JP3321210B2 - Analysis and evaluation system for aspherical shapes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aspherical shape analysis and evaluation system, and more particularly to an aspherical shape analysis and evaluation system using a line scanning type shape measuring instrument.

[0002]

2. Description of the Related Art Conventionally, when evaluating the shape of an aspherical lens or the like, a shape deviation was confirmed by a hologram method using a master lens finished with high precision. Value) cannot be accurately grasped, and the master lens is expensive.
Therefore, recently, an evaluation system capable of automatically evaluating such an aspherical shape has been proposed.

An example of this kind of aspherical shape analysis and evaluation system is disclosed in Japanese Patent Application Laid-Open No. 3-33635. This evaluation system measures by a form tally surf (shape measuring machine), applies a plurality of measurement data to an aspheric surface equation such as the following equation (1), and estimates a coefficient or the like in this equation to perform regression. A curve is obtained, and a deviation from the regression curve at each measurement point is graphically displayed.

[0004]

(Equation 1)

[0005]

However, in such a conventional aspherical shape analysis and evaluation system,
As described above, in order to estimate the coefficients and the like of a complex aspherical expression,
The process required considerable effort and labor, and could not be easily measured. In addition, in order to reduce such labor, a coefficient other than the paraxial curvature radius R among the coefficients of the aspheric expression is fixed to a design value, and only the paraxial curvature radius R is changed (input is repeated). However, if an aspherical expression closest to the shape data is obtained, labor is still required, and a subjective judgment of the measurer is involved, so that accurate evaluation cannot be performed.

Accordingly, an object of the present invention is to provide an analysis / evaluation system for an aspherical shape which does not require a subjective judgment of a measurer and does not require inputting, and further aims to improve the measurement accuracy. I do.

[0007]

In order to achieve the above object, the invention according to claim 1 is an analysis of an aspherical shape for analyzing and evaluating the aspherical shape based on measurement data of a shape measuring machine for measuring the aspherical shape. In an evaluation system, a data capturing unit that captures measurement data from the shape measuring device, and a position and a tilt of an aspheric axis are searched for from the measurement data captured by the data capturing unit. Correction means for correcting the measurement error based on, and only the paraxial radius of curvature is changed in the coefficients of the predetermined design aspherical expression, the shape measurement data corrected by the correction means and the shape data based on the design aspherical expression Estimating means for automatically estimating an aspheric expression having an optimum paraxial curvature radius such that a deviation of the shape measurement data is minimized;
The deviation from the shape data based on the spherical equation is calculated using the low frequency component and the high frequency.
And a separating means for separating into wave components .

[0008]

According to the first aspect of the present invention, when measurement data is taken into the data acquisition means from the shape measuring device which measures the aspherical shape, first, the position and inclination of the aspherical axis are obtained by the correction means, and the aspherical surface is obtained. The measurement error is corrected based on the position and inclination of the axis. Next, the deviation between the corrected shape measurement data and the shape data based on the design aspherical expression is minimized while changing only the paraxial curvature radius in the coefficients of the predetermined design aspherical expression by the estimating means. Is automatically estimated with the optimal paraxial radius of curvature. Therefore, it is possible to eliminate the trouble of the input by the measurer and to perform the accurate shape evaluation without the subjective judgment. Also before
Aspherical expression with shape measurement data and optimal paraxial radius of curvature
The deviation from the shape data based on the
Component and surface roughness component
Can be evaluated separately, and the accuracy of the evaluation can be improved.

[0009]

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 to 4 show an embodiment of an aspherical shape analysis and evaluation system according to the first and second aspects of the present invention.
First, the configuration will be described.

In FIG. 1A, reference numeral 10 denotes a line scanning type shape measuring device (for example, a known form Talysurf), and the shape measuring device 10 is for measuring an object to be measured (not shown) having an aspherical shape. Measures shape and evaluates aspheric shape
The measurement data is sent to 20. FIG.
As shown in (b), the aspherical shape evaluation system 20 includes a data acquisition circuit 21, a first arithmetic circuit 22, and a second arithmetic circuit 23.
And data output circuit
Reference numeral 21 denotes a data capturing unit that captures the shape measurement data sent from the shape measuring device 10 and exchanges data with the first arithmetic unit 22.

The first arithmetic circuit 22 and the second arithmetic circuit 23 are constituted by a microcomputer or the like. The first arithmetic circuit 22 searches the position of the aspheric axis of the aspheric surface from the data in the data acquisition circuit 21. A search circuit and a correction circuit for correcting the inclination of the aspherical axis indicated by α in FIG. 2 by determining the inclination of the data distribution with respect to the aspherical axis from the left-right symmetry (both circuits constitute correction means) An estimating circuit (estimating means) that functions and further estimates an optimal aspherical expression having a paraxial curvature radius R (hereinafter referred to as an optimal R aspherical expression).
It is designed to function as.

In the first arithmetic circuit 22, at the time when the inclination α of the aspherical axis is corrected by the correction circuit, FIG.
Can be set, and the data at this time becomes pure aspherical shape data of the measured object. Further, the estimation circuit calculates the coefficients (R, K, E of the equation (1)) of a predetermined design aspherical equation (an aspherical equation similar to the equation (1)) based on the shape data as shown in FIG. _J ), the deviation between the shape data based on the aspherical formula having the paraxial radius of curvature R and the corrected measurement data while changing only the paraxial radius of curvature R from the design value. smallest such paraxial radius of curvature R (hereinafter, optimum near that axis curvature radius R _s) the by automatically estimated, estimates the optimal R aspheric expression.
For this estimation, a method such as a least square method, a damped least square method, or an experimental regression analysis can be used.

The second arithmetic circuit 23 includes a data acquisition circuit 21
Curve calculation which calculates the deviation between each measurement data taken into the device and the shape data based on the optimal R aspherical formula, and calculates an approximate curve from the deviation data by a method such as moving average or polynomial approximation Includes circuitry.
As shown in FIG. 4, this approximation curve indicates the low-frequency component of the deviation data corresponding to the error component (large error component) of the spherical surface shape of the measured object. This is a high-frequency component of deviation data corresponding to the roughness component (small error component) of the surface of the device under test.
That is, the second arithmetic circuit 23 is a separating unit that separates a deviation between the shape measurement data and the shape data based on the aspherical expression having the optimum paraxial curvature radius into a low-frequency component and a high-frequency component.

The output device 24 is a device for outputting at least both the curve corresponding to the optimum R aspherical surface equation and the approximated curve. The error of the aspherical shape is displayed on a screen or printed on recording paper by the approximated curve. . It goes without saying that not only the output of the shape error component (large error component) but also the output of the surface roughness component is possible. Next, the operation will be described.

First, the shape of the spherical surface of the object to be measured is measured by the shape measuring device 10 and the measured data is taken from the shape measuring device 10 into the data taking circuit 21.
First, the position of the aspherical axis is searched from the measurement data in the data acquisition circuit 21 by the search circuit 22.
The inclination α of the aspherical axis is obtained from the left-right symmetry of the data distribution with respect to the aspherical axis, and the measurement data is corrected so that the inclination α becomes zero. At this point, a coordinate system as shown in FIG. 3 is set, and pure aspherical shape data of the measured object is obtained.

Next, based on such shape data, the optimum R aspherical surface equation is estimated while only the paraxial radius of curvature R is gradually changed from the design value among a plurality of coefficients of the predetermined design aspherical surface equation. You. Next, by the second arithmetic circuit 23,
The deviation between each measurement data taken into the data taking-in circuit 21 and the shape data based on the optimal R aspherical formula is calculated,
An approximation curve is calculated from the deviation data, and a deviation between the approximation curve and the measurement data is calculated, so that the output device 24 automatically outputs the aspherical shape error of the measured object.

As described above, in the present embodiment, the first arithmetic circuit 22
Of the paraxial curvature radius R in the coefficients of the given design aspherical equation
The optimum R aspherical formula is automatically estimated so that the deviation between the shape measurement data (the data corrected for the inclination) and the shape data based on the design aspherical formula is minimized while changing only the aspherical formula. Therefore, the operator does not have to make any input, and the subjective judgment of the operator is not included.
It becomes an analysis evaluation system that can perform accurate shape evaluation.

Further, as described above, the deviation between the shape measurement data and the shape data based on the aspherical expression having the optimum paraxial curvature radius is separated into a low-frequency component and a high-frequency component.
The shape error component and the surface roughness component can be evaluated separately, and the evaluation of the aspherical shape error, which has been quite difficult in the past, can be performed with high accuracy.

[0020]

According to the first aspect of the present invention, the measurement data is fetched from the shape measuring instrument that measures the aspherical shape to the data fetching means, and the position and inclination of the aspherical axis are obtained by the correcting means to reduce the measurement error. After correction, the deviation between the corrected data and the shape data based on the design aspheric expression is minimized while changing only the paraxial curvature radius in the coefficients of the predetermined design aspheric expression by the estimating means. Since the aspherical expression having the optimal paraxial radius of curvature is automatically estimated, it is possible to eliminate the trouble of the input of the measurer and to prevent the subjective judgment from being entered, thereby enabling accurate shape evaluation. An analysis and evaluation system for an aspherical shape that can be provided can be provided. In addition, the shape measurement data and the optimal paraxial curvature half
The deviation from the shape data based on the aspherical expression with a diameter is low.
Since it is separated into a high frequency component and a high frequency component, the shape error component
And surface roughness components can be evaluated separately, improving the accuracy of evaluation
be able to.

[0021]

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of an aspherical shape analysis and evaluation system according to the present invention, wherein (a) is a schematic block diagram of the whole;
(B) is a block diagram of the analysis evaluation system.

FIG. 2 is a graph showing shape measurement data before the inclination correction.

FIG. 3 is a graph showing shape measurement data after the inclination correction.

FIG. 4 shows the spherical component of the measured data for the optimal aspheric formula;
FIG. 3 is an explanatory diagram illustrating a relationship between an aspherical surface component and a roughness component.

[Explanation of symbols]

 10 Shape measuring machine 20 Aspherical surface shape evaluation system 21 Data acquisition circuit (Data acquisition means) 22 First operation circuit (Correction means, Estimation means) 23 Second operation circuit (Separation means)

Claims (1)

(57) [Claims] 1. An aspherical shape analysis / evaluation system for analyzing and evaluating an aspherical shape based on measurement data of a shape measuring device for measuring an aspherical shape, the data taking in the measurement data from the shape measuring device. Means for searching the position and inclination of the aspherical axis from the measurement data captured by the data capturing means, and correcting the measurement error based on the position and inclination of the aspherical axis; and a predetermined design aspherical type. An aspheric formula having an optimum paraxial curvature radius such that the deviation between the shape measurement data corrected by the correction means and the shape data based on the design aspheric formula is minimized by changing only the paraxial curvature radius in the coefficient. Estimating means for automatically estimating an aspheric surface having the shape measurement data and an optimum paraxial radius of curvature
The deviation from the shape data based on the
An aspherical shape analysis / evaluation system , comprising: a separation unit for separating an aspheric surface.