Measuring tehnology for optical element for obtaining measurement error optical element

Patent metadata

Field	Value
Publication number	US-2016003706-A1
Application number	US-201414322912-A
Country	US
Kind code	A1
Filing date	Jul 3, 2014
Priority date	Jul 3, 2014
Publication date	Jan 7, 2016
Grant date	—

Abstract

A measuring method for an optical element for obtaining a plurality of measurement errors of the optical element is disclosed, which comprises steps of irradiating a laser ray to an overall portion of the optical element, wherein the optical element is supported as one of a horizontal state and a vertical state; rotating continuously the optical element with 360 degrees to reflect the laser ray to obtain a reflected light wavefront picture from the reflected laser ray; analyzing the reflected light wavefront picture to obtain a plurality of aberration characteristics information, respectively, each being one of a sine and a cosine wave functions of a wavefront error for each of the plurality of specified rotation angles; analyzing a plurality of interference factors each for the plurality of measurement errors on each of the plurality of aberration characteristics information, respectively; calculating and extracting a plurality of classified aberration characteristics information for each of the plurality of specified rotation angles of the optical element from each of the plurality of aberration characteristics information according to the plurality of measurement errors, respectively; and analyzing each of the plurality of classified aberration characteristics information to obtain an error amount corresponding to each of the plurality of measurement errors, respectively.

First claim

What is claimed is:

1 . A measuring method for an optical element for obtaining a plurality of measurement errors of the optical element, comprising steps of:
(a) irradiating a laser ray to an entirety of the optical element, wherein the optical element is supported as one of a horizontal state and a vertical state; (b) rotating continuously the optical element with 360 degrees to reflect the laser ray to obtain a reflected light wavefront picture from the reflected laser ray for each of a plurality of specified rotation angles of the optical element; (c) analyzing the reflected light wavefront picture for each of a plurality of specified rotation angles of the optical element to obtain a plurality of aberration characteristics information, respectively, each being one of a sine and a cosine wave functions of a wavefront error for each of the plurality of specified rotation angles of the optical element; (d) analyzing a plurality of interference factors each for the plurality of measurement errors on each of the plurality of aberration characteristics information, respectively, for each of the plurality of specified rotation angles of the optical element; (e) calculating and extracting a plurality of classified aberration characteristics information for each of the plurality of specified rotation angles of the optical element from each of the plurality of aberration characteristics information according to the plurality of measurement errors, respectively, for each of the plurality of specified rotation angles of the optical element; and (f) analyzing each of the plurality of classified aberration characteristics information for each of the plurality of specified rotation angles of the optical element to obtain an error amount corresponding to each of the plurality of measurement errors, respectively.

2 . The method as claimed in claim 1 , wherein the aberration information is a polynomial formed by a sum of a plurality of Zernike coefficients each corresponding to one of the plurality of aberration information.

3 . The method as claimed in claim 2 , wherein the step (d) further comprises steps of:
comparing each of the plurality of aberration characteristics information with an ideal sine function and an ideal cosine function to obtain an amplitude difference and a constant amplitude deviation for each of the plurality of specified rotation angles of the optic element, respectively, the amplitude difference and the constant amplitude deviation indicating at least one of the plurality of interference factors, for each of the specified rotation angles of the optical element; and
if the optical element is an axial symmetric element,
if a supporting and holding unit for supporting and holding the optical element is fixed stationary with respect to a rotation of the optical element, and if each of the aberration characteristics information has the constant amplitude deviation independent on one of the plurality of specified rotation angles corresponding thereto, determining the constant amplitude deviation as a sum of an overall measurement system error, a holding error, and an optical element gravity error among the plurality of measurement errors, for each of the specified rotation angles of the optical element;

if the supporting and holding unit rotates with the supporting and holding unit, and if the aberration characteristics information has a constant amplitude deviation independent on one of the plurality of specified rotation angles corresponding thereto, determining the amplitude difference is contributed from the overall measurement system error and the optical element and the optical element gravity error, for each of the specified rotation angles of the optical element;
if a sine wave or a cosine wave having a period equivalent to a plurality of holding angles of the holding unit holding the optical element exists in the ideal sine function and the ideal cosine function, determining the amplitude difference of the period of the sine wave or cosine wave is resulted from a holding error owing to the holding unit, for each of the specified rotation angles of the optical element; and
deducting the amplitude differences resulted from the holding error, the optical element gravity error, and the overall system measurement error from each of the plurality of aberration characteristics information, and determining the amplitude difference of a remaining portion of each of the plurality of aberration characteristics information associated with the rotation of the optical element as a lens manufacture residual-shape error, for each of the specified rotation angles of the optical element; and
if the optical element has a particular angular symmetric weight-reducing structure at a rear side thereof, and the weight-reducing structure has a set of particular weight-reducing angles,
if the supporting and holding unit is maintained stationary with respect to the rotation of the optical element, if the plurality of aberration characteristics information has the constant amplitude deviation independent on one of the plurality of specified rotation angles corresponding thereto, determining the constant amplitude deviation is a sum of the overall measurement system error and the holding error, and deducting a sine wave or cosine wave having a period associated with the set of weight-reducing angles from each of the plurality of aberration characteristics information, determining the amplitude difference in a remaining portion of each of the plurality of aberration characteristics information as being resulted from the optical element gravity error, for each of the specified rotation angles of the optical element;
if the holding element rotates with the optical element, and if each of the plurality of aberration information has a constant amplitude deviation independent on the plurality of specified rotation angles of the optical element, determining the constant amplitude deviation is resulted from the overall system measurement error, and determining the amplitude difference on a sine or cosine wave in each of the plurality of aberration characteristics information having a period associated with the set of particular weight-reducing angles as being resulted from the optical element gravity error, for each of the specified rotation angles of the optical element; and
deducting the holding error, the optical element gravity error, and the overall system measurement error from each of the plurality of aberration characteristics information, and determining the amplitude difference of a remaining portion of each of the plurality of aberration characteristics information associated with the rotation of the optical element as the lens manufacture residual-shape error, for each of the specified rotation angles of the optical element.

4 . The method as claimed in claim 3 , wherein the step (e) further comprises a step of:
separating a plurality of classified aberration characteristics information from each of the plurality of aberration characteristics information according to the analyzed system measurement error, the optical element gravity error, the holding error, and the mirror manufacture residual-shape error, and the amplitude difference corresponding to each of the measurement errors, for each of the specified rotation angles of the optical element.

5 . The method as claimed in claim 4 , wherein the step (f) comprises a step of:
determining the plurality of error amounts according to the amplitude difference on each of the plurality of classified aberration characteristics, for each of the specified rotation angles of the optical element.

6 . The method as claimed in claim 1 , wherein the specific rotation angles of the optical element has a number 12 .

7 . A comput

Assignees

• Nat Applied Res Laboratories

Inventors

• Chang Shenq-Tsong
• Lin Wei-Cheng
• Huang Ting-Ming

Classifications

• G01M11/005

  Testing of reflective surfaces, e.g. mirrors · CPC title

• G01M11/0271 Primary

  by using interferometric methods · CPC title

• G01M11/0257

  by analyzing the image formed by the object to be tested · CPC title