JPH06129944A - Analysis and evaluation system for aspherical shapes - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to provide an analysis / evaluation system for an aspherical shape that does not require subjective judgment of the measurer and does not require any input, and further to improve the measurement accuracy. With the goal. [Structure] A data capturing circuit 21 that captures the measurement data from the shape measuring instrument 10, and a position and an inclination of an aspherical surface axis are searched from the measurement data captured by the circuit 21, and a measurement error is corrected based on the search result. It has a first arithmetic circuit 22.
The arithmetic circuit 22 further adjusts the parallax radius of curvature within the coefficient of the predetermined design aspherical expression while varying the paraxial curvature radius so as to minimize the deviation between the measured data and the shape data based on the design aspherical expression. Automatically estimate an aspherical expression with an axial radius of curvature. It is preferable to provide a second arithmetic circuit 23 for separating the deviation data into a low frequency component and a high frequency component.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, when evaluating the shape of an aspherical lens or the like, a master lens finished with high accuracy was used to confirm the shape deviation by a hologram method. There is a problem that the 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 type of aspherical surface analysis / evaluation system is disclosed in Japanese Patent Laid-Open No. 3-33635. This evaluation system measures by using a foam Talysurf (shape measuring machine), applies a plurality of measurement data to an aspherical formula such as the following formula (1), and estimates the coefficient in this formula to regress. A curve is obtained, and the deviation from this regression curve at each measurement point is displayed graphically.

[0004]

[Equation 1]

[0005]

However, in such a conventional aspherical surface shape analysis / evaluation system,
As mentioned above, to estimate the complex aspherical coefficients, etc.,
The processing required a great deal of labor and time, and an easy measurement could not be performed. Further, in order to reduce such labor, a method of fixing coefficients other than the paraxial radius of curvature R among the coefficients of the aspherical expression to a design value and changing only the paraxial radius of curvature R (repeating input) However, it is still laborious to obtain the aspherical surface formula that is the closest to the shape data, and the subjective judgment of the measurer is involved, so an accurate evaluation cannot be performed.

[0006] Therefore, an object of the present invention is to provide an analysis and evaluation system for an aspherical shape that does not require the subjective judgment of the measurer and does not require any input, and further to improve the measurement accuracy. To do.

[0007]

In order to achieve the above-mentioned object, the invention according to claim 1 analyzes the aspherical surface shape for analyzing and evaluating the aspherical surface shape based on the measurement data of a shape measuring machine for measuring the aspherical surface shape. In the evaluation system, a data capturing means for capturing the measurement data from the shape measuring instrument, and a position and an inclination of the aspherical surface axis are searched for from the measurement data captured by the data capturing means, and the position and the inclination of the aspherical surface axis are obtained. Correction means for correcting the measurement error based on the shape measurement data and the shape data based on the design aspherical expression, which is corrected by the correction means by changing only the paraxial curvature radius in the coefficient of the predetermined design aspherical expression. And an estimating means for automatically estimating an aspherical expression having an optimum paraxial radius of curvature that minimizes the deviation of (1), and the invention according to claim 2 is characterized in that In which characterized in that a separating means for separating the deviation between the shape data based on the aspheric equation with Jo measured data and the optimal paraxial curvature radius and the low and high frequency components.

[0008]

According to the first aspect of the invention, when the measurement data is taken into the data taking-in means from the shape measuring machine which measures the aspherical shape, first, the position and inclination of the aspherical surface axis are obtained by the correcting means, and the aspherical surface is obtained. The measurement error is corrected based on the axis position and tilt. Then, while varying only the paraxial radius of curvature in the coefficient of the predetermined design aspherical surface by the estimating means, the deviation between the corrected shape measurement data and the shape data based on the designed aspherical surface is minimized. The aspherical expression with the optimum paraxial radius of curvature is automatically estimated. Therefore, it is possible to perform accurate shape evaluation without the need for the input of the measurer and without subjective judgment.

According to the second aspect of the present invention, the deviation between the shape measurement data and the shape data based on the aspherical surface having the optimum paraxial radius of curvature 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 accuracy can be improved.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 are views showing an embodiment of the analysis and evaluation system for an aspherical surface according to the invention described in claims 1 and 2.
First, the configuration will be described.

In FIG. 1 (a), 10 is a line-scanning type shape measuring instrument (for example, a well-known foam Talysurf), and the shape measuring instrument 10 is of an object to be measured (not shown) having an aspherical shape. Aspherical shape evaluation system that measures the shape
The measurement data is sent to 20. Figure 1
As shown in (b), the aspherical surface shape evaluation system 20 includes a data acquisition circuit 21, a first arithmetic circuit 22, and a second arithmetic circuit 23.
And a data output circuit 24, and a data acquisition circuit
Reference numeral 21 is a data fetching means for fetching the shape measurement data sent from the shape measuring instrument 10 and exchanging the data with the first computing means 22.

The first arithmetic circuit 22 and the second arithmetic circuit 23 are composed of a microcomputer or the like, and the first arithmetic circuit 22 searches the data in the data fetching circuit 21 for the position of the aspherical axis of the aspherical surface. As a search circuit and a correction circuit (correction means is constituted by both circuits) for correcting the inclination by obtaining the inclination of the aspherical axis indicated by α in FIG. 2 from the left-right symmetry of the data distribution with respect to the aspherical axis. An estimation circuit (estimation means) that functions and further estimates an optimum aspherical expression with a paraxial radius of curvature R (hereinafter referred to as optimum R aspherical expression)
It is supposed to function as.

In the first arithmetic circuit 22, when the inclination α of the aspherical surface axis is corrected by the correction circuit, as shown in FIG.
The coordinate system as shown in can be set, and the data at this time becomes pure aspherical surface shape data of the measured object. Further, the estimating circuit uses the coefficients (R, K, E of the equation (1)) of a predetermined design aspherical equation (aspherical equation similar to the equation (1)) based on the shape data as shown in FIG. (Corresponding to _J ), while changing only the paraxial radius of curvature R from the design value, the deviation between the shape data based on the aspherical expression having the paraxial radius of curvature R and the corrected measured data is The optimum R aspherical expression is estimated by automatically estimating the minimum paraxial radius of curvature R (hereinafter referred to as the optimum paraxial radius of curvature R _s ).
For this estimation, a method such as a least square method, a damping least square method, or an experimental regression analysis can be used.

The second arithmetic circuit 23 is a data fetch circuit 21.
Approximate curve calculation that includes a calculation circuit that calculates a deviation between each measurement data taken in and the shape data based on the optimum R aspherical surface formula, and that calculates an approximate curve from the deviation data by a method such as moving average or polynomial approximation Contains the circuit.
As shown in FIG. 4, this approximate curve shows the low-frequency component of the deviation data corresponding to the error component (large error component) of the spherical surface shape of the object to be measured, and the deviation between the approximation curve and the deviation data is It is a high frequency component of the deviation data corresponding to the surface roughness component (small error component) of the object to be measured.
That is, the second arithmetic circuit 23 serves as a separating means for separating the deviation between the shape measurement data and the shape data based on the aspherical surface having the optimum paraxial radius of curvature 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 expression and the approximate curve, and the error of the aspherical surface shape is displayed on the screen or printed on the recording paper by the approximated curve. . It goes without saying that not only the shape error component (large error component) but also the surface roughness component can be output. Next, the operation will be described.

First, the shape measuring instrument 10 measures the spherical shape of the object to be measured, and when the measurement data is fetched from the shape measuring instrument 10 into the data fetching circuit 21, the first arithmetic circuit
The 22 search circuit first searches for the position of the aspherical axis from the measurement data in the data acquisition circuit 21, and then
The inclination α of the aspherical surface axis is obtained from the left-right symmetry of the data distribution with respect to the aspherical surface axis, and the measured data is corrected to a value when the inclination is zero. At this point, the coordinate system as shown in FIG. 3 is set, and pure aspherical surface shape data of the measured object is obtained.

Next, based on such shape data, the optimum R aspherical surface formula is estimated while gradually changing only the paraxial radius of curvature R from the design value among a plurality of coefficients of a predetermined design aspherical surface formula. It Next, by the second arithmetic circuit 23,
The deviation between each measurement data captured by the data capturing circuit 21 and the shape data based on the optimum R aspherical surface formula is calculated,
An approximate curve is calculated from the deviation data, and the deviation between the approximate curve and the measurement data is calculated, so that the output device 24 automatically outputs the aspherical shape error of the object to be measured.

As described above, in this embodiment, the first arithmetic circuit 22
Paraxial radius of curvature R
The optimum R aspherical surface formula is automatically estimated so that the deviation between the shape measurement data (data corrected for inclination) and the shape data based on the design aspherical surface surface is minimized while changing only the above. Therefore, it is not necessary for the measurer to input, and the subjective judgment of the measurer is not included,
It becomes an analysis and evaluation system that enables accurate shape evaluation.

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

[0020]

According to the first aspect of the invention, the measurement data is fetched from the shape measuring machine measuring the aspherical shape into the data fetching means, and the position and inclination of the aspherical surface axis are obtained by the correcting means to eliminate the measurement error. After the correction, the estimating means changes only the paraxial radius of curvature in the coefficient of the predetermined design aspherical expression, and minimizes the deviation between the corrected data and the shape data based on the design aspherical expression. Since the aspherical expression with the optimum paraxial radius of curvature is automatically estimated, it is possible to eliminate the time and effort of the operator's input, as well as to avoid subjective judgment, and to perform accurate shape evaluation. It is possible to provide an analysis / evaluation system of an aspherical shape that can be performed.

According to the second aspect of the present invention, 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 separately evaluated, and the evaluation accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an analysis and evaluation system for an aspherical shape according to the present invention, in which (a) is an overall schematic block diagram,
(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 is a spherical component of measurement data for the optimum aspherical expression,
It is explanatory drawing which shows the relationship of 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 arithmetic circuit (correction means, estimation means) 23 Second arithmetic circuit (separation means)

Claims (2)

[Claims] 1. An aspherical surface shape analysis / evaluation system for analyzing and evaluating the aspherical surface shape based on measurement data of a shape measuring machine for measuring an aspherical surface shape, wherein the data acquisition is for taking in measurement data from the shape measuring machine. Means, a correction means for searching the position and the inclination of the aspherical surface axis from the measurement data taken in by the data acquisition means, and correcting the measurement error based on the position and the inclination of the aspherical surface axis, An aspherical surface formula having an optimum paraxial radius of curvature such that only the paraxial radius of curvature is changed in the coefficient and the deviation between the shape measurement data corrected by the correction means and the shape data based on the design aspherical surface formula is minimized. An aspherical surface shape analyzing and evaluating system, which comprises: 2. A separating means for separating a deviation between the shape measurement data and the shape data based on an aspherical surface having an optimum paraxial radius of curvature into a low frequency component and a high frequency component. 1. The analysis and evaluation system of aspherical shape according to 1.