portion (side surface) 212 ... reference portion (upper surface)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshiro Kikuchi 2-43-2 Hatagaya, Shibuya-ku, Tokyo Inside Olympus Optical Industries Co., Ltd. (72) Kimihiko Nishioka 2-43-2 Hatagaya, Shibuya-ku, Tokyo F-term (reference) in Olympus Optical Co., Ltd. NN16 NN18 NN21

Claims (3)

[Claims] 1. A shape measuring method comprising: three-dimensional coordinate measuring means for measuring three-dimensional coordinates of a test object; and means for obtaining a shape from measurement data obtained by the three-dimensional coordinate measuring means. And equipment. 2. The shape measuring method and apparatus according to claim 1, wherein said three-dimensional coordinate measuring means determines the eccentricity of the optical element or the mold by the eccentricity measuring means. 3. The shape measuring method and apparatus according to claim 2, wherein an optical method is used as the eccentricity measuring means of the optical element or the mold.